Identification of interferon-τ isoforms expressed by the peri-implantation goat ( Capra hircus) conceptus

Abstract

Interferon-tau (IFN-τ) is the maternal recognition of pregnancy factor in pecoran ruminants. The aims of this study were to identify the various IFN-τ transcripts in the peri-implantation caprine (ca) conceptus and to compare these nucleotide sequences phylogenetically with established mRNA sequences from the goat. Conceptuses ( n=5) were collected from Boer crossbred and Angora female goats by laparotomy at days 17 and 18 of pregnancy. Total cellular RNA was extracted and RT-PCR was performed by standard procedures using a DNA polymerase with proofreading activity and gene-specific primers complimentary to non-coding regions of the published caIFN-τ sequence. Nine distinct nucleotide sequences were isolated that encode five distinct caIFN-τ proteins. These caIFN-τ have greater sequence homology with ovine IFN-τ (94–96% nucleotide identity; 90–93% amino acid identity) than with bovine IFN-τ (<92% nucleotide identity; <85% amino acid identity). The novel caIFN-τ isoforms contained pronounced nucleotide and amino acid sequence identity with one another (97–99% nucleotide identity; 94–99% amino acid identity) but only moderate sequence identity with the previously identified caIFN-τ (94–96% nucleotide identity; 87–90% amino acid identity). In conclusion, multiple caIFN-τ mRNA species are expressed during peri-implantation conceptus development and distinct clusters of caIFN-τ genes appear to have evolved in this species.