Molecular Population Genetics of Coat-Color Variation in Pocket Mice

这项拟议的研究的主要目标是确定在生活在明暗两种底物上的浅色和深色岩石口袋鼠种群中导致自然毛色变化的突变。具体地说，拟议的研究将(1)记录新墨西哥州和亚利桑那州六个成对地点的小鼠毛色的变化和土壤颜色的环境异质性，其中每对地点由一个光和一个暗地点组成，(2)进行筛选以确定导致观察到的表型差异的基因，(3)在涉及表型差异的基因座上描述突变等位基因，以及(4)在来自暗和光地点的群体样本中描述毛色基因的遗传变异。总而言之，这些研究将(1)确定导致毛色变化的不同基因的数量和相对影响，(2)确定色素差异是否主要是由于结构变化、调节变化，或两者兼而有之，(3)确定深色毛色是否在不同的种群中独立进化，如果是，确定是否涉及相同或不同的突变，以及(4)确定基因组某一位置的选择在多大程度上塑造了连锁中性位点的遗传变异模式。生物学的一个中心目标是明确地将具有生态重要性的性状的基因型与表型联系起来。这一直是一个难以实现的目标，因为大多数性状的遗传基础还没有被很好地理解。啮齿动物的毛色变化是响应局部适应的表型变化的经典例子：在许多物种中，背部毛皮的颜色与动物生活的土壤的颜色非常匹配。一个世纪以来，室内毛色的遗传学研究已经产生了丰富的候选基因和突变效应的数据库。口袋鼠毛色的显著表型变异和实验室小鼠克隆的候选色素沉积基因的结合，为研究自然界关键形态性状背后的遗传变异提供了一个无与伦比的机会。

9981810NachmanThe primary objective of the proposed research is to identifymutations responsible for naturally occurring coat-color variation inpopulations of light and dark rock pocket mice that live on light and darksubstrates. In particular, the proposed research will (1) documentvariation in coat color of mice and environmental heterogeneity in soilcolor for six paired localities in New Mexico and Arizona where each pairconsists of one light and one dark locality, (2) conduct a screen toidentify genes contributing to the observed phenotypic differences, (3)characterize mutant alleles at the loci implicated in phenotypicdifferences, and (4) characterize genetic variation at coat-color loci inpopulation samples from dark and light localities. Together, these studieswill (1) identify the number and relative effects of different genescontributing to coat color variation, (2) determine whether pigmentationdifferences are due primarily to structural changes, regulatory changes, orboth, (3) determine whether dark coat-color has evolved independently indifferent populations, and if it has, determine whether the same ordifferent mutations are involved, and (4) determine the extent to whichselection at one site in the genome has shaped patterns of geneticvariation at linked neutral sites. A central goal in biology is to explicitly connect genotype withphenotype for traits that are ecologically important. This has been anelusive goal because the genetic basis of most traits is not wellunderstood. Coat-color variation in rodents is a classic example ofphenotypic variation in response to local adaptation: in many species,dorsal pelage color closely matches the color of the soil on which theanimals live. A century of research on the genetics of coat color in housemice has produced a rich database of candidate genes and mutant effects.The combination of striking phenotypic variation in coat-color of pocketmice (Chaetodipus intermedius) and candidate pigmentation loci cloned inthe laboratory mouse presents an unparalleled opportunity to investigatethe genetic variation underlying a key morphological trait in nature.