An important gap exists in textbooks (or atlases) of dysmorphology used by health-care professionals to help diagnose genetic syndromes. The lack of varied phenotypic images in available atlases limits the utility of these atlases as diagnostic tools in globally diverse populations, causing geneticists difficulty in diagnosing conditions in individuals of different ancestral backgrounds who may present with variable morphological features. Proposals to address the underinclusion of images from diverse populations in existing atlases can take advantage of the Internet and digital photography to create new resources that take into account the broad global diversity of populations affected by genetic disease. Creating atlases that are more representative of the global population will expand resources available to care for diverse patients with these conditions, many of whom have been historically underserved by the medical system. However, such projects also raise ethical questions that are grounded in the complex intersection of imagery, medicine, history, and race and ethnicity. We consider here the benefits of producing such a resource while also considering ethical and practical concerns, and we offer recommendations for the ethical creation, structure, equitable use, and maintenance of a diverse morphological atlas for clinical diagnosis.
ethics; dysmorphology; genetics; global health; diverse populations
Rising rates of obesity and type 2 diabetes (T2D) are impending major threats to the health of African populations, but the extent to which they differ between rural and urban settings in Africa and upon migration to Europe is unknown. We assessed the burden of obesity and T2D among Ghanaians living in rural and urban Ghana and Ghanaian migrants living in different European countries.
A multi-centre cross-sectional study was conducted among Ghanaian adults (n = 5659) aged 25–70 years residing in rural and urban Ghana and three European cities (Amsterdam, London and Berlin). Comparisons between groups were made using prevalence ratios (PRs) with adjustments for age and education.
In rural Ghana, the prevalence of obesity was 1.3 % in men and 8.3 % in women. The prevalence was considerably higher in urban Ghana (men, 6.9 %; PR: 5.26, 95 % CI, 2.04–13.57; women, 33.9 %; PR: 4.11, 3.13–5.40) and even more so in Europe, especially in London (men, 21.4 %; PR: 15.04, 5.98–37.84; women, 54.2 %; PR: 6.63, 5.04–8.72). The prevalence of T2D was low at 3.6 % and 5.5 % in rural Ghanaian men and women, and increased in urban Ghanaians (men, 10.3 %; PR: 3.06; 1.73–5.40; women, 9.2 %; PR: 1.81, 1.25–2.64) and highest in Berlin (men, 15.3 %; PR: 4.47; 2.50–7.98; women, 10.2 %; PR: 2.21, 1.30–3.75). Impaired fasting glycaemia prevalence was comparatively higher only in Amsterdam, and in London, men compared with rural Ghana.
Our study shows high risks of obesity and T2D among sub-Saharan African populations living in Europe. In Ghana, similarly high prevalence rates were seen in an urban environment, whereas in rural areas, the prevalence of obesity among women is already remarkable. Similar processes underlying the high burden of obesity and T2D following migration may also be at play in sub-Saharan Africa as a consequence of urbanisation.
Electronic supplementary material
The online version of this article (doi:10.1186/s12916-016-0709-0) contains supplementary material, which is available to authorized users.
Obesity; Type 2 diabetes; Migrants; Ethnic minority groups; Europe; Sub-Saharan Africa
The metabolically healthy obesity (MHO) phenotype is an important obesity subtype in which obesity is not accompanied by any metabolic comorbidity. However, the underlying molecular mechanisms remain elusive. In this study, a shotgun proteomics approach to identify circulating biomolecules and pathways associated with MHO was used.
The subjects were 20 African‐American women: 10 MHO cases and 10 metabolically abnormal individuals with obesity (MAO) controls. Serum proteins were detected and quantified using label‐free proteomics. Differential expression of proteins between the two groups was analyzed, and the list of differentially expressed proteins was analyzed to determine enriched biological pathways.
Twenty proteins were differentially expressed between MHO and controls. These proteins included: hemoglobin subunits (HBA1, P = 6.00 × 10−18), haptoglobin‐related protein (HPR, P = 1.2 × 10−15), apolipoproteins (APOB‐100, P = 1.50 × 10−40; APOA4, P = 1.1 × 10−14), retinol‐binding protein 4 (RBP4, P = 7.1 × 10−08), and CRP (P = 2.0 × 10−04). MHO was associated with lower levels of proinflammatory and higher levels of anti‐inflammatory biomarkers when compared with MAO. Pathway analysis showed enrichment of lipids and inflammatory pathways, including LXR/RXR and FXR/RXR activation, and acute phase response signaling.
These findings suggested that protection from dysregulated inflammatory and lipid processes were primary molecular hallmarks of MHO. The candidate biomarkers (AHSG, RBP4, and APOA4) identified in this study are potential prognostic markers for MHO.
The recent feasibility of genome-wide studies of adaptation in human populations has provided novel insights into biological pathways that have been affected by adaptive pressures. However, only a few African populations have been investigated using these genome-wide approaches. Here, we performed a genome-wide analysis for evidence of recent positive selection in a sample of 120 individuals of Wolaita ethnicity belonging to Omotic-speaking people who have inhabited the mid- and high-land areas of southern Ethiopia for millennia. Using the 11 HapMap populations as the comparison group, we found Wolaita-specific signals of recent positive selection in several human leukocyte antigen (HLA) loci. Notably, the selected loci overlapped with HLA regions that we previously reported to be associated with podoconiosis–a geochemical lymphedema of the lower legs common in the Wolaita area. We found selection signals in PPARA, a gene involved in energy metabolism during prolonged food deficiency. This finding is consistent with the dietary use of enset, a crop with high-carbohydrate and low-fat and -protein contents domesticated in Ethiopia subsequent to food deprivation 10 000 years ago, and with metabolic adaptation to high-altitude hypoxia. We observed novel selection signals in CDKAL1 and NEGR1, well-known diabetes and obesity susceptibility genes. Finally, the SLC24A5 gene locus known to be associated with skin pigmentation was in the top selection signals in the Wolaita, and the alleles of single-nucleotide polymorphisms rs1426654 and rs1834640 (SLC24A5) associated with light skin pigmentation in Eurasian populations were of high frequency (47.9%) in this Omotic-speaking indigenous Ethiopian population.
Reduced glomerular filtration rate defines chronic kidney disease and is associated with cardiovascular and all-cause mortality. We conducted a meta-analysis of genome-wide association studies for estimated glomerular filtration rate (eGFR), combining data across 133,413 individuals with replication in up to 42,166 individuals. We identify 24 new and confirm 29 previously identified loci. Of these 53 loci, nineteen associate with eGFR among individuals with diabetes. Using bioinformatics, we show that identified genes at eGFR loci are enriched for expression in kidney tissues and in pathways relevant for kidney development and transmembrane transporter activity, kidney structure, and regulation of glucose metabolism. Chromatin state mapping and DNase I hypersensitivity analyses across adult tissues demonstrate preferential mapping of associated variants to regulatory regions in kidney but not extra-renal tissues. These findings suggest that genetic determinants of eGFR are mediated largely through direct effects within the kidney and highlight important cell types and biologic pathways.
The serial founder model of modern human origins predicts that the phylogeny of ancestries exhibits bifurcating, tree-like behavior. Here, we tested this prediction using three methods designed to investigate gene flow in autosome-wide genotype data from 3,528 unrelated individuals from 163 global samples. Specifically, we investigated whether Cushitic ancestry has an East African or Middle Eastern origin. We found evidence for non-tree-like behavior in the form of four migration events. First, we found that Cushitic ancestry is a mixture of ancestries closely related to Arabian ancestry and Nilo-Saharan or Omotic ancestry. We found evidence for additional migration events in the histories of: 1) Indian and Arabian ancestries, 2) Kalash ancestry, and 3) Native American and Northern European ancestries. These findings, based on analysis of ancestry of present-day humans, reveal migration in the distant past and provide new insights into human history.
Primary vesicoureteral reflux (PVUR) is the most common malformation of the kidney and urinary tract and reflux nephropathy is a major cause of chronic kidney disease in children. Recently, we reported mutations in tenascin XB (TNXB) as a cause of PVUR with joint hypermobility.
To define the role of rare variants in tenascin genes in the etiology of PVUR, we screened a cohort of patients with familial PVUR (FPVUR) and non-familial PVUR (NFPVUR) for rare missense variants in TNXB and tenascin C (TNC) genes after excluding mutations in ROBO2 and SOX17.
We identified 134 individuals from 112 families with PVUR, we excluded two families with mutations in ROBO2. We found rare missense variants in TNXB in the remaining 110 families comprising of 5/55 (9%) of families with FPVUR and 2/55 (4%) of NFPVUR. There were no differences in high-grade reflux, or renal parenchymal scarring between patients with and without TNXB variants. All patients with TNXB rare variants that were tested exhibited joint hypermobility. Overall we were able to identify causes of FPVUR in 7/57 (12%) families (9% in TNXB and 3% in ROBO2).
In conclusion, a rare missense variant in TNXB in combination with a positive family history of VUR and joint hypermobility may represent a non-invasive method to diagnose PVUR and warrants further evaluation in other cohorts.
VUR; Tenascin genes; Joint hypermobility; UTI; reflux nephropathy
The recent feasibility of genome-wide studies of adaptation in human populations has provided novel insights into biological pathways that have been affected by adaptive pressures. However, only a few African populations have been investigated using these genome-wide approaches. Here, we performed a genome-wide analysis for evidence of recent positive selection in a sample of 120 individuals of Wolaita ethnicity belonging to Omotic speaking people that have inhabited the mid- and high-land areas of southern Ethiopia for millennia. Using the eleven HapMap populations as the comparison group, we found Wolaita-specific signals of recent positive selection in several HLA loci. Notably, the selected loci overlapped with HLA regions that we previously reported to be associated with podoconiosis – a geochemical lymphedema of the lower legs common in the Wolaita area. We found selection signals in PPARA, a gene involved in energy metabolism during prolonged food deficiency. This finding is consistent with the dietary use of enset, a crop with high carbohydrate and low fat and protein contents domesticated in Ethiopia subsequent to food deprivation 10,000 years ago, and with metabolic adaptation to high altitude hypoxia. We observed novel selection signals in CDKAL1 and NEGR1, well-known diabetes and obesity susceptibility genes. Finally, the SLC24A5 gene locus known to be associated with skin pigmentation was in the top selection signals in the Wolaita, and the alleles of SNPs rs1426654 and rs1834640 (SLC24A5) associated with light skin pigmentation in Eurasian populations were of high frequency (47.9%) in this Omotic speaking indigenous Ethiopian population.
natural selection; population genetics; human leukocyte antigen (HLA); metabolism; podoconiosis; Ethiopia
Reduced glomerular filtration rate defines chronic kidney disease and is associated with cardiovascular and all-cause mortality. We conducted a meta-analysis of genome-wide association studies for estimated glomerular filtration rate (eGFR), combining data across 133,413 individuals with replication in up to 42,166 individuals. We identify 24 new and confirm 29 previously identified loci. Of these 53 loci, 19 associate with eGFR among individuals with diabetes. Using bioinformatics, we show that identified genes at eGFR loci are enriched for expression in kidney tissues and in pathways relevant for kidney development and transmembrane transporter activity, kidney structure, and regulation of glucose metabolism. Chromatin state mapping and DNase I hypersensitivity analyses across adult tissues demonstrate preferential mapping of associated variants to regulatory regions in kidney but not extra-renal tissues. These findings suggest that genetic determinants of eGFR are mediated largely through direct effects within the kidney and highlight important cell types and biological pathways.
Reduced glomerular filtration rate (eGFR) is a hallmark of chronic kidney disease. Here, Pattaro et al. conduct a meta-analysis to discover several new loci associated with variation in eGFR and find that genes associated with eGFR loci often encode proteins potentially related to kidney development.
Diabetes is a leading risk factor for impaired kidney function, an indicator of chronic kidney disease. The aim of this study was to examine the association between type 2 diabetes (T2D) and impaired kidney function among adults in sub-Saharan Africa (SSA).
Participants were enrolled from Ghana, Kenya, and Nigeria. Impaired kidney function was based on an estimated glomerular filtration rate <60 ml/min/1.73 m2. Using logistic regression models, we conducted case–control analyses to estimate the multivariate-adjusted association of T2D and kidney function.
We used data from 4815 participants for whom the mean (SD) age was 48 (15) years, 41% were male and 46% had T2D. Those with T2D were more likely to have impaired kidney function [13.4% (95% CI: 11.9–14.7)] compared to those without T2D [4.8% (95% CI: 4.0–5.6)], p-value <0.001. The multivariate odds ratio of impaired kidney function among those with type 2 diabetes was 1.50 (95% CI: 1.17–1.91) p-value = 0.001, compared to those without T2D. Also, individuals with T2D who were at least 60 years old, obese, hypertensive or dyslipidemic were more likely to have impaired kidney function compared to those without T2D.
T2D was associated with 50% increased risk of impaired kidney function in this sample of adults from SSA. Interventions targeted at prevention, early diagnosis, and management of T2D are likely to reduce the burden of kidney disease in SSA.
impaired kidney function; type 2 diabetes; kidney disease; sub-Saharan Africa; diabetic kidney disease
Genome wide association studies (GWAS) for type 2 diabetes (T2D) undertaken in European and Asian ancestry populations have yielded dozens of robustly associated loci. However, the genomics of T2D remains largely understudied in sub-Saharan Africa (SSA), where rates of T2D are increasing dramatically and where the environmental background is quite different than in these previous studies. Here, we evaluate 106 reported T2D GWAS loci in continental Africans. We tested each of these SNPs, and SNPs in linkage disequilibrium (LD) with these index SNPs, for an association with T2D in order to assess transferability and to fine map the loci leveraging the generally reduced LD of African genomes. The study included 1775 unrelated Africans (1035 T2D cases, 740 controls; mean age 54 years; 59% female) enrolled in Nigeria, Ghana, and Kenya as part of the Africa America Diabetes Mellitus (AADM) study. All samples were genotyped on the Affymetrix Axiom PanAFR SNP array. Forty-one of the tested loci showed transferability to this African sample (p < 0.05, same direction of effect), 11 at the exact reported SNP and 30 others at SNPs in LD with the reported SNP (after adjustment for the number of tested SNPs). TCF7L2 SNP rs7903146 was the most significant locus in this study (p = 1.61 × 10−8). Most of the loci that showed transferability were successfully fine-mapped, i.e., localized to smaller haplotypes than in the original reports. The findings indicate that the genetic architecture of T2D in SSA is characterized by several risk loci shared with non-African ancestral populations and that data from African populations may facilitate fine mapping of risk loci. The study provides an important resource for meta-analysis of African ancestry populations and transferability of novel loci.
genetic association; replication; fine-mapping; type 2 diabetes; sub Saharan Africa
Hyperuricemia and associated cardio-metabolic disorders are more prevalent in African Americans than in European Americans. We used genome-wide admixture mapping and association testing to identify loci with ancestry effects on serum uric acid levels.
We analyzed 1,976 African Americans from Washington, D.C, including 1,322 individuals from 328 pedigrees and 654 unrelated individuals, enrolled in the Howard University Family Study. We performed admixture mapping and genome-wide association testing using ~800 k autosomal single-nucleotide polymorphisms (SNPs). We performed fine mapping by dense genotyping. We assessed functionality by a combination of bioinformatic annotation, reporter gene assays, and gel shift experiments. We also analyzed 12,641 individuals enrolled in the National Health and Nutrition Examination Survey.
We detected a genome-wide significant locus on chromosome 11p15.4 at which serum uric acid levels increased with increasing African ancestry, independent of kidney function. Fine-mapping identified two independent signals in the β-globin locus. The ancestral allele at SNP rs2855126, located upstream of the hemoglobin, gamma A gene HBG1, was associated with increased serum uric acid levels and higher expression of a reporter gene relative to the derived allele. Hyperuricemia was associated with increased risk of hypertension in 3,767 African Americans (Odds Ratio = 2.48, p = 2.71 × 10− 19).
Given that increased expression of γ-globin leads to increased levels of fetal hemoglobin which confers protection against malaria, we hypothesize that evolution in Africa of protection against malaria may have occurred at the cost of increased serum uric acid levels, contributing to the high rates of hyperuricemia and associated cardio-metabolic disorders observed in African Americans.
Electronic supplementary material
The online version of this article (doi:10.1186/s12881-015-0249-z) contains supplementary material, which is available to authorized users.
African American; Ancestry; Gamma-globin; Health disparity; Hypertension; Malaria; Uric acid
We surveyed 26 quantitative traits and disease outcomes to understand the proportion of phenotypic variance explained by local ancestry in admixed African Americans. After inferring local ancestry as the number of African-ancestry chromosomes at hundreds of thousands of genotyped loci across all autosomes, we used a linear mixed effects model to estimate the variance explained by local ancestry in two large independent samples of unrelated African Americans. We found that local ancestry at major and polygenic effect genes can explain up to 20 and 8% of phenotypic variance, respectively. These findings provide evidence that most but not all additive genetic variance is explained by genetic markers undifferentiated by ancestry. These results also inform the proportion of health disparities due to genetic risk factors and the magnitude of error in association studies not controlling for local ancestry.
ancestry; complex traits; health disparities; phenotypic variance explained; random effects
Adipose tissues play important role in the pathophysiology of obesity-related diseases including type 2 diabetes (T2D). To describe gene expression patterns and functional pathways in obesity-related T2D, we performed global transcript profiling of omental adipose tissue (OAT) in morbidly obese individuals with or without T2D.
Twenty morbidly obese (mean BMI: about 54 kg/m2) subjects were studied, including 14 morbidly obese individuals with T2D (cases) and 6 morbidly obese individuals without T2D (reference group). Gene expression profiling was performed using the Affymetrix U133 Plus 2.0 human genome expression array. Analysis of covariance was performed to identify differentially expressed genes (DEGs). Bioinformatics tools including PANTHER and Ingenuity Pathway Analysis (IPA) were applied to the DEGs to determine biological functions, networks and canonical pathways that were overrepresented in these individuals.
At an absolute fold-change threshold of 2 and false discovery rate (FDR) < 0.05, 68 DEGs were identified in cases compared to the reference group. Myosin X (MYO10) and transforming growth factor beta regulator 1 (TBRG1) were upregulated. MYO10 encodes for an actin-based motor protein that has been associated with T2D. Telomere extension by telomerase (HNRNPA1, TNKS2), D-myo-inositol (1, 4, 5)-trisphosphate biosynthesis (PIP5K1A, PIP4K2A), and regulation of actin-based motility by Rho (ARPC3) were the most significant canonical pathways and overlay with T2D signaling pathway. Upstream regulator analysis predicted 5 miRNAs (miR-320b, miR-381-3p, miR-3679-3p, miR-494-3p, and miR-141-3p,) as regulators of the expression changes identified.
This study identified a number of transcripts and miRNAs in OAT as candidate novel players in the pathophysiology of T2D in African Americans.
Obesity; Global gene expression; Type 2 diabetes; African Americans
The fixation index Fst plays a central role in ecological and evolutionary genetic studies. The estimators of Wright (F^st1), Weir and Cockerham (F^st2), and Hudson et al. (F^st3) are widely used to measure genetic differences among different populations, but all have limitations. We propose a minimum variance estimator F^stm using F^st1 and F^st2. We tested F^stm in simulations and applied it to 120 unrelated East African individuals from Ethiopia and 11 subpopulations in HapMap 3 with 464,642 SNPs. Our simulation study showed that F^stm has smaller bias than F^st2 for small sample sizes and smaller bias than F^st1 for large sample sizes. Also, F^stm has smaller variance than F^st2 for small Fst values and smaller variance than F^st1 for large Fst values. We demonstrated that approximately 30 subpopulations and 30 individuals per subpopulation are required in order to accurately estimate Fst.
Africa is home to genetically diverse human populations. We compared the genetic structure of the Wolaita ethnic population from southern Ethiopia (WETH, n=120) with HapMap populations using genome-wide variants. We investigated allele frequencies of 443 clinically and pharmacogenomically relevant genetic variants in WETH compared to HapMap populations. We found that WETH were genetically most similar to the Kenya Maasai and least similar to the Japanese in HapMap. Variant alleles associated with increased risk of adverse reactions to drugs used for treating tuberculosis (rs1799929 and rs1495741 in NAT2), thromboembolism (rs7294, rs9923231 and rs9934438 in VKORC1), and HIV/AIDS and solid tumors (rs2242046 in SLC28A1) had significantly higher frequencies in WETH compared to African ancestry HapMap populations. Our results illustrate that clinically relevant pharmacogenomic loci display allele frequency differences among African populations. We conclude that drug dosage guidelines for important global health diseases should be validated in genetically diverse African populations.
pharmacogenomics; global health; tuberculosis; HIV/AIDS; warfarin; Ethiopia
This article is an outcome of the African Craniofacial Anomalies Research Network (AfriCRAN) Human Hereditary and Health (H3A) grant planning meeting in 2012 in Lagos, Nigeria. It describes the strengths of a multidisciplinary team approach to solving complex genetic traits in the craniofacial region. It also highlights the different components and argues for the composition of similar teams to fast track the discovery of disease genes, diagnostic tools, improved clinical treatment and ultimately prevention of diseases.
Genomics; Africa; Multidisciplinary team
Given the importance of Africa to studies of human origins and disease susceptibility, detailed characterisation of African genetic diversity is needed. The African Genome Variation Project (AGVP) provides a resource to help design, implement and interpret genomic studies in sub-Saharan Africa (SSA) and worldwide. The AGVP represents dense genotypes from 1,481 and whole genome sequences (WGS) from 320 individuals across SSA. Using this resource, we find novel evidence of complex, regionally distinct hunter-gatherer and Eurasian admixture across SSA. We identify new loci under selection, including for malaria and hypertension. We show that modern imputation panels can identify association signals at highly differentiated loci across populations in SSA. Using WGS, we show further improvement in imputation accuracy supporting efforts for large-scale sequencing of diverse African haplotypes. Finally, we present an efficient genotype array design capturing common genetic variation in Africa, showing for the first time that such designs are feasible.
Focal segmental glomerulosclerosis (FSGS) is a histological lesion with many causes including inherited genetic defects with significant proteinuria being the predominant clinical finding at presentation. Mutations in COL4A3 and COL4A4 are known to cause Alport syndrome, thin basement membrane nephropathy, and to result in pathognomonic glomerular basement membrane findings. Secondary FSGS is known to develop in classic Alport Syndrome at later stages of the disease. Here, we present seven families with rare or novel variants in COL4A3 or COL4A4 (six with single and one with two heterozygous variants) from a cohort of 70 families with a diagnosis of hereditary FSGS. The predominant clinical findings at diagnosis were proteinuria associated with hematuria. In all seven families, there were individuals with nephrotic range proteinuria with histologic features of FSGS by light microscopy. In one family, electron microscopy showed thin glomerular basement membrane, but four other families had variable findings inconsistent with classical Alport nephritis. There was no recurrence of disease after kidney transplantation. Families with COL4A3 and COL4A4 variants that segregated with disease represent 10% of our cohort. Thus, COL4A3 and COL4A4 variants should be considered in the interpretation of next-generation sequencing data from such patients. Furthermore, this study illustrates the power of molecular genetic diagnostics in the clarification of renal phenotypes.
focal segmental glomerulosclerosis; podocyte; proteinuria; Alport syndrome
Despite evidence of an association between variants at the apolipoprotein L1 gene (APOL1) locus and a spectrum of related kidney diseases, underlying biological mechanisms remain unknown. An earlier preliminary study published by our group showed that an APOL1 variant (rs73885319) modified the association between high-density lipoprotein cholesterol (HDLC) and estimated glomerular filtration rate (eGFR) in African Americans. To further understand this relationship, we evaluated the interaction in two additional large cohorts of African Americans for a total of 3,592 unrelated individuals from the Howard University Family Study (HUFS), the Natural History of APOL1-Associated Nephropathy Study (NHAAN), and the Atherosclerosis Risk in Communities Study (ARIC). The association between HDLC and eGFR was determined using linear mixed models, and the interaction between rs73885319 genotype and HDLC was evaluated using a multiplicative term.
Among individuals homozygous for the risk genotype, a strong inverse HDLC-eGFR association was observed, with a positive association in others (p for the interaction of the rs73885319 × HDLC =0.0001). The interaction was similar in HUFS and NHAAN, and attenuated in ARIC. Given that ARIC participants were older, we investigated an age effect; age was a significant modifier of the observed interaction. When older individuals were excluded, the interaction in ARIC was similar to that in the other studies.
Based on these findings, it is clear that the relationship between HDLC and eGFR is strongly influenced by the APOL1 rs73885319 kidney risk genotype. Moreover, the degree to which this variant modifies the association may depend on the age of the individual. More detailed physiological studies are warranted to understand how rs73885319 may affect the relationship between HDLC and eGFR in individuals with and without disease and across the lifespan.
Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-1645-7) contains supplementary material, which is available to authorized users.
Apolipoprotein L1; High-density lipoprotein cholesterol; African ancestry; Glomerular filtration rate
The stability of biomarkers in stored biomedical samples is crucial, especially when storage is for extended periods of time. High-sensitivity CRP (Hs-CRP) is a biomarker of low grade inflammation that is extensively used to identify and study cardiovascular and/or inflammatory processes in clinical care and large epidemiologic studies. Therefore, assessing Hs-CRP stability in archived samples at a given temperature is important to insure precision of measurements over time and the validity of studies using archived samples.
We evaluated the stability of Hs-CRP in 30 randomly selected human serum samples by measuring Hs-CRP concentrations in freshly collected sample [Hs-CRP (0)] and in the same set of samples after 7–11 years of storage at −80°C [Hs-CRP (LT)].
Hs-CRP did not significantly change up to 11 years of storage at −80°C as shown by a negligible median difference between Hs-CRP (0) and Hs-CRP (LT), delta(Hs-CRP (0)- Hs-CRP (LT)=−0.01, p=0.45. There was a good concordance and agreement between Hs-CRP (0) and Hs-CRP (LT) as measured respectively by Lin's coefficient of correlation (ρC= 0.98) and Bland-Altman analysis (mean difference=−0.02, 95% CI [−0.04–0.0045] p=0.107). In addition, the data also suggest that the time elapsed between collection and Hs-CRP measurement does not affect Hs-CRP stability over time when samples are kept under the appropriate conditions.
Long-term storage at −80°C for up to 11 years did not significantly affect the stability of serum Hs-CRP. Given the cost and time for collecting fresh samples, this observation represents an important finding for biomedical research and clinical care.
C-reactive protein; archived samples; long-term storage; stability; biomedical research
African American men have higher blood pressure levels and consequentially higher prevalence of hypertension compared to men from other ethnic groups in the United States. Socio-familial factors in childhood have been found to play an important role in hypertension, but few studies have examined this relationship among African American men. We investigated whether childhood family living arrangements are independently associated with mean blood pressure and hypertension in a cross-sectional sample of 515 unrelated African American male participants aged 20 years and older enrolled in the Howard University Family Study between 2001 and 2008. African American men who lived with both parents compared to the reference group of men who never lived with both parents during their lifetime had lower systolic blood pressure [−4.4 mmHg (95% Confidence Interval: −7.84, −0.96)], pulse pressure [−3.9 mmHg (95% Confidence Interval: −6.28, −1.51)] and mean arterial blood pressure [−2.0 mmHg (95% Confidence Interval: −4.44, 0.51)]. This protective effect was more pronounced among men who lived with both parents for 1 to 12 years of their lives; they had decreased systolic blood pressure [−6.5 mmHg, (95% Confidence Interval: −10.99, −1.95)], pulse pressure [−5.4 mmHg, (95% Confidence Interval: −8.48, −2.28)], mean arterial pressure [−3.3 mmHg, (95% Confidence Interval: −6.56, 0.00)], and a 46% decreased odds of developing hypertension (OR = 0.54; 95% Confidence Interval: 0.30, 0.99). No statistically significant associations were found for diastolic blood pressure. These results provide preliminary evidence that childhood family structure exerts a long-term influence on blood pressure among African American men.
Blood Pressure; Hypertension; African Americans; Family Characteristics; Social Environment
The burdens of type 2 diabetes (T2D) and cardiovascular diseases (CVD) are increasingin Africa. T2D and CVD are the result of the complex interaction between inherited characteristics, lifestyle, and environmental factors. The epidemic of obesity is largely behind the exploding global incidence of T2D. However, not all obese individuals develop diabetes and positive family history is a powerful risk factor for diabetes and CVD. Recent implementations of high throughput genotyping and sequencing approaches have advanced our understanding of the genetic basis of diabetes and CVD by identifying several genomic loci that were not previously linked to the pathobiology of these diseases. However, African populations have not been adequately represented in these global genomic efforts. Here, we summarize the state of knowledge of the genetic epidemiology of T2D and CVD in Africa and highlight new genomic initiatives that promise to inform disease etiology, public health and clinical medicine in Africa.
Type 2 diabetes; cardiovascular diseases; genetics; epidemiology; Africa
Rapid advances in human genomic research are increasing the availability of genomic data for secondary analysis. Particularly in the case of vulnerable African populations, ethics and informed consent processes need to be transparent¿both to ensure participant protection, as well as to share skills and to evolve best practice for informed consent from a shared knowledge base. An open dialogue between all stakeholders can facilitate this.
Informed consent; Secondary use; Ethics; Africa
Nonsyndromic clefts of the lip and palate [NSCLP] are complex genetic traits. Together, they are classified as one of the most common birth defects with a prevalence of 1/700 live births. Genome-wide association studies [GWAS] for non-syndromic cleft lip with or without cleft palate [NSCL[P]] revealed significant association for common single nucleotide polymorphisms near genes involved in craniofacial development i.e. MAFB, PAX7, VAX1, ARHGAP29 (ABCA4 locus), and IRF6. Sequencing of protein coding regions of the NSCL[P] GWAS candidate genes or adjacent genes suggest a role for rare functional variants. Replication studies in the African population did not observe any significant association with the GWAS candidate genes. On the other hand, the role of rare functional variants in GWAS candidate genes has not been evaluated in the African population. We obtained saliva samples from case triads in Nigeria and Ethiopia for Sanger sequencing of the GWAS candidate genes [MAFB, PAX7, VAX1, ARHGAP29, and IRF6] in order to identify rare functional variants. A total of 220 African samples [140 Nigerians and 80 Ethiopians] were sequenced and we found the following new rare variants— p.His165Asn in the MAFB gene, p.Asp428Asn in the PAX7, a splice-site variant that creates a new donor splice-site in PAX7. We also found three previously reported missense variants p.Gly466Ser in PAX7; p.Leu913Ser and Arg955His in ARHGAP29. No de novo mutations were found. Future genome-wide association and sequencing studies should be conducted using samples from Africa in order to identify new molecular genetic factors that contribute to the etiology of NSCLP.
Africa; GWAS; rare variants