Genetic Etilogy of Renal Agenesis in the ACI Rat

描述（由申请人提供）：单侧肾发育不全（URA）是人类常见的发育缺陷，发生率约为1/500-1000活产婴儿。受影响个体的后代中URA的频率明显高于一般人群，表明遗传因素有助于URA的发生。ACI大鼠自发表现出URA，发生率约为15%。在ACI品系与两个未受影响的大鼠品系哥本哈根（COP）和布朗挪威（BN）之间的一系列遗传杂交中，我们已经将一个遗传位点定位于大鼠14号染色体（RNO 14），命名为Renag 1（肾发育不全1），该位点在这些杂交中作为URA的主要（如果不是唯一的）决定因素。Renag 1的ACI等位基因以不完全显性和不完全外显的方式赋予URA。这项研究的总体目标是充分确定ACI大鼠肾发育不全的遗传和胚胎学基础。具体目标1是精细定位Renagl在大鼠14号染色体上的位置。我们已经将Renag 1映射到RNO 14上大约15 centiMorgan（cM）的间隔。为了将Renag 1的位置定义为接近0.5 cM的分辨率，我们将产生多达400个受URA影响的（BN x ACI）F2后代，并在Renag 1区域的高密度标记处确定这些大鼠的基因型。BN等位基因在标记处的纯合性将排除该标记位于Renag 1内。具体目的2是确定ACI大鼠肾发育不全的胚胎学基础。ACI雌性大鼠将在交配后的规定时间点处死，收获发育中的胚胎，切片并进行显微镜检查。当第一个可辨别的缺陷发生在ACI大鼠肾脏发育的知识将提供新的和潜在的重要见解，何时何地与Renag 1相关的分子缺陷表现出来。具体目标3是比较ACI和BN大鼠品系中肾脏发育期间Pax 2、Gdnf和Ret的表达。正常的肾脏发育需要Pax 2、Gdnf和Ret的协调表达。我们推测，Renag 1相关的缺陷，导致URA的ACI大鼠可能会导致定性和/或定量的差异，Pax 2，Gdnf和/或Ret表达相对于BN大鼠。在ACI和BN大鼠品系中，将在蛋白质和mRNA水平上评价肾脏发育期间这些基因的表达。完成这些目标后，我们将更好地了解ACI大鼠肾发育不全的遗传基础，并将能够评估该动物模型与人类肾发育不全的相关性。

DESCRIPTION (provided by applicant): Unilateral renal agenesis (URA) is a common developmental defect in humans, occurring at a frequency of approximately 1 in 500-1000 live births. The frequency of URA in offspring of affected individuals is markedly higher than in the general population, indicating that genetic factors contribute to the genesis of URA. ACI rats spontaneously exhibit URA at an incidence of approximately 15%. In a series of genetic crosses between the ACI strain and two unaffected rat strains, Copenhagen (COP) and Brown Norway (BN), we have mapped to rat chromosome 14 (RNO14) a genetic locus, designated Renag1 (Renal agenesis 1), mat serves as the major, if not sole, determinant of URA in these crosses. The ACI allele of Renag 1 acts in an incompletely dominant and incompletely penetrant manner to confer URA. The overall goals of this proposed research are to define fully the genetic and embryologic bases of renal agenesis in the ACI rat. Specific Aim 1 is to fine map the location of Renagl on rat chromosome 14. We have mapped Renag1 to an approximate 15 centiMorgan (cM) interval on RNO14. To define the location of Renag1 to a resolution approaching 0.5 cM, we will generate up to 400 URA-affected (BN x ACI)F2 progeny and determine the genotypes of these rats at markers placed at a high density across the Renag1 region. Homozygosity for the BN allele at a marker will exclude that marker from residing within Renag1. Specific Aim 2 is to define the embryologic bases of renal agenesis in the ACI rat ACI females will be sacrificed at defined time points after mating and the developing embryos will be harvested, sectioned and examined microscopically. Knowledge of when the first discernable defect in renal development occurs in the ACI rat will provide novel and potentially important insights into when and where the molecular defect associated with Renag1 is manifested. Specific Aim 3 is to compare expression of Pax2, Gdnf and Ret during renal development in the ACI and BN rat strains. Proper renal development requires coordinated expression of Pax2, Gdnf and Ret. We hypothesize that Renag1-associated defect leading to URA in the ACI rat may result in qualitative and/or quantitative differences in Pax2, Gdnf and/or Ret expression relative to the BN rat. Expression of these genes during renal development will be evaluated at the protein and mRNA levels in both the ACI and BN rat strains. Upon completion of these Aims, we will better understand the genetic bases of renal agenesis in the ACI rat and will be able to assess the relevance of this animal model to renal agenesis in humans.