Seasonal transcriptome profile analysis in mammary glands of Sewa sheep: a lactation perspective

The Sewa sheep has an important economic value. This study selected mammary gland tissues from Sewa sheep during summer (S) and autumn (A) for transcriptome sequencing to explore the molecular regulatory mechanisms affecting lactation performance. In this experiment, 3566 differentially expressed genes (DEGs) were identified, of which 1837 were up-regulated, and 1729 were down-regulated. DEGs were implicated in the 20 most highly enriched pathways, according to analyses using the Kyoto Encyclopedia of Genes and Genomes and Gene Ontology, such as cell adhesion molecules and Rap1 signalling pathways, which are involved in mammary gland development and milk fat production. Using RT-qPCR, we analysed the expression levels of eight genes across two distinct lactation periods. Our results indicated that butyrophilin subfamily 1 member A (BTN1A1), fatty acid binding protein 3 (FABP3), perilipin 2 (PLIN2) and stearoyl-coA desaturase (SCD) were downregulated. Conversely, stearoyl-coA desaturase 5 (SCD5), cluster of differentiation 52 (CD52), perilipin 1 (PLIN1) and potassium inwardly-rectifying channel, subfamily j, member 3 (KCNJ3) exhibited upregulated expression. These genes are primarily related to protein and fat metabolism, synthesis and milk fat formation, indicating the performance differences in mammary glands during various lactation periods may be due to the differential expression of related genes. These findings provide foundational data for mining candidate genes related to sheep lactation regulation and mammary gland development and provide insights into the mechanism of lactation regulation in sheep.