Résumé
Objective To identify the candidate genes in the vicinity of a susceptibility locus (urinary albumin 1,UA-1) contributing to the development of albuminuria in type 2 diabetic KK/Ta mice. Methods Total RNA was extracted from the kidneys of KK/Ta (n=3) and BALB/c (n=2) mice at 20 weeks of age.The gene expression profile in kidney was investigated using the Affymetrix Murine Genome U74Av2 array.Competitive RT-PCR was used to confirm the differential expression of syndecan-4 which located in the vicinity of UA-1.Genome DNA was extracted from KK/Ta and BALB/c mice.DNA sequence analysis of the coding and promotor region of syndecan-4 gene was conducted. Results In the vicinity of the susceptibility locus (UA-1)contributing to the development of albuminuria in type 2 diabetic KK/Ta mice,10 candidate genes that showed differential expression were identified.Among them,the gene expression of syndecan-4in KK/Ta kidneys at 20 weeks of age was up-regulated by 26.1 times of age-matched BALB/c kidneys.Sequence analysis revealed two synonymous polymorphisms in the coding region (A93C and T216C) and three polymorphisms in the promoter region (-T263C,-T396C and -G669A) of the syndecan-4 gene.The TATA box was found at 321 bp upstream from the transcription start site,and the T263C polymorphism was located in the binding site of transcription factor Clox.Conclusions Syndecan-4 gene is mapped in the vicinity of the susceptibility locus contributing to the development of albuminuria in type 2 diabetes.The gene expression of syndecan-4 in KK/Ta kidneys is up-regulated than that in age-matched BALB/c kidneys at 20 weeks of age.Thus syndecan-4 may be one of the potential candidate genes responsible for diabetic nephropathy.Sequence differences in the promoter region influence the expression levels of syndecan-4 genes in KK/Ta kidneys.