Ophthalmology

To characterize the genotypic and phenotypic spectrum of foveal hypoplasia (FH). Multicenter, observational study. A total of 907 patients with a confirmed molecular diagnosis of albinism, PAX6, SLC38A8, FRMD7, AHR, or achromatopsia from 12 centers in 9 countries (n = 523) or extracted from publicly available datasets from previously reported literature (n = 384). Individuals with a confirmed molecular diagnosis and availability of foveal OCT scans were identified from 12 centers or from the literature between January 2011 and March 2021. A genetic diagnosis was confirmed by sequence analysis. Grading of FH was derived from OCT scans. Grade of FH, presence or absence of photoreceptor specialization (PRS+ vs. PRS-), molecular diagnosis, and visual acuity (VA). The most common genetic etiology for typical FH in our cohort was albinism (67.5%), followed by PAX6 (21.8%), SLC38A8 (6.8%), and FRMD7 (3.5%) variants. AHR variants were rare (0.4%). Atypical FH was seen in 67.4% of achromatopsia cases. Atypical FH in achromatopsia had significantly worse VA than typical FH (P < 0.0001). There was a significant difference in the spectrum of FH grades based on the molecular diagnosis (chi-square = 60.4, P < 0.0001). All SLC38A8 cases were PRS- (P = 0.003), whereas all FRMD7 cases were PRS+ (P < 0.0001). Analysis of albinism subtypes revealed a significant difference in the grade of FH (chi-square = 31.4, P < 0.0001) and VA (P = 0.0003) between oculocutaneous albinism (OCA) compared with ocular albinism (OA) and Hermansky-Pudlak syndrome (HPS). Ocular albinism and HPS demonstrated higher grades of FH and worse VA than OCA. There was a significant difference (P < 0.0001) in VA between FRMD7 variants compared with other diagnoses associated with FH. We characterized the phenotypic and genotypic spectrum of FH. Atypical FH is associated with a worse prognosis than all other forms of FH. In typical FH, our data suggest that arrested retinal development occurs earlier in SLC38A8, OA, HPS, and AHR variants and later in FRMD7 variants. The defined time period of foveal developmental arrest for OCA and PAX6 variants seems to demonstrate more variability. Our findings provide mechanistic insight into disorders associated with FH and have significant prognostic and diagnostic value

A tapetal-like fundus reflex in a healthy male: evidence against a role in the pathophysiology of retinal degeneration?

Purpose: To report on the retinal function and structure in a 37-year-old male who presented with a tapetal-like reflex (TLR) indistinguishable from that seen in female carriers of X-linked retinitis pigmentosa (XLRP). Methods: Clinical examination included dark adaptometry, full-field electroretinography (ERG), multifocal ERG, optical coherence tomography, and fundus autofluorescence photography. Molecular genetic testing included screening for known mutations in autosomal dominant, autosomal recessive, and X linked retinitis pigmentosa (RP) genes with a commercially available chip, and sequencing analysis of retinitis pigmentosa GTPase regulator (RPGR)-open reading frame 15 (ORF15). Results: Fundus examination revealed a bilateral TLR, which is typical of female carriers of XLRP. Imaging studies and electrophysiological testing was unremarkable, except for a significant increase in full-field ERG amplitudes after prolonged dark adaptation as compared to after standard dark adaptation. Mutation screening was negative. Conclusions: TLR was found for the first time, to the best of our knowledge, in a male subject. There were no definitive signs of retinal degeneration, suggesting that this reflex in itself is not necessarily a precursor of the retinal degeneration that can be seen in female carriers of XLRP

Deletions and rearrangements of the H19/IGF2 enhancer region in patients with Silver-Russell syndrome and growth retardation

Silver–Russell syndrome (SRS) is characterised by prenatal and postnatal growth retardation, dysmorphic facial features, and body asymmetry. In 35–60% of SRS cases the paternally methylated imprinting control region (ICR) upstream of the H19 gene (H19-ICR) is hypomethylated, leading to downregulation of IGF2 and bi-allelic expression of H19. H19 and IGF2 are reciprocally imprinted genes on chromosome 11p15. The expression is regulated by the imprinted methylation of the ICR, which modulates the transcription of H19 and IGF2 facilitated by enhancers downstream of H19. A promoter element of IGF2, IGF2P0, is differentially methylated equivalently to the H19-ICR, though in a small number of SRS cases this association is disrupted—that is, hypomethylation affects either H19-ICR or IGF2P0. Three pedigrees associated with hypomethylation of IGF2P0 in the probands are presented here, two with paternally derived deletions, and one with a balanced translocation of inferred paternal origin. They all have a breakpoint within the H19/IGF2 enhancer region. One proband has severe growth retardation, the others have SRS. This is the first report of paternally derived structural chromosomal mutations in 11p15 causing SRS. These cases define a novel aetiology of the growth retardation in SRS, namely, dissociation of IGF2 from its enhancers. <br/

Genome-wide DNA methylation analysis of transient neonatal diabetes type 1 patients with mutations in ZFP57

AbstractBackground: Transient neonatal diabetes mellitus 1 (TNDM1) is a rare imprinting disorder characterized byintrautering growth retardation and diabetes mellitus usually presenting within the first six weeks of life andresolves by the age of 18 months. However, patients have an increased risk of developing diabetes mellitus type 2later in life. Transient neonatal diabetes mellitus 1 is caused by overexpression of the maternally imprinted genesPLAGL1 and HYMAI on chromosome 6q24. One of the mechanisms leading to overexpression of the locus ishypomethylation of the maternal allele of PLAGL1 and HYMAI. A subset of patients with maternal hypomethylationat PLAGL1 have hypomethylation at additional imprinted loci throughout the genome, including GRB10, ZIM2(PEG3), MEST (PEG1), KCNQ1OT1 and NESPAS (GNAS-AS1). About half of the TNDM1 patients carry mutations in ZFP57,a transcription factor involved in establishment and maintenance of methylation of imprinted loci. Our objectivewas to investigate whether additional regions are aberrantly methylated in ZFP57 mutation carriers.Methods: Genome-wide DNA methylation analysis was performed on four individuals with homozygous orcompound heterozygous ZFP57 mutations, three relatives with heterozygous ZFP57 mutations and five controls.Methylation status of selected regions showing aberrant methylation in the patients was verified usingbisulfite-sequencing.Results: We found large variability among the patients concerning the number and identity of the differentiallymethylated regions, but more than 60 regions were aberrantly methylated in two or more patients and a novelregion within PPP1R13L was found to be hypomethylated in all the patients. The hypomethylated regions incommon between the patients are enriched for the ZFP57 DNA binding motif.Conclusions: We have expanded the epimutational spectrum of TNDM1 associated with ZFP57 mutations andfound one novel region within PPP1R13L which is hypomethylated in all TNDM1 patients included in this study.Functional studies of the locus might provide further insight into the etiology of the disease

Molecular characterization of melanoma cases in Denmark suspected of genetic predisposition

Both environmental and host factors influence risk of cutaneousmelanoma (CM), and worldwide, the incidence varies depending on constitutional determinants of skin type and pigmentation, latitude, and patterns of sun exposure. We performed genetic analysis of CDKN2A , CDK4 , BAP1, MC1R, and MITFp.E318K in Danish high-risk melanoma cases and found CDKN2A germline mutations in 11.3% of CM families with three or more affected individuals, including four previously undescribed mutations. Rare mutations were also seen in CDK4 and BAP1, while MC1R variants were common, occurring at more than twice the frequency compared to Danish controls. The MITF p.E318K variant similarly occurred at an approximately three-fold higher frequency in melanoma cases than controls. To conclude, we propose that mutation screening of CDKN2A and CDK4 in Denmark should predominantly be performed in families with at least 3 cases of CM. In addition, we recommend that testing of BAP1 should not be conducted routinely in CM families but should be reserved for families with CM and uveal melanoma, or mesothelioma