Differential expression of ruminant ZNF496 variants: Association with quantitative trait locus affecting bovine milk concentration and fertility.

A single nucleotide polymorphism in the intergenic region upstream of the ZNF496 gene on Bos taurus chromosome 7 displayed significant population-wide linkage disequilibrium with milk protein percentage in the Israeli Holstein population. The frequency of the allele associated with increased protein concentration was 10%. This single nucleotide polymorphism was located in the promoter region from which a 10-exon transcript of the bovine and the ovine ZNF496 genes are transcribed. The gene architecture was similar to the mouse ortholog Zkscan17. A 5-exon murine antisense transcript was complementary to the 5' untranslated Zkscan17 region that included a sequence domain conserved between mouse and ruminants, suggesting a regulatory function. In the bovine ZNF496 chromosomal region, segregation of a quantitative trait locus (QTL) for milk protein percentage was confirmed in a daughter design sire family. Concordance was not obtained between QTL status of bulls and any of the polymorphisms in the functional elements of ZNF496. This excludes these variations as the causative polymorphism under the assumption of no epigenetic effect for this locus. However, ZNF496 variants were differentially expressed in bovine ovaries, and only the paternal variant was expressed in liver and kidney in a sheep family with polymorphic ZNF496 sequence. Thus, the search for the mutation underlying the minor QTL allele, which is a top economically favorable allele in Israeli Holstein cattle, may be complicated by the presence of an imprinting center in this QTL confidence interval.