Comparative transcriptome profiling of dairy goat microRNAs from dry period and peak lactation mammary gland tissues

Abstract

Background: MicroRNAs (miRNAs) are small noncoding RNA molecules that serve as important post-transcriptional gene expression regulators by targeting messenger RNAs for post-transcriptional endonucleolytic cleavage or translational inhibition. miRNAs play important roles in many biological processes. Extensive high-throughput sequencing studies of miRNAs have been performed in several animal models. However, little is known about the diversity of these regulatory RNAs in goat (Capra hircus), which is one of the most important agricultural animals and the oldest domesticated species raised worldwide. Goats have long been used for their milk, meat, hair (including cashmere), and skins throughout much of the world.

Results: In this study, two small RNA libraries were constructed based on dry period and peak lactation dairy goat mammary gland tissues and sequenced using the Illumina-Solexa high-throughput sequencing technology. A total of 346 conserved and 95 novel miRNAs were identified in the dairy goat. miRNAs expression was confirmed by qRT-PCR in nine tissues and in the mammary gland during different stages of lactation. In addition, several candidate miRNAs that may be involved in mammary gland development and lactation were found by comparing the miRNA expression profiles in different tissues and developmental stages of the mammary gland.

Conclusions: This study reveals the first miRNAs profile related to the biology of the mammary gland in the dairy goat. The characterization of these miRNAs could contribute to a better understanding of the molecular mechanisms of lactation physiology and mammary gland development in the dairy goat.

Figure 1. The size distribution of the small RNAs found in the mammary gland during the dry period and peak lactation.

Figure 2. Prediction of the fold-back structure of 10 caprine miRNA precursors.

The precursor sequences were obtained by amplifying the corresponding miRNAs gene from goat genomic DNA. The mature miRNA sequences in the precursors are indicated in red.

Figure 3. qRT-PCR validation and expression analysis of conserved miRNAs in the dairy goat.

Error bars represent one standard deviation of three different biological replicates.