Melatonin improves the vitrification of sheep morulae by modulating transcriptome.

Embryo vitrification technology is widely used in livestock production, but freezing injury has been a key factor hindering the efficiency of embryo production. There is an urgent need to further analyze the molecular mechanism of embryo damage by the vitrification process. In the study, morulae were collected from Hu sheep uterine horns after superovulation and sperm transfusion. Morulae were Cryotop vitrified and warmed. Nine morulae were in the vitrified control group (frozen), and seven morulae were vitrified and warmed with 10-5 M melatonin (melatonin). Eleven non-frozen morulae were used as controls (fresh). After warming, each embryo was sequenced separately for library construction and gene expression analysis. p < 0.05 was used to differentiate differentially expressed genes (DEG). The results showed that differentiated differentially expressed genes (DEG) in vitrified morulae were mainly enriched in protein kinase activity, adhesion processes, calcium signaling pathways and Wnt, PI3K/AKT, Ras, ErbB, and MAPK signaling pathways compared to controls. Importantly, melatonin treatment upregulated the expression of key pathways that increase the resistance of morulae against vitrification induced damage. These pathways include kinase activity pathway, ErbB, and PI3K/Akt signaling pathway. It is worth mentioning that melatonin upregulates the expression of XPA, which is a key transcription factor for DNA repair. In conclusion, vitrification affected the transcriptome of in vivo-derived Hu sheep morulae, and melatonin had a protective effect on the vitrification process. For the first time, the transcriptome profiles caused by vitrification and melatonin in sheep morulae were analyzed in single embryo level. These data obtained from the single embryo level provide an important molecular mechanism for further optimizing the cryopreservation of embryos or other cells.

Investigation of SNP markers for the melatonin production trait in the Hu sheep with bulked segregant analysis.

BACKGROUND: As an important reproductive hormone, melatonin plays an important role in regulating the reproductive activities of sheep and other mammals. Hu sheep is a breed favoring for meat, with prolific traits. In order to explore the relationship between melatonin and reproductive function of Hu sheep, 7,694,759 SNPs were screened out through the whole genome sequencing analysis from high and low melatonin production Hu sheep. RESULTS: A total of 68,673 SNPs, involving in 1126 genes, were identified by ED association analysis. Correlation analysis of SNPs of AANAT/ASMT gene and MTNR1A/MTNR1B gene were carried out. The melatonin level of CG genotype 7,981,372 of AANAT, GA genotype 7,981,866 of ASMT and GG genotype 17,355,171 of MTNR1A were higher than the average melatonin level of 1.64 ng/mL. High melatonin Hu sheep appear to have better multiple reproductive performance. CONCLUSIONS: By using different methods, three SNPs which are associated with high melatonin production trait have been identified in Hu sheep. These 3 SNPs are located in melatonin synthetase AANAT/ASMT and receptor MTNR1A, respectively. Considering the positive association between melatonin production and reproductive performance in ruminants, these three SNPs can be served as the potential molecular markers for breading Hu sheep with the desirable reproductive traits.

Melatonin promotes the growth and development of lambs by increasing growth hormone and testosterone, targeting on apoptosis signaling pathway and intestinal microflora.

Melatonin is an indole-like neuroendocrine hormone. A large number of studies have shown that melatonin can improve production performance of ewes, but it is not clear in lambs. In this study, the growth and development of the 2-month-old lambs implanted with melatonin were monitored for 60 days. The results showed that the growth rate of body weight and body skew length of lambs with melatonin treatment were significantly improved compared to the controls. The similar results were also observed in red blood cell count, hematocrit, red blood cell volume distribution width, the levels of growth hormone, testosterone, immunoglobulin A, immunoglobulin M and albumin. In addition, the cross sectional area of muscle fibers and adipose cells of lambs with melatonin implantation were also significantly increased compared to the controls (P<0.05). To further explore the potential mechanisms, the muscle and adipose tissue were selected for transcriptome sequencing. KEGG enrichment results showed that melatonin regulated the expression of genes related to apoptotic signaling pathway in muscle and adipocytes. Since the intestinal microbiota are involved in the nutritional balance and animal growth, the 16SrRNA sequencing related to the intestinal microbiota was also performed. The data indicated that the structural differences of fecal microflora mainly occur in the pathways of Cardiovascular disease, Excretory system and Signaling molecules and interaction. In brief, melatonin promotes the growth and development of lambs. The potential mechanisms may be that melatonin increased the growth hormone and testosterone mediated apoptosis signaling pathway and regulated intestinal microbial flora. Our results provide valuable information for melatonin to improve the production of sheep husbandry in the future.