BackgroundCopy number variants (CNVs) are a well-recognized cause of genetic disease; however, methods for their identification are often gene-specific, excluded as ‘routine’ in screens of genetically heterogeneous disorders, and not implemented in most next-generation sequencing pipelines. For this reason, the contribution of CNVs to non-syndromic hearing loss (NSHL) is most likely under-recognized. We aimed to incorporate a method for CNV identification as part of our standard analysis pipeline and to determine the contribution of CNVs to genetic hearing loss.MethodsWe used targeted genomic enrichment and massively parallel sequencing to isolate and sequence all exons of all genes known to cause NSHL. We completed testing on 686 patients with hearing loss with no exclusions based on type of hearing loss or any other clinical features. For analysis we used an integrated method for detection of single nucleotide changes, indels and CNVs. CNVs were identified using a previously published method that utilizes median read-depth ratios and a sliding-window approach.ResultsOf 686 patients tested, 15.2% (104) carried at least one CNV within a known deafness gene. Of the 38.9% (267) of individuals for whom we were able to determine a genetic cause of hearing loss, a CNV was implicated in 18.7% (50). We identified CNVs in 16 different genes including 7 genes for which no CNVs have been previously reported. CNVs of STRC were most common (73% of CNVs identified) followed by CNVs of OTOA (13% of CNVs identified).ConclusionCNVs are an important cause of NSHL and their detection must be included in comprehensive genetic testing for hearing loss.

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.

Our understanding of hereditary hearing loss has greatly improved since the discovery of the first human deafness gene. These discoveries have only accelerated due to the great strides in DNA sequencing technology since the completion of the human genome project. Here, we review the immense impact that these developments have had in both deafness research and clinical arenas. We review commonly used genomic technologies as well as the application of these technologies to the genetic diagnosis of hereditary hearing loss and to the discovery of novel deafness genes.

Missense mutations in the cone opsins have been identified as a relatively common cause of red/green color vision defects, with the most frequent mutation being the substitution of arginine for cysteine at position 203 (C203R). When the corresponding cysteine is mutated in rhodopsin, it disrupts proper folding of the pigment, causing severe, early onset retinitis pigmentosa. While the C203R mutation has been associated with loss of cone function in color vision deficiency, it is not known what happens to cones expressing this mutant opsin. Here, we used high-resolution retinal imaging to examine the cone mosaic in two individuals with genes encoding a middle-wavelength sensitive (M) pigment with the C203R mutation. We found a significant reduction in cone density compared to normal and color-deficient controls, accompanying disruption in the cone mosaic in both individuals, and thinning of the outer nuclear layer. The C203R mosaics were different from that produced by another mutation (LIAVA) previously shown to disrupt the cone mosaic. Comparison of these mosaics provides insight into the timing and degree of cone disruption and has implications for the prospects for restoration of vision loss associated with various cone opsin mutations.color vision ͉ cone mosaic ͉ photopigment ͉ retinal imaging ͉ rhodopsin N ormal human color vision is trichromatic and derives from the presence of three spectrally distinct cone types: long-, middle-, and short-wavelength-sensitive (L, M, and S). Redgreen color vision defects are characterized by the absence of either L or M cone function and they affect about one in 12 Caucasian males. Inherited red-green defects can be linked to disruptions at the X-chromosome opsin gene locus, where the Land M-cone opsin genes reside in a head-to-tail array (1). Most of these disruptions involve gross gene rearrangements (2-6). However, it is becoming appreciated that missense mutations underlie a significant proportion of red-green defects (5-8). This raises the question of what impact these missense mutations have on the viability of the cones.Some insight comes from rhodopsin. There are Ͼ130 distinct rhodopsin mutations, involving at least 89 sites within the molecule (data compiled from refs. 9-17.) With rare exception (e.g., refs. 9 and 18), each of these mutations has been associated with either retinitis pigmentosa (RP) or congenital stationary night blindness. Rhodopsin and the cone opsins have structural similarities and similar functional demands. Thus, it is reasonable to hypothesize that mutations in the cone opsins homologous to those in rhodopsin that cause retinitis pigmentosa would affect the viability of the cones.The most common missense mutation in the cone opsins is a substitution of cytosine for thymine at nucleotide position 1101, which corresponds to a substitution of arginine for cysteine at amino acid position 203 (C203R) (Fig. S1). The corresponding mutation in rhodopsin (C187Y) disrupts proper folding of the pigment, causing severe, early onset retinitis pigmentos...