Open Access Research article

A SNP in intron 8 of CD46 causes a novel transcript associated with mastitis in Holsteins

Xiuge Wang1, Jifeng Zhong1, Yundong Gao1, Zhihua Ju1 and Jinming Huang12*

Author Affiliations

1 Dairy Cattle Research Center, Shandong Academy of Agricultural Sciences, No.159 North of Industry Road, Jinan, Shandong 250131, China

2 Division of Animal Sciences, University of Missouri, Columbia, MO 65211, USA

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BMC Genomics 2014, 15:630  doi:10.1186/1471-2164-15-630

Published: 28 July 2014

Abstract

Background

The membrane protein CD46, a ubiquitous cell surface pathogen receptor, can bind Streptococcus to trigger cell autophagy, which is a critical step in the control of infection.

Results

In this study, we found a new splice variant designated CD46 transcript variant (CD46-TV). The splice variant is characterized by the retention of a 48 bp sequence from intron 8 of the bovine CD46 gene, which encodes a putative protein enlarged by 16 amino acids. CD46-TV mRNA was found to be over expressed in mastitis-infected mammary gland tissues relative to healthy tissues. A single nucleotide polymorphism (c. 1033ā€‰+ā€‰2184 Cā€‰>ā€‰T) in the exonic splicing enhancer (ESE) motif region was shown to result in the CD46-TV aberrant splice variant through constructing alternative alleles using the pSPL3 exon capturing vector and transfecting these into 293 T cells. Allelic frequency in 56,682 individuals belonging to 112 Bos taurus, Bos indicus, Bos javanicus, Bos grunniens and Bos mutus, etc. suggests that the C allele (80.09%) is the ancestral allele. Association analysis found that the mean genomic estimated breeding values (gEBV) for milk somatic cell score and the occurrence of clinical mastitis, as well as the milk somatic cell score of Chinese Holsteins with the CT genotype was lower than those of individuals with either the CC or TT genotypes. The mean gEBV for udder health synthesis for the TT genotype was greater than those for the CC or CT genotypes.

Conclusions

Our findings suggest that the CD46 gene likely plays a critical role in the risk of mastitis caused by Streptococcus in dairy cows via an alternative splicing mechanism caused by a functional mutation in intron 8. Our data also underline the importance of variation within ESEs in regulating transcript processing.

Keywords:
CD46; Alternative splicing; Functional SNP; Cattle; Mini-gene system