Collaborative Research: QTL Analysis of a Cave Fish

这项研究的长期目标是了解使一个物种的所有个体都独一无二的发育遗传差异的本质，并将不同物种彼此区分开来。为此，将研究两种关系密切但基因不同的鱼类之间的差异。墨西哥利乐，Astyanax mexicanus，有一些种群生活在河流中，另一些种群生活在洞穴中。洞穴形式与它们的地表亲戚不同，它们的眼睛和色素都大大减少。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。其他感官过度发展以弥补视觉的缺失：如嗅觉、味觉和感知振动和电流的能力。它们不仅能在永恒的黑暗中生存，还能在洞穴中茁壮成长。这个物种的基因组将在一个精细的尺度上绘制，使用微卫星DNA标记，在洞穴和地表形式之间的杂交。杂交物种的图谱和进一步分析将允许检测和表征导致洞穴和地表形态差异的基因（QTL）。研究结果将给出性状差异的“遗传结构”的估计：涉及的基因数量、个体影响的大小，以及它们在基因组中的相对位置。一些主要效应QTL的位置信息将用于基因的鉴定和克隆；这将有助于它们的功能分析。研究结果将揭示与复杂特征的发育和维持有关的遗传途径，比如脊椎动物的眼睛和感觉系统的其他方面，对色素沉着、行为和新陈代谢的控制。研究结果还将揭示区分种群和物种的遗传差异的本质，以及性状相关性对进化变化的限制。

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.