Postnatal ovarian development and its relationship with steroid hormone receptors in JiNing Grey goats

Transcriptome analysis revealed the characteristics and functions of long non-coding RNAs in the hypothalamus during sexual maturation in goats

The hypothalamus is an essential neuroendocrine area in animals that regulates sexual development. Long non-coding RNAs (lncRNAs) are hypothesized to regulate physiological processes related to animal reproduction. However, the regulatory mechanism by which lncRNAs participate in sexual maturity in goats is poorly known, particularly from birth to sexual maturation. In this study, RNAseq analysis was conducted on the hypothalamus of four developmental stages (1day (D1, n = 5), 2 months (M2, n = 5), 4 months (M4, n = 5), and 6 months (M6, n = 5)) of Jining grey goats. The results showed that a total of 237 differentially expressed lncRNAs (DELs) were identified in the hypothalamus. Among these, 221 DELs exhibited cis-regulatory effects on 693 target genes, while 24 DELs demonstrated trans-regulatory effects on 63 target genes. The target genes of these DELs are mainly involved in biological processes related to energy metabolism, signal transduction and hormone secretion, such as sphingolipid signaling pathway, adipocytokine signaling pathway, neurotrophic signaling pathway, glutamatergic synapse, P53 signaling pathway and GnRH signaling pathway. In addition, XR_001918477.1, TCONS_00077463, XR_001918760.1, and TCONS_00029048 and their potential target genes may play a crucial role in the process of goat sexual maturation. This study advances our understanding of lncRNA in hypothalamic tissue during sexual maturation in goats and will give a theoretical foundation for improving goat reproductive features.

Characterization of MicroRNA expression profiles in the ovarian tissue of goats during the sexual maturity period

BACKGROUND

The ovary is an important reproductive organ in mammals, and its development directly affects the sexual maturity and reproductive capacity of individuals. MicroRNAs (miRNAs) are recognized as regulators of reproductive physiological processes in various animals and have been shown to regulate ovarian development through typical targeting and translational repression. However, little is known about the regulatory role of miRNAs in ovarian tissue development during sexual maturity in goats. To comprehensively profile the different physiological stages of sexual maturation in goats, we performed small-RNA sequencing of ovarian tissue samples collected at four specific time points (1 day after birth (D1), 2 months old (M2), 4 months old (M4), and 6 months old (M6)). In addition, we used ELISAs to measure serum levels of reproductive hormones to study their temporal changes.

RESULTS

The results showed that serum levels of gonadotropin-releasing hormone, follicle-stimulating hormone, luteinizing hormone, oestradiol, progesterone, oxytocin, and prolactin were lower in goats at the D1 stage than at the other three developmental stages (P < 0.05). The secretion patterns of these seven hormones show a similar trend, with hormone levels reaching their peaks at 4 months of age. A total of 667 miRNAs were detected in 20 libraries, and 254 differentially expressed miRNAs and 3 groups of miRNA clusters that had unique expression patterns were identified (|log2-fold change|> 1, FDR < 0.05) in the 6 comparison groups. RT‒qPCR was employed to confirm that the expression pattern of the 15 selected miRNAs was consistent with the Illumina sequencing results. Gene ontology analyses revealed significant enrichment of GO terms such as cell proliferation regulation, epithelial cell development, and amino acid transport, as well as important signaling pathways including the MAPK signaling pathway, the PI3K-Akt signaling pathway, and the oestrogen signaling pathway. Further miRNA‒mRNA regulation network analysis revealed that 8 differentially expressed miRNAs (chi-miR-1343, chi-miR-328-3p, chi-miR-877-3p, chi-miR-296-3p, chi-miR-128-5p, chi-miR-331-3p, chi-miR-342-5p and chi-miR-34a) have important regulatory roles in ovarian cell proliferation, hormone secretion and metabolism-related biological processes.

CONCLUSIONS

Overall, our study investigated the changes in serum hormone and miRNA levels in the ovaries. These data provide a valuable resource for understanding the molecular regulatory mechanisms of miRNAs in ovarian tissue during the sexual maturity period in goats.

Genome-wide detection of selective signals for fecundity traits in goats (Capra hircus)

Fecundity in livestock is an economically important complex quantitative trait that is influenced by both genetics and the environment. However, the underlying genetic mechanism of reproductive performance in goats has not been well investigated. To investigate the genomic basis of fecundity in goats, genomic sequencing data of the Jining grey goat (a high prolificacy breed in China) were collected, as well as data for other commonly available goat breeds, and a mass of genomic variants were generated after variation calling. We screened the Jining grey goat (20 individuals) using a selective sweep with the Asian wild goat population (5 individuals), and potential candidate genes were proposed, such as STIM1, ESR1, LRRC14B and SLC9A3. Among, STIM1 is a most promising one associated with high reproductive capacity. When compared to Chinese domestic goats with low fecundity (17 individuals), the genes including MLLT10, SPIRE2, TCF25, ZNF276 and FANCA were screened, and the SPIRE2 gene was thought to be associated with fecundity traits. Meanwhile, the functional enrichment of these candidate genes revealed that they were involved in biological processes of mammary gland morphogenesis, uterus development, gastrulation, mesoderm morphogenesis and formation, and blood vessel development, which might undergo natural or artificial selection during reproductive trait formation in goats. Thus, our findings could enrich the genetic basis of reproductive trait selection during goat domestication, which may serve to improve goat breeding practices.

Genomic Signatures of Selection Associated With Litter Size Trait in Jining Gray Goat

Litter size (LS), an important economic trait in livestock, is so complicate that involves many aspects of reproduction, the underlying mechanism of which particularly in goat has always been scanty. To uncover the genetic basis of LS, the genomic sequence of Jining Gray goat groups (one famous breed for high prolificacy in China) with LS 1, 2, and 3 for firstborn was analyzed, obtaining 563.67 Gb sequence data and a total of 31,864,651 high-quality single nucleotide polymorphisms loci were identified. Particularly, the increased heterozygosity in higher LS groups, and large continuous homozygous segments associated with lower LS group had been uncovered. Through an integrated analysis of three popular methods for detecting selective sweeps (Fst, nucleotide diversity, and Tajima’s D statistic), 111 selected regions and 42 genes associated with LS were scanned genome wide. The candidate genes with highest selective signatures included KIT, KCNH7, and KMT2E in LS2 and PAK1, PRKAA1, and SMAD9 in LS3 group, respectively. Meanwhile, functional terms of programmed cell death involved in cell development and regulation of insulin receptor signaling pathway were mostly enriched with 42 candidate genes, which also included reproduction related terms of steroid metabolic process and cellular response to hormone stimulus. In conclusion, our study identified novel candidate genes involving in regulation of LS in goat, which expand our understanding of genetic fundament of reproductive ability, and the novel insights regarding to LS would be potentially applied to improve reproductive performance.

Hydrogen-rich water ameliorates rat placental stress induced by water restriction

Dehydration is one of the intrauterine abnormalities that could lead to fetal growth retardation and to increase the risk of a variety of adult diseases later in life. This study were to determine the impact of hydrogen-rich water (HRW) supplementation on placental angiotensin II type 1 receptor and placental oxidative stress induced by water restriction. Pregnant Wistar rat were randomly assigned to one of the three groups (n =12 per group). In control group, pure water and food were supplied ad libitum. Water restriction group and HRW group were respectively given pure water and HRW with free access to food, excepting only one hour was available for drinking from day 7 to day 17 of pregnancy. The placental damages and biomarkers of stress were detected by histopathology, immunohistochemistry and western blot, as well as serological test were performed. We demonstrated that maternal water restriction resulted in reduced urine volume and increased serum osmotic pressure, along with decreased fetus weight and crown-rump length. Although placental weight and the number of fetuses had no significant difference among groups, the placental efficiency significantly increased after the oral administration of HRW to the mothers. Meanwhile, the serological derivatives of reactive oxygen metabolites decreased, a significant improvement of placental microstructure with more developed junctional zone and denser labyrinth was manifested, the upregulated expression of angiotensin II type 1 receptor, nuclear factoκB, malondialdehyde, 8-hydroxydeoxyguanosine, p38, c-Jun N-terminal kinase and down-regulation of superoxide dismutase were revealed in the placenta. Collectively, HRW administration is able to effectively attenuate placental stress induced by water restriction.

Genome-Wide Analysis on the Landscape of Transcriptomes and Their Relationship With DNA Methylomes in the Hypothalamus Reveals Genes Related to Sexual Precocity in Jining Gray Goats

The Jining Gray goat is famous for its sexual precocity; however, the exact regulatory mechanism is still unknown. The hypothalamus is the key centrum in the process of animal reproduction, especially in signal transduction, and the initiation of puberty. The identification of potential genes and pathways in the hypothalamus of Jining Gray goat is critical to understanding the regulatory mechanism of sexual precocity in these goats. In this study, mRNA transcriptome analysis of the hypothalamus of juvenile and pubertal goats revealed eight genes (NTS, ADORA1, CRH, UCN3, E2F2, PDGFRB, GNRH1, and CACNA1C) and three pathways [neuroactive ligand-receptor interaction; gonadotropin-releasing hormone (GnRH) signal; melanoma] that are involved in this regulation. Subsequent methylation analysis on differentially methylated region (DMR) genes revealed the potential regulation network that influences pubertal onset. Correlation analysis verified the methylation level of some DMR genes correlates negatively with expression level. Integrated analysis between transcriptomes and methylomes identified 80 candidate genes involved in GnRH and neuroactive ligand signal pathways, of which CACNA1C and CRH were differentially expressed genes (DEGs) influenced by methylation level. The GnRH gene was the only DEG not affected by its methylation level. In summary, in this study, we identified eight genes and three pathways that are related to pubertal onset in Jining Gray goats, and the expression of CACNA1C and CRH genes of the GnRH and neuroactive ligand signal pathways were influenced by DNA methylation, while that of the GnRH gene was not affected.

Exome sequencing reveals genetic differentiation due to high-altitude adaptation in the Tibetan cashmere goat (Capra hircus)

BACKGROUND

The Tibetan cashmere goat (Capra hircus), one of the most ancient breeds in China, has historically been a critical source of meat and cashmere production for local farmers. To adapt to the high-altitude area, extremely harsh climate, and hypoxic environment that the Tibetan cashmere goat lives in, this goat has developed distinct phenotypic traits compared to lowland breeds. However, the genetic components underlying this phenotypic adaptation remain largely unknown.

RESULTS

We obtained 118,700 autosomal SNPs through exome sequencing of 330 cashmere goats located at a wide geographic range, including the Tibetan Plateau and low-altitude regions in China. The great majority of SNPs showed low genetic differentiation among populations; however, approximately 2-3% of the loci showed more genetic differentiation than expected under a selectively neutral model. Together with a combined analysis of high- and low-altitude breeds, we revealed 339 genes potentially under high-altitude selection. Genes associated with cardiovascular system development were significantly enriched in our study. Among these genes, the most evident one was endothelial PAS domain protein 1 (EPAS1), which has been previously reported to be involved in complex oxygen sensing and significantly associated with high-altitude adaptation of human, dog, and grey wolf. The missense mutation Q579L that we identified in EPAS1, which occurs next to the Hypoxia-Inducible Factor-1 (HIF-1) domain, was exclusively enriched in the high-altitude populations.

CONCLUSIONS

Our study provides insights concerning the population variation in six different cashmere goat populations in China. The variants in cardiovascular system-related genes may explain the observed phenotypic adaptation of the Tibetan cashmere goat.