Molecular Cloning of the B4GALNT2 Gene and Its Single Nucleotide Polymorphisms Association with Litter Size in Small Tail Han Sheep.

Xiaofei Guo,Benmeng Liang,Ran Di,Mingxing Chu,Xiaosheng Zhang,Xiaoyun He,Qiuyue Liu,Xiangyu Wang,Jinlong Zhang,Wenping Hu

doi:10.3390/ani8100160

Abstract

Simple SummaryIn French Lacaune sheep, the B4GALNT2 (beta-1, 4-N-acetyl-galactosaminyl transferase 2) gene was considered as the potential gene for a FecL (mutation), which regulates the ovine ovulation rate. Three specific mutation sites linked with the FecL mutation have not been previously found in 11 sheep breeds. However, two mutations of g.36946470C > T and g.36933082C > T in the exon of B4GALNT2 were found to have had a significant effect on the litter size in the first parity for Small Tail Han (STH) Sheep (p < 0.05). B4GALNT2, which is mainly expressed in ovine ovary, also plays an important role in sheep reproduction. Furthermore, we discovered two transcription start sites (TSS) of B4GALNT2 in its 5′-flanking region in ovine granule cells in vitro.A new fecundity gene named the FecL (mutation), which regulates the ovulation rate, was discovered in French Lacaune sheep. The B4GALNT2 (beta-1, 4-N-acetyl-galactosaminyl transferase 2) gene was considered as the potential FecL mutation gene. This study explores whether the effect of the FecL mutation exists in other sheep breeds, and the features of the B4GALNT2 gene in terms of the molecular structure and its expression profile. Using Sanger sequencing, we found that high and low fecundity breeds from among 11 measured sheep breeds all had no variation in the three specific mutation sites, which were linked with the FecL mutation. However, two mutations of g.36946470C > T and g.36933082C > T in the exon of B4GALNT2 had a significant effect on litter size in the first parity for Small Tail Han (STH) Sheep (p < 0.05). Two transcription start sites (TSS) of B4GALNT2 in its 5′-flanking region were discovered in ovine granule cells in vitro, through the RACE (Rapid amplification of cDNA ends) method. Except for in the kidney and oviduct, no significant difference in expression levels had been found between STH sheep and Tan sheep breeds. The B4GALNT2 gene, as a candidate for FecL, may have a relationship with the differences in litter size in STH sheep. B4GALNT2 is mainly expressed in the ovine ovary, which also suggests that B4GALNT2 plays an important role in sheep reproduction.

Highlights

On account of annual mutton production being determined by annual sheep slaughter rates and individual average meat yield, high levels of ewe reproduction are important to superior carcass traits in meat sheep production
The most efficient of the three Fec genes, Bone Morphogenetic Protein-15 (BMP15) [6,7,8,9,10], Growth and Differentiation Factor-9 (GDF9) [10,11,12,13], and Bone Morphogenetic Protein receptor type-1B (BMPR1B) have all belonged to the Bone Morphogenetic Protein (BMP) system [5]
Based on previous data from the whole-genome sequencing (WGS) performed by our research team, seven SNPs of the B4GALNT2 gene were detected in 99 experimental sheep [26,27]; we explored the frequency of the seven SNPs in Small Tail Han (STH) sheep and studied their relationship with litter size

Summary

Introduction

On account of annual mutton production being determined by annual sheep slaughter rates and individual average meat yield, high levels of ewe reproduction are important to superior carcass traits in meat sheep production. Litter size and the ovulation rate (OR), involved in reproduction traits, could be regulated by the action of single genes with major effects, called fecundity (Fec) genes [3,4]. Fec genes that affect ovine litter size and OR [5]. A newly founded FecL gene named beta-1, 4-N-acetyl-galactosaminyl transferase 2 (B4GALNT2), encoding for a glycosylation enzyme, which was not related to the BMP family, recently attracted the attention of researchers [17]

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