Mu Gen Liu

Genome-wide association identifies a susceptibility locus for coronary artery disease in the Chinese Han population

Coronary artery disease (CAD) causes more than 700,000 deaths each year in China. Previous genome-wide association studies (GWAS) in populations of European ancestry identified several genetic loci for CAD, but no such study has yet been reported in the Chinese population. Here we report a three-stage GWAS in the Chinese Han population. We identified a new association between rs6903956 in a putative gene denoted as C6orf105 on chromosome 6p24.1 and CAD (P = 5.00 × 10−3, stage 2 validation; P = 3.00 × 10−3, P = 1.19 × 10−8 and P = 4.00 × 10−3 in three independent stage 3 replication populations; P = 4.87 × 10−12, odds ratio = 1.51 in the combined population). The minor risk allele A of rs6903956 is associated with decreased C6orf105 mRNA expression. We report the first GWAS for CAD in the Chinese Han population and identify a SNP, rs6903956, in C6orf105 associated with susceptibility to CAD in this population.

A splicing mutation in the COL7A1 gene causes autosomal dominant dystrophic epidermolysis bullosa pruriginosa.

Epidermolysis bullosa (EB) is characterized by fragile skin and recurrent blister formation due to minor mechanical friction or trauma. The prevalence is estimated to be one in every 20 000 live births. Dystrophic EB (DEB) is a scarring form of EB in which the blister is below the level of the lamina densa. Both autosomal dominant DEB (DDEB) and autosomal recessive DEB (RDEB) are caused by mutations in the collagen type VII gene, COL7A1 (MIM 120120). The COL7A1 gene encodes a 2944 amino acid protein of the anchoring fibril, which holds the two layers of skin together. Mutations causing RDEB spread over the entire protein: most are nonsense mutations, deletions, insertions, and splicing mutations causing frame-shift. In contrast, missense mutations causing DDEB cluster in the collagenous domain and are mostly substitutions of the glycine residues immediately after the short noncollagenous interruption sequences by other amino acid residues.

c. 359T > C mutation of the MYH14 gene in two autosomal dominant non-syndromic hearing impairment families with common ancestor

OBJECTIVE To identify the gene mutation for two Chinese families with autosomal dominant non-syndromic hearing impairment(NSHI). METHODS Two NSHI pedigrees with common ancestor were identified by clinical examination and family investigation. Linkage analysis was performed for all known NSHI loci, and all exons and exon-intron boundaries of the non-muscle myosin heavy chain 14 (MYH14) gene were amplified by PCR and sequenced. RESULTS The disease-causing gene of these 2 pedigrees was fine mapped to the DFNA4 locus on 19q13.33. A heterozygous transition of c. 359T>C (p.S120L) in MYH14 gene was identified. The mutation was detected in all patients but not in normal members in the two families. CONCLUSION It is the first report that mutation in MYH14 gene can cause dominant non-syndromic hearing impairment in Asian population, suggesting that MYH14 gene can be a disease-causing gene of Chinese patients with hearing impairment.

Identification of VEGFR3 gene mutation in a Chinese family with autosomal dominant primary congenital lymphoedema

OBJECTIVE To identify the disease-causing gene in a four-generation Chinese family with 9 members affected with primary congenital lymphoedema (PCL, also known as Milroy disease). METHODS Linkage analysis was performed with a few microsatellite markers flanking the candidate genetic loci for PCL, including 3 known genes associated with autosomal dominant PCL. For mutation analysis, VEGFR3 gene was sequenced with DNA from the proband. Direct DNA sequencing of exon 25 of the VEGFR3 gene was performed in all family members. RESULTS The disease gene in the family was mapped to chromosome 5q35.3 with a maximum Lod score of 2.07. Direct DNA sequencing of VEGFR3 gene revealed a heterozygous C to T transition at nucleotide 3341, resulting in p.Pro1114Leu mutation. The p.Pro1114Leu mutation co-segregated with all affected individuals in the family. CONCLUSION This study identified a C3341T (p.Pro1114Leu) mutation in the VEGFR3 gene in a Chinese family with PCL, provided evidence that VEGFR3 mutation can cause PCL in Chinese.

Analysis of USH2A gene mutation in a Chinese family affected with Usher syndrome

OBJECTIVE To investigate the disease-causing mutation in a Chinese family affected with Usher syndrome type II. METHODS All of the 11 members from the family underwent comprehensive ophthalmologic examination and hearing test, and their genomic DNA were isolated from venous leukocytes. PCR and direct sequencing of USH2A gene were performed for the proband. Wild type and mutant type minigene vectors containing exon 42, intron 42 and exon 43 of the USH2A gene were constructed and transfected into Hela cells by lipofectamine reagent. Reverse transcription (RT)-PCR was carried out to verify the splicing of the minigenes. RESULTS Pedigree analysis and clinical diagnosis indicated that the patients have suffered from autosomal recessive Usher syndrome type II. DNA sequencing has detected a homozygous c.8559-2A>G mutation of the USH2A gene in the proband, which has co-segregated with the disease in the family. The mutation has affected a conserved splice site in intron 42, which has led to inactivation of the splice site. Minigene experiment has confirmed the retaining of intron 42 in mature mRNA. CONCLUSION The c.8559-2A>G mutation in the USH2A gene probably underlies the Usher syndrome type II in this family. The splice site mutation has resulted in abnormal splicing of USH2A pre-mRNA.