ABSTRACT
Objective:To identify the disease-causing mutation in a Chinese family with Stickler syndrome type 1.Methods:The pedigree investigation was conducted.A Chinese family with Stickler syndrome type 1 was enrolled in the Shantou International Eye Center in June 2012.Medical history collection and clinical examinations, such as vision, intraocular pressure, slit lamp microscopy and fundus, were carried out in all the included family members and the diagnosis was made by clinical experts.Total genomic DNAs were extracted from the peripheral blood samples (5 ml) obtained from 5 patients and 4 healthy members.The potential variant of the proband's father Ⅲ-5 were screened by whole exome sequencing (WES) and stepwise bioinformatic analysis.The segregation and mutation conformation of the variant was verified by Sanger sequencing.The pathogenicity of the variant was predicted by SIFT, Polyphen2, and MutationTaster.Conservation and three-dimensional structure of amino acid mutation were analyzed by multiple sequence alignment and UniProt.This study adhered to the Declaration of Helsinki.The study protocol was approved by the Ethics Committee of Joint Shantou International Eye Center (No.EC20110310[2]-P02).Written informed consent was obtained from each subject or the guardian.Results:An autosomal dominant inherence in 39 members of 4 generations including 15 patients and 24 phenotypically normal members was found in the family.The proband (Ⅳ-4) showed high myopia, retinal detachment and strabismus in the right eye, and the left eye was blind.A patient (Ⅲ-5) showed high myopia and cataract in the right eye, atrophy in the left eye.A patient (Ⅳ-9) showed binocular high myopia.A heterozygous variation, c.1693C>T: p.Arg565Cys, within the exon 26 of COL2A1 gene was revealed in patient Ⅲ-5, which was only found in the patients and not in phenotypically normal members, indiacating co-separation in this family.The variant was predicted to be a severe damage by SIFT, Polyphen2 and MutationTaster.The amino acid mutation at position 565 was highly conservative among human, mouse, rat, bovine and Xenopus laevis, which caused the arginine to cysteine substitution at the X position in triple helix repeat region Gly-X-Y, affecting the function of fibrous protein and becoming pathogenic. Conclusions:Variant c.1693C>T: p.Arg565Cys in COL2A1 gene is disease-causing in this family and this is the first report about the variant in China.
ABSTRACT
Background Stickler syndrome is a genetic connective tissue disorder that affects the ocular,skeletal,orofacial and auditory systems.To determine the gene mutation loci can offer a basis for genetic diagnosis and management of Stickler syndrome.Objective The aim of this study was to research the clinical characteristics of a pedigree with Stickler syndrome and identify the disease-causing gene mutation.Methods This study was approved by Ethic Committee of Peking Union Medical College Hospital.The clinical study and pedigree analysis were performed in one family with Stickler syndrome type Ⅰ (STL Ⅰ).Nine family members were examined with informed consent.The entire coding regions of COL2A1 gene with flanking intronic regions were amplified by PCR and directly sequenced.The detected sequence change was confirmed to be mutationloci by examining whether they existed in normal control individuals.Mutant proteins were predicted with online software.Results There were 4 generations and 11 members in this family,and 2 members died,including 1 patient.Three patients were found in 9living families.Inheritance of this family complicd with an autosomal dominant inheritance mode.All affected individuals showed the consistent phenotypes with STL Ⅰ,including high myopia,membranous vitreous anomaly and surface central flat,short nose,palatoschisis,etc.Mutation screening of COL2A1 gene revealed that the first base of intron 12 was deleted(IVS12+1G del).Nucleotide sequence analysis showed that this mutation led to the functional abnormal of this gene by forming termination cordon in advance.This mutation occurred in all affected individuals,however,no mutation was observed in any unaffected member or 100 normal unrelated individuals.Conclusions This study identifies a novel splice-site mutation(IVS12+ 1G del)in COL2A1 gene in a Chinese STL Ⅰ pedigree.This is the first report on a mutation in a Chinese STL Ⅰ family.
ABSTRACT
Objective:To investigate a large Chinese family in which 9 patients over 4 generations were diagnosed with a form of autosomal dominant spondyloepimphyseal dysplasia(SEMD).Mothods:X-Ray radiograph of proand at 18-month showed absence of secondary ossification centra of femoral heads.His father at 24-year presented severe spondyloepiphyseal changes that principally involved the vertebral bodies,the femoral necks and femoral heads and characterized by generalized platyspondyly with thoracolumbar scoliosis,irregular femoral necks,absent ossification of femoral heads,flat acetabular roofs and coxa vara.The other patients had similar clinical and radiological features.Haplotyping was performed with leukocyte DNA for 5 micosatellite repeat markers from chromosome 12 and the result showed COL2A1 gene as a candidate gene.A total of 54 exons and promoter of COL2A1 gene were amplified and sequenced from all patients and available normal relatives.In addition,exon 23 of COL2A1 gene was amplified and sequenced from 10 controls simultaneously.Results:All patients were identified a 1510(G→A) transition in exon 23 of COL2A1 gene that caused a change from a COL2A1 coding region in available glycine to serine at amino acid position 504.No mutation was found in the normal relatives and 10 controls. Conclusion:The mutation of COL2A1 gene is responsible for this form of SEDC of the family.This is the first familial report of SEDC relating to 1510G→A mutation of COL2A1 gene.The detailed clinical radiogram data will be useful for extending the phenotypic spectrum of type Ⅱcollagenopathies.