Identification of novel variants in the COL4A4 gene in Korean patients with thin basement membrane nephropathy.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Baek
Jeong-In
JI
Department of Biology, College of Natural Sciences, Kyungpook National University, Daegu, Korea.
Choi
Su-Jin
SJ
Park
Sun-Hee
SH
Choi
Ji-Young
JY
Kim
Chan-Duck
CD
Kim
Yong-Lim
YL
Kim
Un-Kyung
UK
D001483:Base Sequence; D001485:Basement Membrane / Q000473:pathology*; D024141:Collagen Type IV / Q000235:genetics*; D004252:DNA Mutational Analysis; D015433:Glomerulonephritis, Membranous / Q000235:genetics* / Q000473:pathology; D006801:Humans; D007723:Korea; D015810:Linkage Disequilibrium; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic
C466620:COL4A4 protein, human; D024141:Collagen Type IV