Screening and functional investigation of miRNAs regulating milk fat metabolism in dairy goat mammary gland

Fat metabolism is a complicated process regulated by a series of factors. microRNAs (miRNAs) are a class of negative regulator of proteins and play crucial roles in many biological processes, including fat metabolism. Although there have been some researches indicating that miRNAs could influence the milk fat metabolism through targeting some factors, little is known about the effect of miRNAs on goat milk fat metabolism. Here we utilized an improved miRNA detection assay, S-Poly(T), to profile the expression of miRNAs in the goat mammary gland in early-lactation and dry-lactation. Overall, we found 146 miRNAs expression changed between early-lactation and dry-lactation, with 81 up-regulation and 65 down-regulation, among which the miR-27a, miR-200a and miR-200c have been reported to be involved in the milk fat metabolism process. To investigate the connection between the miRNA regulation and this physiological process in a more comprehensive way, here we profiled the differential miRNAs expression between early-lactation and dry-lactation in goat mammary gland with S-Poly(T) real method, including 267 Capra hircus primary miRNAs and 793 Bos taurus primary miRNAs from miRBase (http://www.mirbase.org/) and the new discovered miRNAs by Solexa sequencing. As Capra hircus and Bos taurus share high sequence homology with each other, some raw data or referenced data are overlapping. We have marked out the overlapping data, and details can be found in the additional materials (S1-first screening). All the miRNAs with four-fold change and p-value smaller than 0.05 were chosen as candidates.