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Backgrounds: Transforming growth factor-β (TGF-β) type I receptor (TGFβRI) and type II receptor (TGFβRII) are the members of the TGFβ superfamily, which are potent regulators of cell proliferation and differentiation in many organ systems, and they play key roles in multiple aspects of follicle development., Objectives: We aimed to explore the characterization, expression analysis of TGFβRI and TGFβRII genes, and the association with litter size in Tibetan sheep., Methods: In this study, we cloned the complete coding sequences of TGFβRI and TGFβRII genes in Tibetan sheep and analyzed their genomic structures., Results: The results showed that percentages of sequences homology of the two proteins in Tibetan sheep were the most similar to Ovis aries (100%), followed by Bos mutus (99%). The RT-qPCR showed that two genes were expressed widely in the different tissues of Tibetan sheep. The TGFβRI expression was the highest in the lung (p < 0.05), followed by the spleen and ovary (p < 0.05). The TGFβRII expression was significantly higher in uterus than that in lung and ovary (p < 0.05). In addition, the χ 2 test indicated that all ewes in the population were in Hardy-Weinberg equilibrium, and the population was in medium or low polymorphic information content status. We also found four Single Nucleotide Polymorphism (SNPs), g.9414A > G, g.28881A > G, g.28809T > C, g.10429G > A in sheep TGFβRI gene and g.63940C > T, g.63976C > T, g.64538C > T, g.64504T > A in TGFβRII gene. Three genotypes, except for g.64504T > A, and three haplotypes were identified in each gene. linkage disequilibrium analysis indicated that there was strong linkage disequilibrium in each gene. The association analysis showed that the four SNPs of TGFβRI were associated with litter size (p < 0.05), and g.63940C > T of TGFβRII was confirmed to be associated with litter size (p < 0.05)., Conclusions: Based on these preliminary results, we can assume that TGFβ receptors (TGFβRI and TGFβRII) may play an important role in sheep reproduction., (© 2022 The Authors. Veterinary Medicine and Science published by John Wiley & Sons Ltd.)

Tibetan sheep is a unique breed living in Qinghai‐Tibet Plateau. Since MSTN/Smad signaling pathway plays a critical role in the regulation of muscle development, we aimed to study the mutton quality, mRNA expression of main transduction genes in the MSTN/Smad signaling pathway, and the effects of those genes on the mutton quality of Tibetan sheep in this study. Six‐month‐old Qinghai‐Tibetan sheep were selected, slaughtered, and their Longissimus lumborum, semitendinosus muscle, arm triceps, and quadriceps femoris muscle were collected. The mutton quality was evaluated, and gene expression and their association with the mutton quality were analyzed using RT‐qPCR. The results showed that the indexes of mutton quality were not significantly different between ewes and rams (p >.05) except for Warner–Bratzler shear force (WBSF) (p <.05). A total of 21 different fatty acids were detected in the muscles of Tibetan sheep, including nine types of SFA, four types of MUFA, and eight types of PUFA. The main transduction genes of the MSTN/Smad signaling pathway were found to be widely expressed in muscle tissues, but no significant differences were observed (p >.05). The correlation analysis of the main genes and mutton quality showed that MSTN was significantly correlated with redness and cooking time; Smad2, Smad3, Smad4, and TGFβRI had significant positive correlations with marbling in arm triceps; Smad3 and TGFβRII had strong negative correlations with pH24 h in Longissimus lumborum; Smad2 was negatively correlated with drip loss in Longissimus lumborum. In short, the expression level of MSTN in muscles was positively correlated with Smad2, Smad3, and Smad4 genes and negatively correlated with TGFβRII genes. Thus, the results of this study provide a theoretical basis for the regulation mechanism of the MSTN/Smad pathway on mutton quality. [ABSTRACT FROM AUTHOR]

SMAD1, SMAD2, and SMAD3 are important transcription factors downstream of the TGF-β/SMAD signaling pathway that mediates several physiological processes. In the current study, we used cloning sequencing, RT-qPCR, bioinformatics methods and iMLDR technology to clone the coding region of Tibetan sheep genes, analyze the protein structure and detect the tissue expression characteristics of Tibetan sheep genes, and detect the polymorphisms of 433 Tibetan sheep and analyze their correlation with litter size. The results showed that the ORFs of the SMAD1, SMAD2 and SMAD3 genes were 1398 bp, 1404 bp and 1278 bp, respectively, and encoded 465, 467 and 425 amino acids, respectively. The SMAD1, SMAD2, and SMAD3 proteins were all unstable hydrophilic mixed proteins. SMAD1, SMAD2 and SMAD3 were widely expressed in Tibetan sheep tissues, and all were highly expressed in the uterus, spleen, ovary and lung tissues. Litter sizes of the genotype CC in the SMAD1 gene g.10729C>T locus were significantly higher than that of CT (p < 0.05). In the SMAD3 gene g.21447C>T locus, the genotype TT individuals showed a higher litter size than the CC and CT genotype individuals (p < 0.05). These results preliminarily demonstrated that SMAD1, SMAD2 and SMAD3 were the major candidate genes that affected litter size traits in Tibetan sheep and could be used as a molecular genetic marker for early auxiliary selection for improving reproductive traits during sheep breeding. [ABSTRACT FROM AUTHOR]

Simple Summary: Selection of molecular markers used in the marker-assisted selection of the litter size of sheep is critically essential. In this study, we identified single nucleotide polymorphisms (SNPs), g.51537A>G in SMAD5 and g.319C>T in SMAD7, from Tibetan sheep, and they were genotyped. The expression patterns of SMAD4, SMAD5 and SMAD7 in the tissues of Tibetan sheep were determined. Furthermore, we also performed an association analysis of the SNPs with litter size. The results indicated that SMAD4, SMAD5 and SMAD7 were extensively expressed in the various tissues of Tibetan sheep. Sequence analysis showed that SMAD4 contained 1662 bp encoding 533 amino acids, SMAD5 contained 1667 bp encoding 465 amino acids and SMAD7 contained 1408 bp encoding 427 amino acids. Alignment analysis showed that the amino acid sequence of the three proteins shared high similarity with sheep, yak, cattle, dog, human, pig, chimpanzee, rhesus monkey and house mouse. Furthermore, association analysis showed that both g.51537A>G in SMAD5 and g.319C>T in SMAD7 were not significantly associated with litter size of Tibetan sheep. SMAD4, SMAD5 and SMAD7 belonging to the transforming growth factor β (TGF-β) superfamily are indispensable for oocyte formation and development, ovarian organogenesis and folliculogenesis. However, only a few studies have investigated the characteristics of SMAD4, SMAD5 and SMAD7 in Tibetan sheep and the effect of their polymorphism on litter size. In this study, we examined the expression of SMAD4, SMAD5 and SMAD7 in 13 tissues of Tibetan sheep by reverse transcription-quantitative polymerase chain reaction. Further, cDNA of these genes was cloned, sequenced and subjected to bioinformatics analysis. DNA sequencing was also used to detect single nucleotide polymorphisms (SNPs). However, iM-LDRTM technology was used for SNP genotyping. Associations between polymorphisms and litter size were analyzed using data from genotyping of 433 Tibetan sheep. The results showed that the expression of SMAD4, SMAD5 and SMAD7 genes was ubiquitous in the tissues of Tibetan sheep, such as the ovary, uterus and oviduct, hypothalamus, hypophysis, heart, liver, spleen, lung, kidney, rumen, duodenum and longissimus dorsi. However, the expression was unbalanced and upregulated in the spleen, lung, ovary and uterus and downregulated in the longissimus dorsi. The bioinformatics analysis showed that SMAD4, SMAD5 and SMAD7 in Tibetan sheep encoded proteins of 533, 465 and 427 amino acids, respectively. Sequence homology analysis of the three proteins among other animals showed that the sequences of SMAD4, SMAD5 and SMAD7 of Tibetan sheep were similar to those in sheep, yak, cattle, dog, human, pig, chimpanzee, rhesus monkey and house mouse. Two synonymous mutations, g.51537A>G and g.319C>T, were detected in SMAD5 and SMAD7, respectively. The associations of these SNPs and litter size were determined, and it was found that both g.51537A>G and g.319C>T have no significant effect on the litter size of Tibetan sheep. The results provided novel insights into the molecular characterization, expression profiles and polymorphisms of SMAD4, SMAD5 and SMAD7 in Tibetan sheep, but our results do not support associations between these genes and the litter size of Tibetan sheep. [ABSTRACT FROM AUTHOR]