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1.  Further analysis of previously implicated linkage regions for Alzheimer's disease in affected relative pairs 
BMC Medical Genetics  2009;10:122.
Background
Genome-wide linkage studies for Alzheimer's disease have implicated several chromosomal regions as potential loci for susceptibility genes.
Methods
In the present study, we have combined a selection of affected relative pairs (ARPs) from the UK and the USA included in a previous linkage study by Myers et al. (Am J Med Genet, 2002), with ARPs from Sweden and Washington University. In this total sample collection of 397 ARPs, we have analyzed linkage to chromosomes 1, 9, 10, 12, 19 and 21, implicated in the previous scan.
Results
The analysis revealed that linkage to chromosome 19q13 close to the APOE locus increased considerably as compared to the earlier scan. However, linkage to chromosome 10q21, which provided the strongest linkage in the previous scan could not be detected.
Conclusion
The present investigation provides yet further evidence that 19q13 is the only chromosomal region consistently linked to Alzheimer's disease.
doi:10.1186/1471-2350-10-122
PMCID: PMC2791756  PMID: 19951422
2.  The chromosome 9p21 variant interacts with vegetable and wine intake to influence the risk of cardiovascular disease: a population based cohort study 
BMC Medical Genetics  2014;15:1220.
Background
Chromosome 9p21 variants are associated with cardiovascular disease (CVD) but not with any of its known risk markers. However, recent studies have suggested that the risk associated with 9p21 variation is modified by a prudent dietary pattern and smoking. We tested if the increased risk of CVD by the 9p21 single nucleotide polymorphism rs4977574 is modified by intakes of vegetables, fruits, alcohol, or wine, and if rs4977574 interacts with environmental factors on known CVD risk markers.
Methods
Multivariable Cox regression analyses were performed in 23,949 individuals from the population-based prospective Malmö Diet and Cancer Study (MDCS), of whom 3,164 developed CVD during 15 years of follow-up. The rs4977574 variant (major allele: A; minor allele: G) was genotyped using TaqMan® Assay Design probes. Dietary data were collected at baseline using a modified diet history method. Cross-sectional analyses were performed in 4,828 MDCS participants with fasting blood levels of circulating risk factors measured at baseline.
Results
Each rs4977574 G allele was associated with a 16% increased incidence of CVD (95% confidence interval (CI), 1.10–1.22). Higher vegetable intake (hazard ratio (HR), 0.95 [CI: 0.91–0.996]), wine intake (HR, 0.91 [CI: 0.86–0.96]), and total alcohol consumption (HR, 0.92 [CI: 0.86–0.98]) were associated with lower CVD incidence. The increased CVD incidence by the G allele was restricted to individuals with medium or high vegetable intake (Pinteraction = 0.043), and to non- and low consumers of wine (Pinteraction = 0.029). Although rs4977574 did not associate with any known risk markers, stratification by vegetable intake and smoking suggested an interaction with rs4977574 on glycated hemoglobin and high-density lipoprotein cholesterol (Pinteraction = 0.015 and 0.049, respectively).
Conclusions
Our results indicate that rs4977574 interacts with vegetable and wine intake to affect the incidence of CVD, and suggest that an interaction may exist between environmental risk factors and rs4977574 on known risk markers of CVD.
Electronic supplementary material
The online version of this article (doi:10.1186/s12881-014-0138-x) contains supplementary material, which is available to authorized users.
doi:10.1186/s12881-014-0138-x
PMCID: PMC4331503  PMID: 25551366
Cardiovascular disease; Chromosome 9p21; Diet; Gene; Gene–diet interactions
3.  Single nucleotide polymorphisms in DNA repair genes as risk factors associated to prostate cancer progression 
BMC Medical Genetics  2014;15(1):143.
Background
Besides serum levels of PSA, there is a lack of prostate cancer specific biomarkers. It is need to develop new biological markers associated with the tumor behavior which would be valuable to better individualize treatment. The aim of this study was to elucidate the relationship between single nucleotide polymorphisms (SNPs) in genes involved in DNA repair and prostate cancer progression.
Methods
A total of 494 prostate cancer patients from a Spanish multicenter study were genotyped for 10 SNPs in XRCC1, ERCC2, ERCC1, LIG4, ATM and TP53 genes. The SNP genotyping was made in a Biotrove OpenArray® NT Cycler. Clinical tumor stage, diagnostic PSA serum levels, and Gleason score at diagnosis were obtained for all participants. Genotypic and allelic frequencies were determined using the web-based environment SNPator.
Results
SNPs rs11615 (ERCC1) and rs17503908 (ATM) appeared as risk factors for prostate cancer aggressiveness. Patients wild homozygous for these SNPs (AA and TT, respectively) were at higher risk for developing cT2b – cT4 (OR = 2.21 (confidence interval (CI) 95% 1.47 – 3.31), p < 0.001) and Gleason scores ≥ 7 (OR = 2.22 (CI 95% 1.38 – 3.57), p < 0.001), respectively. Moreover, those patients wild homozygous for both SNPs had the greatest risk of presenting D’Amico high-risk tumors (OR = 2.57 (CI 95% 1.28 – 5.16)).
Conclusions
Genetic variants at DNA repair genes are associated with prostate cancer progression, and would be taken into account when assessing the malignancy of prostate cancer.
Electronic supplementary material
The online version of this article (doi:10.1186/s12881-014-0143-0) contains supplementary material, which is available to authorized users.
doi:10.1186/s12881-014-0143-0
PMCID: PMC4316399  PMID: 25540025
Single nucleotide polymorphism; ERCC1; ATM; Prostate cancer; OpenArray; DNA repair; Spanish cohort
4.  Genetic associations of Nrf2-encoding NFE2L2 variants with Parkinson’s disease – a multicenter study 
BMC Medical Genetics  2014;15:131.
Background
The transcription factor Nrf2, encoded by the NFE2L2 gene, is an important regulator of the cellular protection against oxidative stress. Parkinson’s disease is a neurodegenerative disease highly associated with oxidative stress. In a previously published study, we reported associations of NFE2L2 haplotypes with risk and age at onset of idiopathic Parkinson’s disease in a Swedish discovery material and a Polish replication material. Here, we have extended the replication study and performed meta-analyses including the Polish material and four new independent European patient-control materials. Furthermore, all SNPs included in the haplotype windows were investigated individually for associations with Parkinson’s disease in meta-analyses including all six materials.
Methods
Totally 1038 patients and 1600 control subjects were studied. Based on previous NFE2L2 haplotype associations with Parkinson’s disease, five NFE2L2 tag SNPs were genotyped by allelic discrimination and three functional NFE2L2 promoter SNPs were genotyped by sequencing. The impact of individual SNPs and haplotypes on risk and age at onset of Parkinson’s disease were investigated in each material individually and in meta-analyses of the obtained results.
Results
Meta-analyses of NFE2L2 haplotypes showed association of haplotype GAGCAAAA, including the fully functional promoter haplotype AGC, with decreased risk (OR = 0.8 per allele, p = 0.012) and delayed onset (+1.1 years per allele, p = 0.048) of Parkinson’s disease. These results support the previously observed protective effect of this haplotype in the first study. Further, meta-analyses of the SNPs included in the haplotypes revealed four NFE2L2 SNPs associated with age at onset of Parkinson’s disease (rs7557529 G > A, −1.0 years per allele, p = 0.042; rs35652124 A > G, −1.1 years per allele, p = 0.045; rs2886161 A > G, −1.2 years per allele, p = 0.021; rs1806649 G > A, +1.2 years per allele, p = 0.029). One of these (rs35652124) is a functional SNP located in the NFE2L2 promoter. No individual SNP was associated with risk of Parkinson’s disease.
Conclusion
Our results support the hypothesis that variation in the NFE2L2 gene, encoding a central protein in the cellular protection against oxidative stress, may contribute to the pathogenesis of Parkinson’s disease. Functional studies are now needed to explore these results further.
Electronic supplementary material
The online version of this article (doi:10.1186/s12881-014-0131-4) contains supplementary material, which is available to authorized users.
doi:10.1186/s12881-014-0131-4
PMCID: PMC4335439  PMID: 25496089
Parkinson’s disease; PD; Nrf2; NFE2L2; Meta-analysis; Multicenter; SNP; Haplotype; Risk factor
5.  A study of genes encoding cytokines (IL6, IL10, TNF), cytokine receptors (IL6R, IL6ST), and glucocorticoid receptor (NR3C1) and susceptibility to bronchopulmonary dysplasia 
BMC Medical Genetics  2014;15(1):120.
Background
Bronchopulmonary dysplasia (BPD) is a common chronic lung disease associated with very preterm birth. The major risk factors include lung inflammation and lung immaturity. In addition, genetic factors play an important role in susceptibility to moderate-to-severe BPD. In this study, the aim was to investigate whether common polymorphisms of specific genes that are involved in inflammation or differentiation of the lung have influence on BPD susceptibility.
Methods
Genes encoding interleukin-6 (IL6) and its receptors (IL6R and IL6ST), IL-10 (IL10), tumor necrosis factor (TNF), and glucocorticoid receptor (NR3C1) were assessed for associations with moderate-to-severe BPD susceptibility. Five IL6, nine IL6R, four IL6ST, one IL10, two TNF, and 23 NR3C1 single nucleotide polymorphisms (SNPs) were analyzed in very preterm infants born in northern Finland (56 cases and 197 controls) and Canada (58 cases and 68 controls). IL-6, TNF and gp130 contents in umbilical cord blood, collected from very preterm infants, were studied for associations with the polymorphisms. Epistasis (i.e., interactions between SNPs in BPD susceptibility) was also examined. SNPs showing suggestive associations were analyzed in additional replication populations from Finland (39 cases and 188 controls) and Hungary (29 cases and 40 controls).
Results
None of the studied SNPs were associated with BPD nor were the IL6, TNF or IL6ST SNPs associated with cord blood IL-6, TNF and gp130, respectively. However, epistasis analysis suggested that SNPs in IL6ST and IL10 were associated interactively with risk of BPD in the northern Finnish population; however, this finding did not remain significant after correction for multiple testing and the finding was not replicated in the other populations.
Conclusions
We conclude that the analyzed SNPs within IL6, IL6R, IL6ST, IL10, TNF, and NR3C1 were not associated with BPD. Furthermore, there was no evidence that the studied SNPs directly contribute to the cord blood protein contents.
Electronic supplementary material
The online version of this article (doi:10.1186/s12881-014-0120-7) contains supplementary material, which is available to authorized users.
doi:10.1186/s12881-014-0120-7
PMCID: PMC4258941  PMID: 25409741
Bronchopulmonary dysplasia; Epistasis; Glucocorticoid receptor; Interleukin; Preterm infant; Single nucleotide polymorphism
6.  Association of cholesteryl ester transfer protein (CETP) gene polymorphism, high density lipoprotein cholesterol and risk of coronary artery disease: a meta-analysis using a Mendelian randomization approach 
BMC Medical Genetics  2014;15(1):118.
Background
Recent randomized controlled trials have challenged the concept that increased high density lipoprotein cholesterol (HDL-C) levels are associated with coronary artery disease (CAD) risk reduction. The causal role of HDL-C in the development of atherosclerosis remains unclear. To increase precision and to minimize residual confounding, we exploited the cholesteryl ester transfer protein (CETP)-TaqIB polymorphism as an instrument based on Mendelian randomization.
Methods
The Mendelian randomization analysis was performed by two steps. First, we conducted a meta-analysis of 47 studies, including 23,928 cases and 27,068 controls, to quantify the relationship between the TaqIB polymorphism and the CAD risk. Next, the association between the TaqIB polymorphism and HDL-C was assessed among 5,929 Caucasians. We further employed Mendelian randomization to evaluate the causal effect of HDL-C on CAD based on the findings from the meta-analysis.
Results
The overall comparison of the B2 allele with the B1 allele yielded a significant risk reduction of CAD (P < 0.0001; OR = 0.88; 95% CI: 0.84–0.92) with substantial between-study heterogeneity (I2 = 55.2%; Pheterogeneity <0.0001). The result was not materially changed after excluding the Hardy-Weinberg Equilibrium (HWE)-violation studies. Compared with B1B1 homozygotes, Caucasian carriers of the B2 allele had a 0.25 mmol/L increase in HDL-C level (95% CI: 0.20–0.31; P <0.0001; I2 = 0; Pheterogeneity =0.87). However, a 1 standard deviation (SD) elevation in HDL-C levels due to the TaqIB polymorphism, was marginal associated with CAD risk (OR =0.79; 95% CI: 0.54–1.03; P =0.08).
Conclusions
Taken together, our results lend support to the concept that increased HDL-C cannot be translated into a reduction in CAD risk.
Electronic supplementary material
The online version of this article (doi:10.1186/s12881-014-0118-1) contains supplementary material, which is available to authorized users.
doi:10.1186/s12881-014-0118-1
PMCID: PMC4258818  PMID: 25366166
Coronary artery disease; High density lipoprotein cholesterol; Polymorphism; Mendelian randomization
7.  Genome-wide linkage and exome analyses identify variants of HMCN1 for splenic epidermoid cyst 
BMC Medical Genetics  2014;15(1):115.
Background
Splenic epidermoid cyst is a benign tumor-like lesion affecting the spleen and sometimes occurs in familial form. The causality of such rare diseases remain challenging, however recently, with the emergence of exome re-sequencing, the genetics of many diseases have been unveiled. In the present study, we performed a combinatorial approach of genome-wide parametric linkage and exome analyses for a moderate-sized Japanese family with frequent occurrence of splenic epidermoid cyst to identify the genetic causality of the disease.
Methods
Twelve individuals from the family were subject to SNP typing and exome re-sequencing was done for 8 family members and 4 unrelated patients from Kosovo. Linkage was estimated using multi-point parametric linkage analysis assuming a dominant mode of inheritance. All of the candidate variants from exome analysis were confirmed by direct sequencing.
Results
The parametric linkage analysis suggested two loci on 1q and 14q with a maximal LOD score of 2.5 . Exome generated variants were prioritized based on; impact on the protein coding sequence, novelty or rareness in public databases, and position within the linkage loci. This approach identified three variants; variants of HMCN1 and CNTN2 on 1q and a variant of DDHD1 on 14q. The variant of HMCN1 (p.R5205H) showed the best co-segregation in the family after validation with Sanger sequencing. Additionally, rare missense variants (p.A4704V, p.T5004I, and p.H5244Q) were detected in three unrelated Kosovo patients. The identified variants of HMCN1 are on conserved domains, particularly the two variants on calcium-binding epidermal growth factor domain.
Conclusions
The present study, by combining linkage and exome analyses, identified HMCN1 as a genetic causality of splenic epidermoid cyst. Understanding the biology of the disease is a key step toward developing innovative approaches of intervention.
Electronic supplementary material
The online version of this article (doi:10.1186/s12881-014-0115-4) contains supplementary material, which is available to authorized users.
doi:10.1186/s12881-014-0115-4
PMCID: PMC4258954  PMID: 25338956
Exome re-sequencing; Splenic epidermoid cyst; HMCN1; Linkage analysis
8.  Mapping the deletion endpoints in individuals with 22q11.2 Deletion Syndrome by droplet digital PCR 
BMC Medical Genetics  2014;15(1):106.
Background
Chromosome 22q11.2 deletion syndrome (22q11DS) is the most common human microdeletion syndrome and is associated with many cognitive, neurological and psychiatric disorders. The majority of individuals have a 3 Mb deletion while others have a nested 1.5 Mb deletion, but rare atypical deletions have also been described. To date, a study using droplet digital PCR (ddPCR) has not been conducted to systematically map the chromosomal breakpoints in individuals with 22q11DS, which would provide important genotypic insight into the various phenotypes observed in this syndrome.
Methods
This study uses ddPCR to assess copy number (CN) changes within the chromosome 22q11 deletion region and allows the mapping of the deletion endpoints. We used eight TaqMan assays interspersed throughout the deleted region of 22q11.2 to characterize the deleted region of chromosome 22 in 80 individuals known to have 22q11DS by FISH. Ten EvaGreen assays were used for finer mapping of the six identified individuals with 22q11DS atypical deletions and covering different regions of chromosome 22.
Results
ddPCR provided non-ambiguous CN measurements across the region, confirmed the presence of the deletion in the individuals screened, and led to the identification of five differently sized and located deletions. The majority of the participants (n = 74) had the large 3 Mb deletions, whereas three had the smaller 1.5 Mb deletions, and the remaining three had an interstitial deletion of different size.
Conclusions
The lower cost, rapid execution and high reliability and specificity provided by ddPCR for CN measurements in the 22q11 region constitutes a significant improvement over the variable CN values generated by other technologies. The ability of the ddPCR approach, to provide a high resolution mapping of deletion endpoints may result in the identification of genes that are haplo-insufficient and play a role in the pathogenesis of 22q11DS. Finally, this methodology can be applied to the characterization of other microdeletions throughout the genome.
doi:10.1186/s12881-014-0106-5
PMCID: PMC4258952  PMID: 25312060
Droplet digital PCR; 22q11DS; qPCR; copy number; LCR
9.  A novel single base pair duplication in WDR62 causes primary microcephaly 
BMC Medical Genetics  2014;15(1):107.
Background
Primary microcephaly is a disorder of the brain resulting in a reduced head circumference that can come along with intellectual disability but with hardly any other neurological abnormalities.
Case presentation
In this study we report on three Pakistani males from a consanguineous family with 2, 4 and 25 years, diagnosed with autosomal recessive primary microcephaly. By genotyping, Sanger sequencing and using bioinformatical approaches the disease causing mutation was identified and evaluated.
Conclusion
By using a 250K SNP array, we were able to detect an 11Mb large autozygous region in the MCPH2 locus on chromosome 19q13.12. Sequencing of the associated gene, WDR62, revealed the frameshift causing single base pair duplication, c.2527dupG. This mutation is predicted to affect the structural features of WDR62 which in turn changes the conformation and function of the protein. Aspartic acid (D) at position 843 was found to be conserved among various ortholog species. The present findings will be helpful in genetic diagnosis of patients and future studies of WDR62.
doi:10.1186/s12881-014-0107-4
PMCID: PMC4258795  PMID: 25303973
Autosomal recessive primary microcephaly (MCPH); MCPH2 locus; WDR62; Mutation
10.  Paraganglioma and pheochromocytoma upon maternal transmission of SDHD mutations 
BMC Medical Genetics  2014;15(1):111.
Background
The SDHD gene encodes a subunit of the mitochondrial tricarboxylic acid cycle enzyme and tumor suppressor, succinate dehydrogenase. Mutations in this gene show a remarkable pattern of parent-of-origin related tumorigenesis, with almost all SDHD-related cases of head and neck paragangliomas and pheochromocytomas attributable to paternally-transmitted mutations.
Methods
Here we explore the underlying molecular basis of three cases of paraganglioma or pheochromocytoma that came to our attention due to apparent maternal transmission of an SDHD mutation. We used DNA analysis of family members to establish the mode of inheritance of each mutation. Genetic and immunohistochemical studies of available tumors were then carried out to confirm SDHD-related tumorigenesis.
Results
We found convincing genetic and immunohistochemical evidence for the maternally-related occurrence of a case of pheochromocytoma, and suggestive evidence in a case of jugular paraganglioma. The third case appears to be a phenocopy, a sporadic paraganglioma in an SDHD mutation carrier with no immunohistochemical or DNA evidence to support a causal link between the mutation and the tumor. Microsatellite analysis in the tumor of patient 1 provided evidence for somatic recombination and loss of the paternal region of chromosome 11 including SDHD and the maternal chromosome including the centromere and the p arm.
Conclusions
Transmission of SDHD mutations via the maternal line can, in rare cases, result in tumorigenesis. Despite this finding, the overwhelming majority of carriers of maternally-transmitted mutations will remain tumor-free throughout life.
doi:10.1186/s12881-014-0111-8
PMCID: PMC4259087  PMID: 25300370
Paraganglioma; Pheochromocytoma; SDHD; Imprinting; Parent-of-origin
11.  A novel GLI3 mutation affecting the zinc finger domain leads to preaxial-postaxial polydactyly-syndactyly complex 
BMC Medical Genetics  2014;15(1):110.
Background
Polydactyly is a highly common congenital limb defect. Extra digits may appear as an isolated anomaly or as a part of a syndrome. Mutations in GLI3 have been shown to cause Greig cephalopolysyndactyly, Pallister-Hall syndrome and non-syndromic polydactyly. Genotype-phenotype correlation studies of GLI3 mutations suggest a model by which mutations in the zinc-finger domain (ZFD) of GLI3 likely lead to syndromic polydactyly. Here we describe a rare case of autosomal dominant heterozygous missense mutation in the ZFD of GLI3 leading to a variable polydactyly-syndactyly complex.
Case presentation
A large Jewish Moroccan family presented with apparently autosomal dominant heredity of bilateral thumb polydactyly in hands and feet combined with post-axial polydactyly type B or type A. Syndactyly was evident in most patients’ hands and feet. Apart from head circumference beyond 90th percentile in some of the affected individuals, none had craniofacial dysmorphism. A novel GLI3 c.1802A > G (p.His601Arg) mutation was found in all affected individuals.
Conclusion
We demonstrate that a mutation in the ZFD domain of GLI3 leads to phenotypic variability, including an isolated limb phenotype. Thus, the variability in phenotypes caused by mutations in this master developmental regulator is more profound than has been previously suggested.
Electronic supplementary material
The online version of this article (doi:10.1186/s12881-014-0110-9) contains supplementary material, which is available to authorized users.
doi:10.1186/s12881-014-0110-9
PMCID: PMC4256830  PMID: 25267529
Polydactyly; Syndactyly; GCPS; GLI3; Mutation; C2H2; Zinc finger
12.  CYP1B1 mutations in patients with primary congenital glaucoma from Saudi Arabia 
BMC Medical Genetics  2014;15(1):109.
Background
CYP1B1 is the most commonly mutated gene in primary congenital glaucoma (PCG). This study was undertaken to identify mutations in CYP1B1 in the Western region of Saudi Arabia.
Methods
Blood of patients who had typical findings of PCG, were screened by direct sequencing of all coding exons and splice junctions of the CYP1B1 gene.
Results
34 patients were studied; 18 patients belonged to 8 families, and 16 patients were non-familial, isolated PCG. Consanguinity was found in 27/34 (79.4%) of cases. All patients were diagnosed to have bilateral PCG at birth except one child, who had glaucoma in the right eye. More males (61.8%) were affected than females (38.2%). 79.4% (27/34) of patients were solved with pathogenic mutations and 20.6% (7/34) remained unsolved. Of the solved ones, 22.2% (6/27) of patients carry a pathogenic allele on one allele while the other allele remained yet to be determined. Direct sequencing of exon 2 revealed two pathogenic variants (p.Gly61Glu, p.Glu229Lys). P.Gly61Glu substitution was found both homozygously in 63% (17/27) of cases, and heterozygously in one patient. P.Glu229Lys variant was found heterozygous in 3.7% (1/27) of cases. One pathogenic variant (p.Arg469Trp) was found in exon 3, and is present homozygously in 14.8% (4/27) of cases while four patients have this variant heterozygously. All mutations were reported previously in the Saudi population, except p.Glu229Lys. Severe cases were associated with p.Gly61Glu, and p.Arg469Trp in 50% and 30% of ten patients respectively.
Conclusions
This study confirms that CYP1B1 mutations are the most frequent cause of PCG in the Saudi population, with p.Gly61Glu being the major disease-associated mutation. P.Glu229Lys is a newly discovered mutation in our PCG patients. Patient lacking mutation in CYP1B1 gene seems likely, to have another genetic loci involved in the pathogenesis of the disease, and need further study. Genetic studies of recessive diseases such as PCG is important in consanguineous populations, since it will increase awareness and allows genetic counseling to be offered to patients and their relatives. This will not only reduce the disease to be inherited to future generations, but will also reduce the disease burden in the community.
doi:10.1186/s12881-014-0109-2
PMCID: PMC4258803  PMID: 25261878
Congenital; Glaucoma; Gene; Mutation; CYP1B1
13.  Genetic determinants of glucose-6-phosphate dehydrogenase activity in Kenya 
BMC Medical Genetics  2014;15:93.
Background
The relationship between glucose-6-phosphate dehydrogenase (G6PD) deficiency and clinical phenomena such as primaquine-sensitivity and protection from severe malaria remains poorly defined, with past association studies yielding inconsistent and conflicting results. One possibility is that examination of a single genetic variant might underestimate the presence of true effects in the presence of unrecognized functional allelic diversity.
Methods
We systematically examined this possibility in Kenya, conducting a fine-mapping association study of erythrocyte G6PD activity in 1828 Kenyan children across 30 polymorphisms at or around the G6PD locus.
Results
We demonstrate a strong functional role for c.202G>A (rs1050828), which accounts for the majority of variance in enzyme activity observed (P=1.5×10−200, additive model). Additionally, we identify other common variants that exert smaller, intercorrelated effects independent of c.202G>A, and haplotype analyses suggest that each variant tags one of two haplotype motifs that are opposite in sequence identity and effect direction. We posit that these effects are of biological and possible clinical significance, specifically noting that c.376A>G (rs1050829) augments 202AG heterozygote risk for deficiency trait by two-fold (OR = 2.11 [1.12 - 3.84], P=0.014).
Conclusions
Our results suggest that c.202G>A is responsible for the majority of the observed prevalence of G6PD deficiency trait in Kenya, but also identify a novel role for c.376A>G as a genetic modifier which marks a common haplotype that augments the risk conferred to 202AG heterozygotes, suggesting that variation at both loci merits consideration in genetic association studies probing G6PD deficiency-associated clinical phenotypes.
doi:10.1186/s12881-014-0093-6
PMCID: PMC4236593  PMID: 25201310
G6PD deficiency; Malaria
14.  The relationship between diastolic blood pressure and coronary artery calcification is dependent on single nucleotide polymorphisms on chromosome 9p21.3 
BMC Medical Genetics  2014;15:89.
Background
Single nucleotide polymorphisms (SNPs) within the 9p21.3 genomic region have been consistently associated with coronary heart disease (CHD), myocardial infarction, and quantity of coronary artery calcification (CAC), a marker of subclinical atherosclerosis. Prior studies have established an association between blood pressure measures and CAC. To examine mechanisms by which the 9p21.3 genomic region may influence CHD risk, we investigated whether SNPs in 9p21.3 modified associations between blood pressure and CAC quantity.
Methods
As part of the Genetic Epidemiology Network of Arteriopathy (GENOA) Study, 974 participants underwent non-invasive computed tomography (CT) to measure CAC quantity. Linear mixed effects models were used to investigate whether seven SNPs in the 9p21.3 region modified the association between blood pressure levels and CAC quantity. Four SNPs of at least marginal significance in GENOA for a SNP-by-diastolic blood pressure (DBP) interaction were then tested for replication in the Framingham Heart Study’s Offspring Cohort (N = 1,140).
Results
We found replicated evidence that one SNP, rs2069416, in CDKN2B-AS1, significantly modified the association between DBP and CAC quantity (combined P = 0.0065; Bonferroni-corrected combined P = 0.0455).
Conclusions
Our results represent a novel finding that the relationship between DBP and CAC is dependent on genetic variation in the 9p21.3 region. Thus, variation in 9p21.3 may not only be an independent genetic risk factor for CHD, but also may modify the association between DBP levels and the extent of subclinical coronary atherosclerosis.
doi:10.1186/s12881-014-0089-2
PMCID: PMC4168694  PMID: 25185447
Epidemiology; Genetics of cardiovascular disease; Atherosclerosis risk factors; Other arteriosclerosis
15.  Biotinidase deficiency: clinical and genetic studies of 38 Brazilian patients 
BMC Medical Genetics  2014;15:96.
Background
Biotinidase deficiency (BD) is an inborn error of metabolism in which some genetic variants correlate with the level of enzyme activity. Biotinidase activity, however, may be artifactually low due to enzyme lability, premature birth, and jaundice; this hinders both phenotypic classification and the decision to implement therapy. This study sought to characterize the clinical and genetic profile of a sample of Brazilian patients exhibiting reduced biotinidase activity.
Methods
This observational, multicenter study used a convenience sampling strategy, with sequencing of exons 2, 3, and 4 of the BTD gene.
Results
The sample comprised 38 individuals with biochemical phenotypes defined a priori on the basis of biotinidase activity in serum/plasma (2 with profound deficiency, 9 with partial deficiency, 15 heterozygous, 1 borderline between partial deficiency and heterozygosity, 2 borderline between heterozygous and normal) or dried blood spot sample (n = 9, all with unspecified deficiency). Most patients were from Southern Brazil (n = 29/38) and were identified by neonatal screening (n = 33/38). Parental consanguinity was reported in two cases. The most commonly found genetic variants were c.1330G > C (p.D444H), c.755A > G (p.D252G), and c.[511G > A;1330G > C] (p.[A171T;D444H]), with allele frequencies of 50%, 9.4%, and 5.4% respectively. Three novel pathogenic variants were identified (c.119 T > C or p.L40P, c.479G > A or p.C160Y, and c.664G > A or p.D222N). Twenty-nine patients had two pathogenic variants detected (with cis/trans status ascertained in 26/29), six had only one variant, and three had no pathogenic variants detected. Genotyping confirmed the original phenotypic classification based on enzyme activity in 16/26 cases. Three polymorphic variants were identified in control individuals, of which two were nonpathogenic (c.1171C > T or p.P391S and c.1413 T > C or p.C471C, with a frequency of 1.5% and 5.5% respectively) and one pathogenic (c.1330G > C, frequency 4%).
Conclusions
Our findings suggest that partial BD is the most common form of BD in Brazil, and expand current knowledge on the allelic heterogeneity of this condition.
doi:10.1186/s12881-014-0096-3
PMCID: PMC4236587  PMID: 25174816
Low biotinidase; Genetic variants; Neonatal screening; Brazil
16.  Apparently synonymous substitutions in FGFR2 affect splicing and result in mild Crouzon syndrome 
BMC Medical Genetics  2014;15:95.
Background
Mutations of fibroblast growth factor receptor 2 (FGFR2) account for a higher proportion of genetic cases of craniosynostosis than any other gene, and are associated with a wide spectrum of severity of clinical problems. Many of these mutations are highly recurrent and their associated features well documented. Crouzon syndrome is typically caused by heterozygous missense mutations in the third immunoglobulin domain of FGFR2.
Case presentation
Here we describe two families, each segregating a different, previously unreported FGFR2 mutation of the same nucleotide, c.1083A>G and c.1083A>T, both of which encode an apparently synonymous change at the Pro361 codon. We provide experimental evidence that these mutations affect normal FGFR2 splicing and document the clinical consequences, which include a mild Crouzon syndrome phenotype and reduced penetrance of craniosynostosis.
Conclusions
These observations add to a growing list of FGFR2 mutations that affect splicing and provide important clinical information for genetic counselling of families affected by these specific mutations.
doi:10.1186/s12881-014-0095-4
PMCID: PMC4236556  PMID: 25174698
Craniosynostosis; Crouzon syndrome; Expressivity; FGFR2; Penetrance; Splicing; Synonymous substitution
17.  Further delineation of Loeys-Dietz syndrome type 4 in a family with mild vascular involvement and a TGFB2 splicing mutation 
BMC Medical Genetics  2014;15:91.
Background
The Loeys-Dietz syndrome (LDS) is a rare autosomal dominant disorder characterized by thoracic aortic aneurysm and dissection and widespread systemic connective tissue involvement. LDS type 1 to 4 are caused by mutations in genes of the TGF-β signaling pathway: TGFBR1 and TGFBR2 encoding the TGF-β receptor (LDS1 and LDS2), SMAD3 encoding the TGF-β receptor cytoplasmic effector (LDS3), and TGFB2 encoding the TGF-β2 ligand (LDS4). LDS4 represents the mildest end of the LDS spectrum, since aneurysms are usually observed in fourth decade and the progression of the disease is slower than in the other forms.
Case presentation
We report the clinical and molecular findings of an LDS4 Italian family. Genetic testing included TGFBR1, TGFBR2, SMAD3, and TGFB2 analysis by Sanger sequencing. In order to verify the effect of the identified splice mutation, RT-PCR analysis was performed.
The proband, a 57-year-old woman, showed high palate, hypoplasic uvula, easy bruising, joint hypermobility, chronic pain, scoliosis, multiple relapsing hernias, dural ectasia, and mitral valve prolapse. Magnetic resonance angiography revealed tortuosity and ectasia of carotid, vertebral, cerebral, and segmental pulmonary arteries. Arterial aneurysm and dissection never occurred. Her 39- and 34-year-old daughters presented with a variable degree of musculoskeletal involvement. Molecular analysis disclosed the novel c.839-1G>A splice site mutation in the TGFB2 gene. This mutation activates a cryptic splice acceptor site in exon 6 leading to frameshift, premature termination codon and haploinsufficiency (p.Gly280Aspfs*41).
Conclusions
Our data confirm that loss-of-function mutations in TGFB2 gene do not always lead to aggressive vascular phenotypes and that articular and skeletal signs are prevalent, therefore suggesting that LDS4 must be considered in patients with sparse signs of LDS and related disorders also in the absence of vascular events.
doi:10.1186/s12881-014-0091-8
PMCID: PMC4236574  PMID: 25163805
Loeys-Dietz syndrome type 4; TGFB2; TGF-ß2; Splicing mutation
18.  Recurrent 8q13.2-13.3 microdeletions associated with Branchio-oto-renal syndrome are mediated by human endogenous retroviral (HERV) sequence blocks 
BMC Medical Genetics  2014;15:90.
Background
Human endogenous retroviral (HERV) sequences are the remnants of ancient retroviral infection and comprise approximately 8% of the human genome. The high abundance and interspersed nature of homologous HERV sequences make them ideal substrates for genomic rearrangements. A role for HERV sequences in mediating human disease-associated rearrangement has been reported but is likely currently underappreciated.
Methods and Results
In the present study, two independent de novo 8q13.2-13.3 microdeletion events were identified in patients with clinical features of Branchio-Oto-Renal (BOR) syndrome. Nucleotide-level mapping demonstrated the identical breakpoints, suggesting a recurrent microdeletion including multiple genes such as EYA1, SULF1, and SLCO5A1, which is mediated by HERV1 homologous sequences.
Conclusions
These findings raise the potential that HERV sequences may more commonly underlie recombination of dosage sensitive regions associated with recurrent syndromes.
doi:10.1186/s12881-014-0090-9
PMCID: PMC4152767  PMID: 25135225
De novo 8q13.2-13.3 microdeletion; Human endogenous retroviral (HERV) sequences; Branchio-oto-renal syndrome; Mesomelia-synostoses syndrome
19.  A novel COL4A1 gene mutation results in autosomal dominant non-syndromic congenital cataract in a Chinese family 
BMC Medical Genetics  2014;15:97.
Background
Almost one-third of congenital cataracts are primarily autosomal dominant disorders, which are also called autosomal dominant congenital cataract, resulting in blindness and clouding of the lens. The purpose of this study was to identify the disease-causing mutation in a Chinese family affected by bilateral, autosomal dominant congenital cataract.
Methods
The detection of candidate gene mutation and the linkage analysis of microsatellite markers were performed for the known candidate genes. Molecular mapping and cloning of candidate genes were used in all affected family members to screen for potential genetic mutations and the mutation was confirmed by single enzyme digestion.
Results
The proband was diagnosed with isolated, congenital cataract without the typical clinical manifestations of cataract, which include diabetes, porencephaly, sporadic intracerebral hemorrhage, and glomerulopathy. A novel mutation, c.2345 G > C (Gly782Ala), in exon 31 of the collagen type IV αlpha1 (COL4A1) gene, which encodes the collagen alpha-1(IV) chain, was found to be associated with autosomal dominant congenital cataract in a Chinese family. This mutation was not found in unaffected family members or in 200 unrelated controls. Sequence analysis confirmed that the Gly782 amino acid residue is highly conserved.
Conclusions
The novel mutation (c.2345 G > C) of the COL4A1 gene is the first report of a non-syndromic, autosomal dominant congenital cataract, thereby highlighting the important role of type IV collagen in the physiological and optical properties of the lens.
doi:10.1186/s12881-014-0097-2
PMCID: PMC4236509  PMID: 25124159
Type IV collagen; COL4A1; Non-syndromic congenital cataract
20.  Novel GALT variations and mutation spectrum in the Korean population with decreased galactose-1-phosphate uridyltransferase activity 
BMC Medical Genetics  2014;15:94.
Background
Classic galactosemia (OMIM #230400) is an autosomal recessive metabolic disorder caused by a deficiency of the galactose-1-phosphate uridyltransferase (GALT, EC2.7.7.12) protein due to mutations in the GALT gene. The aim of this study was to provide a comprehensive and updated mutation spectrum of GALT in a Korean population.
Methods
Thirteen unrelated patients screened positive for galactosemia in a newborn screening program were included in this study. They showed a reduced GALT enzyme activity in red blood cells. Direct sequencing of the GALT gene and in silico analyses were done to evaluate the impact of novel variations upon GALT enzyme activity. We also reviewed previous reports for GALT mutations in Koreans.
Results
We identified six novel likely pathogenic variations including three missense (p.Ala101Asp, p.Tyr165His, and p.Pro257Thr), one small deletion/insertion [c.826_827delinsAA (p.Ala276Asn)], one frameshift (p.Asn96Serfs*5), and one splicing (c.378-1G > C) likely pathogenic variations. The most frequent variation was the Duarte variant (c.940A > G, 35.3%), followed by c.507G > C (p.Gln169His, 9.6%), among 34 Korean patients. Other mutations were widely scattered. None of the eight common mutations used for targeted mutation analysis in Western countries including p.Gln188Arg, p.Ser135Leu, p.Lys285Asn, p.Leu195Pro, p.Tyr209Cys, p.Phe171Ser, c.253-2A > G, and a 5 kb deletion, had been found in Koreans until this study.
Conclusions
Considering the mutation spectrum in Koreans, direct sequence analysis of entire GALT exons is recommended for accurate diagnosis. The mutations responsible for GALT deficiency in the Korean population were clearly different from those of other populations.
doi:10.1186/s12881-014-0094-5
PMCID: PMC4236512  PMID: 25124065
Galactosemia; Galactose-1-phosphate uridyltransferase; GALT; Metabolic disease; Mutation
21.  Alternative splicing in osteoclasts and Paget’s disease of bone 
BMC Medical Genetics  2014;15:98.
Background
Mutations in the SQSTM1/p62 gene have been reported in Paget’s disease of bone (PDB), but they are not sufficient to induce the pagetic osteoclast (OC) phenotype. We hypothesized that specific RNA isoforms of OC-related genes may contribute to the overactivity of pagetic OCs, along with other genetic predisposing factors.
Methods
Alternative splicing (AS) events were studied using a PCR-based screening strategy in OC cultures from 29 patients with PDB and 26 healthy donors (HD), all genotyped for the p62P392L mutation. Primer pairs targeting 5223 characterized AS events were used to analyze relative isoform ratios on pooled cDNA from samples of the four groups (PDB, PDBP392L, HD, HDP392L). Of the 1056 active AS events detected in the screening analysis, 192 were re-analyzed on non-amplified cDNA from each subject of the whole cohort.
Results
This analysis led to the identification of six AS events significantly associated with PDB, but none with p62P392L. The corresponding genes included LGALS8, RHOT1, CASC4, USP4, TBC1D25, and PIDD. In addition, RHOT1 and LGALS8 genes were upregulated in pagetic OCs, as were CASC4 and RHOT1 genes in the presence of p62P392L. Finally, we showed that the proteins encoded by LGALS8, RHOT1, USP4, TBC1D25, and PIDD were expressed in human OCs.
Conclusion
This study allowed the identification of hitherto unknown players in OC biology, and our findings of a differential AS in pagetic OCs may generate new concepts in the pathogenesis of PDB.
doi:10.1186/s12881-014-0098-1
PMCID: PMC4143580  PMID: 25115182
Alternative splicing; Osteoclast; Paget’s disease of bone; p62/SQSTM1
22.  Association study of two inflammation-related polymorphisms with susceptibility to hepatocellular carcinoma: a meta-analysis 
BMC Medical Genetics  2014;15:92.
Background
Inflammation is a response of body tissues to injury or irritation. Small RNAs, such as miR-146a and miR-499, participate in various processes of tumorigenesis. A recent study indicates that inflammation and abnormal immune responses may promote malignant progression in cancer development, indicating that inflammation-related polymorphisms such as miR-146a rs2910164 and miR-499 rs3746444 are crucial. However, studies on the association of these two polymorphisms with hepatocellular carcinoma (HCC) are inconclusive and inconsistent. We aimed at accessing the combined result of reported studies and make a more precise estimate of the relationship.
Methods
Meta-analysis was performed on the associations between the miR-146a rs2910164 C > G and miR-499 rs3746444 T > C polymorphisms and hepatocellular carcinoma, using: allele contrast, dominant, and recessive models. A total of 12 studies(8 on miR-146a rs2910164 and 4 on miR-499 rs3746444) with three populations (Chinese, Korean, Turkish) were included in this study.
Results
Results show that both allele frequency and genotype distributions of miR-146a rs2910164 polymorphism are significantly associated with susceptibility to HCC (G versus C: OR = 1.153, 95% CI 1.083–1.228, P < 0.001; GC versus CC: OR = 1.165, 95% CI 1.054–1.286, P = 0.003; GG versus CC: OR = 1.361, 95% CI 1.192–1.553, P < 0.001; GG/GC versus CC: OR = 1.213, 95% CI 1.104–1.333, P < 0.001; GG versus GC/CC: OR = 1.210, 95% CI 1.080–1.356, P < 0.001). Our data suggest that people with G allele have a higher susceptibility to HCC as compared to those with C allele. However, meta-analysis failed to detect associations between miR-499 rs3746444 and HCC risk under each genetic model tested. Subgroup analysis showed that Chinese population with CC genotype are more vulnerable to HCC (OR = 2.171, 95% CI = 1.149–4.104, P = 0.017) than those with TT genotype.
Conclusions
We conclude that rs2910164 in miR-146a may confer susceptibility to HCC, especially in the Chinese population. No significant association was found between miR-499 rs3746444 and HCC, but subgroup study showed that subjects with CC genotype are more vulnerable to HCC than TT genotype in the Chinese population.
doi:10.1186/s12881-014-0092-7
PMCID: PMC4236519  PMID: 25108400
23.  Genetic similarities between tobacco use disorder and related comorbidities: an exploratory study 
BMC Medical Genetics  2014;15:85.
Background
Tobacco use disorder (TUD), defined as the use of tobacco to the detriment of a person’s health or social functioning, is associated with various disorders. We hypothesized that mutual variation in genes may partly explain this link. The aims of this study were to make a non-exhaustive inventory of the disorders using (partially) the same genetic pathways as TUD, and to describe the genetic similarities between TUD and the selected disorders.
Methods
We developed a 3 stage approach: (i) selection of genes influencing TUD using Gene2Mesh and Ingenuity Pathway Analysis (IPA), (ii) selection of disorders associated with the selected genes using IPA and (iii) genetic similarities between disorders associated with TUD using Jaccard distance and cluster analyses.
Results
Fourteen disorders and thirty-two genes met our inclusion criteria. The Jaccard distance between pairs of disorders ranged from 0.00 (e.g. oesophageal cancer and malignant hypertension) to 0.45 (e.g. bladder cancer and addiction). A lower number in the Jaccard distance indicates a higher similarity between the two disorders. Two main clusters of genetically similar disorders were observed, one including coexisting disorders (e.g. addiction and alcoholism) and the other one with the side-effects of smoking (e.g. gastric cancer and malignant hypertension).
Conclusions
This exploratory study partly explains the potential genetic components linking TUD to other disorders. Two principle clusters of disorders were observed (i) coexisting disorders of TUD and (ii) side-effects of TUD disorders. A further deepening of this observation in a real life study should allow strengthening this hypothesis.
doi:10.1186/1471-2350-15-85
PMCID: PMC4119471  PMID: 25060307
Cardiovascular disorders; Comorbidity; Genetics; Network; Psychiatric disorders; Public Health Genomics; Tobacco use disorder; Tobacco smoking
24.  A novel CISD2 intragenic deletion, optic neuropathy and platelet aggregation defect in Wolfram syndrome type 2 
BMC Medical Genetics  2014;15:88.
Background
Wolfram Syndrome type 2 (WFS2) is considered a phenotypic and genotypic variant of WFS, whose minimal criteria for diagnosis are diabetes mellitus and optic atrophy. The disease gene for WFS2 is CISD2. The clinical phenotype of WFS2 differs from WFS1 for the absence of diabetes insipidus and psychiatric disorders, and for the presence of bleeding upper intestinal ulcers and defective platelet aggregation. After the first report of consanguineous Jordanian patients, no further cases of WFS2 have been reported worldwide. We describe the first Caucasian patient affected by WFS2.
Case presentation
The proband was a 17 year-old girl. She presented diabetes mellitus, optic neuropathy, intestinal ulcers, sensorineural hearing loss, and defective platelet aggregation to ADP. Genetic testing showed a novel homozygous intragenic deletion of CISD2 in the proband. Her brother and parents carried the heterozygous mutation and were apparently healthy, although they showed subclinical defective platelet aggregation. Long runs of homozygosity analysis from SNP-array data did not show any degree of parental relationship, but the microsatellite analysis confirmed the hypothesis of a common ancestor.
Conclusion
Our patient does not show optic atrophy, one of the main diagnostic criteria for WFS, but optic neuropathy. Since the “asymptomatic” optic atrophy described in Jordanian patients is not completely supported, we could suppose that the ocular pathology in Jordanian patients was probably optic neuropathy and not optic atrophy. Therefore, as optic atrophy is required as main diagnostic criteria of WFS, it might be that the so-called WFS2 could not be a subtype of WFS. In addition, we found an impaired aggregation to ADP and not to collagen as previously reported, thus it is possible that different experimental conditions or inter-patient variability can explain different results in platelet aggregation. Further clinical reports are necessary to better define the clinical spectrum of this syndrome and to re-evaluate its classification.
doi:10.1186/1471-2350-15-88
PMCID: PMC4121299  PMID: 25056293
CISD2; Optic neuropathy; Non-autoimmune diabetes mellitus; Novel mutation; Platelet aggregation; Sensorineural hearing loss; SNP-array; Upper intestinal ulcers; Wolfram syndrome
25.  Spectrum of phenotypic anomalies in four families with deletion of the SHOX enhancer region 
BMC Medical Genetics  2014;15:87.
Background
SHOX alterations have been reported in 67% of patients affected by Léri-Weill dyschondrosteosis (LWD), with a larger prevalence of gene deletions than point mutations. It has been recently demonstrated that these deletions can involve the SHOX enhancer region, rather that the coding region, with variable phenotype of the affected patients.
Here, we report a SHOX gene analysis carried out by MLPA in 14 LWD patients from 4 families with variable phenotype.
Case presentation
All patients presented a SHOX enhancer deletion. In particular, a patient with a severe bilateral Madelung deformity without short stature showed a homozygous alteration identical to the recently described 47.5 kb PAR1 deletion. Moreover, we identified, for the first time, in three related patients with a severe bilateral Madelung deformity, a smaller deletion than the 47.5 kb PAR1 deletion encompassing the same enhancer region (ECR1/CNE7).
Conclusions
Data reported in this study provide new information about the spectrum of phenotypic alterations showed by LWD patients with different deletions of the SHOX enhancer region.
doi:10.1186/1471-2350-15-87
PMCID: PMC4112833  PMID: 25056248
Madelung deformity; MLPA; SHOX; Short stature

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