Artificial long days and daily contact with bucks induce ovarian but not oestrous activity during the non-breeding season in Mediterranean goat females

Comparative Analysis and Identification of Differentially Expressed microRNAs in the Hypothalamus of Kazakh Sheep Exposed to Different Photoperiod Conditions

MicroRNAs (miRNA) plays an important role in several mammalian biological regulatory processes by post-transcriptionally regulating gene expression. However, there is little information on the miRNAs involved in the photoperiodism pathway that controls seasonal activity. To enhance our knowledge on the effect of different photoperiod conditions on miRNA, we divided Kazakh sheep into two groups: one exposed to a long photoperiod (LP, 16L:8D) and another with exposed to a short photoperiod (SP, 8L:16D) under supplemental feeding conditions. Further we compared the related miRNAs and target genes between the two groups. Fifteen differentially expressed miRNAs were identified, which were associated with 310 regulatory pathways covering photoperiodism, reproductive hormones, and nutrition. The miR-136-GNAQ pair was selected and validated as a differentially expressed, and a dual-luciferase reporter assay showed that the negative feedback loop existed between them. Examination of the expression profile revealed that the GNAQ expression was low in the estrous females both under LP and SP conditions, but high expression of GNAQ was observed in the anestrous females under LP conditions. Moreover, functional analysis revealed that KISS1 and GnRH expression was upregulated when GNAQ expression was downregulated in the hypothalamic cells, whereas DIO2 and TSHB expression was downregulated. Thus, miR-136-GNAQ might act as a switch in the regulation of seasonal estrus under different photoperiod conditions. These findings further enrich our understanding of the relationship between miRNAs and seasonal regulation of reproductive activity. Furthermore, our study provides novel insights into the miRNA-mediated regulatory mechanisms for overcoming photoinhibition in the seasonally breeding mammals, such as Kazakh sheep.

Nutritional status affects the microRNA profile of the hypothalamus of female sheep

Recent studies on the seasonal regulation of the oestrous cycle in sheep have focussed mainly on the responses to photoperiod. However, the brain systems that control reproductive activity also respond to nutritional inputs, although the molecular mechanisms involved are not completely understood. One possibility is that small, non-coding RNAs, such as micro-RNAs (miRNAs), have significant influence. In the present study, the amounts and characteristics of miRNAs in hypothalamus from oestrous and anestrous ewes, fed low- or high-nutrient diets, were compared using Illumina HiSeq sequencing technology. In total, 398 miRNAs, including 261 novel miRNAs, were identified in ewes with an enhanced nutritional status (HEN), whereas 384 miRNAs, including 247 novel miRNAs, were identified in the ewes with a lesser nutritional status (HAN). There were eight conserved and 140 novel miRNAs expressed differentially between the two libraries. Based on quantitative real-time polymerase chain reaction, six miRNAs were assessed to verify the accuracy of the library database. Moreover, the correlation between the miRNA target and several upstream and downstream genes in the oestrus-related pathways were also verified in hypothalamus nerve cells. According to the results, nutritional status plays an important role in oestrous regulation in sheep, and the hypothalamic processes and pathways induced by nutritional signals (folic acid and tyrosine) are different from those induced by photoperiodic regulation of oestrus. We have expanded the repertoire of sheep miRNAs that could contribute to the molecular mechanisms that regulate the initiation of oestrous cycles in anestrous ewes in response to the influence of nutritional status.

Systematic review and meta-analysis of the efficacy of reproductive management practices used to induce resumption of ovarian cyclical activity in anestrous does

Reproductive management practices that use hormones, sociosexual biostimulation, nutritional management, or abiotic factors are used to induce the resumption of reproduction in anestrous does. However, their overall efficacy remains uncertain; therefore, the identification of evidence-based management recommendations to manipulate anestrous in goats is important. Electronic databases were searched to retrieve reports on studies using interventions based on hormonal, sociosexual, nutritional, and abiotic factors. Only experimental studies in which a group of anestrous does was treated and compared against an untreated group were included. Estrus, ovulation, and pregnancy were primary outcomes, whereas the onset of estrus after treatment, the ovulation rate, and the number of anovulatory days were secondary outcomes. Odds ratio (OR) and mean differences were used to synthesize pooled data, and random effects models were used to calculate them. Seventy studies involving 3974 goats met the inclusion criteria. Unclear risk of bias for random sequence generation and allocation concealment predominated across studies. Pooled data for hormonal, sociosexual, and abiotic interventions showed a significant, though variable, increase in estrus (OR range 7.15-144.80), ovulation (OR range 6.08-56.95), and pregnancy (OR range 3.94-30.8). Hormonal treatments significantly reduced the onset of estrus, whereas abiotic interventions failed to reduce the number of anovulatory days. Secondary outcomes were not assessed in trials using sociosexual approaches. Finally, except for pregnancy, no significant efficacy was observed for studies using nutritional management. In conclusion, reproductive management practices using sociosexual approaches showed the highest efficacy for restoring reproductive activity in anestrous does.

Identification and analysis of microRNAs-mRNAs pairs associated with nutritional status in seasonal sheep

Given the important role of nutritional status for reproductive performance, we aimed to explore the potential microRNA (miRNA)-mRNA pairs and their regulatory roles associated with nutritional status in seasonal reproducing sheep. Individual ewes were treated with and without 0.3 kg/day concentrates, and the body condition score, estrus rate, and related miRNAs and target genes were compared. A total of 261 differentially expressed miRNAs were identified, including 148 hypothalamus-expressed miRNAs and 113 ovary-expressed miRNAs, and 349 target genes were predicted to be associated with nutritional status and seasonal reproduction in sheep. Ultimately, the miR-200b-GNAQ pair was screened and validated as differentially expressed, and a dual luciferase reporter assay showed that miR-200b could bind to the 3'-untranslated region of GNAQ to mediate the hypothalamic-pituitary-ovarian axis. Thus, miR-200b and its target gene GNAQ likely represent an important negative feedback loop, providing a link between nutritional status and seasonal reproduction in sheep toward enhancing reproductive performance and productivity.