Relative abundance of tissue mRNA and association of the single nucleotide polymorphism of the goat NGF gene with prolificacy

Potential Candidate Genes Associated with Litter Size in Goats: A Review

This review examines genetic markers associated with litter size in goats, a key reproductive trait impacting productivity in small ruminant farming. Goats play a vital socioeconomic role in both low- and high-income regions; however, their productivity remains limited due to low reproductive efficiency. Litter size, influenced by multiple genes and environmental factors, directly affects farm profitability and sustainability by increasing the output per breeding cycle. Recent advancements in genetic research have identified key genes and pathways associated with reproductive traits, including gonadotropin-releasing hormone (GnRH), inhibin (INHAA), Kit ligand (KITLG), protein phosphatase 3 catalytic subunit alpha (PPP3CA), prolactin receptor (PRLR), POU domain class 1 transcription factor 1 (POU1F1), anti-Müllerian hormone (AMH), bone morphogenetic proteins (BMP), growth differentiation factor 9 (GDF9), and KISS1 and suppressor of mothers against decapentaplegic (SMAD) family genes, among others. These genes regulate crucial physiological processes such as folliculogenesis, hormone synthesis, and ovulation. Genome-wide association studies (GWASs) and transcriptomic analyses have pinpointed specific genes linked to increased litter size, highlighting their potential in selective breeding programs. By incorporating genomic data, breeding strategies can achieve higher selection accuracy, accelerate genetic gains, and improve reproductive efficiency. This review emphasizes the importance of genetic markers in optimizing litter size and promoting sustainable productivity in goat farming.

Analysis of goat PPP6C mRNA profile, detection of genetic variations, and their associations with litter size

The Protein Phosphatase 6 Catalytic Subunit (PPP6C) is evolutionarily a conserved gene in eukaryotes known to play a significant role in mammalian reproduction. This study aimed to investigate expression patterns of PPP6C and explore its association with litter size in Shaanbei white cashmere (SBWC) goats. Initially, we determined the mRNA expression levels of PPP6C in both male and female goats across multiple tissues. The results showed that PPP6C mRNA was expressed in multiple tissues, with higher levels in the testis and fallopian tubes, suggesting its involvement in goat reproduction. Additionally, we identified a novel 19 bp InDel within the PPP6C gene in a population of 1030 SBWC goats, which exhibited polymorphism. Statistical analysis revealed a significant association between the19 bp InDel mutation and litter size (P < 0.05). Subsequent, bioinformatics analysis, including linkage disequilibrium (LD) block and selective scanning, highlighted the linkage tendency among most InDel loci did not stand out within B-8 block, there were still some InDel loci linked to the 19 bp within a relatively narrow region. Furthermore, comparative analysis with Bezoars, these selective signals all indicated that this gene was under higher selection pressure, implying that the 19 bp InDel locus within the PPP6C is potentially associated with domesticated traits, particularly in relation to litter size. The results of the present study suggest that the PPP6C is a vital candidate gene affecting prolificacy in goats, with implications for selective breeding programs for goat breeds.

Litter Size of Sheep (Ovis aries): Inbreeding Depression and Homozygous Regions

Ovine litter size (LS) is an important trait showing variability within breeds. It remains largely unknown whether inbreeding depression on LS exists based on genomic homozygous regions, and whether the homozygous regions resulted from inbreeding are significantly associated with LS in sheep. We here reanalyze a set of single nucleotide polymorphism (SNP) chip of six breeds to characterize the patterns of runs of homozygosity (ROH), to evaluate inbreeding levels and inbreeding depressions on LS, and to identify candidate homozygous regions responsible for LS. Consequently, unique ROH patterns were observed among six sheep populations. Inbreeding depression on LS was only found in Hu sheep, where a significant reduction of 0.016, 0.02, and 0.02 per 1% elevated inbreeding FROH4-8, FROH>8 and the total inbreeding measure was observed, respectively. Nine significantly homozygous regions were found for LS in Hu sheep, where some promising genes for LS possibly via regulation of the development of oocytes (NGF, AKT1, and SYCP1), fertilization (SPAG17, MORC1, TDRD9, ZFYVE21, ADGRB3, and CKB), embryo implantation (PPP1R13B, INF2, and VANGL1) and development (DPPA2, DPPA4, CDCA4, CSDE1, and ADSSL1), and reproductive health (NRG3, BAG5, CKB, and XRCC3) were identified. These results from the present study would provide insights into the genetic management and complementary understandings of LS in sheep.

Genetic Effects of Single Nucleotide Polymorphisms in the Goat GDF9 Gene on Prolificacy: True or False Positive?

Simple Summary

As an important regulator factor, which was secreted by female oocytes, the growth differentiation factor 9 (GDF9) plays an essential role during the growth and differentiation of ovarian follicles. Single nucleotide polymorphisms (SNPs) within the GDF9 gene have been found to be involved in reproductive traits in livestock, and some of these mutations have been used as the effective makers in animal molecular breeding. However, it is remarkable that the SNPs of the goat GDF9 gene have not been systematically sorted and analyzed from the reported studies, which leads to an inability to find effective loci that could be applied in improving the prolificacy of goats via the molecular breeding method. In this study, we gathered and sorted 45 SNPs of the goat GDF9 gene from all relevant studies and the National Center for Biotechnology Information Search database (NCBI), and especially analyzed and discussed the relationship between part controversial and potentially effective SNPs and the reproductive traits. The results indicated that non-synonymous SNPs A240V, Q320P, and V397I and synonymous SNPs L61L, N121N, and L141L were six “true” positive SNPs in improving goat fertility. Nevertheless, the regulation pathways and the specific mechanism of these six SNPs on goat fecundity are not clear, which still need further study in more goat breeds and a large sample size. These results provided an effective tool for follow-up research studies on the molecular genetic breeding of goats’ reproductive traits.

Abstract

Goat reproductive traits are complex quantitative traits controlled by polygenes and multipoint. To date, some high-fertility candidate genes in livestock have been unearthed and the growth differentiation factor 9 (GDF9) gene is one of them, which plays a crucial role in early folliculogenesis. According to the relevant previous studies and the National Center for Biotechnology Information Search database (NCBI), a total of 45 single nucleotide polymorphisms (SNPs) have been detected in the goat GDF9 gene, but which one or which ones have important effects on goat fecundity is still uncertain. Hence, in order to find effective molecular markers for goat genetic breeding and accelerate the goat improvement, this study summarized and classified the above 45 SNPs into four kinds, as well as compared and analyzed the same SNP effects and the different SNPs linkage effects on the reproductive traits in different goat breeds. Since there were many SNPs in the goat GDF9 gene, only 15 SNPs have been identified in more than 30 goat breeds worldwide and they showed different effects on the litter size. Therefore, this study mainly chose these 15 SNPs and discussed their relationship with goat productivity. Results showed that three non-synonymous SNPs A240V, Q320P, and V397I and three synonymous ones L61L, N121N, and L141L played a “true” role in the litter size trait in many goat breeds around the world. However, the regulatory mechanisms still need further research. These results provide an effective tool for follow-up research developing the goat molecular breeding strategies and improving the goat reproductive traits.

Excessive nerve growth factor impairs bidirectional communication between the oocyte and cumulus cells resulting in reduced oocyte competence

BACKGROUND

Excessive nerve growth factor (NGF) is commonly found in the follicular fluid of patients with polycystic ovary syndrome (PCOS). Furthermore, oocytes from PCOS patients exhibit lower developmental competence. The purpose of this study was to explore the association between excessive NGF and low oocyte competence in vitro.

METHODS

Excessive NGF was added to mouse cumulus oocyte complexes (COCs) cultured in vitro to investigate meiotic maturation of the oocyte. After culture, mRNA expression levels of Pfkp and Ldha genes in cumulus cells (CCs) and Gdf9, Bmp15 and Fgf8 genes in oocytes, were determined by real-time quantitative polymerase chain reaction (qPCR). We also investigated the mRNA content of Pfkp and Ldha in CCs from PCOS and non-PCOS patients.

RESULTS

Excessive NGF significantly inhibited oocyte meiotic maturation. The inhibitory effect was mediated by the NGF high-affinity receptor, NTRK1. mRNA content of Pfkp and Ldha genes in CCs was significantly reduced by excessive NGF stimulation. Moreover, the expression levels of Gdf9, Bmp15 and Fgf8 were also decreased in oocytes, and was induced by excessive NGF-stimulated CCs. In addition, lower expression levels of Pfkp and Ldha in CCs were identified in Chinese PCOS patients with excessive NGF (PCOS, 22 ± 2.63 ng/ml, n = 13; non-PCOS, 7.18 ± 2.42 ng/ml, n = 9; p < 0.01) in the follicular fluid, suggesting a potential association between excessive NGF and decreased glycolysis in the CCs of women with PCOS.

CONCLUSIONS

Excessive NGF impairs bidirectional communication between oocyte and cumulus cells, which might be related to low oocyte competence.