Molecular mechanisms underlying parallel Agouti adaptation in Peromyscus

描述（由申请人提供）：实验室小鼠的毛色突变为哺乳动物色素沉着的细胞和发育过程提供了重要的见解，并作为人类疾病的模型。例如，与人类肥胖特别相关的是，在Agouti基因的调控区域有几个显性的、变浅的突变。这些突变导致Agouti蛋白的异位表达，并与实验室小鼠中严重的多效性效应相关，包括胚胎致死、糖尿病、贪食、肿瘤易感性和肥胖。最近的研究表明，人类Agouti同源基因的变异与肥胖之间也存在类似的联系。初步证据表明，Agouti调控区域的显性突变也导致了居住在内布拉斯加州沙山地区的天然Peromyscus maniculatus（鹿鼠）种群的浅色皮毛；然而，这种表型（“宽波段agouti”）似乎不伴有主要的多效性效应。比较自然生物和实验室生物中发生的突变，分别显示出低和高程度的多向性，可能有助于深入了解Agouti调控的本质。因此，本研究的主要目标是查明在两个地理上分离的马尼乌鳢种群中导致浅色毛色的突变。这一目标需要成功完成三个具体的研究目标。首先，将对在内布拉斯加州沙山地区内外多个地点收集的260个个体进行表型（个体背毛的带状模式和分光光度测量）和中性遗传变异（来自SNP标记）测量。其次，利用含有Agouti基因的Peromyscus BAG序列，通过比较序列分析确定候选调控区域，一旦确定候选区域，将进行Agouti核苷酸变异与野生种群毛色表型之间的关联研究。第三，将对居住在新墨西哥州图拉罗萨盆地的P. maniculatus种群进行采样，并对在内布拉斯加州种群中发现的候选snp进行基因分型，以确定相同的分子机制是否导致这个地理上遥远的种群具有相似的表型。相关性：这项研究与NIH的使命直接相关，因为它将识别和分子表征Agouti突变，这将为哺乳动物色素沉着和人类肥胖的当前模型提供信息。

DESCRIPTION (provided by applicant): Coat color mutations in laboratory mice have provided important insights into the cellular and developmental processes underlying mammalian pigmentation and have served as models for human disease. Of particular relevance to human obesity, for example, are several dominant, coat-lightening mutations in the regulatory region of the Agouti gene. These mutations lead to ectopic expression of the Agouti protein and are associated with severe pleiotropic effects that include embryonic lethality, diabetes, hyperphagia, tumor susceptibility, and obesity in laboratory mice. Recent work suggests a similar link between variation in the human homologue of Agouti and obesity. Preliminary evidence indicates that a dominant mutation in the Agouti regulatory region is also responsible for light coat color in natural Peromyscus maniculatus (deer mouse) populations inhabiting the Sand Hills region of Nebraska; however, this phenotype ("wide-band agouti") appears to be unaccompanied by major pleiotropic effects. Comparison of mutations occurring in natural and laboratory organisms, which show low and high degrees of pleiotropy respectively, may provide insight into the nature of Agouti regulation. Therefore, the broad goal of this research is to pinpoint the mutation(s) responsible for light coat color in two geographically separated populations of P. maniculatus. This goal will require successful completion of three specific research aims. First, phenotypic (banding patterns on individual dorsal hairs and spectrophotometric measurements) and neutral genetic variation (from SNP markers) will be measured for 260 individuals collected at multiple locations within and outside of the Sand Hills region of Nebraska. Second, Peromyscus BAG sequences containing the Agouti gene will be used to identify candidate regulatory regions by comparative sequence analysis and once candidate regions are identified, association studies will be conducted between nucleotide variation in Agouti and coat color phenotypes from wild populations. Third, P. maniculatus populations inhabiting the Tularosa Basin, New Mexico will be sampled and genotyped for candidate SNPs identified in the Nebraska populations to determine whether the same molecular mechanism is responsible for a similar phenotype in this geographically distant population. Relevance: This research is of direct relevance to the mission of NIH because it will identify and molecularly characterize Agouti mutations, which will inform current models of mammalian pigmentation and human obesity.