Human cells in vivo are exposed to a topographically rich, 3-dimenisional environment which provides extracellular cues initiating a cascade of biochemical signals resulting in changes in cell behavior. One primary focus of our group is the development of biomimetic substrates with anisotropic nanoscale topography to elucidate the mechanisms by which physical surface cues are translated into biochemical signals. To investigate changes in gene expression as a result of nanotopographic cues, Human Umbilical Vein Endothelial Cells (HUVECs) were cultured on chemically identical flat and 400 nm pitch nanogrooved surfaces. After 12 hours, RNA was harvested for an Affymetrix HG U133 Plus 2.0 gene array. Of over 47,000 possible gene probes, 3171 had at least a two-fold difference in expression between the control flat and 400 nm pitch. The gene ontology groups with the most significant increase in expression are involved in protein modification and maintenance, similar to cells upregulating chaperone and protein synthesis genes in response to physical stresses. The most significant decreases in expression were observed with cell cycle proteins, including cyclins and checkpoint proteins. Extracellular matrix proteins, including integrins, collagens, and laminins, are almost uniformly down regulated on the 400 nm pitch surfaces compared to control. The down regulation of one of these genes, integrin beta 1, was confirmed via quantitative PCR. Together, these gene array data, in addition to our studies of cell behavior on nanoscale surfaces, contribute to our understanding of the signaling pathways modulated by topographical surface cues.
gene array; nanotopgraphy; endothelial cell; ECM; integrin
Objectives. To determine if therapy with pioglitazone HCl and tretinoin could slow disease progression in patients with ALS. Levels of tau and pNFH in the cerebrospinal fluid were measured to see if they could serve as prognostic indicators. Methods. 27 subjects on stable doses of riluzole were enrolled. Subjects were randomized to receive pioglitazone 30 mg/d and tretinoin 10 mg/BID for six months or two matching placebos. ALSFRS-R scores were followed monthly. At baseline and at the final visit, lumbar punctures (LPs) were performed to measure cerebrospinal fluid (CSF) biomarker levels. Results. Subjects treated with tretinoin, pioglitazone, and riluzole had an average rate of decline on the ALSFRS-R scale of −1.02 points per month; subjects treated with placebo and riluzole had a rate of decline of −.86 (P = .18). Over six months of therapy, CSF tau levels decreased in subjects randomized to active treatment and increased in subjects on placebo. Further higher levels of pNF-H at baseline correlated with a faster rate of progression. Conclusion. ALS patients who were treated with tretinoin and pioglitazone demonstrated no slowing on their disease progression. Interestingly, the rate of disease progression was strongly correlated with levels of pNFH in the CSF at baseline.
To determine the cause of autosomal dominant hearing loss segregating in an American family.
Otologic and audiometric examination was performed on affected family members. Genome wide parametric multipoint linkage mapping using a dominant model was performed with Affymetrix 50K GeneChip data. Direct sequencing was used to confirm the causative mutation.
In American family 467 segregating autosomal dominant nonsyndromic hearing loss (ADNSHL), a novel heterozygous missense mutation (c.362T>C; p.F121S) was identified in the COCH gene. This mutation was also associated with vestibular dysfunction typical of other DFNA9 families. However, affected family members also exhibited memory loss and night blindness.
The novel COCH mutation affects the functionally important LCCL domain where most DFNA9 mutations have been localized. The onset of the hearing loss, in the second or third decade of life, is earlier than in most DFNA9 families. The progression of hearing loss and vestibular dysfunction in the American family is typical of other DFNA9 families with mutations in this domain. Memory loss and night blindness have not been previously reported in DFNA9 families.
DFNA9; COCH gene; hearing loss; vestibular dysfunction; missense mutation
Mutations in the FUS gene have recently been described as a cause of familial ALS, but their role in the pathogenesis of sporadic ALS is unclear. We undertook mutational screening of all coding exons of FUS in 228 sporadic ALS cases, and, as previous reports suggest that exon 15 represents a mutational hotspot, we sequenced this exon in an additional 1,295 sporadic cases. Six variants in six different cases were found, indicating that FUS mutations can underlie apparently sporadic ALS, but account for less than 1% of this form of disease.
amyotrophic lateral sclerosis; sporadic disease; FUS; Italy; United States of America
We developed a generalized framework for multiplexed resequencing of targeted regions of the human genome on the Illumina Genome Analyzer using degenerate indexed DNA sequence barcodes ligated to fragmented DNA prior to sequencing. Using this method, the DNA of multiple HapMap individuals was simultaneously sequenced at several ENCODE (ENCyclopedia of DNA Elements) regions. We then evaluated the use of Bayes factors for discovering and genotyping polymorphisms from aligned sequenced reads. If we required that predicted polymorphisms be either previously identified by dbSNP or be visually evident upon reinspection of archived ENCODE traces, we observed a false-positive rate of 11.3% using strict thresholds (Ks>1,000) for predicting variants and 69.6% for lax thresholds (Ks>10). Conversely, false-negative rates ranged from 10.8% to 90.8%, with those at stricter cut-offs occurring at lower coverage (< 10 aligned reads). These results suggest that >90% of genetic variants are discoverable using multiplexed sequencing provided sufficient coverage at the polymorphic base.
Myosin VIIA mutations have been associated with non-syndromic hearing loss (DFNB2; DFNA11) and Usher syndrome type 1B (USH1B). We report clinical and genetic analyzes of a consanguineous Iranian family segregating autosomal recessive non-syndromic hearing loss (ARNSHL). The hearing impairment was mapped to the DFNB2 locus using Affymetrix 50K GeneChips; direct sequencing of the MYO7A gene was completed. The Iranian family (L-1419) was shown to segregate a novel homozygous missense mutation (c.1184G>A) that results in a p.R395H amino acid substitution in the motor domain of the myosin VIIA protein. Since one affected family member had significantly less severe hearing loss we used a candidate approach to search for a genetic modifier. This novel MYO7A mutation is the first reported to cause DFNB2 in the Iranian population and this DFNB2 family is the first to be associated with a potential modifier. The absence of vestibular and retinal defects, and less severe low frequency hearing loss, is consistent with the phenotype of a recently reported Pakistani DFNB2 family. Thus, we conclude this family has non-syndromic hearing loss (DFNB2) rather than Usher syndrome type 1B (USH1B), providing further evidence that these two diseases represent discrete disorders.
DFNB2; genetic modifier; MYO7A gene; missense mutation; motor domain; myosin VIIA protein; USH1B
We recently reported evidence for an association between the individual variation in normal human episodic memory and a common variant of the KIBRA gene, KIBRA rs17070145 (T-allele). Since memory impairment is a cardinal clinical feature of Alzheimer’s disease (AD), we investigated the possibility of an association between the KIBRA gene and AD using data from neuronal gene expression, brain imaging studies, and genetic association tests. KIBRA was significantly over-expressed and 3 of its 4 known binding partners under-expressed in AD-affected hippocampal, posterior cingulate and temporal cortex regions (p<0.010, corrected) in a study of laser capture microdissected neurons. Using positron emission tomography in a cohort of cognitively normal, late-middle-aged persons genotyped for KIBRA rs17070145, KIBRA T non-carriers exhibited lower glucose metabolism than did carriers in posterior cingulate and precuneus brain regions (P<0.001, uncorrected). Lastly, non-carriers of the KIBRA rs17070145 T-allele had increased risk of late-onset AD in an association study of 702 neuropathologically verified expired subjects (p=0.034; OR=1.29) and in a combined analysis of 1026 additional living and expired subjects (p=0.039; OR=1.26). Our findings suggest that KIBRA is associated with both individual variation in normal episodic memory and predisposition to AD.
genetics; imaging; expression profiling; memory
This study aimed at contributing to the elucidation of the genetic basis of age-related hearing impairment (ARHI), a common multifactorial disease with an important genetic contribution as demonstrated by heritability studies. We conducted a genome-wide association study (GWAS) in the Finnish Saami, a small, ancient, genetically isolated population without evidence of demographic expansion. The choice of this study population was motivated by its anticipated higher extent of LD, potentially offering a substantial power advantage for association mapping. DNA samples and audiometric measurements were collected from 352 Finnish Saami individuals, aged between 50 and 75 years. To reduce the burden of multiple testing, we applied principal component (PC) analysis to the multivariate audiometric phenotype. The first three PCs captured 80% of the variation in hearing thresholds, while maintaining biologically important audiometric features. All subjects were genotyped with the Affymetrix 100 K chip. To account for multiple levels of relatedness among subjects, as well as for population stratification, association testing was performed using a mixed model. We summarised the top-ranking association signals for the three traits under study. The top-ranked SNP, rs457717 (P-value 3.55 × 10−7), was associated with PC3 and was localised in an intron of the IQ motif-containing GTPase-activating-like protein (IQGAP2). Intriguingly, the SNP rs161927 (P-value 0.000149), seventh-ranked for PC1, was positioned immediately downstream from the metabotropic glutamate receptor-7 gene (GRM7). As a previous GWAS of a European and Finnish sample set already suggested a role for GRM7 in ARHI, this study provides further evidence for the involvement of this gene.
Saami; isolated population; mixed model; genome-wide association study; age-related hearing impairment; presbycusis
The Saami from Fennoscandia are believed to represent an ancient, genetically isolated population with no evidence of population expansion. Theoretical work has indicated that under this demographic scenario, extensive linkage disequilibrium (LD) is generated by genetic drift. Therefore, it has been suggested that the Saami would be particularly suited for genetic association studies, offering a substantial power advantage and allowing more economic study designs. However, no study has yet assessed this claim. As part of a GWAS for a complex trait, we evaluated the relative power for association studies of common variants in the Finnish Saami. LD patterns in the Saami were very similar to those in the non-African HapMap reference panels. Haplotype diversity was reduced and, on average, levels of LD were higher in the Saami as compared with those in the HapMap panels. However, using a ‘hidden' SNP approach we show that this does not translate into a power gain in association studies. Contrary to earlier claims, we show that for a given set of common SNPs, genomic coverage attained in the Saami is similar to that in the non-African HapMap panels. Nevertheless, the reduced haplotype diversity could potentially facilitate gene identification, especially if multiple rare variants play a role in disease etiology. Our results further indicate that the HapMap is a useful resource for genetic studies in the Saami.
Saami; genome-wide association studies; linkage disequilibrium; population isolates
To investigate the cause of autosomal recessive non-syndromic hearing loss (ARNSHL) segregating in two consanguineous Iranian families.
Otologic and audiometric examinations were performed on affected members of each family. Genome-wide parametric multipoint linkage mapping using a recessive model was performed with Affymetrix 50K GeneChips or short tandem repeat polymorphisms (STRPs). Direct sequencing was used to confirm the causative mutation in each family.
In two Iranian families, L-1651 and L-8600606, segregating ARNSHL that mapped to the DFNB7/11 locus, homozygosity for a reported splice site mutation (c.776+1G>A) and a novel deletion (c.1589_1590delCT; p.S530*) were identified in the TMC1 gene, respectively.
Consistent with the previously reported phenotype in DFNB7/11 families, the two Iranian families segregate congenital, profound hearing impairment. However, in family L-1651 one affected family member (IV:3) has milder hearing impairment than expected, suggesting a potential genetic modifier effect. These results indicate that DFNB7/11 is a common form of genetic hearing loss in Iran since this population is the source of six of the 29 TMC1 mutations reported worldwide.
DFNB7/11; TMCI gene; deletion; splice site mutation
A causal role of mutations in multiple general transcription factors in neurodevelopmental disorders including autism suggested that alterations in global levels of gene expression regulation might also relate to disease risk in sporadic cases of autism. This premise can be tested by evaluating for changes in the overall distribution of gene expression levels. For instance, in mice, variability in hippocampal-dependent behaviors was associated with variability in the pattern of the overall distribution of gene expression levels, as assessed by variance in the distribution of gene expression levels in the hippocampus. We hypothesized that a similar change in variance might be found in children with autism. Gene expression microarrays covering greater than 47,000 unique RNA transcripts were done on RNA from peripheral blood lymphocytes (PBL) of children with autism (n = 82) and controls (n = 64). Variance in the distribution of gene expression levels from each microarray was compared between groups of children. Also tested was whether a risk factor for autism, increased paternal age, was associated with variance. A decrease in the variance in the distribution of gene expression levels in PBL was associated with the diagnosis of autism and a risk factor for autism, increased paternal age. Traditional approaches to microarray analysis of gene expression suggested a possible mechanism for decreased variance in gene expression. Gene expression pathways involved in transcriptional regulation were down-regulated in the blood of children with autism and children of older fathers. Thus, results from global and gene specific approaches to studying microarray data were complimentary and supported the hypothesis that alterations at the global level of gene expression regulation are related to autism and increased paternal age. Global regulation of transcription, thus, represents a possible point of convergence for multiple etiologies of autism and other neurodevelopmental disorders.
A distinct structural change in the trabecular meshwork (TM) of patients with primary open-angle glaucoma (POAH) is the increase in fibrillar extracellular matrix (ECM) in the juxtacanalicular region of the TM. Transforming growth factor (TGF)-β2 signaling may be involved, as TGF-β2 is significantly increased in the aqueous humor of patients with POAG. In cultured human TM cells, TGF-β2 causes an increase in ECM deposition, an effect that is blunted or prevented, if BMP7 is added in combination with TGF-β2. In order to know more about the signaling network that is induced in HTM cells treated with BMP7, TGF-β2 or the combination of both factors, we identified differentially regulated genes by microarray analysis, and confirmed selected genes by quantitative RT-PCR, Western blotting, or immunohistochemistry. We observed multiple effects of both TGF-β2 and BMP7 on the expression of a considerable number of genes involved in growth factor signaling, ECM structure and turnover, and modification of the cytoskeleton. Among the genes that were found to be regulated were CAPZA1, CDC42BPB, EFEMP1, FGF5, FSTL3, HBEGF, LTBP1, LTBP2, MATN2, NRP1, SERPINE1, SH3MD1, SMTN, SMAD7, TFPI2, TNFAIP6, and VEGF. Since SMAD7 encodes for Smad7, an inhibitory Smad that acts in a negative feedback loop to inhibit TGF-β activity, we silenced Smad7 mRNA in cultured human TM cells by a specific small interfering RNA. Silencing of its mRNA caused a substantial knock down of Smad7 in TM cells. Following combined BMP7/TGF-β2 treatment, the antagonizing effect of BMP7 on TGF-β2 induced CTGF expression was abolished. We conclude that Smad7 is the key molecular switch that inhibits TGF-β2 signaling, and mediates the blunting effects of BMP7 on TGF-β2 in TM cells. A therapeutic modulation of Smad7 might be a promising approach to influence ECM turnover in the TM and to treat POAG.
Smad7; TGF-β2; BMP7; trabecular meshwork; extracellular matrix
The prevalence of common chronic non-communicable diseases (CNCDs) far overshadows the prevalence of both monogenic and infectious diseases combined. All CNCDs, also called complex genetic diseases, have a heritable genetic component that can be used for pre-symptomatic risk assessment. Common single nucleotide polymorphisms (SNPs) that tag risk haplotypes across the genome currently account for a non-trivial portion of the germ-line genetic risk and we will likely continue to identify the remaining missing heritability in the form of rare variants, copy number variants and epigenetic modifications. Here, we describe a novel measure for calculating the lifetime risk of a disease, called the genetic composite index (GCI), and demonstrate its predictive value as a clinical classifier. The GCI only considers summary statistics of the effects of genetic variation and hence does not require the results of large-scale studies simultaneously assessing multiple risk factors. Combining GCI scores with environmental risk information provides an additional tool for clinical decision-making. The GCI can be populated with heritable risk information of any type, and thus represents a framework for CNCD pre-symptomatic risk assessment that can be populated as additional risk information is identified through next-generation technologies.
To use clinical and genetic analyses to determine the mutation causing autosomal recessive non-syndromic hearing loss (ARNSHL) segregating in two consanguineous Iranian families.
Members of each family received otologic and audiometric examination for the type and extent of hearing loss. Linkage mapping using Affymetrix 50K GeneChips and STRP analysis localized the hearing loss in both families to the DFNB3 locus. Direct sequencing of the MYO15A gene was completed on affected members of both families.
Family L-3165 segregated a novel homozygous missense mutation (c.6371G>A) that results in a p.R2124Q amino acid substitution in the myosin XVa protein. While family L-896 segregated a novel homozygous missense (c.6555C>T) mutation resulting in a p.P2073S amino acid change.
These are the first MYO15A mutations reported to cause DFNB3 sensorineural hearing loss in the Iranian population. Like other mutations located in the myosin tail homology 4 (MyTH4) domain, the p.R2124Q and p.P2073S mutations are predicted to disrupt the function of the myosin XVa protein, which is integral to the mechanosensory activity of hair cells in the inner ear.
DFNB3; MYO15A gene; missense mutation
In a genome-wide association study of structural brain degeneration, we mapped the 3D profile of temporal lobe volume differences in 742 brain MRI scans of Alzheimer’s disease patients, mildly impaired, and healthy elderly subjects. After searching 546,314 genomic markers, 2 single nucleotide polymorphisms (SNPs) were associated with bilateral temporal lobe volume (P < 5×10−7). One SNP, rs10845840, is located in the GRIN2B gene which encodes the N-Methyl-D-Aspartate (NMDA) glutamate receptor NR2B subunit. This protein - involved in learning and memory, and excitotoxic cell death - has age-dependent prevalence in the synapse and is already a therapeutic target in Alzheimer’s disease. Risk alleles for lower temporal lobe volume at this SNP were significantly over-represented in AD and MCI subjects versus controls (odds ratio = 1.273; P = 0.039) and were associated with the mini-mental state exam (MMSE; t = −2.114; P = 0.035) demonstrating a negative effect on global cognitive function. Voxelwise maps of genetic association of this SNP with regional brain volumes, revealed intense temporal lobe effects (FDR correction at q = 0.05; critical P = 0.0257). This study uses large-scale brain mapping for gene discovery with implications for Alzheimer’s disease.
While the clinical and neuropathological characterization of Alzheimer’s Disease (AD) is well defined, our understanding of the progression of pathologic mechanisms in AD remains unclear. Post-mortem brains from individuals who did not fulfill clinical criteria for AD may still demonstrate measurable levels of AD pathologies to suggest that they may have presented with clinical symptoms had they lived longer or are able to stave off disease progression. Comparison between such individuals and those clinically diagnosed and pathologically confirmed to have AD will be key in delineating AD pathogenesis and neuroprotection. In this study, we expression profiled laser capture microdissected non-tangle bearing neurons in 6 post-mortem brain regions that are differentially affected in the AD brain from 10 non-demented individuals demonstrating intermediate AD neuropathologies (NDAD; Braak stage of II through IV and CERAD rating of moderate to frequent) and evaluated this data against that from individuals who have been diagnosed with late onset AD as well as healthy elderly controls. We identified common statistically significant expression changes in both NDAD and AD brains that may establish a degenerative link between the two cohorts, in addition to NDAD specific transcriptomic changes. These findings pinpoint novel targets for developing earlier diagnostics and preventative therapies for AD prior to diagnosis of probable AD. We also provide this high-quality, low post-mortem interval (PMI), cell-specific, and region-specific NDAD/AD reference data set to the community as a public resource.
Laser capture microdissection; Affymetrix microarrays; Expression profiling; Neuron; Transcriptomics
Alzheimer’s Disease (AD) is the most widespread form of dementia during the later stages of life. If improved therapeutics are not developed, the prevalence of AD will drastically increase in the coming years as the world’s population ages. By identifying differences in neuronal gene expression profiles between healthy elderly persons and individuals diagnosed with AD, we may be able to better understand the molecular mechanisms that drive AD pathogenesis, including the formation of amyloid plaques and neurofibrillary tangles. In this study, we expression profiled histopathologically normal cortical neurons collected with laser capture microdissection (LCM) from six anatomically and functionally discrete postmortem brain regions in 34 AD-afflicted individuals, using Affymetrix Human Genome U133 Plus 2.0 microarrays. These regions include the entorhinal cortex, hippocampus, middle temporal gyrus, posterior cingulate cortex, superior frontal gyrus, and primary visual cortex. This study is predicated on previous parallel research on the postmortem brains of the same six regions in 14 healthy elderly individuals, for which LCM neurons were similarly processed for expression analysis. We identified significant regional differential expression in AD brains compared with control brains including expression changes of genes previously implicated in AD pathogenesis, particularly with regards to tangle and plaque formation. Pinpointing the expression of factors that may play a role in AD pathogenesis provides a foundation for future identification of new targets for improved AD therapeutics. We provide this carefully phenotyped, laser capture microdissected intraindividual brain region expression data set to the community as a public resource.
expression profiling; neuron; Affymetrix microarrays; laser capture microdissection
Age-related hearing impairment (ARHI), or presbycusis, is the most prevalent sensory impairment in the elderly. ARHI is a complex disease caused by an interaction between environmental and genetic factors. Here we describe the results of the first whole genome association study for ARHI. The study was performed using 846 cases and 846 controls selected from 3434 individuals collected by eight centers in six European countries. DNA pools for cases and controls were allelotyped on the Affymetrix 500K GeneChip® for each center separately. The 252 top-ranked single nucleotide polymorphisms (SNPs) identified in a non-Finnish European sample group (1332 samples) and the 177 top-ranked SNPs from a Finnish sample group (360 samples) were confirmed using individual genotyping. Subsequently, the 23 most interesting SNPs were individually genotyped in an independent European replication group (138 samples). This resulted in the identification of a highly significant and replicated SNP located in GRM7, the gene encoding metabotropic glutamate receptor type 7. Also in the Finnish sample group, two GRM7 SNPs were significant, albeit in a different region of the gene. As the Finnish are genetically distinct from the rest of the European population, this may be due to allelic heterogeneity. We performed histochemical studies in human and mouse and showed that mGluR7 is expressed in hair cells and in spiral ganglion cells of the inner ear. Together these data indicate that common alleles of GRM7 contribute to an individual's risk of developing ARHI, possibly through a mechanism of altered susceptibility to glutamate excitotoxicity.
Previously, utilizing a series of genome-wide association, brain imaging and gene expression studies we implicated the KIBRA gene and the RhoA/ROCK pathway in hippocampal-mediated human memory. Here we show that peripheral administration of the ROCK inhibitor hydroxyfasudil improves spatial learning and working memory in the rodent model. This study supports the action of ROCK on learning and memory, suggests the potential value of ROCK inhibition for the promotion of cognition in humans and highlights the powerful potential of unbiased genome-wide association studies to inform potential novel uses for existing pharmaceuticals.
learning; memory; ROCK; fasudil; aging
DFNB24; RDX; splice site mutation
Neurofibrillary tangles (NFT), a cardinal neuropathological feature of Alzheimer's disease (AD) that is highly correlated with synaptic loss and dementia severity, appear to be partly attributable to increased phosphorylation of the microtubule stabilizing protein tau at certain AD-related residues. Identifying the kinases involved in the pathologic phosphorylation of tau may provide targets at which to aim new AD-modifying treatments.
We report results from a screen of 572 kinases in the human genome for effects on tau hyperphosphorylation using a loss of function, high-throughput RNAi approach. We confirm effects of three kinases from this screen, the eukaryotic translation initiation factor 2 α kinase 2 (EIF2AK2), the dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A (DYRK1A), and the A-kinase anchor protein 13 (AKAP13) on tau phosphorylation at the 12E8 epitope (serine 262/serine 356). We provide evidence that EIF2AK2 effects may result from effects on tau protein expression, whereas DYRK1A and AKAP13 are likely more specifically involved in tau phosphorylation pathways.
These findings identify novel kinases that phosphorylate tau protein and provide a valuable reference data set describing the kinases involved in phosphorylating tau at an AD-relevant epitope.
We conducted a genome-wide association pooling study for cutaneous melanoma and performed validation in samples totalling 2019 cases and 2105 controls. Using pooling we identified a novel melanoma risk locus on chromosome 20 (rs910873, rs1885120), with replication in two further samples (combined P <1 × 10-15). The odds ratio is 1.75 (1.53, 2.01), with evidence for stronger association in early onset cases.
Summary: For many genome-wide association (GWA) studies individually genotyping one million or more SNPs provides a marginal increase in coverage at a substantial cost. Much of the information gained is redundant due to the correlation structure inherent in the human genome. Pooling-based GWA studies could benefit significantly by utilizing this redundancy to reduce noise, improve the accuracy of the observations and increase genomic coverage. We introduce a measure of correlation between individual genotyping and pooling, under the same framework that r2 provides a measure of linkage disequilibrium (LD) between pairs of SNPs. We then report a new non-haplotype multimarker multi-loci method that leverages the correlation structure between SNPs in the human genome to increase the efficacy of pooling-based GWA studies. We first give a theoretical framework and derivation of our multimarker method. Next, we evaluate simulations using this multimarker approach in comparison to single marker analysis. Finally, we experimentally evaluate our method using different pools of HapMap individuals on the Illumina 450S Duo, Illumina 550K and Affymetrix 5.0 platforms for a combined total of 1 333 631 SNPs. Our results show that use of multimarker analysis reduces noise specific to pooling-based studies, allows for efficient integration of multiple microarray platforms and provides more accurate measures of significance than single marker analysis. Additionally, this approach can be extended to allow for imputing the association significance for SNPs not directly observed using neighboring SNPs in LD. This multimarker method can now be used to cost-effectively complete pooling-based GWA studies with multiple platforms across over one million SNPs and to impute neighboring SNPs weighted for the loss of information due to pooling.
Supplementary information: Supplementary data are available at Bioinformatics online.
Fracture healing requires controlled expression of thousands of genes. Only a small fraction of these genes have been isolated and fewer yet have been shown to play a direct role in fracture healing. The purpose of this study was threefold: (1) to develop a reproducible open femur model of fracture healing that produces consistent fracture calluses for subsequent RNA extraction, (2) to use this model to determine temporal expression patterns of known and unknown genes using DNA microarray expression profiling, and (3) to identify and validate novel gene expression in fracture healing. In the initial arm of the study, a total of 56 wild-type C57BL/6 mice were used. An open, stabilized diaphyseal femur fracture was created. Animals were killed at 1, 5, 7, 10, 14, 21, and 35 days after surgery and the femurs were harvested for analysis. At each time point, fractures were radiographed and sectioned for histologic analyses. Tissue from fracture callus at all stages following fracture yielded reproducibly large amounts of mRNA. Expression profiling revealed that genes cluster by function in a manner similar to the histologic stages of fracture healing. Based on the expression profiling of fracture tissue, temporal expression patterns of several genes known to be involved in fracture healing were verified. Novel expression of multiple genes in fracture callous tissue was also revealed including leptin and leptin receptor. In order to test whether leptin signaling is required for fracture repair, mice deficient in leptin or its receptor were fractured using the same model. Fracture calluses of mice deficient in both leptin or leptin receptor are larger than wild-type mice fractures, likely due to a delay in mineralization, revealing a previously unrecognized role of leptin signaling in fracture healing. This novel model of murine fracture repair is useful in examining both global changes in gene expression as well as individual signaling pathways, which can be used to identify specific molecular mechanisms of fracture healing.
animal model; cDNA microarray; fracture healing; leptin
Myocilin is a 55–57 kDa secreted glycoprotein and member of the olfactomedin family, which is mutated in some forms of primary open-angle glaucoma. To assess the effects of elevated amounts of myocilin on aqueous humor outflow dynamics in an in vivo system, transgenic βB1-crystallin-MYOC mice have been developed that strongly overexpress myocilin in their eyes. The transgenic overexpression of myocilin results in an almost five-fold increase of secreted normal myocilin in the aqueous humor of βB1-crystallin-MYOC mice. In the present study, we wanted to use βB1-crystallin-MYOC as a tool to identify the response of ocular tissues to the presence of higher than normal amounts of myocilin, and to identify changes in gene expression that could help to shed light on the functional in vivo properties of myocilin. RNA was isolated from ocular tissues of βB1-crystallin-MYOC mice and wild-type littermates. Changes in gene expression were determined by hybridization of gene microarrays and confirmed by real-time RT-PCR and western blotting. The expression of genes that had been found to be differentially regulated in βB1-crystallin-MYOC mice was further analyzed in cultured human trabecular meshwork (HTM) cells treated with recombinant myocilin. Although βB1-crystallin-MYOC mice do not have an obvious phenotype, a statistically significant up- and downregulation of several distinct genes was found when compared to gene expression in wild-type littermates. Among the genes that were found to be differentially regulated were Wasl, Ceacam1, and Spon2, which are involved in cell adhesion and cell-matrix interactions. Differences in expression were also found for Six1 which encodes for a transcription factor, and for Pftk1 whose gene product is a cdc2-related protein kinase. The expression of these genes was also found to be regulated in vitro in HTM cells treated with recombinant myocilin. Substantially higher amounts in ocular tissues of βB1-crystallin-MYOC mice were found for connexin 46 and αB-crystallin. In addition, several genes that encode for olfactomedin proteins showed distinct changes in expression. Olfml3 was significantly downregulated, while Lphn1, Lphn2, and Lphn3 were significantly upregulated. Our findings support a role for myocilin in modulating cellular adhesion, and suggest functional processes that involve other proteins of the olfactomedin family.
N-WASP; CEACAM1; mindin; αB-crystallin; trabecular meshwork