MicroRNAs are small, noncoding RNA molecules that regulate gene expression at the post-transcriptional level and play an important role in various biological processes. Although most microRNAs expression profiles studies have been performed in humans or rodents, relatively limited knowledge also exists in other mammalian species. The identification of the full repertoire of microRNAs expressed in the lactating mammary gland of Capra hircus would significantly increase our understanding of the physiology of lactating mammary glands. In this study, two libraries were constructed using the lactating mammary gland tissues of Laoshan dairy goats (Capra hircus) during peak and late lactation. Solexa high-throughput sequencing technique and bioinformatics were used to determine the abundance and differential expression of the microRNAs between peak and late lactation. As a result, 19,044,002 and 7,385,833 clean reads were obtained, respectively, and 1,113 conserved known microRNAs and 31 potential novel microRNA candidates were identified. A total of 697 conserved microRNAs were significantly differentially expressed with a P-value<0.01, 272 microRNAs were up-regulated and 425 microRNAs were down-regulated during peak lactation. The results were validated using real-time quantitative RT-PCR. 762,557 annotated mRNA transcripts were predicted as putative target gene candidates. The GO annotation and KEGG pathway analysis suggested that differentially expressed microRNAs were involved in mammary gland physiology, including signal transduction, and cell-cell and cell-extracellular communications. This study provided the first global of the microRNA in Capra hircus and expanded the repertoire of microRNAs. Our results have great significance and value for the elucidation of complex regulatory networks between microRNAs and mRNAs and for the study of mammary gland physiology and lactation.

The sheep is an important domestic animal and model for many types of medically relevant research. An investigation of gene expression in ovine muscle would significantly advance our understanding of muscle growth. RNA-seq is a recently developed analytical approach for transcriptome profiling via high-throughput sequencing. Although RNA-seq has been recently applied to a wide variety of organisms, few RNA-seq studies have been conducted in livestock, particularly in sheep. In this study, two cDNA libraries were constructed from the biceps brachii of one Small-tailed Han sheep (SH) and one Dorper sheep (DP). The Illumina high-throughput sequencing technique and bioinformatics were used to determine transcript abundances and characteristics. For the SH and DP libraries, we obtained a total of 50,264,608 and 52,794,216 high quality reads, respectively. Approximately two-thirds of the reads could be mapped to the sheep genome. In addition, 40,481 and 38,851 potential coding single nucleotide polymorphisms (cSNPs) were observed, respectively, of which a total of 59,139 cSNP coordinates were different between the two samples. Up to 5,116 and 5,265 respective reference genes had undergone 13,827 and 15,684 alternative splicing events. A total of 6,989 reference genes were extended at the 5’, 3’ or both ends, and 123,678 novel transcript units were found. A total of 1,300 significantly differentially expressed genes were identified between the two libraries. These results suggest that there are many differences in the muscle transcriptomes between these two animals. This study addresses a preliminary analysis and offers a foundation for future genomic research in the sheep.

microRNAs (miRNAs) perform critical roles in various biological and metabolic processes by regulating gene expression at the post-transcriptional level. To investigate the functional roles of miRNAs in the lactating mammary gland of Capra hircus, a library was constructed from the lactating mammary glands of Laoshan dairy goats (C. hircus) during early lactation. The miRNA expression profiles were systematically screened, and miRNAs were identified and characterized using Solexa deep-sequencing technology and bioinformatics. As a result, a total of 18,031,615 clean reads were obtained representing 305,711 unique sRNAs. A total of 12,086,616 sRNAs representing 3,701 unique sRNAs matched the known Bos taurus miRNA precursors in miRBase 17.0, and 300 known miRNAs and 15 miRNA were discovered. In addition, 131 novel miRNAs sequences were also obtained, and 147,703 putative targets were predicted. GO and KEGG pathway analysis showed that the majority of targets were involved in cellular processes and metabolic pathways. The 290 known miRNAs, 14 miRNA and 38 novel miRNAs were validated by sequencing a second library that was constructed from the same tissues as the first library. Our study provided the first large-scale identification and characterization of miRNAs in the mammary gland tissue of the dairy goat. The results indicate that the regulation of miRNA-mediated gene expression occurs during early lactation in dairy goats. This study significantly enriches the C. hircus miRNA repertoire and provides a reference for the elucidation of complex miRNA-mediated regulatory networks for gene expression in the physiology and developmental progression of the lactating mammary gland.

BackgroundThroughout a long period of adaptation and selection, sheep have thrived in a diverse range of ecological environments. Mongolian sheep is the common ancestor of the Chinese short fat-tailed sheep. Migration to different ecoregions leads to changes in selection pressures and results in microevolution. Mongolian sheep and its subspecies differ in a number of important traits, especially reproductive traits. Genome-wide intraspecific variation is required to dissect the genetic basis of these traits.ResultsThis research resequenced 3 short fat-tailed sheep breeds with a 43.2-fold coverage of the sheep genome. We report more than 17 million single nucleotide polymorphisms and 2.9 million indels and identify 143 genomic regions with reduced pooled heterozygosity or increased genetic distance to each other breed that represent likely targets for selection during the migration. These regions harbor genes related to developmental processes, cellular processes, multicellular organismal processes, biological regulation, metabolic processes, reproduction, localization, growth and various components of the stress responses. Furthermore, we examined the haplotype diversity of 3 genomic regions involved in reproduction and found significant differences in TSHR and PRL gene regions among 8 sheep breeds.ConclusionsOur results provide useful genomic information for identifying genes or causal mutations associated with important economic traits in sheep and for understanding the genetic basis of adaptation to different ecological environments.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3212-2) contains supplementary material, which is available to authorized users.

In this study, we characterized differentially expressed genes (DEGs) between the muscle transcriptomes of Small-tailed Han sheep and Dorper sheep and predicted novel transcript units using high-throughput RNA sequencing technology. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that 1,300 DEGs were involved in cellular processes, metabolic pathways, and the actin cytoskeleton pathway. Importantly, we identified 34 DEGs related to muscle cell development and differentiation. Additionally, we were able to optimize the gene structure and predict the untranslated regions (UTRs) for some of the DEGs. Among the 123,678 novel predicted transcript units (TUs), 15,015 units were predicted protein sequences. The reliability of the sequencing data was verified through qRT-PCR analysis of 12 genes. These results will provide useful information for functional genetic research in the future.

In recent years, studies related to the expression profiles of miRNAs in the dairy goat mammary gland were performed, but regulatory mechanisms in the physiological environment and the dynamic homeostasis of mammary gland development and lactation are not clear. In the present study, sequencing data analysis of early and late lactation uncovered a total of 1,487 unique miRNAs, including 45 novel miRNA candidates and 1,442 known and conserved miRNAs, of which 758 miRNAs were co-expressed and 378 differentially expressed with P < 0.05. Moreover, 76 non-redundant target genes were annotated in 347 GO consortiums, with 3,143 candidate target genes grouped into 33 pathways. Additionally, 18 predicted target genes of 214 miRNAs were directly annotated in mammary gland development and used to construct regulatory networks based on GO annotation and the KEGG pathway. The expression levels of seven known miRNAs and three novel miRNAs were examined using quantitative real-time PCR. The results showed that miRNAs might play important roles in early and late lactation during dairy goat mammary gland development, which will be helpful to obtain a better understanding of the genetic control of mammary gland lactation and development.

MicroRNAs are small noncoding RNAs that can regulate gene expression, and they can be involved in the regulation of mammary gland development. The differential expression of miRNAs during mammary gland development is expected to provide insight into their roles in regulating the homeostasis of mammary gland tissues. To screen out miRNAs that should have important regulatory function in the development of mammary gland from miRNA expression profiles and to predict their function, in this study, the target genes of differentially expressed miRNAs in the lactating mammary glands of Laoshan dairy goats are predicted, and then the functions of these miRNAs are analyzed via bioinformatics. First, we screen the expression patterns of 25 miRNAs that had shown significant differences during the different lactation stages in the mammary gland. Then, these miRNAs are clustered according to their expression patterns. Computational methods were used to obtain 215 target genes for 22 of these miRNAs. Combining gene ontology annotation, Fisher's exact test, and KEGG analysis with the target prediction for these miRNAs, the regulatory functions of miRNAs belonging to different clusters are predicted.

MicroRNAs (miRNAs) play an important role in regulating mammary gland development and lactation. We previously analyzed miRNA expression profiles in Laoshan dairy goat mammary glands at the early (20 d postpartum), peak (90 d postpartum) and late lactation (210 d postpartum) stages. To further enrich and clarify the miRNA expression profiles during the lactation physiological cycle, we sequenced miRNAs in the mammary gland tissues of Laoshan dairy goats at three newly selected stages: the late lactation (240 d postpartum), dry period (300 d postpartum) and late gestation (140 d after mating) stages. We obtained 4038 miRNAs and 385 important miRNA families, including mir-10, let-7 and mir-9. We also identified 754 differentially expressed miRNAs in the mammary gland tissue at the 3 different stages and 6 groups of miRNA clusters that had unique expression patterns. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that GO terms such as mammary gland development (GO:0030879) and mammary gland morphogenesis (GO:0060443) and important signaling pathways, including the insulin signaling pathway (chx04910), hippo signaling pathway (chx04390) and estrogen signaling pathway (chx04915), were enriched. We screened miRNAs and potential target genes that may be involved in the regulation of lactation, mammary gland growth and differentiation, cell apoptosis, and substance transport and synthesis and detected the expression patterns of important genes at the three stages. These miRNAs and critical target genes may be important factors for mammary gland development and lactation regulation and potentially valuable molecular markers, which may provide a theoretical reference for further investigation of mammary gland physiology.