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导致柏林肥胖小鼠（BFMI）肥胖的机制。该小鼠在小鼠3号染色体（jObes 1基因座）上携带自发突变，导致特别是在青春期的高脂肪沉积。精细定位、互补测试和基因表达研究已经确定Bardet Biedl综合征7（Bbs 7）基因为最可能的候选基因。Bbs 7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，大脑改变。Bbs 7的标准蛋白质序列已被排除为BFMI小鼠中缺陷的原因。序列数据和表达谱提供了证据，调节作用序列变异导致替代Bbs 7表达模式。此外，突变的DNA区域之间的相互作用可以影响Bbs 7及其邻近基因的表达。为了确定不同组织功能障碍的潜在机制，我们打算进行以下研究：（一）将对Bbs 7周围的基因组区域进行测序，以填补现有的缺口，并允许鉴定BFMI和其他小鼠近交系之间不同的单序列变体或全单倍型，在互补测试中测试它们。(2)将在不同细胞类型和不同基因型中检查Bbs 7转录变体的表达，以发现表达模式和基因型之间的关联。(3)将在转基因小鼠中测试两种潜在作用的BFMI突变的功能。(4)染色体构象捕获研究将用于测试Bbs 7区域的突变对该区域基因表达的影响。根据已确定的症状和可能的调节作用突变，BFMI小鼠中的Bbs 7是一个合适的模型，用于阐明导致超重和多效性效应的调节机制。拟议的考试将提高我们的理解调控序列变异如何改变性状变异。

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.