Hybrid minigene splicing assay verifies the pathogenicity of a novel splice site variant in the COL1A1 gene of a chinese patient with osteogenesis imperfecta type I.

BACKGROUND: Osteogenesis imperfecta (OI) is a rare genetic bone disease associated with brittle bones and fractures. Among all known types, OI type I is the most common type and characterized by increased bone fragility, low bone mass, distinctly blue-gray sclera, and susceptibility to conductive hearing loss beginning in adolescence. Mutations in genes encoding type I collagen (COL1A1 and COL1A2) contribute to the main pathogenic mechanism of OI. METHODS: Subtle mutation of the COL1A1 gene in the proband was detected by targeted next-generation sequencing (NGS) and confirmed by Sanger sequencing. We then assessed the effect of the mutation on the splicing of the COL1A1 gene by bioinformatics prediction and hybrid minigene splicing assay (HMSA). RESULTS: A novel splice site mutation c.1821+1 G>C was discovered in the proband by NGS and further confirmed by Sanger sequencing, which was also simultaneously identified from the proband's mother and elder sister. Bioinformatics predicted that this mutation would result in a disappearance of the 5' donor splice site in intron 26, thereby leading to abnormal splicing and generation of premature stop codon. The follow-up experimental data generated by HMSA was consistent with this prediction. CONCLUSION: Our study identified a novel splice site mutation that caused OI type I in the proband by abnormal splicing and demonstrated that combined applications of NGS, bioinformatics and HMSA are comprehensive and effective methods for diagnosis and aberrant splicing study of OI.

[Analysis of COL1A1 gene mutation in an ethnic Han Chinese family from Henan affected with osteogenesis imperfecta].

OBJECTIVE: To identify potential mutation of COL1A1 gene in an ethnic Han Chinese family from Henan affected with osteogenesis imperfecta (OI). METHODS: Peripheral blood samples were collected from all 11 members of the family and 50 healthy adults for the extraction of genomic DNA. All exons and introns of the COL1A1 gene were amplified by polymerase chain reaction and subjected to direct sequencing. Mutations found in the proband were analyzed through comparison with other members of the family, 50 healthy individuals and sequence from the GenBank. RESULTS: Fifteen sequence variants were discovered, which included 1 missense mutation, 1 synonymous mutation and 13 intronic mutations. All of the 4 patients from the family were detected as having carried a novel heterozygous missense mutation (c.4193T>G, p.I1398S) in exon 50 of the COL1A1 gene. The father of the proband has carried the same mutation but had a normal phenotype. The same mutation was not found in other healthy members of the family. CONCLUSION: The OI type of this family may have been autosomal dominant with incomplete penetrance or autosomal recessive associated with COL1A1 gene mutations.

Phenotype and genotype analysis of Chinese patients with osteogenesis imperfecta type V.

Osteogenesis imperfecta (OI) type V is an autosomal-dominant disease characterized by calcification of the forearm interosseous membrane, radial head dislocation, a subphyseal metaphyseal radiodense line, and hyperplastic callus formation. The causative mutation, c.-14C>T in the 5'-untranslated region of IFITM5, was recently discovered to be involved in this disease. However, in spite of the little genotypic variability, considerable phenotypic variability has been recognized in two cohorts of patients, the majority of whom were Caucasians. Using exome sequencing, we identified the same heterozygous mutation in four Chinese families with OI type V. This study confirms the molecular cause of OI type V and describes the phenotype of Chinese patients with this disorder. In conclusion, the phenotype of Chinese patients was generally similar to that of Caucasian patients.

Descriptive epidemiology of selected heritable birth defects in Texas.

BACKGROUND: Few population-based studies exist on descriptive epidemiologic characteristics of rare heritable birth defects. The number of birth defect cases in the Texas Birth Defects Registry (one of the largest active birth defects surveillance systems in the world) enabled us to examine six different heritable disorders (aqueductal stenosis, infantile polycystic kidney disease, achondroplasia, thanatophoric dwarfism, chondrodysplasia/dwarfism not otherwise specified (NOS), and osteogenesis imperfecta) for a variety of descriptive demographic variables. METHODS: The Texas Birth Defects Registry was used to identify infants or fetuses with heritable birth defects. Crude prevalence rates were calculated and Poisson regression was used to test the association of each demographic variable (e.g., maternal age) with each of the selected genetic birth defects. RESULTS: White non-Hispanics exhibited higher rates of achondroplasia and osteogenesis imperfecta than other race/ethnic groups. Lower maternal education level and to a lesser extent, paternal education level, was associated with higher rates of several disorders. The birth prevalence rate for achondroplasia decreased from 1999 through 2006. CONCLUSION: The use of a large birth defects registry provides a sufficient count of cases to perform some basic epidemiologic analysis on selected rare heritable birth defects.

Haplotype frequencies of the collagen type-I genes in the Italian population.

We have determined the frequencies of six restriction fragment length polymorphisms (RFLPs) of type-I collagen genes in a random sample of 100 subjects. Alpha 1 gene (COL1A1) DNA polymorphisms, FG2/MspI, 2FC6/RsaI, and NST70/RsaI, had polymorphism information content (PIC) values of 0.35, 0.32, and 0.26, respectively. Alpha 2 gene (COL1A2) RFLPs, NJ3/EcoRI, Hf32/RsaI, and Hf32/MspI had PIC values of 0.36, 0.35, and 0.25, respectively. The combined haplotype PIC values were 0.71 at the COL1A1 locus and 0.73 for COL1A2. Two COL1A1 and two COL1A2 RFLPs were more polymorphic than in the English population, making them better markers for the analysis of Italian families affected by osteogenesis imperfecta and some other inherited collagen diseases.