Previous studies have shown that BMPR1B promotes follicular development and ovarian granulosa cell proliferation, thereby affecting ovulation in mammals. In this study, the expression and polymorphism of the BMPR1B gene associated with litter size in small-tail Han (STH) sheep were determined. The expression of BMPR1B was detected in 14 tissues of STH sheep during the follicular phase as well as in the hypothalamic–pituitary–gonadal (HPG) axis of monotocous and polytocous STH sheep during the follicular and luteal phases using quantitative polymerase chain reaction (qPCR). Sequenom MassARRAY^® single nucleotide polymorphism (SNP) technology was also used to detect the polymorphism of SNPs in seven sheep breeds. Here, BMPR1B was highly expressed in hypothalamus, ovary, uterus, and oviduct tissue during the follicular phase, and BMPR1B was expressed significantly more in the hypothalamus of polytocous ewes than in monotocous ewes during both the follicular and luteal phases (P<0.05). For genotyping, we found that genotype and allele frequencies of three loci of the BMPR1B gene were extremely significantly different (P<0.01) between the monotocous and polytocous groups. Association analysis results showed that the g.29380965A>G locus had significant negative effects on the litter size of STH sheep, and the combination of g.29380965A>G and FecB (Fec – fecundity and B – Booroola; A746G) at the BMPR1B gene showed that the litter size of AG–GG, AA–GG, and GG–GG genotypes was significantly higher compared with other genotypes (P<0.05). This is the first study to find a new molecular marker affecting litter size and to systematically analyze the expression of BMPR1B in different fecundity and physiological periods of STH sheep.

This study aimed to provide insights into molecular regulation and mitochondrial functionality under hypoxia by exploring the mechanism of adaptation to hypoxia, blood indexes, tissue morphology, mRNA/miRNA regulation, mitochondrial dynamics, and functional changes in Tibetan sheep raised at different altitudes. With regard to blood indexes and myocardial morphology, the HGB, HCT, CK, CK-MB, LDH, LDH1, SOD, GPX, LDL level, and myocardial capillary density were significantly increased in the sheep at higher altitudes (p < 0.05). The RNA-seq results suggested the DEmRNAs and DEmiRNAs are mainly associated with the PI3K-Akt, Wnt, and PPAR signaling pathways and with an upregulation of oncogenes (CCKBR, GSTT1, ARID5B) and tumor suppressor factors (TPT1, EXTL1, ITPRIP) to enhance the cellular metabolism and increased ATP production. Analyzing mRNA–miRNA coregulation indicated the mitochondrial dynamics and functions to be significantly enriched. By analyzing mitochondrial dynamics, mitochondrial fusion was shown to be significantly increased and fission significantly decreased in the heart with increasing altitude (p < 0.05). There was a significant increase in the density of the mitochondria, and a significant decrease in the average area, aspect ratio, number, and width of single mitochondrial cristae with increasing altitudes (p < 0.05). There was a significant increase in the NADH, NAD+ and ATP content, NADH/NAD+ ratio, and CO activity, while there was a significant decrease in SDH and CA activity in various tissues with increasing altitudes (p < 0.05). Accordingly, changes in the blood indexes and myocardial morphology of the Tibetan sheep were found to improve the efficiency of hemoglobin-carrying oxygen and reduce oxidative stress. The high expression of oncogenes and tumor suppressor factors might facilitate cell division and energy exchange, as was evident from enhanced mitochondrial fission and OXPHOS expression; however, it reduced the fusion and TCA cycle for the further rapid production of ATP in adaptation to hypoxia stress. This systematic study has for the first time delineated the mechanism of hypoxia adaptation in the heart of Tibetan sheep, which is significant for improving the ability of the mammals to adapt to hypoxia and for studying the dynamic regulation of mitochondria during hypoxia conditions.

Glycolysis and heat shock proteins (HSPs) play an important role in hypoxia-intolerant species during hypoxia conditions. This study was conducted to evaluate the differences of glycolysis and heat shock proteins (HSPs) in Gannan yaks (Bos grunniens), with the main goal of understanding how the response to hypoxia changes with altitude. Here, the genes and enzymes of glycolysis and HSPs were detected in heart, liver, lung, kidney, and longissimus dorsi from Gannan yaks at different altitude (2500 and 3500 m) using qPCR, western blot, and enzyme kits. The results showed that the expression of HIF1A and PDK4 was increased with altitude (P<0.01) in above tissues. Significantly increased lactate dehydrogenase (LDH), adenosine triphosphate (ATP), and nicotinamide adenine dinucleotide (NADH) levels and the ratio of NADH/NAD⁺ were also observed in heart, lung, and longissimus dorsi tissues (P<0.05), as well as a decreased citric acid (CA) level (P<0.05). Furthermore, we observed significant global increases in the protein and mRNA expression levels of both the ATP-independent HSP27 and the ATP-dependent HSP60 during hypoxic conditions (P<0.01). These findings revealed that hypoxia-reprogrammed glucose metabolism promotes energy supply via up-regulated glycolysis and weakness of the tricarboxylic acid (TCA) cycle. HSPs were activated and the prioritization of cytoprotective protein chaperone functions over energy conservation in yak under hypoxic conditions. These results are useful to better understand the unique adaptability of yak, allowing them to survive in hypoxia conditions.

The myogenic differentiation of muscle satellite cells (MuSCs) is an important biological process that plays a key role in the regeneration and repair of skeletal muscles. However, the mechanisms regulating myoblast myogenesis require further investigation. In this study, we found that STEAP3 is involved in myogenic differentiation based on the Yunan black pig MuSCs model in vitro using cell transfection and other methods. Furthermore, the expression of myogenic differentiation marker genes MyoG and MyoD and the number of myotubes formed by the differentiation of cells from the si-STEAP3 treated group were significantly decreased but increased in the STEAP3 overexpression group compared to that in the control group. STEAP3 played a role in iron ion metabolism, affecting myogenic differentiation via the uptake of iron ions and enhancing IRP-IRE homeostasis. STEAP3 also activated the PI3K/AKT pathway, thus promoting myoblast differentiation of Yunan black pig MuSCs. The results of this study showed that STEAP3 overexpression increased intracellular iron ion content and activated the homeostatic IRP-IRE system to regulate intracellular iron ion metabolism.

This study investigated meat quality, nutritional characteristics, and transcriptomic regulation in Yunan (YN) black pigs and Huainan (HN) black pigs (n = 6 each). Analysis of fatty acid composition revealed that HN black pigs possessed significantly higher levels of most fatty acids compared to YN black pigs. Notably, the contents of monounsaturated fatty acid C18:1n9c and polyunsaturated fatty acid C18:2n6c in HN black pigs were 1.94-fold and 2.65-fold higher, respectively, than those in YN black pigs. The α-linolenic acid content was also significantly elevated in HN black pigs, indicating an overall higher fatty acid content. Regarding amino acid differences, HN black pigs exhibited significantly higher levels of aspartic acid, glutamic acid, histidine, as well as superior composition of total amino acids, total umami amino acids, and essential amino acids, which contribute to enhanced flavor characteristics and nutritional balance. Transcriptome analysis identified 526 differentially expressed genes in HN vs. YN. KEGG enrichment analysis showed that these genes were involved in many adipogenesis and lipid metabolism signaling pathways, such as biosynthesis of unsaturated fatty acids, fatty acid elongation, apelin signaling pathway and lysine degradation. By integrating transcriptome and protein–protein interaction (PPI) network analyses, we identified key meat quality-related genes: ELOVL6, PRKAG3, ROCK2, and MYH11. miRNA profiling identified ssc-miR-133b, ssc-miR-206, and miR-205 as key regulators of meat quality. This study provides a valuable theoretical foundation for understanding the molecular mechanisms underlying pork quality and offers insights for its future improvement.

The hypothalamus plays a vital role in reproductive processes. Previous studies have identified hypothalamic miRNAs involved in mammalian reproduction, but the miRNA profiles induced by photoperiod changes remain unclear. In this study, we investigated the effects of photoperiod on hypothalamic microRNA (miRNA) regulation by analyzing miRNA expression patterns in Sunite sheep under three different photoperiod conditions—short photoperiod (SP), short-to-long photoperiod transition (SLP), and long photoperiod (LP) —with three biological replicates per group, using miRNA-sequencing technology. A total of 57, 47, and 12 differentially expressed miRNAs (DEMs) were revealed between SP vs. LP, SP vs. SLP, and LP vs. SLP, respectively. We constructed a co-expression network of DEMs and their target genes, identified oar-miR-370-5p, oar-miR-10b, and oar-miR-3957-3p as the miRNAs with the highest numbers of predicted target mRNAs based on interaction analysis. Functional annotation analysis demonstrated that the target genes of DEMs were enriched in multiple KEGG pathways, among which the most significant pathways associated with reproduction included the GnRH signaling pathway, prolactin signaling pathway, VEGF signaling pathway, and Wnt signaling pathway. These findings elucidate the dynamic changes in hypothalamic miRNA expression under varying photoperiods and provide crucial insights into the molecular mechanisms of underlying seasonal estrus in sheep, laying a foundation for future functional validation studies.