The role of sirtuins and uncoupling proteins on vascular aging: The Northern Manhattan Study experience

Aging affects all organs. Arteries, in particular, are among the most affected. Vascular aging (VA) is defined as age-associated changes in function and structure of vessels. Classical VA phenotypes are carotid intima-media thickness (IMT), carotid plaque (CP), and arterial stiffness (STIFF). Individuals have different predisposition to these VA phenotypes and their associated risk of cardiovascular events. Some develop an early vascular aging (EVA), and others are protected and identified as having supernormal vascular aging (SUPERNOVA). The mechanisms leading to these phenotypes are not well understood. In the Northern Manhattan Study (NOMAS), we found genetic variants in the 7 Sirtuins (SIRT) and 5 Uncoupling Proteins (UCP) to be differently associated with risk to developing VA phenotypes. In this article, we review the results of genetic-epidemiology studies to better understand which of the single nucleotide polymorphisms (SNPs) in SIRT and UCP are responsible for both EVA and SUPERNOVA.

Identifying X-Chromosome Variants Associated with Age-Related Macular Degeneration

Purpose

In genome-wide association studies (GWAS), X chromosome (ChrX) variants are often not investigated. Sex-specific effects and ChrX-specific quality control (QC) are needed to examine these effects. Previous analyses identified 52 autosomal variants associated with age-related macular degeneration (AMD) via the International AMD Genomics Consortium (IAMDGC), but did not analyze ChrX. Therefore, our goal was to investigate ChrX variants for association with AMD.

Methods

We genotyped 29,629 non-Hispanic White (NHW) individuals (M/F:10,404/18,865; AMD12,087/14723) via a custom chip and imputed after ChrX-specific QC (XWAS 3.0) using the Michigan Imputation Server. Imputation generated 1,221,623 variants on ChrX. Age, informative PCs, and subphenotyeps were covariates for logistic association analyses with Fishers correction. Gene/pathway analyses were performed with VEGAS, GSEASNP, ICSNPathway, DAVID, and mirPath.

Results

Logistic association on NHW individuals with sex correction, identified variants in/near the genes SLITRK4, ARHGAP6, FGF13 and DMD associated with AMD (P<1x10 -6 ,Fishers combined-corrected). Via association testing of subphenotypes of choroidal neovascularization and geographic atrophy (GA), variants in DMD associated with GA (P<1x10 -6 , Fishers combined-corrected). Via gene-based analysis with VEGAS, several genes were associated with AMD (P<0.05, both truncated tail strength/truncated product P) including SLITRK4 and BHLHB9 . Pathway analysis using GSEASNP and DAVID showed genes associated with nervous system development (FDR: P:0.02), and blood coagulation (FDR: P:0.03). Variants in the region of a microRNA (miR) were associated with AMD (P<0.05, truncated tail strength/truncated product P). Via DIANA mirPath analysis, downstream targets of miRs show association with brain disorders and fatty acid elongation (P<0.05). A long-non coding RNA on ChrX near the DMD locus was also associated with AMD (P=4x10 -7 ). Epistatic analysis (t-statistic) for a quantitative trait of AMD vs control including covariates found a suggestive association in the XG gene (P=2x10^-5).

Conclusions

Analysis of ChrX variants demonstrates association with AMD and these variants may be linked to novel pathways. Further analysis is needed to confirm results and to understand their biological significance and relationship with AMD development in worldwide populations.

Genome-wide association study of executive function in a multi-ethnic cohort implicates LINC01362: Results from the northern Manhattan study

Executive function is a cognitive domain with sizable heritability representing higher-order cognitive abilities. Genome-wide association studies (GWAS) of executive function are sparse, particularly in populations underrepresented in medical research. We performed a GWAS on a composite measure of executive function that included measures of mental flexibility and reasoning using data from the Northern Manhattan Study, a racially and ethnically diverse cohort (N = 1077, 69% Hispanic, 17% non-Hispanic Black and 14% non-Hispanic White). Four SNPs located in the long intergenic non-protein coding RNA 1362 gene, LINC01362, on chromosome 1p31.1, were significantly associated with the composite measure of executive function in this cohort (top SNP rs2788328, ß = 0.22, p = 3.1 × 10-10). The associated SNPs have been shown to influence expression of the tubulin tyrosine ligase like 7 gene, TTLL7 and the protein kinase CAMP-activated catalytic subunit beta gene, PRKACB, in several regions of the brain involved in executive function. Together, these findings present new insight into the genetic underpinnings of executive function in an understudied population.

Rare variants in previously identified linkage regions associated with carotid plaque in Dominican Republic families

Carotid plaque is a subclinical measure of atherosclerosis. We have previously shown measures of carotid plaque to be heritable in a sample of 100 Dominican families and found evidence for linkage and association of common variants (CVs) on 7q36, 11p15, 14q32 and 15q23 with plaque presence. Our current study aimed to refine these regions further and identify rare variants (RVs) influencing plaque presence. Therefore, we performed targeted sequencing of the one LOD unit down region on 7q36, 11p15, 14q32 and 15q23 in 12 Dominican families with evidence for linkage to plaque presence. Gene-based RV analyses were performed using the Sequence Association Test for familial data (F-SKAT) under two filtering algorithms; 1. all exonic RVs and 2. non-synonymous RVs. Replication analyses were performed using a sample of 22 Dominican families and 556 unrelated Dominicans with Exome Array data. To identify additional non-synonymous RVs influencing plaque, we looked for co-segregation of RVs with plaque in each of the sequenced families. Our most strongly associated gene with evidence for replication was AMPD3 which showed suggestive association with plaque presence in the sequenced families (exonic RV p = 0.003, nonsynonymous RV p = 0.005) and replication families (exonic RV p = 0.04, nonsynonymous RV p = 0.02). Examination of the sequenced family pedigrees revealed two missense variants on chromosome 11 which co-segregated with plaque presence in one of our families; rs61751342 (located in DENND2B), and rs61760882 (located in RNF141). The rs61751342 missense variant is an eQTL for SCUBE2 in the atrial appendage. Notably, SCUBE2 encodes a protein which interacts with vascular endothelial growth factor (VEGF) receptor 2 to regulate VEGF-induced angiogenesis, thus providing biologic plausibility for this gene in atherosclerosis. In conclusion, using targeted sequencing of previously-identified linkage regions, we have identified suggestive evidence for the role of RVs in carotid plaque pathogenesis.

Peripheral vestibular system: Age-related vestibular loss and associated deficits

Given the interdependence of multiple factors in age-related vestibular loss (e.g., balance, vision, cognition), it is important to examine the individual contributions of these factors with ARVL. While the relationship between the vestibular and visual systems has been well studied (Bronstein et al., 2015), little is known about the association of the peripheral vestibular system with neurodegenerative disorders (Cronin et al., 2017). Further, emerging research developments implicate the vestibular system as an opportunity for examining brain function beyond balance, and into other areas, such as cognition and psychological functioning. Additionally, the bidirectional impact of psychological functioning is understudied in ARVL. Recognition of ARVL as part of a multifaceted aging process will help guide the development of integrated interventions for patients who remain at risk for decline. In this review, we will discuss a wide variety of characteristics of the peripheral vestibular system and ARVL, how it relates to neurodegenerative diseases, and correlations between ARVL and balance, vision, cognitive, and psychological dysfunction. We also discuss clinical implications as well as future directions for research, with an emphasis on improving care for patients with ARVL.

Application of the ACMG/NSGC genetic referral guidelines for hereditary renal cell carcinoma at the University of Miami, from 2014 to 2017

Identifying hereditary syndromes among patients with renal cell carcinoma (RCC) is essential for surveillance of affected individuals and their at-risk family members and for treatment optimization. We conducted a chart review to determine the percentage of patients with RCC who were seen at the University of Miami Health System (UHealth), and met the American College of Medical Genetics (ACMG) and the National Society of Genetic Counselors (NSGC) genetic referral criteria at the University of Miami. Subsequently, we determined the percentage of those who went on to receive genetic evaluation. Patients selected by International Classification of Diseases (ICD) 9/10 codes corresponding to kidney cancer who were at least 18 years of age at the time of diagnosis were included in the study. We included a total of 1443 patients in the final analysis, and after exclusion of charts with incorrect ICD codes, insufficient clinical data, unknown pathology, and patients who were not seen. We used chi-square analysis, ANOVA, and t-test. Of 1443 charts reviewed, 65.7% were male and 34.3% were female. 47.7% self-identified as White, 39.2% as Hispanic, 9.1% as Black, and 4.0% as "other." The mean age of RCC diagnosis was 60.0 ± 12.4 years old. In total, 47.0% of patients met ACMG/NSGC referral criteria for genetic evaluation. Of those, only 4.2% had documented genetic assessment. This study showed a low adherence to ACMG/NSGC genetic referral guidelines at our institution and a need for increasing patients' and practitioners' awareness about the significance of genetic assessment for RCC patients and their family members.

DNA Methylation Variation Is Identified in Monozygotic Twins Discordant for Non-syndromic Cleft Lip and Palate

Non-syndromic cleft lip with or without cleft palate (NSCLP) is the most common craniofacial birth defect. The etiology of NSCLP is complex with multiple genes and environmental factors playing causal roles. Although studies have identified numerous genetic markers associated with NSCLP, the role of epigenetic variation remains relatively unexplored. Because of their identical DNA sequences, monozygotic (MZ) twins discordant for NSCLP are an ideal model for examining the potential contribution of DNA methylation to non-syndromic orofacial clefting. In this study, we compared the patterns of whole genome DNA methylation in six MZ twin pairs discordant for NSCLP. Differentially methylated positions (DMPs) and regions (DMRs) were identified in NSCLP candidate genes, including differential methylation in MAFB and ZEB2 in two independent MZ twin pairs. In addition to DNA methylation differences in NSCLP candidate genes, we found common differential methylation in genes belonging to the Hippo signaling pathway, implicating this mechanosensory pathway in the etiology of NSCLP. The results of this novel approach using MZ twins discordant for NSCLP suggests that differential methylation is one mechanism contributing to NSCLP, meriting future studies on the role of DNA methylation in familial and sporadic NSCLP.

Usher Syndrome in the Inner Ear: Etiologies and Advances in Gene Therapy

Hearing loss is the most common sensory disorder with ~466 million people worldwide affected, representing about 5% of the population. A substantial portion of hearing loss is genetic. Hearing loss can either be non-syndromic, if hearing loss is the only clinical manifestation, or syndromic, if the hearing loss is accompanied by a collage of other clinical manifestations. Usher syndrome is a syndromic form of genetic hearing loss that is accompanied by impaired vision associated with retinitis pigmentosa and, in many cases, vestibular dysfunction. It is the most common cause of deaf-blindness. Currently cochlear implantation or hearing aids are the only treatments for Usher-related hearing loss. However, gene therapy has shown promise in treating Usher-related retinitis pigmentosa. Here we review how the etiologies of Usher-related hearing loss make it a good candidate for gene therapy and discuss how various forms of gene therapy could be applied to Usher-related hearing loss.

Genetics and the Individualized Therapy of Vestibular Disorders

Background: Vestibular disorders (VDs) are a clinically divergent group of conditions that stem from pathology at the level of the inner ear, vestibulocochlear nerve, or central vestibular pathway. No etiology can be identified in the majority of patients with VDs. Relatively few families have been reported with VD, and so far, no causative genes have been identified despite the fact that more than 100 genes have been identified for inherited hearing loss. Inherited VDs, similar to deafness, are genetically heterogeneous and follow Mendelian inheritance patterns with all modes of transmission, as well as multifactorial inheritance. With advances in genetic sequencing, evidence of familial clustering in VD has begun to highlight the genetic causes of these disorders, potentially opening up new avenues of treatment, particularly in Meniere's disease and disorders with comorbid hearing loss, such as Usher syndrome. In this review, we aim to present recent findings on the genetics of VDs, review the role of genetic sequencing tools, and explore the potential for individualized medicine in the treatment of these disorders.

Methods: A search of the PubMed database was performed for English language studies relevant to the genetic basis of and therapies for vestibular disorders, using search terms including but not limited to: “genetics,” “genomics,” “vestibular disorders,” “hearing loss with vestibular dysfunction,” “individualized medicine,” “genome-wide association studies,” “precision medicine,” and “Meniere's syndrome.”

Results: Increasing numbers of studies on vestibular disorder genetics have been published in recent years. Next-generation sequencing and new genetic tools are being utilized to unearth the significance of the genomic findings in terms of understanding disease etiology and clinical utility, with growing research interest being shown for individualized gene therapy for some disorders.

Conclusions: The genetic knowledge base for vestibular disorders is still in its infancy. Identifying the genetic causes of balance problems is imperative in our understanding of the biology of normal function of the vestibule and the disease etiology and process. There is an increasing effort to use new and efficient genetic sequencing tools to discover the genetic causes for these diseases, leading to the hope for precise and personalized treatment for these patients.

Recent advancements in understanding the role of epigenetics in the auditory system

Sensorineural deafness in mammals is most commonly caused by damage to inner ear sensory epithelia, or hair cells, and can be attributed to genetic and environmental causes. After undergoing trauma, many non-mammalian organisms, including reptiles, birds, and zebrafish, are capable of regenerating damaged hair cells. Mammals, however, are not capable of regenerating damaged inner ear sensory epithelia, so that hair cell damage is permanent and can lead to hearing loss. The field of epigenetics, which is the study of various phenotypic changes caused by modification of genetic expression rather than alteration of DNA sequence, has seen numerous developments in uncovering biological mechanisms of gene expression and creating various medical treatments. However, there is a lack of information on the precise contribution of epigenetic modifications in the auditory system, specifically regarding their correlation with development of inner ear (cochlea) and consequent hearing impairment. Current studies have suggested that epigenetic modifications influence differentiation, development, and protection of auditory hair cells in cochlea, and can lead to hair cell degeneration. The objective of this article is to review the existing literature and discuss the advancements made in understanding epigenetic modifications of inner ear sensory epithelial cells. The analysis of the emerging epigenetic mechanisms related to inner ear sensory epithelial cells development, differentiation, protection, and regeneration will pave the way to develop novel therapeutic strategies for hearing loss.

Screening Consanguineous Families for Hearing Loss Using the MiamiOtoGenes Panel

Background: Hearing loss (HL) is one of the most common and genetically heterogeneous sensory disorders in humans. Genetic causes underlie 50-60% of all HL and the majority of these cases exhibit an autosomal recessive model of inheritance. Methods: In our study, we used our targeted custom MiamiOtoGenes panel of 180 HL-associated genes to screen 23 unrelated consanguineous Iranian families with at least two affected children to identify potential causal variants for HL. Results: We identified pathogenic variants in seven genes (MYO7A, CDH23, GIPC3, USH1C, CAPB2, LOXHD1, and STRC) in nine unrelated families with varying HL profiles. These include five reported and four novel mutations. Conclusion: For small consanguineous families that were unsuitable for conventional linkage analysis the employment of the MiamiOtoGenes panel helped identify the genetic cause of HL in a cost-effective and timely manner. This rapid methodology provides for diagnoses of a significant fraction of HL patients, and identifies those who will need more extensive genetic analyses such as whole exome/genome sequencing.

Extreme Phenotype Approach Suggests Taste Transduction Pathway for Carotid Plaque in a Multi-Ethnic Cohort

BACKGROUND AND PURPOSE

Carotid plaque is a heritable trait and a strong predictor of vascular events. Several loci have been identified for carotid plaque, however, studies in minority populations are lacking. Within a multi-ethnic cohort, we have identified individuals with extreme total carotid plaque area (TCPA), that is, higher or lower TCPA than expected based on traditional vascular risk factors (age, sex, smoking, diabetes mellitus, hypertension, etc). We hypothesized that these individuals are enriched with genetic variants accounting for the plaque burden that cannot be explained by traditional vascular risk factors. Herein, we sought to identify the genetic basis for TCPA using the multi-ethnic cohort.

METHODS

Three hundred forty participants (170 from each extreme group) from 3 race/ethnic groups (53% Hispanic, 29% non-Hispanic Black, and 18% non-Hispanic White) were genotyped using a genome-wide single-nucleotide polymorphism (SNP) array and imputed using 1000Genome data. SNP-based analyses using logistic regression and gene-based analyses using VEGAS2 were performed within each race/ethnic group and then meta-analyzed. Genes with P<0.001 were included in an overrepresentation enrichment pathway analysis using WebGestalt. Promising findings were tested for association with ischemic stroke using the MEGASTROKE Consortium data set.

RESULTS

No SNP or gene reached genome-wide significance. In the pathway analysis, GO:0050913 (sensory perception of bitter taste) gene set was significantly enriched (P=4.5×10^-6, false discovery rate=0.04), which was confirmed in MEGASTROKE (P=0.01). Within the GO:0050913 gene set, 3 genes were associated with extreme TCPA in our study (P<0.001): TAS2R20, TAS2R50, and ITPR3. In TAS2R50, rs1376251 is the top SNP and has been associated with myocardial infarction by others. In ITPR3, a SNP with high regulatory potential (rs3818527, RegulomeScore=1f), and ITPR3 itself were among the top SNP-based and gene-based results and showed consistent evidence for association in all ethnic groups (P<0.05).

CONCLUSIONS

Extreme TCPA analysis identified new candidate genes for carotid plaque in understudied populations.

Diagnostic and therapeutic applications of genomic medicine in progressive, late-onset, nonsyndromic sensorineural hearing loss

The progressive, late-onset, nonsyndromic, sensorineural hearing loss (PNSHL) is the most common cause of sensory impairment globally, with presbycusis affecting greater than a third of individuals over the age of 65. The etiology underlying PNSHL include presbycusis, noise-induced hearing loss, drug ototoxicity, and delayed-onset autosomal dominant hearing loss (AD PNSHL). The objective of this article is to discuss the potential diagnostic and therapeutic applications of genomic medicine in PNSHL. Genomic factors contribute greatly to PNSHL. The heritability of presbycusis ranges from 25 to 75%. Current therapies for PNSHL range from sound amplification to cochlear implantation (CI). PNSHL is an excellent candidate for genomic medicine approaches as it is common, has well-described pathophysiology, has a wide time window for treatment, and is amenable to local gene therapy by currently utilized procedural approaches. AD PNSHL is especially suited to genomic medicine approaches that can disrupt the expression of an aberrant protein product. Gene therapy is emerging as a potential therapeutic strategy for the treatment of PNSHL. Viral gene delivery approaches have demonstrated promising results in human clinical trials for two inherited causes of blindness and are being used for PNSHL in animal models and a human trial. Non-viral gene therapy approaches are useful in situations where a transient biologic effect is needed or for delivery of genome editing reagents (such as CRISPR/Cas9) into the inner ear. Many gene therapy modalities that have proven efficacious in animal trials have potential to delay or prevent PNSHL in humans. The development of new treatment modalities for PNSHL will lead to improved quality of life of many affected individuals and their families.

COVID19: A Systematic Approach to Early Identification and Healthcare Worker Protection

The COVID-19 outbreak spread rapidly throughout the globe, with worldwide infections and deaths continuing to increase dramatically. To control disease spread and protect healthcare workers, accurate information is necessary. We searched PubMed and Google Scholar for studies published from December 2019 to March 31, 2020 with the terms “COVID-19,” “2019-nCoV,” “SARS-CoV-2,” or “Novel Coronavirus Pneumonia.” The main symptoms of COVID-19 are fever (83–98.6%), cough (59.4–82%), and fatigue (38.1–69.6%). However, only 43.8% of patients have fever early in the disease course, despite still being infectious. These patients may present to clinics lacking proper precautions, leading to nosocomial transmission, and infection of workers. Potential COVID-19 cases must be identified early to initiate proper triage and distinguish them quickly from similar infections. Early identification, accurate triage, and standardized personal protection protocols can reduce the risk of cross infection. Containing disease spread will require protecting healthcare workers.

Evidence for craniofacial enhancer variation underlying nonsyndromic cleft lip and palate

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is a common birth defect for which only ~ 20% of the underlying genetic variation has been identified. Variants in noncoding regions have been increasingly suggested to contribute to the missing heritability. In this study, we investigated whether variation in craniofacial enhancers contributes to NSCLP. Candidate enhancers were identified using VISTA Enhancer Browser and previous publications. Prioritization was based on patterning defects in knockout mice, deletion/duplication of craniofacial genes in animal models and results of whole exome/whole genome sequencing studies. This resulted in 20 craniofacial enhancers to be investigated. Custom amplicon-based sequencing probes were designed and used for sequencing 380 NSCLP probands (from multiplex and simplex families of non-Hispanic white (NHW) and Hispanic ethnicities) using Illumina MiSeq. The frequencies of identified variants were compared to ethnically matched European (CEU) and Los Angeles Mexican (MXL) control genomes and used for association analyses. Variants in mm427/MSX1 and hs1582/SPRY1 showed genome-wide significant association with NSCLP (p ≤ 6.4 × 10^-11). In silico analysis showed that these enhancer variants may disrupt important transcription factor binding sites. Haplotypes involving these enhancers and also mm435/ABCA4 were significantly associated with NSCLP, especially in NHW (p ≤ 6.3 × 10^-7). Importantly, groupwise burden analysis showed several enhancer combinations significantly over-represented in NSCLP individuals, revealing novel NSCLP pathways and supporting a polygenic inheritance model. Our findings support the role of craniofacial enhancer sequence variation in the etiology of NSCLP.

Variation in SIPA1L2 is correlated with phenotype modification in Charcot- Marie- Tooth disease type 1A

OBJECTIVE

Genetic modifiers in rare disease have long been suspected to contribute to the considerable variance in disease expression, including Charcot-Marie-Tooth disease type 1A (CMT1A). To address this question, the Inherited Neuropathy Consortium collected a large standardized sample of such rare CMT1A patients over a period of 8 years. CMT1A is caused in most patients by a uniformly sized 1.5 Mb duplication event involving the gene PMP22.

METHODS

We genotyped DNA samples from 971 CMT1A patients on Illumina BeadChips. Genome-wide analysis was performed in a subset of 330 of these patients, who expressed the extremes of a hallmark symptom: mild and severe foot dorsiflexion strength impairment. SIPA1L2 (signal-induced proliferation-associated 1 like 2), the top identified candidate modifier gene, was expressed in the peripheral nerve, and our functional studies identified and confirmed interacting proteins using coimmunoprecipitation analysis, mass spectrometry, and immunocytochemistry. Chromatin immunoprecipitation and in vitro siRNA experiments were used to analyze gene regulation.

RESULTS

We identified significant association of 4 single nucleotide polymorphisms (rs10910527, rs7536385, rs4649265, rs1547740) in SIPA1L2 with foot dorsiflexion strength (p < 1 × 10^-7 ). Coimmunoprecipitation and mass spectroscopy studies identified β-actin and MYH9 as SIPA1L2 binding partners. Furthermore, we show that SIPA1L2 is part of a myelination-associated coexpressed network regulated by the master transcription factor SOX10. Importantly, in vitro knockdown of SIPA1L2 in Schwannoma cells led to a significant reduction of PMP22 expression, hinting at a potential strategy for drug development.

INTERPRETATION

SIPA1L2 is a potential genetic modifier of CMT1A phenotypic expressions and offers a new pathway to therapeutic interventions. ANN NEUROL 2019;85:316-330.

PBX-WNT-P63-IRF6 pathway in nonsyndromic cleft lip and palate

Nonsyndromic cleft lip and palate (NSCLP) is one of the most common craniofacial anomalies in humans, affecting more than 135,000 newborns worldwide. NSCLP has a multifactorial etiology with more than 50 genes postulated to play an etiologic role. The genetic pathway comprised of Pbx-Wnt-p63-Irf6 genes was shown to control facial morphogenesis in mice and proposed as a regulatory pathway for NSCLP. Based on these findings, we investigated whether variation in PBX1, PBX2, and TP63, and their proposed interactions were associated with NSCLP. Fourteen single nucleotide variants (SNVs) in/nearby PBX1, PBX2, and TP63 were genotyped in 780 NSCLP families of nonHispanic white (NHW) and Hispanic ethnicities. Family-based association tests were performed for individual SNVs stratified by ethnicity and family history of NSCLP. Gene-gene interactions were also tested. A significant association was found for PBX2 rs3131300 and NSCLP in combined Hispanic families (p = .003) while nominal association was found for TP63 rs9332461 in multiplex Hispanic families (p = .005). Significant haplotype associations were observed for PBX2 in NHW (p = .0002) and Hispanic families (p = .003), and for TP63 in multiplex Hispanic families (.003). An independent case-control group was used to validate findings, and significant associations were found with PBX1 rs6426870 (p = .007) and TP63 rs9332461 (p = .03). Gene-gene interactions were detected between PBX1/PBX2/TP63 with IRF6 in NHW families, and between PBX1 with WNT9B in both NHW and Hispanic families (p < .0018). This study provides the first evidence for a role of PBX1 and PBX2, additional evidence for the role of TP63, and support for the proposed PBX-WNT-TP63-IRF6 regulatory pathway in the etiology of NSCLP.

Genetic screening as an adjunct to universal newborn hearing screening: literature review and implications for non-congenital pre-lingual hearing loss

Objective: Universal newborn hearing screening (UNHS) uses otoacoustic emissions testing (OAE) and auditory brainstem response testing (ABR) to screen all newborn infants for hearing loss (HL), but may not identify infants with mild HL at birth or delayed onset HL. The purpose of this review is to examine the role of genetic screening to diagnose children with pre-lingual HL that is not detected at birth by determining the rate of children who pass UNHS but have a positive genetic screening. This includes a summary of the current UNHS and its limitations and a review of genetic mutations and screening technologies used to detect patients with an increased risk of undiagnosed pre-lingual HL.Design: Literature review of studies that compare UNHS with concurrent genetic screening.Study sample: Infants and children with HLResults: Sixteen studies were included encompassing 137,895 infants. Pathogenic mutations were detected in 8.66% of patients. In total, 545 patients passed the UNHS but had a positive genetic screening. The average percentage of patients who passed UNHS but had a positive genetic screening was 1.4%.Conclusions: This review demonstrates the positive impact of concurrent genetic screening with UNHS to identify patients with pre-lingual HL.

FOXF2 is required for cochlear development in humans and mice

Molecular mechanisms governing the development of the human cochlea remain largely unknown. Through genome sequencing, we identified a homozygous FOXF2 variant c.325A>T (p.I109F) in a child with profound sensorineural hearing loss (SNHL) associated with incomplete partition type I anomaly of the cochlea. This variant is not found in public databases or in over 1000 ethnicity-matched control individuals. I109 is a highly conserved residue in the forkhead box (Fox) domain of FOXF2, a member of the Fox protein family of transcription factors that regulate the expression of genes involved in embryogenic development as well as adult life. Our in vitro studies show that the half-life of mutant FOXF2 is reduced compared to that of wild type. Foxf2 is expressed in the cochlea of developing and adult mice. The mouse knockout of Foxf2 shows shortened and malformed cochleae, in addition to altered shape of hair cells with innervation and planar cell polarity defects. Expressions of Eya1 and Pax3, genes essential for cochlear development, are reduced in the cochleae of Foxf2 knockout mice. We conclude that FOXF2 plays a major role in cochlear development and its dysfunction leads to SNHL and developmental anomalies of the cochlea in humans and mice.

Association of IFT88 gene variants with nonsyndromic cleft lip with or without cleft palate

BACKGROUND

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is a common birth defect with multifactorial etiology. Genetic studies have identified numerous gene variants in association with NSCLP. IFT88 (intraflagellar transport 88) has been suggested to play a major role in craniofacial development, as Ift88 mutant mice exhibit cleft palate and mutations in IFT88 were identified in individuals with NSCLP.

OBJECTIVE

To investigate the association of IFT88 single nucleotide gene variants (SNVs) with NSCLP in a large family data set consisting of non-Hispanic white (NHW) and Hispanic families.

METHODS

Nine SNVs in/nearby IFT88 were genotyped in 482 NHW families and 301 Hispanic NSCLP families. Genotyping was performed using TaqMan® chemistry. Single- and pairwise-SNV association analyses were performed for all families stratified by ethnicity and family history of NSCLP using the family-based association test (FBAT), and association in the presence of linkage (APL). Bonferroni correction was used to adjust for multiple testing and p values ≤.0055 were considered statistically significant.

RESULTS

Significant association was found between IFT88 rs9509311 and rs2497490 and NSCLP in NHW all families (p = .004 and .005, respectively), while nominal associations were found for rs7998361 and rs9509307 (p < .05). Pairwise association analyses also showed nominal associations between NSCLP in both NHW and Hispanic data sets (p < .05). No association was found between individual variants in IFT88 and NSCLP in Hispanics.

CONCLUSIONS

Our results suggest that variation in IFT88 may contribute to NSCLP risk, particularly in multiplex families from a non-Hispanic white population.

Genetic and lifestyle risk factors for MRI-defined brain infarcts in a population-based setting

OBJECTIVE

To explore genetic and lifestyle risk factors of MRI-defined brain infarcts (BI) in large population-based cohorts.

METHODS

We performed meta-analyses of genome-wide association studies (GWAS) and examined associations of vascular risk factors and their genetic risk scores (GRS) with MRI-defined BI and a subset of BI, namely, small subcortical BI (SSBI), in 18 population-based cohorts (n = 20,949) from 5 ethnicities (3,726 with BI, 2,021 with SSBI). Top loci were followed up in 7 population-based cohorts (n = 6,862; 1,483 with BI, 630 with SBBI), and we tested associations with related phenotypes including ischemic stroke and pathologically defined BI.

RESULTS

The mean prevalence was 17.7% for BI and 10.5% for SSBI, steeply rising after age 65. Two loci showed genome-wide significant association with BI: FBN2, p = 1.77 × 10-8; and LINC00539/ZDHHC20, p = 5.82 × 10-9. Both have been associated with blood pressure (BP)-related phenotypes, but did not replicate in the smaller follow-up sample or show associations with related phenotypes. Age- and sex-adjusted associations with BI and SSBI were observed for BP traits (p value for BI, p [BI] = 9.38 × 10-25; p [SSBI] = 5.23 × 10-14 for hypertension), smoking (p [BI] = 4.4 × 10-10; p [SSBI] = 1.2 × 10-4), diabetes (p [BI] = 1.7 × 10-8; p [SSBI] = 2.8 × 10-3), previous cardiovascular disease (p [BI] = 1.0 × 10-18; p [SSBI] = 2.3 × 10-7), stroke (p [BI] = 3.9 × 10-69; p [SSBI] = 3.2 × 10-24), and MRI-defined white matter hyperintensity burden (p [BI] = 1.43 × 10-157; p [SSBI] = 3.16 × 10-106), but not with body mass index or cholesterol. GRS of BP traits were associated with BI and SSBI (p ≤ 0.0022), without indication of directional pleiotropy.

CONCLUSION

In this multiethnic GWAS meta-analysis, including over 20,000 population-based participants, we identified genetic risk loci for BI requiring validation once additional large datasets become available. High BP, including genetically determined, was the most significant modifiable, causal risk factor for BI.

Trans-ethnic kidney function association study reveals putative causal genes and effects on kidney-specific disease aetiologies

Chronic kidney disease (CKD) affects ~10% of the global population, with considerable ethnic differences in prevalence and aetiology. We assemble genome-wide association studies of estimated glomerular filtration rate (eGFR), a measure of kidney function that defines CKD, in 312,468 individuals of diverse ancestry. We identify 127 distinct association signals with homogeneous effects on eGFR across ancestries and enrichment in genomic annotations including kidney-specific histone modifications. Fine-mapping reveals 40 high-confidence variants driving eGFR associations and highlights putative causal genes with cell-type specific expression in glomerulus, and in proximal and distal nephron. Mendelian randomisation supports causal effects of eGFR on overall and cause-specific CKD, kidney stone formation, diastolic blood pressure and hypertension. These results define novel molecular mechanisms and putative causal genes for eGFR, offering insight into clinical outcomes and routes to CKD treatment development.

Estimated glomerular filtration rate (eGFR) is a measure of kidney function used to define chronic kidney disease. Here, Morris et al. perform trans-ethnic genome-wide meta-analyses for eGFR in 312,468 individuals and identify novel loci and downstream putative causal genes.

Modifier Gene Candidates in Charcot-Marie-Tooth Disease Type 1A: A Case-Only Genome-Wide Association Study

BACKGROUND

Charcot-Marie-Tooth disease type 1A (CMT1A) is caused by a uniform 1.5-Mb duplication on chromosome 17p, which includes the PMP22 gene. Patients often present the classic neuropathy phenotype, but also with high clinical variability.

OBJECTIVE

We aimed to identify genetic variants that are potentially associated with specific clinical outcomes in CMT1A.

METHODS

We genotyped over 600,000 genomic markers using DNA samples from 971 CMT1A patients and performed a case-only genome-wide association study (GWAS) to identify potential genetic association in a subset of 644 individuals of European ancestry. A total of 14 clinical outcomes were analyzed in this study.

RESULTS

The analyses yielded suggestive association signals in four clinical outcomes: difficulty with eating utensils (lead SNP rs4713376, chr6 : 30773314, P = 9.91×10-7, odds ratio = 3.288), hearing loss (lead SNP rs7720606, chr5 : 126551732, P = 2.08×10-7, odds ratio = 3.439), decreased ability to feel (lead SNP rs17629990, chr4 : 171224046, P = 1.63×10-7, odds ratio = 0.336), and CMT neuropathy score (lead SNP rs12137595, chr1 : 4094068, P = 1.14×10-7, beta = 3.014).

CONCLUSIONS

While the results require validation in future genetic and functional studies, the detected association signals may point to novel genetic modifiers in CMT1A.

MPZL2 is a novel gene associated with autosomal recessive nonsyndromic moderate hearing loss

While recent studies have revealed a substantial portion of the genes underlying human hearing loss, the extensive genetic landscape has not been completely explored. Here, we report a loss-of-function variant (c.72delA) in MPZL2 in three unrelated multiplex families from Turkey and Iran with autosomal recessive nonsyndromic hearing loss. The variant co-segregates with moderate sensorineural hearing loss in all three families. We show a shared haplotype flanking the variant in our families implicating a single founder. While rare in other populations, the allele frequency of the variant is ~ 0.004 in Ashkenazi Jews, suggesting that it may be an important cause of moderate hearing loss in that population. We show that Mpzl2 is expressed in mouse inner ear, and the protein localizes in the auditory inner and outer hair cells, with an asymmetric subcellular localization. We thus present MPZL2 as a novel gene associated with sensorineural hearing loss.

A dominant variant in the PDE1C gene is associated with nonsyndromic hearing loss

Identification of genes with variants causing non-syndromic hearing loss (NSHL) is challenging due to genetic heterogeneity. The difficulty is compounded by technical limitations that in the past prevented comprehensive gene identification. Recent advances in technology, using targeted capture and next-generation sequencing (NGS), is changing the face of gene identification and making it possible to rapidly and cost-effectively sequence the whole human exome. Here, we characterize a five-generation Chinese family with progressive, postlingual autosomal dominant nonsyndromic hearing loss (ADNSHL). By combining population-specific mutation arrays, targeted deafness genes panel, whole exome sequencing (WES), we identified PDE1C (Phosphodiesterase 1C) c.958G>T (p.A320S) as the disease-associated variant. Structural modeling insights into p.A320S strongly suggest that the sequence alteration will likely affect the substrate-binding pocket of PDE1C. By whole-mount immunofluorescence on postnatal day 3 mouse cochlea, we show its expression in outer (OHC) and inner (IHC) hair cells cytosol co-localizing with Lamp-1 in lysosomes. Furthermore, we provide evidence that the variant alters the PDE1C hydrolytic activity for both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Collectively, our findings indicate that the c.958G>T variant in PDE1C may disrupt the cross talk between cGMP-signaling and cAMP pathways in Ca2+ homeostasis.

BRCA1 and BRCA2 gene variants and nonsyndromic cleft lip/palate

BACKGROUND

Nonsyndromic cleft lip with or without cleft palate (NSCL/P) is a debilitating condition that not only affects the individual, but the entire family. The purpose of this study was to investigate the association of BRCA1 and BRCA2 genes with NSCL/P.

METHODS

Twelve polymorphisms in/nearby BRCA1 and BRCA2 were genotyped using Taqman chemistry. Our data set consisted of 3,473 individuals including 2,191 nonHispanic white (NHW) individuals (from 151 multiplex and 348 simplex families) and 1,282 Hispanic individuals (from 92 multiplex and 216 simplex families). Data analysis was performed using Family-Based Association Test (FBAT), stratified by ethnicity and family history of NSCL/P.

RESULTS

Nominal associations were found between NSCL/P and BRCA1 in Hispanics and BRCA2 in NHW and Hispanics (p < .05). Significant haplotype associations were found between NSCL/P and both BRCA1 and BRCA2 (p ≤ .004).

CONCLUSIONS

Our results suggest a modest association between BRCA1 and BRCA2 and NSCL/P. Further studies in additional populations and functional studies are needed to elucidate the role of these genes in developmental processes and signaling pathways contributing to NSCL/P.

Knockdown of Crispld2 in zebrafish identifies a novel network for nonsyndromic cleft lip with or without cleft palate candidate genes

Orofacial development is a multifaceted process involving tightly regulated genetic signaling networks, that when perturbed, lead to orofacial abnormalities including cleft lip and/or cleft palate. We and others have shown an association between the cysteine-rich secretory protein LCCL domain containing 2 (CRISPLD2) gene and nonsyndromic cleft lip with or without cleft palate (NSCLP). Further, we demonstrated that knockdown of Crispld2 in zebrafish alters neural crest cell migration patterns resulting in abnormal jaw and palate development. In this study, we performed RNA profiling in zebrafish embryos and identified 249 differentially expressed genes following knockdown of Crispld2. In silico pathway analysis identified a network of seven genes previously implicated in orofacial development for which differential expression was validated in three of the seven genes (CASP8, FOS, and MMP2). Single nucleotide variant (SNV) genotyping of these three genes revealed significant associations between NSCLP and FOS/rs1046117 (GRCh38 chr14:g.75746690 T > C, p = 0.0005) in our nonHispanic white (NHW) families and MMP2/rs243836 (GRCh38 chr16:g.55534236 G > A; p = 0.002) in our Hispanic families. Nominal association was found between NSCLP and CASP8/rs3769825 (GRCh38 chr2:g.202111380 C > A; p < 0.007). Overtransmission of MMP2 haplotypes were identified in the Hispanic families (p < 0.002). Significant gene-gene interactions were identified for FOS-MMP2 in the NHW families and for CASP8-FOS in the NHW simplex family subgroup (p < 0.004). Additional in silico analysis revealed a novel gene regulatory network including five of these newly identified and 23 previously reported NSCLP genes. Our results demonstrate that animal models of orofacial clefting can be powerful tools to identify novel candidate genes and gene regulatory networks underlying NSCLP.

Genetic basis of hearing loss in Spanish, Hispanic and Latino populations

Hearing loss (HL) is the most common neurosensory disorder affecting humans. The screening, prevention and treatment of HL require a better understanding of the underlying molecular mechanisms. Genetic predisposition is one of the most common factors that leads to HL. Most HL studies include few Spanish, Hispanic and Latino participants, leaving a critical gap in our understanding about the prevalence, impact, unmet health care needs, and genetic factors associated with hearing impairment among Spanish, Hispanic and Latino populations. The few studies which have been performed show that the gene variants commonly associated with HL in non-Spanish and non-Hispanic populations are infrequently responsible for hearing impairment in Spanish as well as Hispanic and Latino populations (hereafter referred to as Hispanic). To design effective screening tools to detect HL in Spanish and Hispanic populations, studies must be conducted to determine the gene variants that are most commonly associated with hearing impairment in this racial/ethnic group. In this review article, we summarize gene variants and loci associated with HL in Spanish and Hispanic populations. Identifying new genetic variants associated with HL in Spanish and Hispanic populations will pave the way to develop effective screening tools and therapeutic strategies for HL.

Precision medicine in hearing loss

Precision medicine (PM) proposes customized medical care based on a patient's unique genome, biomarkers, environment and behaviors. Hearing loss (HL) is the most common sensorineural disorder worldwide and is frequently caused by a single genetic mutation. With recent advances in PM tools such as genetic sequencing and data analysis, the field of HL is ideally positioned to adopt the strategies of PM. Here, we review current and future applications of PM in HL as they relate to the four core qualities of PM (P4): predictive, personalized, patient-centered, and participatory. We then introduce a strategy for effective incorporation of HL PM into the design of future research studies, electronic medical records, and clinical practice to improve diagnostics, prognostics, and, ultimately, individualized patient treatment. Finally, specific anticipated ethical and economic concerns in this growing era of genomics-based HL treatment are discussed. By integrating PM principles into translational HL research and clinical practice, hearing specialists are uniquely positioned to effectively treat the heterogeneous causes and manifestations of HL on an individualized basis.

Sequencing of Linkage Region on Chromosome 12p11 Identifies PKP2 as a Candidate Gene for Left Ventricular Mass in Dominican Families

Increased left ventricular mass (LVM) is an intermediate phenotype for cardiovascular disease (CVD) and a predictor of stroke. Using families from the Dominican Republic, we have previously shown LVM to be heritable and found evidence for linkage to chromosome 12p11. Our current study aimed to further characterize the QTL by sequencing the 1 LOD unit down region in 10 families from the Dominican Republic with evidence for linkage to LVM. Within this region, we tested 5477 common variants [CVs; minor allele frequency (MAF) ≥5%] using the Quantitative Transmission-Disequilibrium Test (QTDT). Gene-based analyses were performed to test rare variants (RVs; MAF < 5%) in 181 genes using the family-based sequence kernel association test. A sample of 618 unrelated Dominicans from the Northern Manhattan Study (NOMAS) and 12 Dominican families with Exome Array data were used for replication analyses. The most strongly associated CV with evidence for replication was rs1046116 (Discovery families P = 9.0 × 10-4; NOMAS P = 0.03; replication families P = 0.46), a missense variant in PKP2 In nonsynonymous RV analyses, PKP2 was one of the most strongly associated genes (P = 0.05) with suggestive evidence for replication in NOMAS (P = 0.05). PKP2 encodes the plakophilin 2 protein and is a desmosomal gene implicated in arrythmogenic right ventricular cardiomyopathy and recently in arrhythmogenic left ventricular cardiomyopathy, which makes PKP2 an excellent candidate gene for LVM. In conclusion, sequencing of our previously reported QTL identified common and rare variants within PKP2 to be associated with LVM. Future studies are necessary to elucidate the role these variants play in influencing LVM.

Apolipoprotein E Gene Polymorphism and Subclinical Carotid Atherosclerosis: The Northern Manhattan Study

BACKGROUND

Apolipoprotein E (APOE) polymorphism has previously been associated with carotid intima-media thickness (cIMT) in predominantly Caucasian populations. We sought to test the strength of the relationship between APOE-ε4 carrier status and subclinical atherosclerosis in a tri-ethnic population with a large Hispanic representation.

METHODS

We assessed the association between APOE polymorphism and cIMT and plaque burden among 1243 stroke-free individuals (mean age 69 years, 65% Hispanic, 18% black, 17% white) using a sequence of multivariable regression models.

RESULTS

After adjusting for demographics, vascular risk factors and plasma low-density lipoprotein (LDL) levels, APOE-ε4 carrier status was positively associated with cIMT (mean difference, .013 mm; 95% confidence interval, .003-.023 mm). The APOE-ε4 association with cIMT appeared to be segment-specific with greater differences in IMT between APOE-ε4 carriers and noncarriers in the common carotid artery (CCA, .014 mm) and bifurcation (.017 mm) than in the internal carotid artery (ICA) IMT (.007 mm). This relationship was not modified by race-ethnicity. Presence of diabetes modified the ε4-cIMT relationship in CCA (P = .045) and ICA (P = .046). APOE-ε4 carrier status was not associated with plaque presence or plaque area.

CONCLUSIONS

APOE-ε4 carriers had elevated cIMT independent of demographics and vascular risk factors including LDL levels. Diabetes was an effect modifier of the relationship between APOE-ε4 and IMT, such that ε4 carriers with diabetes had greater IMT in the CCA and ICA than those without diabetes. The APOE-IMT relationship was not modified by race-ethnicity.

Genome-wide scan in Hispanics highlights candidate loci for brain white matter hyperintensities

Objective:

To investigate genetic variants influencing white matter hyperintensities (WMHs) in the understudied Hispanic population.

Methods:

Using 6.8 million single nucleotide polymorphisms (SNPs), we conducted a genome-wide association study (GWAS) to identify SNPs associated with WMH volume (WMHV) in 922 Hispanics who underwent brain MRI as a cross-section of 2 community-based cohorts in the Northern Manhattan Study and the Washington Heights–Inwood Columbia Aging Project. Multiple linear modeling with PLINK was performed to examine the additive genetic effects on ln(WMHV) after controlling for age, sex, total intracranial volume, and principal components of ancestry. Gene-based tests of association were performed using VEGAS. Replication was performed in independent samples of Europeans, African Americans, and Asians.

Results:

From the SNP analysis, a total of 17 independent SNPs in 7 genes had suggestive evidence of association with WMHV in Hispanics (p < 1 × 10⁻⁵) and 5 genes from the gene-based analysis with p < 1 × 10⁻³. One SNP (rs9957475 in GATA6) and 1 gene (UBE2C) demonstrated evidence of association (p < 0.05) in the African American sample. Four SNPs with p < 1 × 10⁻⁵ were shown to affect binding of SPI1 using RegulomeDB.

Conclusions:

This GWAS of 2 community-based Hispanic cohorts revealed several novel WMH-associated genetic variants. Further replication is needed in independent Hispanic samples to validate these suggestive associations, and fine mapping is needed to pinpoint causal variants.

Screening of deafness-causing DNA variants that are common in patients of European ancestry using a microarray-based approach

The unparalleled heterogeneity in genetic causes of hearing loss along with remarkable differences in prevalence of causative variants among ethnic groups makes single gene tests technically inefficient. Although hundreds of genes have been reported to be associated with nonsyndromic hearing loss (NSHL), GJB2, GJB6, SLC26A4, and mitochondrial (mt) MT-RNR1 and MTTS are the major contributors. In order to provide a faster, more comprehensive and cost effective assay, we constructed a DNA fluidic array, CapitalBioMiamiOtoArray, for the detection of sequence variants in five genes that are common in most populations of European descent. They consist of c.35delG, p.W44C, p.L90P, c.167delT (GJB2); 309kb deletion (GJB6); p.L236P, p.T416P (SLC26A4); and m.1555A>G, m.7444G>A (mtDNA). We have validated our hearing loss array by analyzing a total of 160 DNAs samples. Our results show 100% concordance between the fluidic array biochip-based approach and the established Sanger sequencing method, thus proving its robustness and reliability at a relatively low cost.

Sickle Cell Trait and Renal Function in Hispanics in the United States: The Northern Manhattan Study

Sickle cell anemia (SCA) is a common hematological disorder among individuals of African descent in the United States; the disorder results in the production of abnormal hemoglobin. It is caused by homozygosity for a genetic mutation in HBB; rs334. While the presence of a single mutation (sickle cell trait, SCT) has long been considered a benign trait, recent research suggests that SCT is associated with renal dysfunction, including a decrease in estimated glomerular filtration rate (eGFR) and increased risk of chronic kidney disease (CKD) in African Americans. It is currently unknown whether similar associations are observed in Hispanics. Therefore, our study aimed to determine if SCT is associated with mean eGFR and CKD in a sample of 340 Dominican Hispanics from the Northern Manhattan Study. Using regression analyses, we tested rs334 for association with eGFR and CKD, adjusting for age and sex. eGFR was estimated using the Chronic Kidney Disease Epidemiology Collaboration equation and CKD was defined as eGFR < 60 mL/min/1.73 m². Within our sample, there were 16 individuals with SCT (SCT carriers). We found that SCT carriers had a mean eGFR that was 12.12 mL/min/1.73m² lower than non-carriers (P=.002). Additionally, SCT carriers had 2.72 times higher odds of CKD compared with non-carriers (P=.09). Taken together, these novel results show that Hispanics with SCT, as found among African Americans with SCT, may also be at increased risk for kidney disease.

Novel genetic loci associated with hippocampal volume

The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (rg=-0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness.

Rare Variants in NOD1 Associated with Carotid Bifurcation Intima-Media Thickness in Dominican Republic Families

Cardiovascular disorders including ischemic stroke (IS) and myocardial infarction (MI) are heritable; however, few replicated loci have been identified. One strategy to identify loci influencing these complex disorders is to study subclinical phenotypes, such as carotid bifurcation intima-media thickness (bIMT). We have previously shown bIMT to be heritable and found evidence for linkage and association with common variants on chromosome 7p for bIMT. In this study, we aimed to characterize contributions of rare variants (RVs) in 7p to bIMT. To achieve this aim, we sequenced the 1 LOD unit down region on 7p in nine extended families from the Dominican Republic (DR) with strong evidence for linkage to bIMT. We then performed the family-based sequence kernel association test (famSKAT) on genes within the 7p region. Analyses were restricted to single nucleotide variants (SNVs) with population based minor allele frequency (MAF) <5%. We first analyzed all exonic RVs and then the subset of only non-synonymous RVs. There were 68 genes in our analyses. Nucleotide-binding oligomerization domain (NOD1) was the most significantly associated gene when analyzing exonic RVs (famSKAT p = 9.2x10^-4; number of SNVs = 14). We achieved suggestive replication of NOD1 in an independent sample of twelve extended families from the DR (p = 0.055). Our study provides suggestive statistical evidence for a role of rare variants in NOD1 in bIMT. Studies in mice have shown Nod1 to play a role in heart function and atherosclerosis, providing biologic plausibility for a role in bIMT thus making NOD1 an excellent bIMT candidate.

Novel genetic loci underlying human intracranial volume identified through genome-wide association

Intracranial volume reflects the maximally attained brain size during development, and remains stable with loss of tissue in late life. It is highly heritable, but the underlying genes remain largely undetermined. In a genome-wide association study of 32,438 adults, we discovered five previously unknown loci for intracranial volume and confirmed two known signals. Four of the loci were also associated with adult human stature, but these remained associated with intracranial volume after adjusting for height. We found a high genetic correlation with child head circumference (ρgenetic = 0.748), which indicates a similar genetic background and allowed us to identify four additional loci through meta-analysis (Ncombined = 37,345). Variants for intracranial volume were also related to childhood and adult cognitive function, and Parkinson's disease, and were enriched near genes involved in growth pathways, including PI3K-AKT signaling. These findings identify the biological underpinnings of intracranial volume and their link to physiological and pathological traits.

Targeted Resequencing of Deafness Genes Reveals a Founder MYO15A Variant in Northeastern Brazil

Identifying the genetic etiology in a person with hearing loss (HL) is challenging due to the extreme genetic heterogeneity in HL and the population-specific variability. In this study, after excluding GJB2 variants, targeted resequencing of 180 deafness-related genes revealed the causative variants in 11 of 19 (58%) Brazilian probands with autosomal recessive HL. Identified pathogenic variants were in MYO15A (10 families) and CLDN14 (one family). Remarkably, the MYO15A p.(Val1400Met) variant was identified in eight families from the city of Monte Santo in the northeast region of Brazil. Haplotype analysis of this variant was consistent with a single founder. No other cases with this variant were detected among 105 simplex cases from other cities of northeastern Brazil, suggesting that this variant is confined to a geographical region. This study suggests that it is feasible to develop population-specific screening for deafness variants once causative variants are identified in different geographical groups.

North Carolina macular dystrophy (MCDR1) caused by a novel tandem duplication of the PRDM13 gene

PURPOSE

To identify the underlying cause of disease in a large family with North Carolina macular dystrophy (NCMD).

METHODS

A large four-generation family (RFS355) with an autosomal dominant form of NCMD was ascertained. Family members underwent comprehensive visual function evaluations. Blood or saliva from six affected family members and three unaffected spouses was collected and DNA tested for linkage to the MCDR1 locus on chromosome 6q12. Three affected family members and two unaffected spouses underwent whole exome sequencing (WES) and subsequently, custom capture of the linkage region followed by next-generation sequencing (NGS). Standard PCR and dideoxy sequencing were used to further characterize the mutation.

RESULTS

Of the 12 eyes examined in six affected individuals, all but two had Gass grade 3 macular degeneration features. Large central excavation of the retinal and choroid layers, referred to as a macular caldera, was seen in an age-independent manner in the grade 3 eyes. The calderas are unique to affected individuals with MCDR1. Genome-wide linkage mapping and haplotype analysis of markers from the chromosome 6q region were consistent with linkage to the MCDR1 locus. Whole exome sequencing and custom-capture NGS failed to reveal any rare coding variants segregating with the phenotype. Analysis of the custom-capture NGS sequencing data for copy number variants uncovered a tandem duplication of approximately 60 kb on chromosome 6q. This region contains two genes, CCNC and PRDM13. The duplication creates a partial copy of CCNC and a complete copy of PRDM13. The duplication was found in all affected members of the family and is not present in any unaffected members. The duplication was not seen in 200 ethnically matched normal chromosomes.

CONCLUSIONS

The cause of disease in the original family with MCDR1 and several others has been recently reported to be dysregulation of the PRDM13 gene, caused by either single base substitutions in a DNase 1 hypersensitive site upstream of the CCNC and PRDM13 genes or a tandem duplication of the PRDM13 gene. The duplication found in the RFS355 family is distinct from the previously reported duplication and provides additional support that dysregulation of PRDM13, not CCNC, is the cause of NCMD mapped to the MCDR1 locus.

Functional Assessment of Clubfoot Associated HOXA9, TPM1, and TPM2 Variants Suggests a Potential Gene Regulation Mechanism

BACKGROUND

Isolated nonsyndromic clubfoot is a common birth defect affecting 135,000 newborns worldwide each year. Although treatment has improved, substantial long-term morbidity persists. Genetic causes have been implicated in family-based studies but the genetic changes have eluded identification. Previously, using a candidate gene approach in our family-based dataset, we identified associations between clubfoot and four single nucleotide polymorphisms (SNPs) located in potential regulatory regions of genes involved in muscle development and patterning (HOXA9) and muscle function (TPM1 and TPM2) were identified.

QUESTIONS/PURPOSES

Four SNPs, rs3801776/HOXA9, rs4075583/TPM1, rs2025126/TPM2, and rs2145925/TPM2, located in potential regulatory regions, were evaluated to determine whether they altered promoter activity.

METHODS

Electrophoretic mobility shift assays were performed on these four SNPs to identify allele-specific DNA-protein interactions. SNPs showing differential banding patterns were assessed for effect on promoter activity by luciferase assay. Undifferentiated (for HOXA9) and differentiated (for TPM1 and TPM2) mouse cells were used in functional assays as a proxy for the in vivo developmental stage.

RESULTS

Functional analyses showed that the ancestral alleles of rs3801776/HOXA9, rs4075583/TPM1, and rs2025126/TPM2 and the alternate allele of rs2145925/TPM2 created allele-specific nuclear protein interactions and caused higher promoter activity. Interestingly, while rs4075583/TPM1 showed an allele-specific nuclear protein interaction, an effect on promoter activity was observed only when rs4075583/TPM1 was expressed in the 1.7kb haplotype construct.

CONCLUSION

Our results show that associated promoter variants in HOXA9, TPM1, and TPM2, alter promoter expression suggesting that they have a functional role. Moreover and importantly, we show that alterations in promoter activity may be observed only in the context of the genomic architecture. Therefore, future studies focusing on proteins binding to these regulatory SNPs may provide important key insights into gene regulation in clubfoot.

CLINICAL RELEVANCE

Identifying the genetic risk signature for clubfoot is important to provide accurate genetic counseling for at-risk families, for development of prevention programs and new treatments.

Spectrum of DNA variants for non-syndromic deafness in a large cohort from multiple continents

Hearing loss is the most common sensory deficit in humans with causative variants in over 140 genes. With few exceptions, however, the population-specific distribution for many of the identified variants/genes is unclear. Until recently, the extensive genetic and clinical heterogeneity of deafness precluded comprehensive genetic analysis. Here, using a custom capture panel (MiamiOtoGenes), we undertook a targeted sequencing of 180 genes in a multi-ethnic cohort of 342 GJB2 mutation-negative deaf probands from South Africa, Nigeria, Tunisia, Turkey, Iran, India, Guatemala, and the United States (South Florida). We detected causative DNA variants in 25 % of multiplex and 7 % of simplex families. The detection rate varied between 0 and 57 % based on ethnicity, with Guatemala and Iran at the lower and higher end of the spectrum, respectively. We detected causative variants within 27 genes without predominant recurring pathogenic variants. The most commonly implicated genes include MYO15A, SLC26A4, USH2A, MYO7A, MYO6, and TRIOBP. Overall, our study highlights the importance of family history and generation of databases for multiple ethnically discrete populations to improve our ability to detect and accurately interpret genetic variants for pathogenicity.

Utility of blood pressure genetic risk score in admixed Hispanic samples

Hypertension is strongly influenced by genetic factors. Although hypertension prevalence in some Hispanic sub-populations is greater than in non-Hispanic whites, genetic studies on hypertension have focused primarily on samples of European descent. A recent meta-analysis of 200,000 individuals of European descent identified 29 common genetic variants that influence blood pressure, and a genetic risk score derived from the 29 variants has been proposed. We sought to evaluate the utility of this genetic risk score in Hispanics. The sample set consists of 1994 Hispanics from two cohorts: the Northern Manhattan Study (primarily Dominican/Puerto Rican) and the Miami Cardiovascular Registry (primarily Cuban/South American). Risk scores for systolic and diastolic blood pressure were computed as a weighted sum of the risk alleles, with the regression coefficients reported in the European meta-analysis used as weights. Association of risk score with blood pressure was tested within each cohort, adjusting for age, age squared, sex, and BMI. Results were combined using an inverse-variance meta-analysis. The risk score was significantly associated with blood pressure in our combined sample (p = 5.65 × 10⁻⁴ for systolic and p = 1.65 × 10⁻³ for diastolic) but the magnitude of the regression coefficients varied by degree of European, African, and Native American admixture. Further studies among other Hispanic sub-populations are needed to elucidate the role of these 29 variants and identify additional genetic and environmental factors contributing to blood pressure variability in Hispanics.

Identification of a Novel Gene on 10q22.1 Causing Autosomal Dominant Retinitis Pigmentosa (adRP)

Whole-genome linkage mapping identified a region on chromosome 10q21.3-q22.1 with a maximum LOD score of 3.0 at 0 % recombination in a six-generation family with autosomal dominant retinitis pigmentosa (adRP). All known adRP genes and X-linked RP genes were excluded in the family by a combination of methods. Whole-exome next-generation sequencing revealed a missense mutation in hexokinase 1, HK1 c.2539G > A, p.Glu847Lys, tracking with disease in all affected family members. One severely-affected male is homozygous for this region by linkage analysis and has two copies of the mutation. No other potential mutations were detected in the linkage region nor were any candidates identified elsewhere in the genome. Subsequent testing detected the same mutation in four additional, unrelated adRP families, for a total of five mutations in 404 probands tested (1.2 %). Of the five families, three are from the Acadian population in Louisiana, one is French Canadian and one is Sicilian. Haplotype analysis of the affected chromosome in each family and the homozygous individual revealed a rare, shared haplotype of 450 kb, suggesting an ancient founder mutation. HK1 is a widely-expressed gene, with multiple, abundant retinal transcripts, coding for hexokinase 1. Hexokinase catalyzes phosphorylation of glucose to glusose-6-phospate, the first step in glycolysis. The Glu847Lys mutation is in a highly-conserved site, outside of the active site or known functional sites.

A multi-ethnic genome-wide association study identifies novel loci for non-syndromic cleft lip with or without cleft palate on 2p24.2, 17q23 and 19q13

Orofacial clefts (OFCs), which include non-syndromic cleft lip with or without cleft palate (CL/P), are among the most common birth defects in humans, affecting approximately 1 in 700 newborns. CL/P is phenotypically heterogeneous and has a complex etiology caused by genetic and environmental factors. Previous genome-wide association studies (GWASs) have identified at least 15 risk loci for CL/P. As these loci do not account for all of the genetic variance of CL/P, we hypothesized the existence of additional risk loci. We conducted a multiethnic GWAS in 6480 participants (823 unrelated cases, 1700 unrelated controls and 1319 case-parent trios) with European, Asian, African and Central and South American ancestry. Our GWAS revealed novel associations on 2p24 near FAM49A, a gene of unknown function (P = 4.22 × 10^-8), and 19q13 near RHPN2, a gene involved in organizing the actin cytoskeleton (P = 4.17 × 10^-8). Other regions reaching genome-wide significance were 1p36 (PAX7), 1p22 (ARHGAP29), 1q32 (IRF6), 8q24 and 17p13 (NTN1), all reported in previous GWASs. Stratification by ancestry group revealed a novel association with a region on 17q23 (P = 2.92 × 10^-8) among individuals with European ancestry. This region included several promising candidates including TANC2, an oncogene required for development, and DCAF7, a scaffolding protein required for craniofacial development. In the Central and South American ancestry group, significant associations with loci previously identified in Asian or European ancestry groups reflected their admixed ancestry. In summary, we have identified novel CL/P risk loci and suggest new genes involved in craniofacial development, confirming the highly heterogeneous etiology of OFCs.

MYO3A Causes Human Dominant Deafness and Interacts with Protocadherin 15-CD2 Isoform

Hereditary hearing loss (HL) is characterized by both allelic and locus genetic heterogeneity. Both recessive and dominant forms of HL may be caused by different mutations in the same deafness gene. In a family with post-lingual progressive non-syndromic deafness, whole-exome sequencing of genomic DNA from five hearing-impaired relatives revealed a single variant, p.Gly488Glu (rs145970949:G>A) in MYO3A, co-segregating with HL as an autosomal dominant trait. This amino acid change, predicted to be pathogenic, alters a highly conserved residue in the motor domain of MYO3A. The mutation severely alters the ATPase activity and motility of the protein in vitro, and the mutant protein fails to accumulate in the filopodia tips in COS7 cells. However, the mutant MYO3A was able to reach the tips of organotypic inner ear culture hair cell stereocilia, raising the possibility of a local effect on positioning of the mechanoelectrical transduction (MET) complex at the stereocilia tips. To address this hypothesis, we investigated the interaction of MYO3A with the cytosolic tail of the integral tip-link protein protocadherin 15 (PCDH15), a core component of MET complex. Interestingly, we uncovered a novel interaction between MYO3A and PCDH15 shedding new light on the function of myosin IIIA at stereocilia tips.

A Mayan founder mutation is a common cause of deafness in Guatemala

Over 5% of the world's population has varying degrees of hearing loss. Mutations in GJB2 are the most common cause of autosomal recessive non-syndromic hearing loss (ARNHL) in many populations. The frequency and type of mutations are influenced by ethnicity. Guatemala is a multi-ethnic country with four major populations: Maya, Ladino, Xinca, and Garifuna. To determine the mutation profile of GJB2 in a ARNHL population from Guatemala, we sequenced both exons of GJB2 in 133 unrelated families. A total of six pathogenic variants were detected. The most frequent pathogenic variant is c.131G>A (p.Trp44*) detected in 21 of 266 alleles. We show that c.131G>A is associated with a conserved haplotype in Guatemala suggesting a single founder. The majority of Mayan population lives in the west region of the country from where all c.131G>A carriers originated. Further analysis of genome-wide variation of individuals carrying the c.131G>A mutation compared with those of Native American, European, and African populations shows a close match with the Mayan population.

Sirtuin/uncoupling protein gene variants and carotid plaque area and morphology

BACKGROUND

Sirtuins and uncoupling proteins have been implicated in cardiovascular diseases by controlling oxidative stress.

AIMS

We sought to investigate the association of sirtuins and uncoupling proteins single nucleotide polymorphisms with total carotid plaque area and morphology measured by ultrasonographic gray scale median.

METHODS

We analyzed 1356 stroke-free subjects (60% women, mean age = 68 ± 9 years) from the Northern Manhattan Study. Multiple linear regression models were used to evaluate the association of 85 single nucleotide polymorphisms in 11 sirtuins/uncoupling protein genes with total plaque area and gray scale median after controlling for demographics, vascular risk factors (RFs), and population stratification. We investigated effect modifications of these relationship by gender and RFs and performed stratified analysis if the interaction effect had P < 0·005.

RESULTS

Among individuals with present plaque (55%), the mean total plaque area was 20·3 ± 20·8 mm(2) and gray scale median 90 ± 29. After adjustment, SIRT6 rs107251 was significantly associated with total plaque area (β = 0·30 per copy of T allele increase, Bonferroni-corrected P = 0·005). T allele carriers of rs1430583 in UCP1 showed a decreased gray scale median in women but not in men. The minor allele carriers of rs4980329 and rs12363280 in SIRT3 had higher gray scale median in men but not in women. Variants in UCP3 gene were significantly associated with higher mean gray scale median in individuals with dyslipidemia.

CONCLUSION

Our findings suggest that polymorphisms in SIRT6/UCP1 genes may be important for increased carotid plaque burden and echodensity, but translation of these findings to an individual risk of cerebrovascular events needs further investigation. Significant associations of rs1430583 in women, rs12363280 in men, and rs1685354 in those with dyslipidemia also deserve further investigations.

Regulatory variant in FZD6 gene contributes to nonsyndromic cleft lip and palate in an African-American family

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is a common birth defect affecting 135,000 newborns worldwide each year. While a multifactorial etiology has been suggested as the cause, despite decades of research, the genetic underpinnings of NSCLP remain largely unexplained. In our previous genome-wide linkage study of a large NSCLP African-American family, we identified a candidate locus at 8q21.3-24.12 (LOD = 2.98). This region contained four genes, Frizzled-6 (FZD6), Matrilin-2 (MATN2), Odd-skipped related 2 (OSR2) and Solute Carrier Family 25, Member 32 (SLC25A32). FZD6 was located under the maximum linkage peak. In this study, we sequenced the coding and noncoding regions of these genes in two affected family members, and identified a rare variant in intron 1 of FZD6 (rs138557689; c.-153 + 432A>C). The variant C allele segregated with NSCLP in this family, through affected and unaffected individuals, and was found in one other NSCLP African-American family. Functional assays showed that this allele creates an allele-specific protein-binding site and decreases promoter activity. We also observed that loss and gain of fzd6 in zebrafish contributes to craniofacial anomalies. FZD6 regulates the WNT signaling pathway, which is involved in craniofacial development, including midfacial formation and upper labial fusion. We hypothesize, therefore, that alteration in FZD6 expression contributes to NSCLP in this family by perturbing the WNT signaling pathway.

Sequencing of candidate genes in Dominican families implicates both rare exonic and common non-exonic variants for carotid intima-media thickness at bifurcation

Through linkage and tagSNP-based association studies in 100 Dominican Republic (DR) families, we previously identified ANLN and AOAH (7p14.3) as candidate genes for carotid intima-media thickness at bifurcation (bIMT). Introns, exons, and flanking regions of ANLN and AOAH were re-sequenced in 151 individuals from nine families with evidence for linkage at 7p14.3. For common variants [CV, minor allele frequency (MAF) ≥5 %], single variant-based analysis was performed. For rare variants (RV, MAF < 5 %), gene-based analysis aggregating all RVs within a gene was performed. CV analysis revealed the strongest signal at rs3815483 (P = 0.0003) in ANLN and rs60023210 (P = 0.00005) in AOAH. In ANLN, RV analysis found suggestive evidence for association with exonic RVs (P = 0.08), and in particular non-synonymous RVs (P = 0.04) but not with all RVs (P = 0.15). The variant alleles of all non-synonymous RVs segregated with the major allele of rs3815483 and were associated with lower bIMT while a novel synonymous RV segregated with the minor allele of rs3815483 and was associated with greater bIMT. Additional analysis in 561 DR individuals found suggestive evidence for association with all ANLN non-synonymous RVs (P = 0.08). In AOAH, no evidence for association with RVs was detected. Instead, conditional analysis revealed that multiple independent intronic CVs are associated with bIMT in addition to rs60023210. We demonstrate the utility of using family-based studies to evaluate the contribution of RVs. Our data suggest two modes of genetic architecture underlying the linkage and association at ANLN (multiple exonic RVs) and AOAH (multiple intronic CVs with uncharacterized functions).