Beverly M. Yashar

Age-related macular degeneration: a high-resolution genome scan for susceptibility loci in a population enriched for late-stage disease.

Age-related macular degeneration (AMD) is a complex multifactorial disease that affects the central region of the retina. AMD is clinically heterogeneous, leading to geographic atrophy (GA) and/or choroidal neovascularization (CNV) at advanced stages. Considerable data exists in support of a genetic predisposition for AMD. Recent linkage studies have provided evidence in favor of several AMD susceptibility loci. We have performed a high-resolution (5-cM) genome scan of 412 affected relative pairs that were enriched for late-stage disease (GA and/or CNV). Nonparametric linkage analysis was performed using two different diagnostic criteria and also by dividing the affected individuals according to GA or CNV phenotype. Our results demonstrate evidence of linkage in regions that were suggested in at least one previous study at chromosomes 1q (236–240 cM in the Marshfield genetic map), 5p (40–50 cM), and 9q (111 cM). Multipoint analysis of affected relatives with CNV provided evidence of additional susceptibility loci on chromosomes 2p (10 cM) and 22q (25 cM). A recently identified Gln5345Arg change in HEMICENTIN-1 on chromosome 1q25 was not detected in 274 affected members in the restricted group with AMD, 346 additional patients with AMD, and 237 unaffected controls. Our results consolidate the chromosomal locations of several AMD susceptibility loci and, together with previous reports, should facilitate the search for disease-associated sequence variants.

Mutations in RPGR and RP2 Account for 15% of Males with Simplex Retinal Degenerative Disease

PURPOSE To determine the proportion of male patients presenting simplex retinal degenerative disease (RD: retinitis pigmentosa [RP] or cone/cone-rod dystrophy [COD/CORD]) with mutations in the X-linked retinal degeneration genes RPGR and RP2. METHODS Simplex males were defined as patients with no known affected family members. Patients were excluded if they had a family history of parental consanguinity. Blood samples from a total of 214 simplex males with a diagnosis of retinal degeneration were collected for genetic analysis. The patients were screened for mutations in RPGR and RP2 by direct sequencing of PCR-amplified genomic DNA. RESULTS We identified pathogenic mutations in 32 of the 214 patients screened (15%). Of the 29 patients with a diagnosis of COD/CORD, four mutations were identified in the ORF15 mutational hotspot of the RPGR gene. Of the 185 RP patients, three patients had mutations in RP2 and 25 had RPGR mutations (including 12 in the ORF15 region). CONCLUSIONS This study represents mutation screening of RPGR and RP2 in the largest cohort, to date, of simplex males affected with RP or COD/CORD. Our results demonstrate a substantial contribution of RPGR mutations to retinal degenerations, and in particular, to simplex RP. Based on our findings, we suggest that RPGR should be considered as a first tier gene for screening isolated males with retinal degeneration.

NOVEL MUTATIONS IN XLRS1 CAUSING RETINOSCHISIS, INCLUDING FIRST EVIDENCE OF PUTATIVE LEADER SEQUENCE CHANGE

Juvenile retinoschisis is an X‐linked recessive disease caused by mutations in the XLRS1 gene. We screened 31 new unrelated patients and families for XLRS1 mutations in addition to previously reported mutations for 60 of our families (Retinoschisis Consortium, Hum Mol Genet 1998;7:1185–1192). Twenty‐three different mutations including 12 novel ones were identified in 28 patients. Mutations identified in this study include 19 missense mutations, two nonsense mutations, one intragenic deletion, four microdeletions, one insertion, and one intronic sequence substitution that is likely to result in a splice site defect. Two novel mutations, c.38T→C (L13P) and c.667T→C (C223R), respectively, present the first genetic evidence for the functional significance of the putative leader peptide sequence and for the functional significance at the carboxyl terminal of the XLRS1 protein beyond the discoidin domain. Mutations in 25 of the families were localized to exons 4–6, emphasizing the critical functional significance of the discoidin domain of the XLRS1 protein. Hum Mutat 14:423–427, 1999.

Ehlers–Danlos syndrome, hypermobility type: A characterization of the patients' lived experience

Hypermobility type Ehlers–Danlos syndrome (EDS‐HT) is an inherited connective tissue disorder clinically diagnosed by the presence of significant joint hypermobility and associated skin manifestations. This article presents a large‐scale study that reports the lived experience of EDS‐HT patients, the broad range of symptoms that individuals with EDS‐HT experience, and the impact these symptoms have on daily functioning. A 237‐item online survey, including validated questions regarding pain and depression, was developed. Four hundred sixty‐six (466) adults (90% female, 52% college or higher degree) with a self‐reported diagnosis of EDS‐HT made in a clinic or hospital were included. The most frequently reported symptoms were joint pain (99%), hypermobility (99%), and limb pain (91%). They also reported a high frequency of other conditions including chronic fatigue (82%), anxiety (73%), depression (69%), and fibromyalgia (42%). Forty‐six percent of respondents reported constant pain often described as aching and tiring/exhausting. Despite multiple interventions and therapies, many individuals (53%) indicated that their diagnosis negatively affected their ability to work or attend school. Our results show that individuals with EDS‐HT can experience a wide array of symptoms and co‐morbid conditions. The degree of constant pain and disability experienced by the majority of EDS‐HT respondents is striking and illustrates the impact this disorder has on quality of life as well as the clinical challenges inherent in managing this complex connective tissue disorder.

Expanding the genetic counseling workforce: program directors’ views on increasing the size of genetic counseling graduate programs

Purpose:Although there is an anticipated need for more genetic counselors, little is known about limitations at the graduate training level. We evaluated opportunities for growth of the genetic counseling (GC) workforce by exploring program directors’ perspectives on increasing number of graduate trainees.Methods:Thirty US-based GC program directors (PDs) were recruited through the Association of Genetic Counseling Program Directors’ listserv. Online surveys and semistructured phone interviews were used to explore factors impacting the expansion of the GC workforce.Results:Twenty-five PDs completed the survey; 18 interviews were conducted. Seventy-three percent said they believe that the workforce is growing too slowly and the number of graduates should increase. Attitudes were mixed regarding whether the job market should be the main factor driving workforce expansion. Thematic analysis of transcripts identified barriers to program expansion in six categories: funding, accreditation requirements, clinical sites, faculty availability, applicant pool, and physical space.Conclusion:General consensus among participants indicates the importance of increasing the capacity of the GC workforce pipeline. Addressing funding issues, examining current accreditation requirements, and reevaluating current education models may be effective strategies to expanding GC program size. Future research on increasing the number of GC programs and a needs assessment for GC services are suggested.Genet Med 18 8, 842–849.

Parents’ Perspectives on Variants of Uncertain Significance from Chromosome Microarray Analysis

Chromosomal microarray analysis (CMA) for unexplained anomalies and developmental delay has improved diagnosis rates, but results classified as variants of uncertain significance (VUS) may challenge both clinicians and families. We explored the impact of such results on families, including parental knowledge, understanding and interpretation. Semi-structured telephone interviews were conducted with parents (N = 14) who received genetic counseling for a VUS in their child. Transcripts were analyzed through an iterative coding process. Participants demonstrated a range of recall and personal interpretation regarding whether test results provided a causal explanation for their children’s health issues. Participants maintained contradictory interpretations, describing results as answers while maintaining that little clarification of their child’s condition had been provided. Reported benefits included obtaining medical services and personal validation. Parents described adaptation/coping processes similar to those occurring after positive test results. Recall of terminology, including “VUS” and precise CMA abnormalities, was poor. However, most demonstrated conceptual understanding of scientific uncertainty. All participants expressed intentions to return for recommended genetics follow-up but had misconceptions about how this would occur. These results provide insight into the patient-and-family experience when receiving uncertain genomic findings, emphasize the importance of exploring uncertainty during the communication process, and highlight areas for potential attention or improvement in the clinical encounter.

An unusual X-linked retinoschisis phenotype and biochemical characterization of the W112C RS1 mutation

A 52-year-old subject harboring an RS1 gene W112C mutation presented with a prominent and asymmetric tapetal-like retinal sheen. Transient ERG responses were smaller and slower in the eye with the more extensive sheen, an association that, to our knowledge, had not been previously reported. An ON-pathway dysfunction explained the abnormalities of the transient but not those of the flicker ERGs. Although in vitro studies showed that the W112C mutant retinoschisin is present only in the cellular fraction and is not secreted, disease expression was remarkably mild, consistent with the notion of the existence of genetic and/or epigenetic disease modifiers.

9p partial monosomy and disorders of sex development: Review and postulation of a pathogenetic mechanism

Deletion of the distal segment of 9p causes a syndrome comprising trigonocephaly, minor anomalies, and intellectual disability. Patients with this condition also frequently present with genitourinary abnormalities including cryptorchidism, hypospadias, ambiguous genitalia, or 46,XY testicular dysgenesis. The region responsible for the gonadal dysgenesis has been localized to 9p24.3 with the likely responsible gene identified as DMRT1. Similar to patients with other molecular causes of 46,XY gonadal dysgenesis, patients with partial del 9p have an increased risk of gonadoblastoma. We present two patients with 46,XY gonadal dysgenesis due to partial 9p monosomy. Both patients were also diagnosed with gonadoblastoma following gonadectomy at an early age. Chromosomal microarray analyses refined the cytogenetic abnormalities and allowed potential genotype–phenotype relationships to be determined. We also review the literature as it pertains to partial 9p monosomy, genital abnormalities and gonadoblastoma and note that a large percentage of affected patients present with two copy number variations. We propose that a two‐hit mechanism may be involved in the incomplete penetrance and variable expressivity of partial 9p monosomy and an abnormal genital phenotype. The significant percentage of gonadoblastoma in patients with 46,XY complete gonadal dysgenesis due to partial 9p monosomy also continues to support the necessity of gonadectomy in this patient population.

Clinical studies of X-linked retinitis pigmentosa in three Swedish families with newly identified mutations in the RP2 and RPGR-ORF15 genes

Purpose: To describe new disease-causing RP2 and RPGR-ORF15 mutations and their corresponding clinical phenotypes in Swedish families with X-linked retinitis pigmentosa (XLRP) and to establish genotype-phenotype correlations by studying the clinical spectrum of disease in families with a known molecular defect. Methods: Seventeen unrelated families with RP and an apparent X-linked pattern of disease inheritance were identified from the Swedish RP registry and screened for mutations in the RP2 and RPGR (for the RP3 disease) genes. These families had been previously screened for the RPGR exons 1–19, and disease-causing mutations were identified in four of them. In the remaining 13 families, we sequenced the RP2 gene and the newly discovered RPGR-ORF exon. Detailed clinical evaluations were then obtained from individuals in the three families with identified mutations. Results: Mutations in RP2 and RPGRORF15 were identified in three of the 13 families. Clinical evaluations of affected males and carrier females demonstrated varying degrees of retinal dysfunction and visual handicap, with early onset and severe disease in the families with mutations in the ORF15 exon of the RPGR gene. Conclusions: A total of seven mutations in the RP2 and RPGR genes have been discovered so far in Swedish XLRP families. All affected individuals express a severe form of retinal degeneration with visual handicap early in life, although the degree of retinal dysfunction varies both in hemizygous male patients and in heterozygous carrier females. Retinal disease phenotypes in patients with mutations in the RPGR-ORF15 were more severe than in patients with mutations in RP2 or other regions of the RPGR .

X-Linked Retinitis Pigmentosa: Current Status

Retinitis pigmentosa (RP) is a clinically and genetically heterogeneous group of retinal degenerative diseases, characterized by nightblindness, progressive restriction of the visual field and pigmentary retinopathy.1 At least 28 different genetic loci have been mapped for autosomal dominant, autosomal recessive, and X-linked forms of RP. [http://www.sph.uth.tmc.edu/Retnet/home.htm] The X-linked RP (XLRP) subtype is the most severe, with an early age of onset and more rapid progression, accounting for 10 to 20% of RP families.2,3 XLRP is also genetically heterogeneous with at least 5 mapped loci: RP2, RP3, RP6, RP23 and RP24, as schematically depicted in Figure 1. By linkage analysis, RP2 is predicted to account for 10–20% of XLRP and RP3 for 70–90%,4–6 depending on the population. Genes for these two major loci have now been cloned. Our laboratory has been involved in the mutational screening and functional analysis of the two identified XLRP genes (RPGR and RP2), as well as the positional cloning of two other XLRP loci (RP6 and RP24). This report summarizes these efforts as well as the current standing of XLRP research.