Dataset Information

Next generation sequencing in a family with autosomal recessive Kahrizi syndrome (OMIM 612713) reveals a homozygous frameshift mutation in SRD5A3.

ABSTRACT: As part of a large-scale, systematic effort to unravel the molecular causes of autosomal recessive mental retardation, we have previously described a novel syndrome consisting of mental retardation, coloboma, cataract and kyphosis (Kahrizi syndrome, OMIM 612713) and mapped the underlying gene to a 10.4-Mb interval near the centromere on chromosome 4. By combining array-based exon enrichment and next generation sequencing, we have now identified a homozygous frameshift mutation (c.203dupC; p.Phe69LeufsX2) in the gene for steroid 5?-reductase type 3 (SRD5A3) as the disease-causing change in this interval. Recent evidence indicates that this enzyme is required for the conversion of polyprenol to dolichol, a step that is essential for N-linked protein glycosylation. Independently, another group has recently observed SRD5A3 mutations in several families with a type 1 congenital disorder of glycosylation (CDG type Ix, OMIM 212067), mental retardation, cerebellar ataxia and eye disorders. Our results show that Kahrizi syndrome and this CDG Ix subtype are allelic disorders, and they illustrate the potential of next-generation sequencing strategies for the elucidation of single gene defects.

SUBMITTER: Kahrizi K

PROVIDER: S-EPMC3039499 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Next generation sequencing in a family with autosomal recessive Kahrizi syndrome (OMIM 612713) reveals a homozygous frameshift mutation in SRD5A3.

Kahrizi Kimia K Hu Cougar Hao CH Garshasbi Masoud M Abedini Seyedeh Sedigheh SS Ghadami Shirin S Kariminejad Roxana R Ullmann Reinhard R Chen Wei W Ropers H-Hilger HH Kuss Andreas W AW Najmabadi Hossein H Tzschach Andreas A

European journal of human genetics : EJHG 20100811 1

As part of a large-scale, systematic effort to unravel the molecular causes of autosomal recessive mental retardation, we have previously described a novel syndrome consisting of mental retardation, coloboma, cataract and kyphosis (Kahrizi syndrome, OMIM 612713) and mapped the underlying gene to a 10.4-Mb interval near the centromere on chromosome 4. By combining array-based exon enrichment and next generation sequencing, we have now identified a homozygous frameshift mutation (c.203dupC; p.Phe6 ...[more]

PMID: 20700148

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Project description:Hereditary hearing impairment is one of the major and common birth defects in Chinese population. Non-syndromic sensorineural hearing loss (NSHL) is the most common types of hereditary hearing impairment. Genotypically and phenotypically NSHL is extremely heterogenous and follow either autosomal dominant or autosomal recessive or X-linked mode of inheritance. Presently, 127 genes have been identified to be associated with both syndromic and (NSHL). Here, we studied a Chinese family with moderate and profound hearing impairment. The proband is a 30-year old Chinese man. The proband was born with normal hearing and at the age of 5-years, the proband was first noticed with hearing impairment. Gradually and progressively the proband was presented with loss of hearing in his both right and left ears at the age of 30 years. The clinical symptoms, age of onset or progression to loss of hearing was similar in both the proband and his younger brother. The proband's parents are phenotypically normal and non-consanguineous. Clinical diagnosis of the proband and his younger brother has been done by classical pure tone audiogram (PTA). Computed Tomography (CT) found no abnormality in bilateral external ear, middle ear and inner ear. Targeted next generation sequencing was performed with a panel of 127 genes reported to be associated with hereditary hearing impairment. A novel homozygous single nucleotide deletion (c.427delT) in exon 4 of ILDR1 gene has been identified in proband and in his younger brother. Sanger sequencing confirmed that proband's father and mother are carrying this mutation in a heterozygous manner. This mutation has not been identified in 100 normal healthy control individuals. This mutation (c.427delT) causes frameshift (p.Tyr143Ilefs∗19) which leads to the formation of a truncated ILDR1 protein of 162 amino acids instead of the wild type ILDR1 protein of 546 amino acids. ILDR1 associated hereditary hearing impairment is very rare and this is the first report of identifying a loss-of-function mutation in ILDR1 gene associated with hereditary hearing impairment in Chinese population. Our present study also emphasized the significance of rapid, accurate and cost-effective screening for the patient with hereditary hearing impairment by targeted next generation sequencing.

Project description:PURPOSE: Retinitis pigmentosa (RP; MIM 268000) is a hereditary disease characterized by poor night vision and progressive loss of photoreceptors, eventually leading to blindness. This degenerative process primarily affects peripheral vision due to the loss of rods. Autosomal recessive RP (arRP) is clinically and genetically heterogeneous. It has been associated with mutations in different genes, including CRB1 (crumbs homolog 1). The aim of this study was to determine the causative gene in a Tunisian patient with arRP born to non-consanguineous parents. METHODS: Four accessible family members were included. They underwent full ophthalmic examination with best-corrected Snellen visual acuity, fundus photography and fluorescein angiography. Haplotype analysis was used to evaluate homozygosity in the family to 20 arRP loci. All exons and intron-exon junctions of candidate genes not excluded by haplotype analysis were PCR amplified and directly sequenced. RESULTS: The proband was a 43-year-old female patient. Best-corrected visual acuity was 20/63 (right eye) and 20/80 (left eye). Visual loss began during the third decade. Funduscopic examination and fluorescein angiography revealed typical advanced RP changes with bone spicule-like pigment deposits in the posterior pole and the midperiphery along with retinal atrophy, narrowing of the vessels, and waxy optic discs. Haplotype analysis revealed homozygosity with microsatellite markers D1S412 and D1S413 on chromosome 1q31.3. These markers flanked CRB1. Our results excluded linkage of all the other arRP loci/genes tested. Sequencing of the 12 coding exons and splice sites of CRB1 disclosed a homozygous missense mutation in exon 7 at nucleotide c. 2291G>A, resulting in an arginine to histidine substitution (p.R764H). CONCLUSIONS: R764H is a novel mutation associated with CRB1-related arRP. Previously, an R764C mutation was reported. Extending the mutation spectrum of CRB1 with additional families is important for genotype-phenotype correlations and characterization of the scope of mutation.

Dataset Information

Next generation sequencing in a family with autosomal recessive Kahrizi syndrome (OMIM 612713) reveals a homozygous frameshift mutation in SRD5A3.

Publications

Next generation sequencing in a family with autosomal recessive Kahrizi syndrome (OMIM 612713) reveals a homozygous frameshift mutation in SRD5A3.

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