Molecular cloning, sequence analysis and tissue expression of bovine imprinted ASCL2 gene
Achaete-scute like-2 (ASCL2) gene is a maternally expressed gene that encodes a lineage-specific transcription factor that is essential for neurectoderm and trophectoderm development and is implicated in pre-natal and post-natal development in mammals. Using comparative genomics, various in silico sequence analyses were performed to characterize the putative imprinted ASCL2 gene. Additionally, tissue expression analysis between Angus, White Fulani, and N’Dama cattle breeds was conducted, as well as a molecular cloning of the gene transcript from bovine placenta. Four site-specific motifs were identified in the basic helix-loop-helix (bHLH) domain that are highly conserved in cattle, humans and mice. Pairwise comparisons of the coding sequence of cattle, human and mice revealed a dN/dS rate ratio that was significantly less than 1 (Z test). Two synonymous single nucleotide polymorphisms (SNPs) were found within 1 kb of the cloned complementary DNA (cDNA) in cattle. Bovine ASCL2 messenger RNA (mRNA) was relatively expressed in eight adult tissues with the ASCL2 gene differentially expressed in the muscle and skin tissues of the three cattle breeds. The conservation of these site-specific motifs for phosphorylation across the three species suggests a post-translational modification of the gene function and activity of the mammalian ASCL2 gene.
Keywords: Cattle, imprinting, motifs, phosphorylation