提高我国种猪生产效率是当务之急，尽管与母猪总产仔数性状相关的候选位点已逐步被揭示，但其分子机制尚不清晰。梅山猪是享誉世界的高产猪种，其繁殖力高于瘦肉型的大白猪等西方引进猪种。卵巢合成和分泌雌二醇、孕酮等类固醇激素，指导着猪卵母细胞发育、妊娠建立和维持、泌乳等生殖过程，是决定妊娠期生殖特征的关键器官。本研究关注妊娠中期第二个胎儿丢失的关键时期，妊娠第49天的卵巢生理过程，通过转录组、蛋白质组和代谢组的多组学比较研究，旨在确定梅山猪和大白郡猪卵巢黄体的基因组、蛋白质组学和代谢组学差异，以揭示母猪高繁殖力的潜在分子遗传机制。结果显示：梅山猪在妊娠中期的转录组和蛋白质组水平上都表现出卵巢类固醇生物合成和丁酸代谢的普遍下调，但血清胆固醇、雌二醇和孕酮水平均高于大白猪；鉴定出类固醇激素途径基因中与猪总产仔数、猪初生窝重和胎重相关的位点；揭示了梅山猪的高繁殖力性状形成的关键因素之一：调控妊娠中期较低的类固醇物质生物合成效率和较高的生殖激素血清水平的平衡，减少妊娠期的胎儿丢失。

Secreted frizzled-related protein 2 (SFRP2), a member of the SFRPs family, is associated with cell growth and differentiation in myogenesis. Our previous study suggested that SFRP2 was a potential target of microRNA (miRNA)-1/206, which was considered as myomiRs. To further explore the biological function and regulation mechanisms of the SFRP2 gene in porcine skeletal muscle development, we first analyzed the sequence structure of the porcine SFRP2 gene. Subsequently, we detected its tissue distribution in adult Tongcheng pigs (a Chinese indigenous breed) and investigated its dynamic expression in developmental skeletal muscle (13 prenatal and 7 postnatal time points) in Tongcheng pigs. An interaction analysis between SFRP2 and myomiRs was also performed. The results showed that the expression pattern of the SFRP2 varied greatly across diverse tissues. It exhibited abundant expression in prenatal skeletal muscle and peaked at 55 days post coitus (E55), and had a lower expression in postnatal skeletal muscle, indicating that the SFRP2 gene might affect porcine embryonic skeletal muscle development. Co-expression analysis revealed that the expression levels of SFRP2 correlated negatively with miRNA-1 (r=–0.570, P-value=0.009) and miRNA-206 (r=–0.546, P-value=0.013), but positively with SFRP1 (r=0.613, P-value=0.004). The bioinformatics analysis and dual luciferase assay verified that the SFRP2 was a putative target of miRNA-1/206 in pigs. Therefore, this study is helpful for understanding the biological function and molecular regulation of the SFRP2 gene during porcine skeletal muscle development.

MicroRNAs (miRNAs), evolutionarily conserved non-coding RNAs in length 21-24 bp, play a critical role in skeletal muscle development. In this study, to explore the function of mircoRNA-127 in porcine skeletal muscle development, eight tissue samples from adult pigs and longissimus muscle samples at 26 developmental stages were collected from Tongcheng and Landrace pigs. The spatial-temporal expression profiles of miRNA-127 were carried out using step-loop quantitative real-time PCR (stem- loop RT-PCR). To explore the molecular functions of miRNA-127, we predicted its target genes and performed functional annotation using bioinformatics methods. Results suggested that miRNA-127 was abundantly expressed in heart, ovary, uterus and spleen tissues and was weakly expressed in liver, lung, kidney and small intestine in both Tongcheng and Landrace pigs. And miRNA-127 showed significant expression differences in heart, ovary, spleen and uterus tissues between these two breeds. miRNA-127 basically kept at a relatively stable high level in middle and later embryonic stages and a low expression level in early embryonic stages and postnatal stages, but the expression levels of miRNA-127 were higher in Tongcheng pigs than in Landrace at most developmental stages. miRNA-127 potentially regulated 240 candidate genes. Results of Gene Ontology and KEGG pathway analysis indicated that these genes could be involved in many molecular functions and mechanisms, such as regulation of the force of heart contraction, regulation of transcription, regulation of T cell differentiation, MAPK signaling pathway and GnRH signaling pathway. Many significantly enriched GO terms and KEGG pathways were related to skeletal muscle development. This study will be helpful to understand the biological function for miRNA-127 and identify candidate gene associated with meat production traits in pigs.

Cellular retinoic acid-binding protein 1 (CRABP1) is a well-conserved member of cytosolic lipid-binding protein family. It is an important modulator of retinoic acid signaling. Long serial analysis of gene expression (LongSAGE) analysis suggested that CRABP1 gene was differentially expressed during prenatal skeletal muscle development in porcine. Here, we obtained the full-length coding region sequence and genomic sequence of the porcine CRABP1 gene and analyzed its genomic structures. Subsequently, we examined CRABP1 chromosome assignment using INRA-University of Minnesota 7 000 porcine radiation hybrid panel (IMpRH) and explored its tissue distribution in adult Tongcheng pigs and dynamical expression profiles in prenatal skeletal muscle (33, 65 and 90 days post coitus, dpc) from Landrace (lean-type) (described as L33, L65 and L90) and Tongcheng pigs (obese-type) (described as T33, T65 and T90). The CRABP1 gene was mapped to chromosome 7q11-q23 and closely linked to the microsatellite marker SWR1928. Quantitative real-time PCR showed that CRABP1 mRNA was highly expressed in lung and stomach, moderately expressed in placenta and uterus, and weakly expressed in other tissues. Moreover, CRABP1 gene was down-regulated during prenatal skeletal muscle development in both Landrace and Tongcheng pigs and it was expressed much higher in T33 than L33. Two single-nucleotide polymorphisms (SNPs) were detected by sequencing and mass spectrometry methods, allele frequency analysis indicated that g. 281 (G>A) and g. 2992 (G>A) were deviated from Hardy-Weinberg equilibrium in the Landrace and DLY (Duroc×(Landrace×Yorkshire)) pig breeds.