No abstract

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.

RXRG (Retinoic X receptor-gamma) gene was originally associated with fetal development and reproduction in human beings and animals, which was used to detect genetic variation that was associated with growth, reproduction, metabolism trait selection and breeding. The aim of this study was to detect RXRG gene mutation of the exon 2 and its association with twinning trait in 313 sheep and calculate litter size, genotype frequency in Chinese Merino, Hu and Kazak sheep. Polymorphism of exon 1, exon 2, exon 10 of RXRG gene in the study were analyzed by PCR-SSCP, which showed that three genotypes of P2 fragment were significantly associated with twinning traits in the analyzed population (P=0.031). Analysis of four groups of sheep showed that there was a predominate gene (B-allele) that have higher twinning rates in these individuals, which indicated that the genotypes can be chosen for twinning according to predominate genotype. In conclusion, our results strongly suggest that polymorphisms of the RXRG gene could be a new choice for sheep breeding and genetics through marker-assisted selection (MAS). Keywords: Sheep, Retinoic X receptor-gamma gene, Twinning trait, PCR-SSCP Koyun RXRG Geninde SNP İdentifikasyonu ve İkizlik İle İlişkisiÖzet RXRG (Retinoik X reseptör-gama) geni ilk olarak hayvan ve insanlarda fetal gelişim ve üreme ile ilişkilendirildi ve büyüme, üreme, metabolizma özellik seleksiyonu ve üreme ile ilgili genetik varyasyonu belirlemek için kullanıldı. Bu çalışmanın amacı, ekzon 2 RXRG gen mutasyonunu ve 313 koyunda ikizlik ile ilişkisini belirleyerek Çin Merinos, Hu ve Kazak koyunlarında yavru sayısı ve genotip frekansını hesaplamaktır. Bu çalışmada RXRG geni exon 1, exon 2 ve exon 10 polimorfizmleri PCR-SSCP ile analiz edildi ve incelenen popülasyon içerisinde P2 parçacığının üç genotipinin anlamlı derecede ikizlik ile ilişkili olduğu belirlendi (P=0.031). Dört grup koyunun analizi sonucunda bir baskın genin (B-allel) bu bireylerde yüksek ikizlik oranına sahip olduğunu ve bu genotipin ikizlik için seçilebileceğini gösterdi. Sonuç olarak, elde ettiğimiz sonuçlar RXRG gen polimorfizminin Marker ilişkili seleksiyon (MAS) yoluyla koyun üretiminde ve genetiğinde kullanılabileceğini önermektedir.