Screening and semi-quantitative RT-PCR analysis of differentially expressed genes in mammary glands between goat and cow

摘要

Although the effect of lactation stage is similar, milk yield and composition (fat and protein contents) differ markedly between goats and cows, and goat milk also has a distinctive flavor. In the present study, because goats and cows exhibit very high homology in their gene coding sequences, the mammary glands in late lactation of 3 Xinong Saanen goats and 3 Holstein cows were chosen to isolate differentially expressed genes in the mammary gland of goat, and a forward suppression subtractive hybridization (SSH) cDNA library was constructed. SSH was performed with cDNA from late lactation mammary glands of cows as the “driver” and cDNA from late lactation mammary glands of goats as the "tester." A total of 50 clones in the SSH library were sequenced. Blastn results revealed that 40 cDNAs had significant sequence homologies with known sequences in the NCBI database, the identified cDNAs only including 5 milk protein genes (αs2, β and К-casein, α-lactalbumin and β-lactoglobulin), the other 10 sequences represent 6 new EST sequences and have been registered in GenBank, the accession nos. are EG588067, EG588068, EG588069, EG588070, EG588071 and EG588072. These five milk protein genes and αs1-casein gene were chosen to examine their expressions through semi-quantitative RT-PCR analysis in mammary gland of goats and cows. The expressions of these genes were all higher in goat mammary gland except αs1-casein. There were significant differences in β casein in the mammary glands between goat and cow. The mRNA abundance of К-casein was very high in mammary glands of the goat and cow, but in milk casein micelles only included 10% К-casein. It is suggested that К-casein had different secretion and transportation mechanisms from other caseins, though they shared similar regulation mechanism[ Acta Zoologica Sinica 53(4): 710–716, 2007].