Identification of molecular mechanisms acting at the jObes1 locus in the Berlin Fat Mouse with effect on juvenile fat deposition

该项目的目的是阐明柏林肥鼠(BFMI)肥胖的机制。这只小鼠在小鼠染色体3(jObes1位点)上有自发突变，这是导致高脂肪沉积的原因，特别是在青春期。精细定位、互补测试和基因表达研究已确定Bardet Biedl综合征7(Bbs7)基因是最有可能的候选基因。Bbs7有助于纤毛的形成，该基因的突变可能导致人类的Bardet-Biedl综合征。像人类一样，BFMI小鼠超重，视网膜退化，大脑发生变化。Bbs7的标准蛋白序列已被排除为BFMI小鼠缺陷的原因。序列数据和表达谱为导致替代Bbs7表达模式的调控作用序列变体提供了证据。此外，突变DNA区域之间的相互作用可能会影响Bbs7以及邻近基因的表达。为了确定不同组织功能障碍的机制，我们打算进行以下研究：(1)Bbs7周围的基因组区域将被测序，以填补现有的空白，并能够识别BFMI与其他小鼠近交系之间不同的单序列变体或整个单倍型，并在互补试验中进行测试。(2)检测Bbs7基因转录变异体在不同细胞类型和不同基因类型中的表达，以寻找表达模式与基因之间的关系。(3)将在转基因小鼠身上测试两个潜在作用的BFMI突变的功能。(4)染色体构象捕获研究将测试Bbs7区突变对该区域基因表达的影响。根据已识别的症状和可能的调节作用突变，BFMI小鼠中的Bbs7是解释导致超重和多效性效应的调节机制的合适模型。拟议的检查将提高我们对调控序列变异如何改变性状变异的理解。

The aim of the project is the elucidation of the mechanism causing obesity in the Berlin Fat Mouse (BFMI). This mouse harbors a spontaneous mutation on mouse chromosome 3 (jObes1 locus) accounting for the high fat deposition particularly during puberty. Fine mapping, complementation tests and gene expression studies have identified the Bardet Biedl Syndrome 7 (Bbs7) gene as most likely candidate gene. Bbs7 contributes to the formation of cilia and mutations in this gene may cause the Bardet-Biedl-Syndrome in humans. Like humans, BFMI mice are overweight, have degraded retinae and alterations in the brain. The standard protein sequence of Bbs7 has been excluded as cause for the defects in BFMI mice. Sequence data and expression profiles provide evidence for regulatory acting sequence variants leading to alternative Bbs7 expression patterns. In addition, interactions between mutated DNA regions could affect the expression of Bbs7 as well as neighboring genes.To identify the mechanisms underlying the malfunction of different tissues, we intend to perform following studies: (1) The genomic region around Bbs7 will be sequenced to fill existing gaps and to allow the identification of single sequence variants or whole haplotypes that differ between BFMI and other mouse inbred lines and to test them in complementation tests. (2) The expression of Bbs7 transcript variants will be examined in different cell types and different genotypes to find an association between expression pattern and genotype. (3) The function of two potentially acting BFMI mutations will be tested in genetically modified mice. (4) Chromosome conformation capture studies will be performed to test the effect of mutations in the Bbs7 region on the expression of genes in this region.With the identified symptoms and the likely regulatory acting mutations, Bbs7 in the BFMI mouse is a suitable model for the elucidation of regulatory mechanisms leading to overweight and pleiotropic effects. The proposed examinations will improve our understanding on how regulatory sequence variants change trait variation.