Expression profiles of the MXD3 gene and association of sequence variants with growth traits in Xianan and Qinchuan cattle.

Max dimerization protein 3 (MXD3) belongs to the MYC superfamily of basic helix-loop-helix leucine zipper transcription factors, and MXD3-MAX heterodimers can bind to promoters of target genes to modulate their expression. The aim of this study was to determine theMXD3mRNA expression levels in various cattle tissues comprising heart, liver, spleen, lung, kidney,Longissimus dorsimuscle and subcutaneous fat in Chinese Qinchuan and Xianan cattle breeds. The RT-qPCR data showed that theMXD3gene was variably expressed between all tissues and at levels that were significantly different between two breeds (p < .05). We used the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to investigate the possible association between single-nucleotide polymorphisms (SNP) within theMXD3gene and five different growth traits in cattle. We found two intronic SNPs (g.2694 C>T and g.3801 T>C) and one SNP in 3 ' untranslated region (3 ' UTR) (g.6263 G>A) ofMXD3gene. Association analysis revealed strong associations between pairwise and triple SNP combinations and the growth traits. Based on these results, we suggest thatMXD3polymorphisms could be useful as molecular markers in the Chinese beef cattle breeding program.