STRUCTURE AND FUNCTION OF NOVEL GENE (BRG1) EXPRESSED IN PANCREATIC BETA CELLS

利用任意引物PCR的差异显示技术，我们从小鼠β细胞系中获得了一个约500bp的片段，该片段在cDNA中被优先扩增。我们将该基因命名为BRG1 （β相关基因1）。在MIN6细胞和大鼠胰岛中，高糖培养组的mRNA表达量明显高于低糖培养组，约为14kb。BRG1 mRNA表达的组织分布表明BRG1基因在小鼠各组织中普遍表达。在睾丸中表达量最高。对约14kb cDNA的几乎整个区域进行了测序和测定。小鼠与人的序列一致性达87 ~ 89%。另一方面，小鼠和果蝇BRG1序列在约84 ~ 324 bp的5个限制性区域中各有67 ~ 74%的序列一致性。推导出的小鼠和人BRG1氨基酸序列（约4400 A.A.）在整个区域的同源性为93.8%。另一方面，小鼠和果蝇BRG1蛋白在c端约3800个氨基酸区有41.8%的同源性。此外，小鼠与秀丽隐杆线虫BRG1蛋白在c端~ 1650个氨基酸区有26.8%的同源性。利用小鼠RH面板对BRG1基因的染色体定位显示，BRG1位于小鼠4号染色体的远端，在那里已经定位了NOD小鼠的一个致糖尿病基因Iddll。第二个研究主题是日本1型糖尿病患者肿瘤坏死因子(TNF)-α基因5'-侧翼区多态性。我们观察到TNFP-D和-B等位基因与1型糖尿病相关，这可能是继发于它们与HLA I类和II类易感等位基因的连锁不平衡。

Utilizing the differential display technique with arbitrarily-primed PCR, we obtained a 〜500bp fragment, which is preferentially amplified in the cDNA from mouse β cell lines. We named the gene as BRG1 (β related gene 1). The mRNA was very large, I.e. 〜14kb, and the levels of expression were higher in the groups cultured with high glucose than low glucose in MIN6 cells and rat islets. Tissue distribution of BRG1 mRNA expression revealed that BRG1 gene was expressed ubiquitously in various mouse tissues. The highest expression was observed in the testes. The almost entire region of 〜14kb cDNA was sequenced and determined. There were 87〜89 % sequence identities between the mouse and the human sequences. On the other hand, sequence identities between mouse and Drosophila BRG1 sequence were 67〜74 % in each of 5 restricted regions of about 84〜324 bp stretches. The deduced BRG1 amino acid sequences for mouse and human (〜4, 400 A.A.) had 93.8 % identity throughout the entire region. On the other hand, there was 41.8 % identity in the C-terminal 〜3,800 amino acid region between mouse and Drosophila BRG1 protein. Moreover, there was 26.8 % identity in the C-terminal 〜1,650 amino acid region between mouse and C. elegans BRG1 protein. The chromosomal mapping of the BRG1 gene using the mouse RH panel revealed that the BRG1 is located at the distal part of mouse chromosome 4, where one of the diabetogenic genes in NOD mouse, Iddll, has been mapped.The second research theme was about the polymorphisms in the 5'-flanking region of the tumor necrosis factor (TNF)-α gene in Japanese type 1 diabetes. We observed that the TNFP-D and -B alleles were associated with type 1 diabetes, which may be secondary to their linkage disequilibria with the susceptible HLA class I and class II alleles.