Identification of a novel mutation in the PTCH gene in a patient with Gorlin-Goltz syndrome with unusual ocular disorders

Sonic Hedgehog Intron Variant Associated With an Unusual Pediatric Cortical Cataract

Purpose

To identify the genetic basis of an unusual pediatric cortical cataract demonstrating autosomal dominant inheritance in a large European–Australian pedigree.

Methods

DNA from four affected individuals were exome sequenced utilizing a NimbleGen SeqCap EZ Exome V3 kit and HiSeq 2500. DNA from 12 affected and four unaffected individuals were genotyped using Human OmniExpress-24 BeadChips. Multipoint linkage and haplotyping were performed (Superlink-Online SNP). DNA from one affected individual and his unaffected father were whole-genome sequenced on a HiSeq X Ten system. Rare small insertions/deletions and single-nucleotide variants (SNVs) were identified in the disease-linked region (Golden Helix SVS). Combined Annotation Dependent Depletion (CADD) analysis predicted variant deleteriousness. Putative enhancer function and variant effects were determined using the Dual-Glo Luciferase Assay system.

Results

Linkage mapping identified a 6.23-centimorgan support interval at chromosome 7q36. A co-segregating haplotype refined the critical region to 6.03 Mbp containing 21 protein-coding genes. Whole-genome sequencing uncovered 114 noncoding variants from which CADD predicted one was highly deleterious, a novel substitution within intron-1 of the sonic hedgehog signaling molecule (SHH) gene. ENCODE data suggested this site was a putative enhancer, subsequently confirmed by luciferase reporter assays with variant-associated gene overexpression.

Conclusions

In a large pedigree, we have identified a SHH intron variant that co-segregates with an unusual pediatric cortical cataract phenotype. SHH is important for lens formation, and mutations in its receptor (PTCH1) cause syndromic cataract. Our data implicate increased function of an enhancer important for SHH expression primarily within developing eye tissues.

Electrophysiological Study of Visual Pathways in Nevoid Basal Cell Carcinoma Syndrome Patients

Introduction

Gorlin-Goltz syndrome (GGS) also known as nevoid basal cell carcinoma syndrome (NBCCS) is a complex rare genetic disorder characterized by a wide range of clinical and radiological manifestations. Ophthalmological alterations have always been reported, but no study on the eventual pattern visual evoked potentials (pVEPs) abnormalities has yet been published.

Purpose

The purpose of the study was to evaluate the functionality of the optic pathways in a group of NBCCS patients through pattern reversal VEPs, after a thorough exclusion of subjects with preexisting ocular and optic pathways pathologies.

Methods

Nineteen NBCCS patients (31 eyes) and 20 healthy controls (40 eyes) have been recruited for this study. All subjects underwent an evaluation of the functionality of the optic pathways through pVEPs with small (120ʹ), medium (60ʹ), and large (15ʹ) check size stimulation.

Results

NBCCS patients showed a statistically significant alteration in the transmission of the macular pathway function when compared to controls. PVEPs analysis confirmed a reduced amplitude and an increased latency of the P100 component, suggesting an involvement of the visual pathway even in the absence of ocular clinical manifestations.

Conclusion

Visual pathways may have been affected both by a subclinical myelination deficit, determined directly by the genetic alteration, as well as by neurological abnormalities typical of this syndrome. Further studies are warranted.

The hedgehog pathway and ocular developmental anomalies

Mutations in effectors of the hedgehog signaling pathway are responsible for a wide variety of ocular developmental anomalies. These range from massive malformations of the brain and ocular primordia, not always compatible with postnatal life, to subtle but damaging functional effects on specific eye components. This review will concentrate on the effects and effectors of the major vertebrate hedgehog ligand for eye and brain formation, Sonic hedgehog (SHH), in tissues that constitute the eye directly and also in those tissues that exert indirect influence on eye formation. After a brief overview of human eye development, the many roles of the SHH signaling pathway during both early and later morphogenetic processes in the brain and then eye and periocular primordia will be evoked. Some of the unique molecular biology of this pathway in vertebrates, particularly ciliary signal transduction, will also be broached within this developmental cellular context.

Ocular manifestations of genetic skin disorders

Genetic skin diseases, or genodermatoses, often have extracutaneous manifestations. Ocular manifestations in particular can have significant clinical implications, like blindness. Other manifestations, such as the corneal opacities that occur in X-linked ichthyosis, are asymptomatic but characteristic of a particular genodermatosis. Ophthalmologic examination can aid in diagnosis when characteristic findings are seen. The genodermatoses with ocular manifestations will be reviewed, but neurocutaneous, syndromes, genetic pigmentary disorders, and genetic metabolic diseases are not included because they are covered elsewhere in this issue.

Review of Ocular Manifestations of Nevoid Basal Cell Carcinoma Syndrome: What an Ophthalmologist Needs to Know

Nevoid basal cell carcinoma syndrome (NBCCS) is a rare, autosomal dominant disorder characterized by multiple basal cell carcinomas (BCCs), odontogenic keratocysts, palmar and/or plantar pits, and ectopic calcifications of the falx cerebri. Myriad ophthalmologic findings are associated with NBCCS, including periocular BCCs, hypertelorism, strabismus, myelinated nerve fibers, and disorders of the retina and retinal pigment epithelium. We performed a literature search in PubMed for articles on the ophthalmologic manifestations of Gorlin syndrome, published between 1984 and 2014. Of 33 papers, 31 were included. Although Gorlin syndrome is due to mutations in a single gene, it displays variable phenotypic expressivity. Therefore, familiarity with this disorder across clinical specialties is necessary to avoid misdiagnosis. The ophthalmologist should be included in the multidisciplinary team for the management of Gorlin syndrome in order to prevent visual loss and improve the quality of life of these patients.