Transcriptomics And Proteomics Analysis On The Regulation Mechanism Of Weaning Stress In Lambs

Hu sheep is a famous breed in China characterized by high prolificacy with an average lambing rate of 256%, and the selection group with high reproduction rate could reached to 300%. The lambs need to wean at an early age for the reasons of multiple fetal or weakness of ewe, insufficient of breast milk, suit to the large scale production, and ewes to give birth to two litters of lambs each year. The previous research mainly focused on the methods of early weaning of lambs and the technical measures to alleviate the weaning stress. However, little is known in the molecular regulation mechanism of weaning process. Twins of neonatal ram Hu lambs were randomly divided into two groups. One lamb from each pair of twins separated from the ewes were artificially reared (AR) with milk replacer after the lambs had been sucking colostrum for three days. The other lambs were ewe-reared (ER) during the whole experiment. On the 15th day, three pairs of twins were slaughtered and samples of the jejunum tissue were quickly harvested and frozen in liquid nitrogen. RNA-seq and iTRAQ were selected to identify the difference expression genes and differentially expressed proteins of intestine of lambs under weaning stress. The results are as follows:1. Histological sectioning was performed to determine the differences in the morphological changes in the intestine between the two groups. Compared with the ER group, the weaned lambs of AR showed structural changes in the small intestine, including shortened villi (villous atrophy) and increased crypt depth (crypt elongation).2. By RNA-seq analysis,24592 genes were found in the intestine tissues and a total of 482 differentially expressed genes were identified (|log2FC|>1 and P<0.05). 235 genes were up-regulated and 247 genes were down-regulated in the intestine of lambs under weaning stress. GO and pathways analysis for different expressed genes showed that differentially expressed genes were mainly involved in regulating the metabolism of nutrients, digestive system, immune system and endocrine system. Four novel genes of ENSOARG00000010572, ENSOARG00000015002, ENSOARG00000009042, and ENSOARG00000014493 related to immune process were identified in this research.3.5338 proteins were identified in the intestine tissues with iTRAQ proteomic technique. To further understand the differentially expressed proteins during the weaning process, relative relaxed criterion of fold change (> 1.2 fold) and p-value (<0.05) was identified as DEPs between AR and ER groups. Finally,389 differentially expressed proteins were identified by iTRAQ analysis, of which 143 were up-regulated and 246 (4.61%) were down-regulated under weaning stress conditions. The protein-protein interaction network results showed that DEPs were mainly enriched for the "regulation of immune response", "metabolism of amino acid, glucose, and fatty acids", "genetic information processing", "cytoskeleton organization", and "extracellular matrix and integrin signaling".In this study, we used multiple omics technology to explore the regulation mechanism in the mRNA level and protein levels of the intestines of lambs during weaning stress.This advanced omics data has expanded our knowledge significantly and has provided new insights into the effects of weaning stress on the intestine.