Assessing parent-of-origin transcriptional effects in Xenopus laevis

描述（由申请人提供）：亲本效应是一种表观遗传现象，表现为杂合子之间的表型差异，取决于亲本的等位基因。能够导致亲本起源效应的主要表观遗传现象是基因组印记。一些印迹位点仅来自母亲的拷贝，而另一些则来自父亲的拷贝。印迹基因在许多复杂性状中起着重要作用，尤其是在早期发育中。尽管基因印记的分类分布仍不确定，但一种被广泛接受的观点认为，在动物中，它仅限于哺乳动物，而且大多数研究都是在小鼠模型中进行的。在更广泛的物种中评估印记存在重大的技术挑战。一个主要的限制因素是缺乏多个具有显著核苷酸水平差异的自交系

DESCRIPTION (provided by applicant): Parent-of-origin effects are epigenetic phenomena that appear as phenotypic differences between heterozygotes depending on the allelic parent of origin. The primary epigenetic phenomenon that can lead to the parent-of-origin effects is genomic imprinting. Some imprinted loci are expressed from the maternal copy only, while others from the paternal copy. Imprinted genes play an important part in a number of complex traits, notably in early development. Though the taxonomic distribution of gene imprinting remains uncertain, a widely-accepted view holds that among animals it is limited to mammals, and most studies had been performed in mouse models. There are significant technical challenges in assessment of imprinting in a wider variety of species. A major limiting factor is lack of multiple inbred lines with significant nucleotide-level differences between them, since the most direct way to identify imprinting involves generation of reciprocal crosses between such lines. In addition, transcriptome-wide surveys of allele-specific expression have only recently become feasible, and the analytical and statistical tools for analysis of such data are still in thir infancy. We have pioneered several technologies for the analysis of allele-specific expression. In collaboration with experts in the biology of the African clawed frog, Xenopus laevis, we have performed preliminary RNA sequencing experiments on mixed crosses between inbred lines that strongly suggest that there are genes in X. laevis that exhibit parent-of-origin imprinting. The goal of this project is to carefully and thoroughly assess this striking hypothesis. In order t do that, we will execute a "zoom in sequencing" approach which consists of a "wide but shallow" round where we screen for candidate genes, complemented by a "deep but narrow" round where we focus in detail on the allelic bias of a set of candidate genes. Identification of parent of-origin imprinting in an amphibian would represent a significant conceptual advance in understanding the evolutionary origins of that epigenetic mechanism and its role in development. Moreover, Xenopus has long been an important tool for in vivo studies in molecular, cell, and developmental biology of vertebrate animals. It is the only vertebrate model system that allows for high-throughput in vivo analyses of gene function and biochemistry. Xenopus as a model for the study of imprinting would allow for the development of screens to identify new targets important for disease and for the design of new therapies involving imprinted genes.