Construction and Characterization of a Goat Mammary Gland cDNA Library

A lactating goat mammary gland cDNA library was constructed by using a modified commercially available cDNA library construction kit protocol. The resulting clones were sequenced and functionally analyzed through cross-species genomic comparison to assess (1) the capacity and functional quality of the constructed library for subsequent research and (2) the efficiency of the procedural modifications. The study resulted in the construction of a high-quality mammary gland cDNA library, which was characterized by (1) the total recombinants number of 1.4 × 10⁷ colony-forming units (cfus) that was at least 10 times greater than the number expected from the application of the standard kit protocol, (2) the recombinants rate of 96%, and (3) the average insert size of 1,082 bp. BLAST analysis of sequenced clones against GenBank databases determined 55.7% of clone redundancy, 22 known function gene clusters, and 29 novel gene clusters. The analysis of the primary gene expression profile showed that 59% of the tested clones were genes that coded for milk proteins while 16% of the clones coded for ribosomal, metabolism, immune response, and translation proteins. The remaining 25% of the tested clones were described as novel genes. Cross-species comparison showed that 77% of characterized gene clusters were successfully identified by using resources from other ruminants and unrelated species. This outcome is in consonance with the common belief that the genomic resources that have been generated across species are potentially powerful tools that could be used for enhancing the molecular understanding of less genomically studied species, such as goat.