Solexa Sequencing of Novel and Differentially Expressed MicroRNAs in Testicular and Ovarian Tissues in Holstein Cattle

Abstract

The posttranscriptional gene regulation mediated by microRNA plays an important role in the development and function of male and female reproductive organs and germ cells in mammals, including cattle. In the present study, we identified novel and differentially expressed miRNAs in the testis and ovary in Holstein cattle by combining the Solexa sequencing with bioinformatics. In total 100 and 104 novel pre-miRNAs were identified in testicular and ovarian tissues, encoding 122 and 136 mature miRNAs, respectively. Of these, 6 miRNAs appear to be bovine-specific. A total of 246 known miRNAs were co-expressed in the testicular and ovarian tissues. Of the known miRNAs, twenty-one testis-specific and nine ovary-specific (1-23 reads) were found. Approximately 30.5% of the known bovine miRNAs in this study were found to have >2-fold differential expression within the two respective reproductive organ systems. The putative miRNA target genes of miRNAs were involved in pathways associated with reproductive physiology. Both known and novel tissue-specific miRNAs are expressed by Real-time quantitative PCR analysis in dairy cattle. This study expands the number of miRNAs known to be expressed in cattle. The patterns of miRNAs expression differed significantly between the bovine testicular and ovarian tissues, which provide important information on sex differences in miRNA expression. Diverse miRNAs may play an important regulatory role in the development of the reproductive organs in Holstein cattle.

Identification of miRNAs associated with the follicular–luteal transition in the ruminant ovary

“…Other studies in this area only reported small-RNA sequencing of whole ovaries, providing little or no information on the potential functional relevance of the identified miRNAs (Ro et al 2007, Mishima et al 2008, Hossain et al 2009, Huang et al 2011. This study compared expression profiles in defined tissue samples encompassing all stages of the physiological follicular-luteal transition.…”

Involvement of miRNAs in ovarian follicular and luteal development

“…In a study using porcine tissues, as many as 673 different miRNA sequences were identified by deep sequencing of whole ovaries , although not all may be bona fide miRNAs (Kozomara & Griffiths-Jones 2011). Ovarian-expressed miRNAs can be mapped throughout the genome; however, chromosomes X and 2 reportedly account for a relatively high number of ovarian miRNAs in several species (Ahn et al 2010, Huang et al 2011. Although ovarian tissues used for miRNA sequencing so far include a range of developmental stages (fetal, pre-pubertal or adult) in different species, in all studies as few as ten miRNAs accounted for more than half of all ovarian miRNA sequences ( Table 1).…”

“…Most of those studies involved analyses on whole ovaries rather than on specific ovarian tissue components, an approach that, although very useful for comprehensive identification of miRNA sequences, provides very limited insight into their functional relevance. miRNAs constitute the most abundant class of small RNAs in the ovary (Ro et al 2007, Mishima et al 2008, Ahn et al 2010, Huang et al 2011. In a study using porcine tissues, as many as 673 different miRNA sequences were identified by deep sequencing of whole ovaries , although not all may be bona fide miRNAs (Kozomara & Griffiths-Jones 2011).…”

“…Small RNA populations have been identified by cloningbased or next-generation sequencing of normal ovarian tissues from human (Landgraf et al 2007), mice (Ro et al 2007, Mishima et al 2008, Ahn et al 2010, pigs , cattle (Hossain et al 2009, Tripurani et al 2010, Huang et al 2011, Miles et al 2012 and sheep (McBride et al 2012). Most of those studies involved analyses on whole ovaries rather than on specific ovarian tissue components, an approach that, although very useful for comprehensive identification of miRNA sequences, provides very limited insight into their functional relevance.…”

The microRNAs important for ovarian and early embryonic development in cattle

“…The development of germ cells is driven by the molecular and cellular changes inside the fetal ovary, which is a prerequisite to the production of mature oocytes capable of fertilization. To identify and study the involvement of miRNAs in germ cell and ovarian development, bovine fetal and adult ovary miRNA libraries were constructed, and over 100 miRNAs were found (22)(23)(24). In the bovine fetal ovary, miR-99a and miR-125b are the most abundant miRNAs, while in the adult ovary, the let-7 family miRNAs have the highest expression, which is considered to be required for timing of cell fate determination.…”