多配体蛋白聚糖4是糖尿病肾病的候选基因

Syndecan-4 is a candidate gene for diabetic nephropathy

目的在2型糖尿病肾病（DN）白蛋白尿易感基因定位的基础上，进一步筛选白蛋白尿易感基因位点（UA-1）区域附近的候选基因。方法提取20周龄雄性KK／Ta（n=3）和BALB／c（n=2）小鼠肾脏总RNA，应用Affymetrix Murine GenomeU74Av2基因芯片检测肾脏基因表达谱。选择UA-1区域的差异表达基因多配体蛋白聚糖4（syndecan-4），竞争性RT-PCR验证基因芯片的结果。提取KK／Ta、BALB／c小鼠的基因组DNA，进行syndecan．4基因编码区和启动子区域的序列分析。结果在2型糖尿病KK／Ta小鼠UA-1区域附近存在着约10个差异表达基因。其中syndecan-4在20周龄KK／Ta小鼠肾脏中的表达上调，为BALB／c小鼠的26．1倍。在syndecan．4基因编码区存在2个基因多态性，分别为A93C和T216C多态性，2者均为同义突变。在syndecan-4基因启动子区域存在3个基因多态性，分别为-T263C、-T396C与-G669A多态性。TATA框位于转录起始位点上游321bp处，-T263C处恰好为转录因子Clox的结合位点。结论syndecan-4基因位于2型糖尿病UA-1附近区域，在20周龄KK／Ta小鼠肾脏中的表达明显上调，是DN的候选基因。syndecan-4启动子处的基因多态性可能为其差异表达的原因。

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 syndeean-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.