Purpose To devise a comprehensive multi-platform genetic testing strategy for inherited retinal disease and describe its performance in 1,000 consecutive families seen by a single clinician. Methods The clinical records of all patients seen by a single retina specialist between January 2010 and June 2016 were reviewed and all patients who met the clinical criteria for a diagnosis of inherited retinal disease were included in the study. Each patient was assigned to one of 62 diagnostic categories and this clinical diagnosis was used to define the scope and order of the molecular investigations that were performed. The number of nucleotides evaluated in a given subject ranged from two (a multiplex allele-specific assay for the most common mutations in BBS1 and BBS10) to nearly 900,000 (the coding sequences, and splice junctions of 305 genes known to cause inherited retinal disease). Results Disease-causing genotypes were identified in 760 families (76%). These genotypes were distributed across 104 different genes. More than 70% of these 104 genes have coding sequences small enough to be efficiently packaged into an adeno-associated virus. Mutations in ABCA4 were the most common cause of disease in this cohort (173 families) while mutations in 80 genes caused disease in five or fewer families (i.e., 0.5% or less). Disease-causing genotypes were identified in 576 of the families without next generation sequencing (NGS). This included 23 families with mutations in the repetitive region of RPGR exon 15 that would have been missed by NGS. Whole exome sequencing of the remaining 424 families revealed mutations in an additional 182, and whole genome sequencing of four of the remaining 242 families revealed two additional genotypes that were invisible by the other methods. Performing the testing in a clinically-focused tiered fashion would be 6.1% more sensitive, 17.7% less expensive and have a significantly lower average false genotype rate than using whole exome sequencing to assess more than 300 genes in all patients (7.1 vs. 128%; p<0.001). Conclusions Genetic testing for inherited retinal disease is now more than 75% sensitive. A clinically-directed tiered testing strategy can increase sensitivity and improve statistical significance without increasing cost.

The extreme genetic heterogeneity of nonsyndromic hearing loss (NSHL) makes genetic diagnosis expensive and time consuming using available methods. To assess the feasibility of targetenrichment and massively parallel sequencing technologies to interrogate all exons of all genes implicated in NSHL, we tested nine patients diagnosed with hearing loss. Solid-phase (NimbleGen) or solution-based (SureSelect) sequence capture, followed by 454 or Illumina sequencing, respectively, were compared. Sequencing reads were mapped using GSMAPPER, BFAST, and BOWTIE, and pathogenic variants were identified using a custom-variant calling and annotation pipeline (ASAP) that incorporates publicly available in silico pathogenicity prediction tools (SIFT, BLOSUM, Polyphen2, and Align-GVGD). Samples included one negative control, three positive controls (one biological replicate), and six unknowns (10 samples total), in which we genotyped 605 single nucleotide polymorphisms (SNPs) by Sanger sequencing to measure sensitivity and specificity for SureSelect-Illumina and NimbleGen-454 methods at saturating sequence coverage. Causative mutations were identified in the positive controls but not in the negative control. In five of six idiopathic hearing loss patients we identified the pathogenic mutation. Massively parallel sequencing technologies provide sensitivity, specificity, and reproducibility at levels sufficient to perform genetic diagnosis of hearing loss.deafness | genomics | Usher syndrome | diagnostics | next-generation sequencing H ereditary sensorineural hearing loss (SNHL) is the most common sensory impairment in humans (1, 2). In developed countries, two-thirds of prelingual-onset SNHL is estimated to have a genetic etiology, of which ∼70% is nonsyndromic hearing loss (NSHL). Eighty percent of NSHL is autosomal recessive nonsyndromic hearing loss (ARNSHL), ∼20% is autosomal dominant (AD), and the remainder is composed of X-linked and mitochondrial forms (1, 3). To date, 134 deafness loci have been identified, and 32 recessive (DFNB), 23 dominant (DFNA) and 2 X-linked (DFNX) genes have been cloned; 8 genes are associated with both ARNSHL and ADNSHL (4).Establishing a genetic diagnosis of NSHL is a critical component of the clinical evaluation of deaf and hard-of-hearing persons and their families. If a genetic cause of hearing loss is determined, it is possible to provide families with prognostic information, recurrence risks, and improved habilitation options. For persons diagnosed with Usher syndrome, preventative measures including sunlight protection and vitamin therapy can be implemented to minimize the rate of progression of retinitis pigmentosa (5). Most current genetic testing strategies for NSHL rely on a gene-specific Sanger sequencing approach. Because mutations in a single gene, GJB2 (DFNB1), account for up to 50% of ARNSHL in many world populations (6), this approach has changed the evaluation of patients with presumed ARNSHL. However, the mutation frequency in other genes in persons with NSHL in outbred populat...

Mutations in ABCA4 cause Stargardt disease and other blinding autosomal recessive retinal disorders. However, sequencing of the complete coding sequence in patients with clinical features of Stargardt disease sometimes fails to detect one or both mutations. For example, among 208 individuals with clear clinical evidence of ABCA4 disease ascertained at a single institution, 28 had only one disease-causing allele identified in the exons and splice junctions of the primary retinal transcript of the gene. Haplotype analysis of these 28 probands revealed 3 haplotypes shared among ten families, suggesting that 18 of the 28 missing alleles were rare enough to be present only once in the cohort. We hypothesized that mutations near rare alternate splice junctions in ABCA4 might cause disease by increasing the probability of mis-splicing at these sites. Next-generation sequencing of RNA extracted from human donor eyes revealed more than a dozen alternate exons that are occasionally incorporated into the ABCA4 transcript in normal human retina. We sequenced the genomic DNA containing 15 of these minor exons in the 28 one-allele subjects and observed five instances of two different variations in the splice signals of exon 36.1 that were not present in normal individuals (P < 10−6). Analysis of RNA obtained from the keratinocytes of patients with these mutations revealed the predicted alternate transcript. This study illustrates the utility of RNA sequence analysis of human donor tissue and patient-derived cell lines to identify mutations that would be undetectable by exome sequencing.

Retinitis pigmentosa (RP) is a genetically heterogeneous heritable disease characterized by apoptotic death of photoreceptor cells. We used exome sequencing to identify a homozygous Alu insertion in exon 9 of male germ cell-associated kinase (MAK) as the cause of disease in an isolated individual with RP. Screening of 1,798 unrelated RP patients identified 20 additional probands homozygous for this insertion (1.2%). All 21 affected probands are of Jewish ancestry. MAK encodes a kinase involved in the regulation of photoreceptor-connecting cilium length. Immunohistochemistry of human donor tissue revealed that MAK is expressed in the inner segments, cell bodies, and axons of rod and cone photoreceptors. Several isoforms of MAK that result from alternative splicing were identified. Induced pluripotent stem cells were derived from the skin of the proband and a patient with non-MAK-associated RP (RP control). In the RP control individual, we found that a transcript lacking exon 9 was predominant in undifferentiated cells, whereas a transcript bearing exon 9 and a previously unrecognized exon 12 predominated in cells that were differentiated into retinal precursors. However, in the proband with the Alu insertion, the developmental switch to the MAK transcript bearing exons 9 and 12 did not occur. In addition to showing the use of induced pluripotent stem cells to efficiently evaluate the pathogenicity of specific mutations in relatively inaccessible tissues like retina, this study reveals algorithmic and molecular obstacles to the discovery of pathogenic insertions and suggests specific changes in strategy that can be implemented to more fully harness the power of sequencing technologies.

Purpose To identify specific mutations causing North Carolina Macular Dystrophy (NCMD). Study Design Whole genome sequencing coupled with RT-PCR analysis of gene expression in human retinal cells. Subjects 141 members of 12 families with NCMD and 261 unrelated control individuals. Methods Genome sequencing was performed on eight affected individuals from three families affected with chromosome-6-linked NCMD (MCDR1) and two individuals affected with chromosome-5-linked NCMD (MCDR3). Variants observed in the MCDR1 locus with frequencies of less than 1% in published databases were confirmed using Sanger sequencing. Confirmed variants absent from all published databases were sought in affected individuals from 8 additional MCDR1 families and the 261 controls. RT-PCR analysis of selected genes was performed in stem-cell-derived human retinal cells. Main Outcome Measure Cosegregation of rare genetic variants with disease phenotype. Results Five sequenced individuals with MCDR1-linked NCMD shared a haplotype of 14 rare variants that spanned one megabase of the disease-causing allele. One of these variants (V1) was absent from all published databases and all 261 controls, but was found in five additional NCMD kindreds. This variant lies in a DNase 1 hypersensitivity site (DHS) upstream of both the PRDM13 and CCNC genes. Sanger sequencing of 1000 base pairs centered on V1 was performed in the remaining four NCMD probands and two additional novel single nucleotide variants (V2 in three families and V3 in a single family) were identified in the DHS within 134 base pairs of the location of V1. A complete duplication of the PRDM13 gene was also discovered in a single family (V4). RT-PCR analysis of PRDM13 expression in developing retinal cells revealed marked developmental regulation. Next generation sequencing of two individuals affected with chromosome-5-linked NCMD revealed a 900kb duplication that included the entire IRX1 gene (V5). The five mutations V1–V5 segregated perfectly in the 102 affected and 39 unaffected members of the 12 NCMD families. Conclusion We have identified five rare mutations that are each capable of arresting the development of the human macula. Four of these strongly implicate the involvement of the gene PRDM13 in macular development, while the pathophysiologic mechanism of the fifth remains unknown but may involve the developmental dysregulation of IRX1.

Background Non-syndromic hearing loss (NSHL) is the most common sensory impairment in humans. Until recently its extreme genetic heterogeneity precluded comprehensive genetic testing. Using a platform that couples targeted genomic enrichment (TGE) and massively parallel sequencing (MPS) to sequence all exons of all genes implicated in NSHL, we test 100 persons with presumed genetic NSHL and in so doing establish sequencing requirements for maximum sensitivity and define MPS quality score metrics that obviate Sanger validation of variants. Methods We examined DNA from 100 sequentially collected probands with presumed genetic NSHL without exclusions due to inheritance, previous genetic testing, or type of hearing loss. We performed TGE using post-capture multiplexing in variable pool sizes followed by Illumina sequencing. We developed a local Galaxy installation on a high performance-computing cluster for bioinformatics analysis. Results To obtain maximum variant sensitivity with this platform 3.2–6.3 million total mapped sequencing reads per sample are required. Quality score analysis showed that Sanger validation is not required for 95% of variants. Our overall diagnostic rate was 42% but varied by clinical features from 0% for persons with asymmetric hearing loss to 56% for persons with bilateral autosomal recessive NSHL. Conclusions These findings will direct the use of TGE and MPS strategies for genetic diagnosis for NSHL. Our diagnostic rate highlights the need for further research on genetic deafness focused on novel gene identification and an improved understanding of the role of non-exonic mutations. The unsolved families we have identified provide a valuable resource to address these areas.

Background Up to 7% of patients with severe-to-profound deafness do not benefit from cochlear implantation. Given the high surgical implantation and clinical management cost of cochlear implantation (> $1 million lifetime cost), prospective identification of the worst performers would reduce unnecessary procedures and healthcare costs. Because cochlear implants bypass the membranous labyrinth but rely on the spiral ganglion for functionality, we hypothesize that cochlear implant (CI) performance is dictated in part by the anatomic location of the cochlear pathology that underlies the hearing loss. As a corollary, we hypothesize that because genetic testing can identify sites of cochlear pathology, it may be useful in predicting CI performance. Methods 29 adult CI recipients with idiopathic adult-onset severe-to-profound hearing loss were studied. DNA samples were subjected to solution-based sequence capture and massively parallel sequencing using the OtoSCOPE® platform. The cohort was divided into three CI performance groups (good, intermediate, poor) and genetic causes of deafness were correlated with audiometric data to determine whether there was a gene-specific impact on CI performance. Results The genetic cause of deafness was determined in 3/29 (10%) individuals. The two poor performers segregated mutations in TMPRSS3, a gene expressed in the spiral ganglion, while the good performer segregated mutations in LOXHD1, a gene expressed in the membranous labyrinth. Comprehensive literature review identified other good performers with mutations in membranous labyrinth-expressed genes; poor performance was associated with spiral ganglion-expressed genes. Conclusions Our data support the underlying hypothesis that mutations in genes preferentially expressed in the spiral ganglion portend poor CI performance while mutations in genes expressed in the membranous labyrinth portend good CI performance. Although the low mutation rate in known deafness genes in this cohort likely relates to the ascertainment characteristics (postlingual hearing loss in adult CI recipients), these data suggest that genetic testing should be implemented as part of the CI evaluation to test this association prospectively.

Proper spatial differentiation of retinal cell types is necessary for normal human vision. Many retinal diseases, such as Best disease and male germ cell associated kinase (MAK)-associated retinitis pigmentosa, preferentially affect distinct topographic regions of the retina. While much is known about the distribution of cell-types in the retina, the distribution of molecular components across the posterior pole of the eye has not been well-studied. To investigate regional difference in molecular composition of ocular tissues, we assessed differential gene expression across the temporal, macular, and nasal retina and retinal pigment epithelium (RPE)/choroid of human eyes using RNA-Seq. RNA from temporal, macular, and nasal retina and RPE/choroid from four human donor eyes was extracted, poly-A selected, fragmented, and sequenced as 100 bp read pairs. Digital read files were mapped to the human genome and analyzed for differential expression using the Tuxedo software suite. Retina and RPE/choroid samples were clearly distinguishable at the transcriptome level. Numerous transcription factors were differentially expressed between regions of the retina and RPE/choroid. Photoreceptor-specific genes were enriched in the peripheral samples, while ganglion cell and amacrine cell genes were enriched in the macula. Within the RPE/choroid, RPE-specific genes were upregulated at the periphery while endothelium associated genes were upregulated in the macula. Consistent with previous studies, BEST1 expression was lower in macular than extramacular regions. The MAK gene was expressed at lower levels in macula than in extramacular regions, but did not exhibit a significant difference between nasal and temporal retina. The regional molecular distinction is greatest between macula and periphery and decreases between different peripheral regions within a tissue. Datasets such as these can be used to prioritize candidate genes for possible involvement in retinal diseases with regional phenotypes.