Linkage disequilibrium and haplotype distribution of the bovine LHX4 gene in relation to growth.

LIM homeobox transcription factor 4 (LHX4) is a LIM homeodomain transcription factor involved in pituitary gland and nervous system development. The aim of this study was to examine the association of the LHX4 polymorphisms with growth traits in beef cattle breed. A total of 7 single nucleotide polymorphyisms (SNPs) have been identified in the coding region and noncoding region of the bovine LHX4 by sequencing pooled DNA samples (Pool-Seq) and PCR-single strand conformation polymorphism (PCR-SSCP) methods. The linkage disequilibrium was assessed in 871 individuals representing four main cattle breeds from China. The SNPs 2-5 and 7-8 were found to be in complete linkage disequilibrium, respectively. The result of haplotype analysis of 13 SNPs showed that 31 haplotypes were found in four Chinese cattle breeds, and 20 genotypes were only found in Nanyang cattle. The statistical analyses indicated that the SNP1-5, and 6 are associated with the body weight at 18, and 6 months of age in Nanyang cattle population (P<0.05), but no significant associations between their twenty combined genotypes. Our results provide evidence that some polymorphisms in LHX4 are associated with growth traits at certain ages, and may be used as candidates for marker-assisted selection and management in cattle.

The effect of haplotype variation in the bovine PAX6 gene.

The transcription factor paired box 6 gene (PAX6) plays a key role during the early development of various organs. In this study, three single nucleotide polymorphisms (SNPs) have been identified in the introns 2, 8 and 11 of the bovine PAX6 gene. 8 haplotypes and 13 diplotypes were revealed and the linkage disequilibrium (LD) was assessed in 817 cows representing four main cattle breeds from China (Nanyang, NY; Qinchuan, QC; Jiaxian, JX; Chinese Holstein, CH). The LD analysis revealed that the additional three SNPs were not in strong LD, the wild haplotype (Hap 1: CTT) and mutant haplotype (Hap 8: TCC) have a frequency of 9.36, 35.61, 18.32, 57.15 % and 15.60, 14.19, 0.83, 0 % in the four cattle populations. The statistical analyses indicated that the SNP2 and 3 are associated with the body weight at birth, 6 and 12 months in NY and JX cattle population (P < 0.01 or P < 0.05); and significant association was detected between 19 (NY) or 13 (JX) diplotype (combined genotypes) and body weight at different ages (birth, 6 and 12 months). Our results provide evidence that some polymorphisms in PAX6 are associated with growth traits at some ages, and may be used as candidates for marker-assisted selection in beef cattle breeding program.