The livestock industry plays an essential role in economic development and food security of a country. Around the globe, small ruminants are used to provide meat, milk and animal-by products (wool ...

The melanocortin 4 receptor (MC4R) gene is expressed in the appetite-regulating areas of the brain and is engaged in the leptin signaling pathway. Although previous studies have identified variants in the coding region of the sheep MC4R gene showing significant associations with birth weight, weaning weight, and backfat thickness, no such associations have been reported for the promoter region. Besides, the essential promoter region of the sheep MC4R has not been delineated. In this study, to better understand the transcriptional regulation of MC4R and to elucidate the association between regulatory variants and haplotypes with body measurement traits in sheep, we cloned and characterized the MC4R promoter. We found that the minimal promoter of the gene is located within the region −1207/−880 bp upstream of the first exon. Real-time quantitative PCR (RT-qPCR) data revealed the mRNA expression of the MC4R gene had a significant difference between sex and age. In the association analysis, eight single nucleotide polymorphisms (SNPs) had a significant association with one or more traits (p < 0.05); of these, two SNPs were novel. Notably, individuals with haplotype H1H2 (CT-GA-GT-GA-GT-GA-GA-CG) were heavier in body weight than other haplotypes. Altogether, variations in the MC4R gene promoter, most notably haplotype H1H2, may greatly benefit marker-assisted selection in sheep.

Detecting signatures of selection can provide a new insight into the mechanism of contemporary breeding and artificial selection and further reveal the causal genes associated to the phenotypic variation. However, the signatures of selection on genes entailing for profitable traits between Chinese commercial and indigenous goats have been poorly interpreted. We noticed footprints of positive selection at MC1R gene containing SNPs genotyped in five Chinese native goat breeds. An experimental distribution of F_ST was built based on approximations of F_ST for each SNP across five breeds. We identified selection using the high F_ST outlier method and found that MC1R candidate gene show evidence of positive selection. Furthermore, adaptive selection pressure on specific codons was determined using different codon based on maximum‐likelihood methods; signature of positive selection in mammalian MC1R was explored in individual codons. Evolutionary analyses were inferred under maximum likelihood models, the HyPhy package implemented in the DATAMONKEY Web Server. The results of codon selection displayed positive diversifying selection at the sites were mainly involved in development of genetic variations in coat color in various mammalian species. Positive diversifying selection inferred with recent evolutionary changes in domesticated goat MC1R provides new insights that the gene evolution may have been modulated by domestication events in goats.

Background: The microscopic process of postnatal testicular development in early-puberty animals is poorly understood. Therefore, in this study, 21 male Yiling goats with average ages of 0, 30, 60, 90, 120, 150 and 180 days old (each age group comprised three goats) were used to study the changes in organs, tissues and transcriptomes during postnatal testicle development to obtain a broad and deep insight into the dynamic process of testicular transition from growth to spermatogenesis in early-puberty animals.Results: The inflection point of testicular weight was at 119 days postpartum (dpp), and the testicular weight increased rapidly from 119 dpp to 150 dpp. Spermatozoa were observed in the testis at 90 dpp by using haematoxylin–eosin staining. We found from the transcriptome analysis of testes that the testicular development of Yiling goat from birth to 180 dpp experienced three stages, namely, growth, transition and spermatogenesis stages. The goats in the testicular growth stage (0–60 dpp) showed a high expression of growth-related genes in neurogenesis, angiogenesis and cell junction, and a low expression of spermatogenesis-related genes. The goats aged 60–120 dpp were in the transitional stage which had a gradually decreased growth-related gene transcription levels and increased spermatogenesis-related gene transcription levels. The goats aged 120–180 dpp were in the spermatogenesis stage. At this stage, highly expressed spermatogenesis-related genes, downregulated testicular growth- and immune-related genes and a shift in the focus of testicular development into spermatogenesis were observed. Additionally, we found several novel hub genes,which may play key roles in spermatogenesis, androgen synthesis and secretion, angiogenesis, cell junction and neurogenesis. Moreover, the results of this study were compared with previous studies on goat or other species, and some gene expression patterns shared in early-puberty mammals were discovered.Conclusions: The postnatal development of the testis undergoes a process of transition from organ growth to spermatogenesis. During this process, spermatogenesis-related genes are upregulated, whereas neurogenesis-, angiogenesis-, cell junction-, muscle- and immune-related genes are downregulated. In conclusion, the multipathway synergy promotes testicular transition from growth to spermatogenesis in early-puberty goats and may be a common rule shared by mammals.