Generation of the wild-type Tsc2 transgenic Eker rat and its effect on renal carcinogenesis.

我们在人类结节性硬化症2基因（TSC2）的大鼠同源基因中发现了Eker大鼠遗传性肾癌的易感种系突变。此外，我们还在Eker大鼠的肾癌甚至肿瘤前病变中发现了野生型Tsc2的体细胞突变和缺失，这表明Tsc2基因具有肿瘤抑制作用。在这项研究中，通过引入野生型Tsc2基因，试图抑制Eker大鼠的表型，即Tsc2突变杂合子的肾癌发生和纯合子Tsc2突变体的胚胎致死。这里使用的转基因由野生型大鼠Tsc2 cDNA（由于选择性剪接事件缺少25和31外显子）和基因组DNA组成，并由Tsc2启动子驱动。该基因在Eker大鼠中成功地抑制了肾癌的发生和胚胎致死性。这些结果为确定Tsc2基因的种系突变是导致Eker大鼠表型的原因提供了最终证据。有趣的是，获救的纯合子Tsc2突变体发展为肾肿瘤和垂体肿瘤，这通常发生在Eker基因中。在这些肿瘤中，野生型Tsc2转基因被体细胞删除，表明这些肿瘤的起始是由Tsc2功能的丧失引起的。本研究建立的对Eker大鼠表型的转基因拯救，将为分析Tsc2基因及其产物的功能，阐明Tsc2基因突变致肿瘤发生的分子机制提供一个有益的体内实验系统。

We have identified a predisposing germline mutation for the Eker rat hereditary renal carcinoma in the rat homelog of human tuberous sclerosis 2 gene (TSC2). Also we have indentified somatic mutations and deletions on the wild-type Tsc2 allel (second hits) in renal carcinomas and even in preneoplastic lesions fom the Eker rat, indicating that the Tsc2 gene functions as a tumor suppressor. In tahis study, an attempt to suppress phenotypes of the Eker rat, the renal carcinogenesis in heterozygotes for Tsc2mutataion and the embryonic lethality in homozygous Tsc2 mutants, was carried out by introduction of a wild-type Tsc2 transgere. The transgene used here consisted of a wild-type rat Tsc2 cDNA (lacking exons 25 and 31 by alternative splicing events) and genomic DNA,and was driven by Tsc2 promoter. By idntroduction of this transgene, both of renalcarcinogenesis and embryonic lethality were successfully suppressed in the Eker rat. These results are final evidence to define the germline mutataion of Tsc2 gene as the cause of Eker rat phenotypes. Interesltingly, rescued homozygous Tsc2 mdutants developed renal tumors as well as pituitary tumors, which often developed in the Eker draats. In these tumors, the wild-type Tsc2 transgene was somatically deleted, indicating that the initiation of these tumors was caused by loss of Tsc2 function. the transgenic rescue for the Eker rat phenotype established in this study will be a usefull in vivo experimental system to analyze the function of Tsc2 gene and its product, and to elucidate molecular mechanism of tumorigenesis caused gy Tsc2 mdutations.