A novel PAX3 mutation in a Korean patient with Waardenburg syndrome type 1 and unilateral branch retinal vein and artery occlusion: a case report

Single-Cell RNA Sequencing Reveals Molecular Features of Heterogeneity in the Murine Retinal Pigment Epithelium

Transcriptomic analysis of the mammalian retinal pigment epithelium (RPE) aims to identify cellular networks that influence ocular development, maintenance, function, and disease. However, available evidence points to RPE cell heterogeneity within native tissue, which adds complexity to global transcriptomic analysis. Here, to assess cell heterogeneity, we performed single-cell RNA sequencing of RPE cells from two young adult male C57BL/6J mice. Following quality control to ensure robust transcript identification limited to cell singlets, we detected 13,858 transcripts among 2667 and 2846 RPE cells. Dimensional reduction by principal component analysis and uniform manifold approximation and projection revealed six distinct cell populations. All clusters expressed transcripts typical of RPE cells; the smallest (C1, containing 1-2% of total cells) exhibited the hallmarks of stem and/or progenitor (SP) cells. Placing C1-6 along a pseudotime axis suggested a relative decrease in melanogenesis and SP gene expression and a corresponding increase in visual cycle gene expression upon RPE maturation. K-means clustering of all detected transcripts identified additional expression patterns that may advance the understanding of RPE SP cell maintenance and the evolution of cellular metabolic networks during development. This work provides new insights into the transcriptome of the mouse RPE and a baseline for identifying experimentally induced transcriptional changes in future studies of this tissue.

Waardenburg syndrome type 2A in a large Iranian family with a novel MITF gene mutation

BACKGROUND

The characteristics of Waardenburg syndrome (WS) as a scarce heritable disorder are sensorineural hearing loss and deficits of pigmentation in the skin, hair, and eye. Here, clinical features and detection of the mutation in the MITF gene of WS2 patients are reported in a sizable Iranian family.

METHODS

A man aged 28-years represented with symptoms of mild unilateral hearing loss (right ear), complete heterochromia iridis, premature graying prior to 30 years of age, and synophrys. In this research, there was a sizable family in Iran comprising three generations with seven WS patients and two healthy members. Whole exome sequencing was applied for proband for the identification of the candidate genetic mutations associated with the disease. The detected mutation in proband and investigated family members was validated by PCR-Sanger sequencing.

RESULTS

A novel heterozygous mutation, NM_198159.3:c.1026dup p.(Asn343Glufs*27), in exon 9 of the MITF gene co-segregated with WS2 in the affected family members. The variant was forecasted as a disease-causing variant by the Mutation Taster. According to the UniProt database, this variant has been located in basic helix-loop-helix (bHLH) domain of the protein with critical role in DNA binding.

CONCLUSIONS

A frameshift was caused by a nucleotide insertion, c.1026dup, in exon 9 of the MITF gene. This mutation is able to induce an early termination, resulting in forming a truncated protein capable of affecting the normal function of the MITF protein. Helpful information is provided through an exactly described mutations involved in WS to clarify the molecular cause of clinical characteristics of WS and have a contribution to better genetic counseling of WS patients.

Frameshift variant in MITF gene in a large family with Waardenburg syndrome type II and a co-segregation of a C2orf74 variant

Waardenburg syndrome (WS) is a hereditary disorder affecting the auditory system and pigmentation of hair, eyes, and skin. Different variants of the disease exist with the involvement of mutation in six genes. The aim of the study is to identify the genetic defects underlying Waardenburg syndrome in a large family with multiple affected individuals. Here, in this study, we recruited a large family with eleven affected individuals segregating WS type 2. We performed whole genome SNP genotyping, whole exome sequencing and segregation analysis using Sanger approach. Whole genome SNP genotyping, whole exome sequencing followed by Sanger validation of variants of interest identified a novel single nucleotide deletion mutation (c.965delA) in the MITF gene. Moreover, a rare heterozygous, missense damaging variant (c.101T>G; p.Val34Gly) in the C2orf74 has also been identified. The C2orf74 is an uncharacterized gene present in the linked region detected by DominantMapper. Variants in MITF and C2orf74 follows autosomal dominant segregation with the phenotype, however, the variant in C2orf74 is incompletely penetrant. We proposed a digenic inheritance of variants as an underlying cause of WS2 in this family.

Four mutations in MITF, SOX10 and PAX3 genes were identified as genetic causes of waardenburg syndrome in four unrelated Iranian patients: case report

Background

Waardenburg syndrome (WS) is a rare genetic disorder. The purpose of this study was to investigate clinical and molecular characteristics of WS in four probands from four different Iranian families.

Case presentation

The first patient was a 1-year-old symptomatic boy with congenital hearing loss and heterochromia iridis with a blue segment in his left iris. The second case was a 1.5-year-old symptomatic girl who manifested congenital profound hearing loss, brilliant blue eyes, and skin hypopigmentation on the abdominal region at birth time. The third patient was an 8-month-old symptomatic boy with developmental delay, mild atrophy, hypotonia, brilliant blue eyes, skin hypopigmentation on her hand and foot, Hirschsprung disease, and congenital profound hearing loss; the fourth patient was a 4-year-old symptomatic boy who showed dystopia canthorum, broad nasal root, synophrys, skin hypopigmentation on her hand and abdomen, brilliant blue eyes, and congenital profound hearing loss. Whole exome sequencing (WES) was used for each proband to identify the underlying genetic factor. Sanger sequencing was performed for validation of the identified mutations in probands and the available family members. A novel heterozygous frameshift mutation, c.996delT (p.K334Sfs*15), on exon 8 of the MITF gene was identified in the patient of the first family diagnosed with WS2A. Two novel de novo heterozygous mutations including a missense mutation, c.950G > A (p.R317K), on exon 8 of the MITF gene, and a frameshift mutation, c.684delC (p.E229Sfs*57), on the exon 3 of the SOX10 gene were detected in patients of the second and third families with WS2A and PCWH (Peripheral demyelinating neuropathy, Central dysmyelinating leukodystrophy, Waardenburg syndrome, Hirschsprung disease), respectively. A previously reported heterozygous frameshift mutation, c.1024_1040del AGCACGATTCCTTCCAA, (p.S342Pfs*62), on exon 7 of the PAX3 gene was identified in the patient of the fourth family with WS1.

Conclusions

An exact description of the mutations responsible for WS provides useful information to explain the molecular cause of clinical features of WS and contributes to better genetic counseling of WS patients and their families.

Two novel mutations of PAX3 and SOX10 were characterized as genetic causes of Waardenburg Syndrome

Background

The objective of this study was to investigate the genetic causes of two probands diagnosed as Waardenburg syndrome (WS type I and IV) from two unrelated Chinese families.

Methods

PAX3 and SOX10 were the main pathogenic genes for WS type I (WS I) and IV (WS IV), respectively; all coding exons of these genes were sequenced on the two probands and their family members. Luciferase reporter assay and co‐immunoprecipitation (CO‐IP) were conducted to verify potential functional outcomes of the novel mutations.

Results

The first proband is a 9 years old girl diagnosed with WS I. A novel PAX3 heterozygous mutation of c.372‐373delGA (p.N125fs) was identified, which results in a frameshift and truncation of PAX3 protein. In family II, a 2 years old girl was diagnosed with WS IV, and Sanger sequencing revealed a de novo SOX10 mutation of c.1114insTGGGGCCCCCACACTACACCGAC (p.Q372fs), a frameshift mutation that extends the amino acid chain of SOX10 protein. Functional studies indicated that the novel mutation of SOX10 had no effects on the interaction of SOX10 and PAX3, but reduced transactivate capacity of melanocyte inducing transcription factor (MITF) promoter. Both PAX3 and SOX10 mutation‐induced defects of MITF transcription might contribute to the WS pathogenesis.

Conclusion

We revealed a novel mutation in PAX3 and a de novo mutation in SOX10, which might account for the underlying pathogenesis of WS. This study expands the database of both PAX10 and PAX3 mutations and improves our understanding of the causes of WS.

Whole genome genotyping mapped regions on chromosome 2 and 18 in a family segregating Waardenburg syndrome type II

Objectives

Waardenburg syndrome is a rare genetic disorder. It is characterized by sensorineural hearing impairment and pigment defects of the skin, hair and iris. In some cases abnormalities in the tissues derived from neural crest have also been reported. Mutations in several genes have been reported as an underlying cause of Waardenburg syndrome. Objective of this study is to identify the chromosomal region(s) associated with Waardenburg syndrome in an extended Saudi family.

Methods

Genomic DNA was extracted from fifteen individuals of a Saudi family segregating Waardenburg syndrome. Whole genome SNP genotyping was performed to identify common identity by descent chromosomal region(s) shared by affected individuals.

Results

Pedigree analysis confirm autosomal dominant inheritance of Waardenburg syndrome type II in a family. Whole genome SNP genotypes were analyzed using AutoSNPa and DominantMapper tools. Shared identity by descent chromosomal regions were identified on chromosome 2 and chromosome 18. Regions were checked for known Waardenburg syndrome genes. No known gene is present in both regions.

Conclusions

In summary, we identified novel chromosomal regions associated with Waardenburg syndrome type II in a Saudi family. Deep sequencing of a complete candidate regions are required to identify the gene underlying Waardenburg syndrome in this family.

Combined Central Retinal Vein And Artery Occlusion In A Patient With Elevated Level Of Factor VIII: A Case Report

Purpose

To report a case of unilateral central retinal vein occlusion (CRVO) with central retinal artery occlusion (CRAO) in a patient with elevated Factor VIII.

Case presentation

A 48-year-old woman presented with a complaint of decreased visual acuity in her left eye that began 6 weeks prior. The patient had diabetes. The best-corrected visual acuity (BCVA) was hand motion, IOP was 34 mmHg, and there was a neovascularization of the iris in the left eye. A complete fundus evaluation including fluorescein angiography showed non-proliferative diabetic retinopathy in the right eye and CRVO with CRAO in the left eye. Systemic evaluation revealed elevated fibrinogen and Factor VIII suggestive of the diagnosis of thrombophilia due to elevated Factor VIII. This symptom was the first sign of the underlying disorder. IOP was normalized 1 week after IOP lowering agents were applied. Intravitreal anti-vascular endothelial growth factor treatment and pan-retinal photocoagulation were performed in the left eye. Additionally, to treat thrombophilia, warfarin treatment was started and flame-shaped retinal hemorrhage with cotton wool patch near the optic disc and around the retinal vascular arcade at the posterior pole had occurred in the right eye during treatment. Then, warfarin treatment was discontinued and retinal hemorrhage was decreased. In the left eye, the BCVA did not change during treatment.

Conclusion

Elevated levels of Factor VIII as an independent risk in the development of venous thromboembolism. Combined cases usually present with severe visual loss and such patients should be thoroughly evaluated to diagnose underlying factors including Factor VIII, and initiate appropriate management at the earliest.