[show abstract][hide abstract] ABSTRACT: Hearing loss is a common communication disorder caused by various environmental and genetic factors. Hereditary hearing loss is very heterogeneous, and most of such cases involve sensorineural defects in the auditory pathway. There are currently 57 known autosomal dominant non-syndromic hearing loss (DFNA) loci, and the causative genes have been identified at 22 of these loci. In the present study, we performed a genome-wide linkage analysis in a Korean family segregating autosomal dominant hearing loss. We observed linkage on chromosome 1p34, and at this locus, we detected a novel mutation consisting of an 18 nucleotide deletion in exon 4 of the KCNQ4 gene, which encodes a voltage-gated potassium channel. We carried out a functional in vitro study to analyze the effects of this mutation (c.664_681del) along with two previously described KCNQ4 mutations, p.W276S and p.G285C. Although the c.664_681del mutation is located in the intercellular loop and the two previously described mutations, p.W276S and p.G285C, are located in the pore region, all mutants inhibit normal channel function by a dominant negative effect. Our analysis indicates that the intercellular loop is as significant as the pore region as a potential site of pathogenic effects on KCNQ4 channel function.
Biochimica et Biophysica Acta 04/2011; 1812(4):536-43. · 4.66 Impact Factor
[show abstract][hide abstract] ABSTRACT: X-linked deafness type 3 (DFN3), the most prevalent X-linked form of hereditary deafness, is caused by mutations in the POU3F4 locus, which encodes a member of the POU family of transcription factors. Despite numerous reports on clinical evaluations and genetic analyses describing novel POU3F4 mutations, little is known about how such mutations affect normal functions of the POU3F4 protein and cause inner ear malformations and deafness. Here we describe three novel mutations of the POU3F4 gene and their clinical characterizations in three Korean families carrying deafness segregating at the DFN3 locus. The three mutations cause a substitution (p.Arg329Pro) or a deletion (p.Ser310del) of highly conserved amino acid residues in the POU homeodomain or a truncation that eliminates both DNA-binding domains (p.Ala116fs). In an attempt to better understand the molecular mechanisms underlying their inner ear defects, we examined the behavior of the normal and mutant forms of the POU3F4 protein in C3H/10T1/2 mesodermal cells. Protein modeling as well as in vitro assays demonstrated that these mutations are detrimental to the tertiary structure of the POU3F4 protein and severely affect its ability to bind DNA. All three mutated POU3F4 proteins failed to transactivate expression of a reporter gene. In addition, all three failed to inhibit the transcriptional activity of wild-type proteins when both wild-type and mutant proteins were coexpressed. Since most of the mutations reported for DFN3 thus far are associated with regions that encode the DNA binding domains of POU3F4, our results strongly suggest that the deafness in DFN3 patients is largely due to the null function of POU3F4.
[show abstract][hide abstract] ABSTRACT: The alpha4 chain of the type 4 collagen family is an important component of the glomerular basement membrane (GBM) in the kidney. It is encoded by the COL4A4 gene, and mutations of this gene are known to be associated with thin basement membrane nephropathy (TBMN). To better understand the contribution of variants in the COL4A4 gene to TBMN, we investigated the sequence of the complete COL4A4 gene in 45 Korean patients with TBMN.
Genomic DNA was obtained from the peripheral blood lymphocytes. For the analysis of the COL4A4 gene, all the exons including splicing sites were amplified by PCR and screened by direct sequencing analysis.
Eight novel COL4A4 sequence variants were found in these patients. Two of these variants, G199R and G1606E, were possibly pathogenic variants affecting the phenotype. None of these variants were observed in 286 chromosomes from normal Korean control subjects. In addition, 39 polymorphisms including 7 novel SNPs were identified in this study.
The frequency of COL4A4 mutations in Korean patients with TBMN is low and the other cases may have mutations in other genes like COL4A3. Screening of the COL4A3 gene and finding a novel causative gene for TBMN will help clarify the pathogenesis of this disorder and perhaps for distinguishing TBMN from Alport syndrome.
The Indian journal of medical research 06/2009; 129(5):525-33. · 2.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: It is known that steroid usage and alcohol abuse are major etiological factors in the development of avascular necrosis (AVN), a bone disease that produces osteonecrosis of the femoral head. The facilitation of fat biosynthesis by steroids and alcohol disrupts the blood supply into the femoral head. SREBP-2 plays a central role in the maintenance of lipid homeostasis through stimulating expression of genes associated with cholesterol biosynthetic pathways. The aim of this study was to examine the association between the polymorphisms of the SREBP-2 gene and AVN susceptibility in the Korean population.
Four single nucleotide polymorphisms (SNP) in the SREBP-2 gene, IVS1+8408 T>C (rs2267439), IVS3-342 G>T (rs2269657), IVS11+414 G>A (rs1052717) and IVS12-1667 G>A (rs2267443), were selected from public databases and genotyped in 443 AVN patients and 273 control subjects by using single-based extension (SBE) genotyping.
The minor allele (C) frequency of rs2267439 showed a significant protective effect on AVN (P = 0.01, OR; 0.75, 95% CI; 0.604-0.935), and the genotype frequencies of this polymorphism were also different from the controls in all alternative analysis models (P range, 0.009-0.03, OR; 0.647-0.744). In contrast, rs1052717 and rs2267443 polymorphisms were significantly associated with AVN risk. Further analysis based on pathological etiology showed that the genotypes of rs2267439, rs1052717 and rs2267443 were also significantly associated with AVN susceptibility in each subgroup.
This study is the first report to evaluate the association between SREBP-2 gene polymorphisms and the susceptibility of AVN in the Korean population.
BMC Medical Genetics 10/2008; 9:94. · 2.54 Impact Factor
[show abstract][hide abstract] ABSTRACT: Microsatellites, short tandem repeats, are useful markers for genetic analysis because of their high frequency of occurrence over the genome, high information content due to variable repeat lengths, and ease of typing. To establish a panel of microsatellite markers useful for genetic studies of the Korean population, the allele frequencies and heterozygosities of 207 microsatellite markers in 119 unrelated Korean, Indian and Pakistani individuals were compared. The average heterozygosity of the Korean population was 0.71, similar to that of the Indian and Pakistani populations. More than 80% of the markers showed heterozygosity of over 0.6 and were valuable as genetic markers for genome-wide screening for disease susceptibility loci in these populations. To identify the allelic distributions of the multilocus genetic data from these microsatellite markers, the population structures were assessed by clustering. These markers supported, with the most probability, three clustering groups corresponding to the three geographical populations. When we assumed only two hypothetical clusters (K), the Korean population was separate from the others, suggesting a relatively deep divergence of the Korean population. The present 207 microsatellite markers appear to reflect the historical and geographical origins of the different populations as well as displaying a similar degree of variation to that seen in previously published genetic data. Thus, these markers will be useful as a reference for human genetic studies on Asians.
Molecules and Cells 05/2008; 25(2):301-4. · 2.21 Impact Factor