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This project's overarching goal is to better understand how heterosis occurs at the molecular level in beef cattle. Because this is a seed grant, one of our chief goals is to generate preliminary data and additional research questions related to molecular heterosis. This project has three primary objectives:1. Generate a powerful dataset of purebred and crossbred samples in-vitro to explore gene expression heterosisWe will use in-vitro fertilization to perform a diallel cross of Bos indicus and Bos taurus cattle to develop hundreds of purebred and crossbred blastocysts. This approach will generate high statistical power to identify deviations in crossbred gene expression in Objective 2. By restricting our analysis to developing embryos, we should be able to identify variation in gene expression without waiting years for mature animals to be conceived and develop. Further, by performing this in the lab, we will observe gene expression differences in F1 embryos in a controlled environment.2. Identify genes that deviate from parent-average expression in F1 individualsUsing the in-vitro fertilized set of embryos, we will perform RNA-Sequencing to identify differentially expressed genes in F1 embryos compared with their purebred contemporaries. Beyond identifying if F1 gene expression differences exist, we aim to understand whether the expression differences are in specific genes, genome-wide or random. We will also explore how crossbred gene expression differences impact genomic networks and biological pathways and processes. 3. Map molecular QTL (additive & non-additive) to identify the genetic variants involved in molecular heterosis.We are also interested in understanding how DNA variants impact the expression of genes at this understudied point in development. We will perform additive and non-additive expression quantitative trait loci (eQTL) mapping on our robust set of RNA-Sequenced blastocysts. These analyses will provide us with a set of variants that change the expression of genes at this critical developmental timepoint.

Rowan, T. N.; Beever, Jo, Ed.; Edwards, Ja, La.; Moorey, Sa, El.
University of Tennessee
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