Collaborative Research: QTL Analysis of a Cave Fish

0216103/0217178 Browsky Tabin这项研究的长期目标是了解使一个物种的所有个体独一无二的发育遗传差异的本质，并将不同的物种彼此区分开来。为此，将研究两种密切相关但基因截然不同的鱼类之间的差异。墨西哥文昌鱼有一些种群生活在河流中，另一些种群生活在洞穴中。洞穴形态与它们的地表近亲不同，因为它们的眼睛和色素沉着都大大减少。它们生活的洞穴提供的食物很少，它们通过发展较慢的新陈代谢来适应这一点。其他感官过度发达，以弥补视觉的缺乏：例如，嗅觉、味觉以及检测振动和电流的能力。它们不仅能在永恒的黑暗中生存下来，还能在洞穴中茁壮成长。这种物种的基因组将通过微卫星DNA标记在洞穴和地表形态之间的杂交中被绘制出精细的图谱。对杂交种的图谱和进一步分析将允许检测和描述导致洞穴和地表形态差异的基因(QTL)。研究结果将对性状差异的“遗传架构”进行估计：所涉及的基因数量及其个体效应的大小，以及它们在基因组中的相对位置。一些主效QTL的位置信息将被用来鉴定和克隆这些基因，这将有助于它们的功能分析。这一结果将阐明复杂特征的发育和维持所涉及的遗传途径，比如脊椎动物的眼睛和感觉系统的其他方面，色素的控制，行为和新陈代谢。这些结果还将揭示区分种群和物种的遗传差异的本质，以及特征相关性对进化变化的制约。

0216103/0217178Browsky Tabin The long term goal of this research is to understand the nature of the developmental genetic differences that make all individuals of a species unique, and distinguish the various species from one another. Towards this end, differences between two types of fishes that are closely related, but genetically distinct, will be studied. The Mexican tetra, Astyanax mexicanus, has some populations that live in rivers and others that live in caves. Cave forms differ from their surface relatives by having greatly reduced eyes and pigmentation. The caves in which they live provide little food and they have adapted to this by developing a slower metabolism. Other senses are overdeveloped to compensate for the lack of vision: e.g., smell, taste and the ability to detect vibration and current. Not only can they survive eternal darkness, they thrive in caves.The genome of this species will be mapped at a fine scale using microsatellite DNA markers, in hybrids between the cave and surface forms. The map and further analysis of the hybrids will permit the detection and characterization of genes (QTL) that are responsible for the differences between cave and surface forms. The results will give estimates of the "genetic architecture" of trait differences: the number of genes involved and magnitudes of their individual effects, and their positions in the genome relative to one another. Positional information of some of the major effect QTL will be used to identify and clone the genes; this will facilitate their functional analysis. The results will shed light on the genetic pathways involved in development and maintenance of complex traits, like the vertebrate eye and other aspects of the sensory system, control of pigmentation, behavior and metabolism. The results will also inform on the nature of genetic differences distinguishing populations and species, and on the constraints on evolutionary change resulting from trait correlations.