Comprehensive Analysis of MicroRNA⁻Messenger RNA from White Yak Testis Reveals the Differentially Expressed Molecules Involved in Development and Reproduction

Role of Acyl-CoA Thioesterase 7 in Regulating Fatty Acid Metabolism and Its Contribution to the Onset and Progression of Bovine Clinical Mastitis

Clinical mastitis (CM) is a prevalent and severe inflammatory disease in dairy cows affecting the mammary glands. Fatty acid (FA) metabolism and associated enzymes are crucial for many physiological and pathological processes in dairy cows. However, the relationships among FA metabolism, FA-associated enzymes, and CM, as well as the mechanisms underlying their interactions, in dairy cows are not fully understood. The aim of this study was to characterize biological process (BP) terms, pathways, and differentially expressed proteins (DEPs) related to FA metabolism from our previous data-independent acquisition proteomic study. Six BPs involving 14 downregulated and 20 upregulated DEPs, and four pathways involving 10 downregulated and 11 upregulated DEPs related to FA synthesis and metabolism were systematically identified. Associated analysis suggested that 12 candidate DEPs obtained from BPs and pathways, especially acyl-CoA thioesterase 7 (ACOT7), regulate long-chain FA (LCFA) elongation and the biosynthesis of unsaturated FAs. Immunohistochemical and immunofluorescence staining results showed that ACOT7 was present mainly in the cytoplasm of mammary epithelial cells. The qRT-PCR and Western blotting results showed that ACOT7 mRNA and protein levels in the mammary glands of the CM group were significantly upregulated compared to those in the healthy group. This evidence indicates that ACOT7 is positively correlated with CM onset and progression in Holstein cows. These findings offer novel insights into the role of FA metabolism and related enzymes in CM and offer potential targets for the development of therapeutic strategies and biomarkers for the prevention and treatment of CM in dairy cows.

The Novel-m0230-3p miRNA Modulates the CSF1/CSF1R/Ras Pathway to Regulate the Cell Tight Junctions and Blood-Testis Barrier in Yak

The yak (Bos grunniens) is a valuable livestock animal endemic to the Qinghai-Tibet Plateau in China with low reproductive rates. Cryptorchidism is one of the primary causes of infertility in male yaks. Compared with normal testes, the tight junctions (TJs) of Sertoli cells (SCs) and the integrity of the blood-testis barrier (BTB) in cryptorchidism are both disrupted. MicroRNAs are hairpin-derived RNAs of about 19-25 nucleotides in length and are involved in a variety of biological processes. Numerous studies have shown the involvement of microRNAs in the reproductive physiology of yak. In this study, we executed RNA sequencing (RNA-seq) to describe the expression profiles of mRNAs and microRNAs in yaks with normal testes and cryptorchidism to identify differentially expressed genes. GO and KEGG analyses were used to identify the biological processes and signaling pathways which the target genes of the differentially expressed microRNAs primarily engaged. It was found that novel-m0230-3p is an important miRNA that significantly differentiates between cryptorchidism and normal testes, and it is down-regulated in cryptorchidism with p < 0.05. Novel-m0230-3p and its target gene CSF1 both significantly contribute to the regulation of cell adhesion and tight junctions. The binding sites of novel-m0230-3p with CSF1 were validated by a dual luciferase reporter system. Then, mimics and inhibitors of novel-m0230-3p were transfected in vitro into SCs, respectively. A further analysis using qRT-PCR, immunofluorescence (IF), and Western blotting confirmed that the expression of cell adhesion and tight-junction-related proteins Occludin and ZO-1 both showed changes. Specifically, both the mRNA and protein expression levels of Occludin and ZO-1 in SCs decreased after transfection with the novel-m0230-3p mimics, while they increased after transfection with the inhibitors, with p < 0.05. These were achieved via the CSF1/CSF1R/Ras signaling pathway. In summary, our findings indicate a negative miRNA-mRNA regulatory network involving the CSF1/CSF1R/Ras signaling pathway in yak SCs. These results provide new insights into the molecular mechanisms of CSF1 and suggest that novel-m0230-3p and its target protein CSF1 could be used as potential therapeutic targets for yak cryptorchidism.

Exploring the Mechanism of H2S Synthesis in Male Bactrian Camel Poll Glands Based on Data Independent Acquisition Proteomics and Non-Targeted Metabolomics

During estrus, the poll glands of male Bactrian Camels (Camelus Bactrianus) become slightly raised, exuding a large amount of pale yellow watery secretion with a characteristic odor that may contain hydrogen sulfide (H2S). However, whether H2S can be synthesized in the poll glands of male Bactrian Camels and its role in inducing camel estrus remains unclear. This study aimed to identify differentially expressed proteins (DEPs) and signaling pathways in the poll gland tissues of male Bactrian Camels using data independent acquisition (DIA) proteomics. Additionally, gas chromatography-mass spectrometry (GC-MS) was performed to identify differentially expressed metabolites (DEMs) in the neck hair containing secretions during estrus in male Bactrian Camels, to explore the specific expression patterns and mechanisms in the poll glands of camels during estrus. The results showed that cystathionine-γ-lyase (CTH) and cystathionine-β-synthase (CBS), which are closely related to H2S synthesis in camel poll glands during estrus, were mainly enriched in glycine, serine, and threonine metabolism, amino acid biosynthesis, and metabolic pathways. In addition, both enzymes were widely distributed and highly expressed in the acinar cells of poll gland tissues in camels during estrus. Meanwhile, the neck hair secretion contains high levels of amino acids, especially glycine, serine, threonine, and cystathionine, which are precursors for H2S biosynthesis. These results demonstrate that the poll glands of male Bactrian Camels can synthesize and secrete H2S during estrus. This study provides a basis for exploring the function and mechanism of H2S in the estrus of Bactrian Camels.

Exploring testicular miRNA profiles during developmental stages in Dezhou donkeys: A preliminary insight

Testicular development and spermatogenesis are complex phenomena controlled by various genetic factors, including miRNA-based post-transcriptional gene expression regulation. Exploring the miRNA expression patterns during testicular development in Dezhou donkeys would enhance our understanding of equine fertility and spermatogenesis. In this investigation, we examined the testicular miRNA profiles at various stages of development. The experimental animals were divided into three groups based on their developmental stages: 2 months old (juvenile: n = 3), 12 months old (adolescent; n = 3) and 24 months old (adult; n = 3) donkeys. Total RNA was extracted from dissected testicles for miRNA sequencing and analysis. In total, 586 miRNAs, including 451 known miRNAs and 135 novel miRNAs, were identified. Among identified miRNAs, 315 displayed age-dependent expression differences. The levels of miRNA expression in the juvenile group were significantly higher than in the adolescent or adult groups. The MiR-483 exhibited the maximum fold change between juvenile and adolescent groups. Several screened genes, including SLC45A4 and TFCP2L1, have been linked to male reproductive pathways in donkeys. In addition, miR-744 was predicted to regulate SPIN2B, a gene implicated in spermatocyte cell cycle progression and genomic integrity of spermatozoa. These results contribute to our comprehension of microRNA regulation during testicular development and spermatogenesis in Dezhou donkeys. The identified microRNAs and their target genes have the potential to serve as biomarkers for evaluating the reproductive capacity of stud donkeys.

Identification and profiling of microRNAs during yak's testicular development

BACKGROUND

Normal testicular development is highly crucial for male reproduction and is a precondition for spermatogenesis that is the production of spermatozoa in the testes. MiRNAs have been implicated in several testicular biological processes, including cell proliferation, spermatogenesis, hormone secretion, metabolism and reproductive regulation. In the present study, we used deep sequencing data to study the functions of miRNAs during testicular development and spermatogenesis, by analyzing the expression patterns of small RNAs in 6-, 18- and 30-month-old yak testis tissues.

RESULTS

A total of 737 known and 359 novel miRNAs were obtained from 6-, 18- and 30-month-old yak testes. In all, we obtained 12, 142 and 139 differentially expressed (DE) miRNAs in 30- vs. 18-, 18- vs. 6-, and 30- vs. 6-month-old testes, respectively. Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of all DE miRNA target genes revealed BMP2, TGFB2, GDF6, SMAD6, TGFBR2 and other target genes as participants in different biological processes, including TGF-β, GnRH, Wnt, PI3K-Akt, MAPK signaling pathways and several other reproductive pathways. In addition, quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was used to detect the expression of seven randomly selected miRNAs in 6-, 18- and 30-month-old testes, and the results were consistent with the sequencing data.

CONCLUSIONS

The differential expression of miRNAs in yak testes at different development stages was characterized and investigated using deep sequencing technology. We believe that the results will contribute to further understanding the functions of miRNAs in regulating the development of yak testes and improving the reproductive performance of male yaks.

HMOX1 Promotes Ferroptosis in Mammary Epithelial Cells via FTH1 and Is Involved in the Development of Clinical Mastitis in Dairy Cows

Ferroptosis is associated with inflammatory diseases as a lethal iron-dependent lipid peroxidation; its role in the development of clinical mastitis (CM) in dairy cows is not well understood. The aim of this study was to identify differentially expressed proteins (DEPs) associated with iron homeostasis and apoptosis, and to investigate further their roles in dairy cows with CM. The results suggested that ferroptosis occurs in the mammary glands of Holstein cows with CM. Using data-independent acquisition proteomics, 302 DEPs included in 11 GO terms related to iron homeostasis and apoptosis were identified. In particular, heme oxygenase-1 (HMOX1) was identified and involved in nine pathways. In addition, ferritin heavy chain 1 (FTH1) was identified and involved in the ferroptosis pathway. HMOX1 and FTH1 were located primarily in mammary epithelial cells (MECs), and displayed significantly up-regulated expression patterns compared to the control group (healthy cows). The expression levels of HMOX1 and FTH1 were up-regulated in a dose-dependent manner in LPS induced MAC-T cells with increased iron accumulation. The expression levels of HMOX1 and FTH1 and iron accumulation levels in the MAC-T cells were significantly up-regulated by using LPS, but were lower than the levels seen with Erastin (ERA). Finally, we deduced the mechanism of ferroptosis in the MECs of Holstein cows with CM. These results provide new insights for the prevention and treatment of ferroptosis-mediated clinical mastitis in dairy animals.

Toll-like Receptor 2 Is Associated with the Immune Response, Apoptosis, and Angiogenesis in the Mammary Glands of Dairy Cows with Clinical Mastitis

Toll-like receptor 2 (TLR2) plays a crucial role in bacterial recognition and the host immune response during infection. However, its function and downstream biological processes (BPs) in the mammary glands (MGs) of Holstein cows with clinical mastitis (CM) are not fully understood. This study aimed to comprehensively identify the BPs and differentially expressed proteins (DEPs) associated with the bacterial response and TLR2 using data-independent acquisition (DIA) proteomic data. A possible mechanism for the action of TLR2 was proposed, and the results suggested that the expression levels of TLR2 and caspase 8 (CASP8) were positively correlated with the apoptosis of MGs. The expression patterns of TLR2 and TEK receptor tyrosine kinase 2 (Tie2) were negatively correlated with angiogenesis. These results indicated that TLR2 might promote apoptosis in mammary epithelial cells (MECs) and vascular endothelial cells (VECs) via upregulation of CASP8 expression, and inhibition of angiogenesis in VECs via downregulation of Tie2 expression in dairy cows with CM. In conclusion, TLR2 is associated with inflammation, apoptosis, and angiogenesis in the MGs of dairy cows with bacteria-induced mastitis. These results contribute to a deeper understanding of the pathogenic mechanisms and provide the knowledge needed for developing the prevention and treatment of dairy mastitis.

DIA proteomics identified the potential targets associated with angiogenesis in the mammary glands of dairy cows with hemorrhagic mastitis

Hemorrhagic mastitis (HM) in dairy cows caused great economic losses in the dairy industry due to decreased milk production and increased costs associated with cattle management and treatment. However, the pathological and molecular mechanisms of HM are not well-understood. The present study aimed to investigate differentially expressed proteins (DEPs) associated with HM according to data-independent acquisition (DIA) proteomics. Compared to the mammary glands of healthylactating Holstein cows (Control, C group), the pathology of the HM group displayed massive alveolar infiltration of hemocytes and neutrophils, and the blood vessels, including arteriole, venules and capillaries were incomplete and damaged, with a loss of endothelial cells. DIA proteomics results showed that a total of 3,739 DEPs and 819 biological process terms were screened in the HM group. We focused on the blood, permeability of blood vessel, vascular and angiogenesis of mammary glands, and a total of 99 candidate DEPs, including 60 up- and 39 down-regulated DEPs, were obtained from the Gene Ontology (GO) and Pathway enrichment analyses. Phenotype prediction and function analysis of the DEPs revealed that three DEPs, particularly Caveolin-1(CAV1), were participated in the regulation of angiogenesis. Immunohistochemical and immunofluorescence staining showed that the CAV1 protein was present mainly in the mammary epithelial cells, vascular endothelial cells and vascular smooth muscle cells. The expression level of CAV1 mRNA and protein in the HM group was significantly down-regulated. The results will be helpful to the further understanding of the pathological and molecular mechanisms of HM in dairy cows.

Sulfur Amino Acid Metabolism and the Role of Endogenous Cystathionine-γ-lyase/H2S in Holstein Cows with Clinical Mastitis

H2S plays an important role in various inflammatory diseases. However, the role of H2S and synthetic enzymes in Holstein cows with CM is unknown. The aim of this study was to identify DEPs associated with sulfide metabolism and further investigate their roles in dairy cows with CM. From 3739 DEPs generated by data-independent acquisition proteomics, we identified a total of 17 DEPs included in 44 GO terms and five KEGG pathways related to sulfide metabolism, including CTH and cystathionine-β-synthase (CBS). Immunohistochemical and immunofluorescence staining results showed that CTH and CBS proteins were present mainly in the cytoplasm of mammary epithelial cells. Endogenous H2S production in the serum of the CM group was significantly lower than that of the healthy Holstein cows. CTH and CBS mRNA and protein levels in the mammary glands of the CM group were significantly downregulated compared to those of the healthy group. These results indicate that CTH and H2S were correlated with the occurrence and development of CM in Holstein cows, which provides important insights into the function and regulatory mechanism of CTH/H2S in Holstein cows.

Comparison of miRNA and mRNA Expression in Sika Deer Testes With Age

To elucidate the complex physiological process of testis development and spermatogenesis in Sika deer, this study evaluated the changes of miRNA and mRNA profiles in the four developmental stages of testis in the juvenile (1-year-old), adolescence (3-year-old), adult (5-year-old), and aged (10-year-old) stages. The results showed that a total of 198 mature, 66 novel miRNAs, and 23,558 differentially expressed (DE) unigenes were obtained; 14,918 (8,413 up and 6,505 down), 4,988 (2,453 up and 2,535 down), and 5,681 (2,929 up and 2,752 down) DE unigenes, as well as 88 (43 up and 45 down), 102 (44 up and 58 down), and 54 (18 up and 36 down) DE miRNAs were identified in 3- vs. 1-, 5- vs. 3-, and 10- vs. 5-year-old testes, respectively. By integrating miRNA and mRNA expression profiles, we predicted 10,790 mRNA-mRNA and 69,883 miRNA-mRNA interaction sites. The target genes were enriched by GO and KEGG pathways to obtain DE mRNA (IGF1R, ALKBH5, Piwil, HIF1A, BRDT, etc.) and DE miRNA (miR-140, miR-145, miR-7, miR-26a, etc.), which play an important role in testis development and spermatogenesis. The data show that DE miRNAs could regulate testis developmental and spermatogenesis through signaling pathways, including the MAPK signaling pathway, p53 signaling pathway, PI3K-Akt signaling pathway, Hippo signaling pathway, etc. miR-140 was confirmed to directly target mutant IGF1R-3'UTR by the Luciferase reporter assays. This study provides a useful resource for future studies on the role of miRNA regulation in testis development and spermatogenesis.

The Distribution, Expression Patterns and Functional Analysis of NR1D1 and NR4A2 in the Reproductive Axis Tissues of the Male Tianzhu White Yak

Nuclear hormone receptors NR1D1 and NR4A2 play important roles in the synthesis and metabolism of hormones that are thought to be strictly regulated by the hypothalamus-pituitary-gonad axis (HPG) tissues via gene expression. However, in the yak, the function and regulatory mechanisms of NR1D1 and NR4A2 are not clearly understood. The current study is aimed to investigate the expression patterns, distribution and functions of these two receptors in HPG tissues in male Tianzhu white yaks. Immunohistochemical staining showed NR1D1 and NR4A2 proteins were present in all yak HPG tissues with differential expression patterns and degrees of staining, particularly in Leydig cells that were strongly positive in accordance with the immunofluorescence results. qRT-PCR and Western blot results suggested that the highest expression levels of NR1D1 and NR4A2 mRNA were present in the hypothalamus, while the expression levels of NR1D1 and NR4A2 proteins were higher in the testis and epididymis than in the hypothalamus or pituitary gland. In addition, expression levels of NR1D1 and NR4A2 mRNA and protein in testicular tissues differed by age. Expression levels were significantly higher at 6 years of age. Gene ontology (GO) and pathway analysis enrichment revealed that NR1D1 may directly regulate the synthesis and metabolism of steroid hormones via interaction with different targets, while NR4A2 may indirectly regulate the synthesis and metabolism of steroid hormones. These results showed that NR1D1 and NR4A2, as important mediators, are involved in the regulation of male yak reproduction, and especially of steroid hormones and androgen metabolism. These results will be helpful for the further understanding of the regulatory mechanisms of NR1D1 and NR4A2 in yak reproduction.

Characteristics of pulmonary microvascular structure in postnatal yaks

Yaks are typical plateau-adapted animals, however the microvascular changes and characteristics in their lungs after birth are still unclear. Pulmonary microvasculature characteristics and changes across age groups were analysed using morphological observation and molecular biology detection in yaks aged 1, 30 and 180 days old in addition to adults. Results: Our experiments demonstrated that yaks have fully developed pulmonary alveolar at birth but that interalveolar thickness increased with age. Immunofluorescence observations showed that microvessel density within the interalveolar septum in the yak gradually increased with age. In addition, transmission electron microscopy (TEM) results showed that the blood–air barrier of 1-day old and 30-days old yaks was significantly thicker than that observed at 180-days old and in adults (P < 0.05), which was caused by the thinning of the membrane of alveolar epithelial cells. Furthermore, Vegfa and Epas1 expression levels in 30-day old yaks were the highest in comparison to the other age groups (P < 0.05), whilst levels in adult yaks were the lowest (P < 0.05). The gradual increase in lung microvessel density can effectively satisfy the oxygen requirements of ageing yaks. In addition, these results suggest that the key period of yak lung development is from 30 to 180 days.

Identification of microRNA transcriptome throughout the lifespan of yak (Bos grunniens) corpus luteum

The corpus luteum (CL) is a temporary organ that plays a critical role for female fertility by maintaining the estrous cycle. MicroRNA (miRNA) is a class of non-coding RNAs involved in various biological processes. However, there exists limited knowledge of the role of miRNA in yak CL. In this study, we used high-throughput sequencing to study the transcriptome dynamics of miRNA in yak early (eCL), middle (mCL) and late-stage CL (lCL). A total of 6,730 miRNAs were identified, including 5,766 known and 964 novels miRNAs. Three miRNAs, including bta-miR-126-3p, bta-miR-143 and bta-miR-148a, exhibited the highest expressions in yak CLs of all the three stages. Most of the miRNAs were 20-24 nt in length and the peak was at 22 nt. Besides, most miRNAs with different lengths displayed significant uracil preference at the 5'-end. Furthermore, 1,067, 280 and 112 differentially expressed (DE) miRNAs were found in eCL vs. mCL, mCL vs. lCL, and eCL vs. lCL, respectively. Most of the DE miRNAs were down-regulated in the eCL vs. mCL and eCL vs. lCL groups, and up-regulated in the mCL vs. lCL group. A total of 18,904 target genes were identified, with 18,843 annotated. Pathway enrichment analysis of the DE miRNAs target genes illustrated that the most enriched cellular process in each group included pathways in cancer, PI3K-Akt pathway, endocytosis, and focal adhesion. A total of 20 putative target genes in 47 DE miRNAs were identified to be closely associated with the formation, function or regression of CL. Three DE miRNAs, including bta-miR-11972, novel-miR-619 and novel-miR-153, were proved to directly bind to the 3'-UTR of their predicated target mRNAs, including CDK4, HSD17B1 and MAP1LC3C, respectively. Both of these DE miRNAs and their target mRNAs exhibited dynamic expression profiles across the lifespan of yak CL. This study presents a general basis for understanding of the regulation of miRNA on yak CL and also provides a novel genetic resource for future analysis of the gene network during the estrous cycle in the yak.

Integrating miRNA and mRNA Profiling to Assess the Potential miRNA-mRNA Modules Linked With Testicular Immune Homeostasis in Sheep

Beyond its well-known role in spermatogenesis and androgen production, mammalian testes are increasingly recognized as an immune-privileged organ for protecting autoantigenic germ cells, especially meiotic and postmeiotic germ cells, from systemic immune responses. Despite its importance, the molecular mechanisms underlying this regulation in mammals, including sheep, are far from known. In this study, we searched for the genes associated with testicular immune privilege and assessed their possible modulating mechanisms by analyzing systematic profiling of mRNAs and miRNAs on testicular tissues derived from prepubertal and postpubertal Tibetan sheep acquired by RNA sequencing. We identified 1,118 differentially expressed (DE) mRNAs associated with immunity (245 increased mRNAs and 873 decreased mRNAs) and 715 DE miRNAs (561 increased miRNAs and 154 decreased miRNAs) in postpubertal testes compared with prepuberty. qPCR validations for 20 DE mRNAs and 16 miRNAs showed that the RNA-seq results are reliable. By using Western blot, the postpubertal testes exhibited decreased protein abundance of CD19 and TGFBR2 (two proteins encoded by DE mRNAs) when compared with prepuberty, consistent with mRNA levels. The subsequent immunofluorescent staining showed that the positive signals for the CD19 protein were observed mainly in Sertoli cells and the basement membrane of pre- and postpubertal testes, as well as the prepubertal testicular vascular endothelium. The TGFBR2 protein was found mostly in interstitial cells and germ cells of pre- and postpubertal testes. Functional enrichment analysis indicated that DE mRNAs were mainly enriched in biological processes or pathways strongly associated with the blood–testis barrier (BTB) function. Many decreased mRNAs with low expression abundance were significantly enriched in pathways related to immune response. Also, multiple key miRNA-target negative correlation regulatory networks were subsequently established. Furthermore, we verified the target associations between either oar-miR-29b or oar-miR-1185-3p and ITGB1 by dual-luciferase reporter assay. Finally, a putative schematic model of the miRNA-mRNA-pathway network mediated by immune homeostasis-related genes was proposed to show their potential regulatory roles in sheep testicular privilege. Taken together, we conclude that many immune-related genes identified in this study are negatively regulated by potential miRNAs to participate in the homeostatic regulation of testicular immune privilege of sheep by sustaining BTB function and inhibiting immune responses under normal physiological conditions. This work offers the first global view of the expression profiles of miRNAs/mRNAs involved in sheep testicular immune privilege and how the genes potentially contribute to immune-homeostatic maintenance.

Characterization of sheep spermatogenesis through single-cell RNA sequencing

Spermatogenesis is an important biological process in male reproduction. The interaction between male germ cells and somatic cells during spermatogenesis, is necessary for male reproductive activities. This cellular heterogeneity has made it difficult to profile distinct cell types at different stages of development. Here, we present the first comprehensive, unbiased single-cell transcriptomic study of sheep spermatogenesis using 10× genomics single cell sequencing (scRNA-seq). We collected scRNA-seq data from 11 772 cells from the adult sheep testis and identified all known germ cells (including early primary spermatocytes, late primary spermatocytes, round spermatids, elongated spermatids, and sperm), and somatic cells (Sertoli cells and Leydig cells), as well as one somatic cell that unexpectedly contained leukocytes. The functional enrichment analysis indicated that several pathways of cell cycle, gamete generation, protein processing, and mRNA surveillance pathways were significantly enriched in testicular germ cell types, and ribosome pathway was significantly enriched in testicular somatic cell types. Further analysis identified several stage-specific marker genes of sheep germ cells, such as EZH2, SOX18, SCP2, PCNA, and PRKCD. Our research explored for the first time of the changes in the transcription level of various cell types during the process of sheep spermatogenesis, providing new insights for sheep spermatogenesis and spermatogenic cell development.

Comparative analysis of Longissimus dorsi tissue from two sheep groups identifies differentially expressed genes related to growth, development and meat quality

From a genetic perspective, the advantages of crossbreeding in sheep are unclear. In the present study, a comparative transcriptomic analysis was performed using Longissimus dorsi tissues from two sheep groups in order to identify differentially expressed genes (DEGs) related to growth, development and meat quality. Compared to Small Tail Han sheep, a total of 874 DEGs were identified in the crossbred sheep. Among these DEGs, 30, 116 and 32 DEGs were related to growth, development and meat quality, respectively. Seven DEGs highlighted by functional analysis as playing crucial roles in growth, development and meat quality were validated by the gene-act-network and co-expression-network. The expression levels of DEG mRNAs and proteins were further confirmed using RT-qPCR and western blot analyses. The results were consistent with the comparative transcriptome data. The data from this transcriptomic analysis will help to understand genetic heterosis and molecular-assisted breeding in sheep.

MiRNAs Expression Profiling of Bovine (Bos taurus) Testes and Effect of bta-miR-146b on Proliferation and Apoptosis in Bovine Male Germline Stem Cells

Spermatogenesis is a complex biological process regulated by well-coordinated gene regulation, including MicroRNAs (miRNAs). miRNAs are endogenous non-coding ribonucleic acids (ncRNAs) that mainly regulate the gene expression at post-transcriptional levels. Several studies have reported miRNAs expression in bull sperm and the process of spermatogenic arrest in cattle and yak. However, studies for the identification of differential miRNA expression and its mechanisms during the developmental stages of testis still remain uncertain. In the current study, we comprehensively analyzed the expression of miRNA in bovine testes at neonatal (3 days after birth, n = 3) and mature (13 months, n = 3) stages by RNA-seq. Moreover, the role of bta-miR-146b was also investigated in regulating the proliferation and apoptosis of bovine male germline stem cells (mGSCs) followed by a series of experiments. A total of 652 miRNAs (566 known and 86 novel miRNAs) were identified, whereas 223 miRNAs were differentially expressed between the two stages. Moreover, an elevated expression level of bta-miR-146b was found in bovine testis among nine tissues, and the functional studies indicated that the overexpression of bta-miR-146b inhibited the proliferation of bovine mGSCs and promoted apoptosis. Conversely, regulation of bta-miR-146b inhibitor promoted bovine mGSCs proliferation. This study provides a basis for understanding the regulation roles of miRNAs in bovine testis development and spermatogenesis.

Mitochondria-related miR-574 reduces sperm ATP by targeting ND5 in aging males

Couples are delaying childbearing in recent decades. While women experience a notable decrease in oocyte production in their late thirties, the effect of advanced paternal age on reproduction is incompletely understood. Herein, we observed that numerous miRNAs, including miR-574, increased in the sperm of aging males, as indicated by high-throughput sequencing. We demonstrated that miR-574 was upregulated in the sperm of two aging mouse models and was related to inferior sperm motility as an adverse predictor. Moreover, we proved that miR-574 suppressed mitochondrial function and reduced cellular ATP production in GC2 cells. Mechanistically, we demonstrated that miR-574 regulated mitochondrial function by directly targeting mt-ND5. Our study revealed an important role of miR-574 in sperm function in aging males and provided a fresh view to comprehend the aging process in sperm.

Comparative Transcriptome Analysis Identifying the Different Molecular Genetic Markers Related to Production Performance and Meat Quality in Longissimus Dorsi Tissues of MG × STH and STH Sheep

Crossbred sheep have many prominent traits, such as excellent production performance and high-quality meat, when compared to local sheep breeds. However, the genetic molecular markers related to these characteristics remain unclear. The crossbred MG × STH (small-tailed Han sheep (STH) × Mongolian sheep (MG)) breed and the STH breed were selected to measure production performance and meat quality. We used 14 indexes of production performance and meat quality, which in the MG × STH population showed significant differences compared to the STH breed. Subsequently, the longissimusdorsi from the two sheep were subjected to comparative transcriptomic analyses to identify differentially expressed genes (DEGs) related to production performance and meat quality. A total of 874 DEGs were identified between the two sheep groups. A total of 110 unique DEGs related to sheep production performance and meat quality were selected as the candidate DEGs. We found 6 production-performance-related and 30 meat-quality-related DEGs through a correlation analysis, including SPARC, ACVRL1, FNDC5 and FREM1. The expression levels of 11 DEGs were validated by real-time PCR, and the results were in accordance with the results of the comparative transcriptomic and correlation analyses. These results will assist in understanding sheep heterosis and molecular marker-assisted selection.

Validation of Suitable Reference Genes for Gene Expression Studies on Yak Testis Development

Simple Summary

Yak (Bos grunniens) provides life materials for herdsmen in high-plateau areas. Improving their low fertility is necessary to meet the demands of the development of the yak industry. The testis is an important organ for male fertility, its development is controlled by a large number of genes. Using real-time reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) to explore the quantitative expression of genes can provide insights for illuminating the molecular mechanisms of testis development, but the RT-qPCR data are influenced by the stability of reference genes (RGs). Unfortunately, no available RGs can normalize the gene expression in yak testis development. In this study, the expression stability of 13 candidate genes in yak testis at different developmental stages was evaluated using five different pieces of software. The results showed that the TATA box-binding protein (TBP) and ubiquitously expressed transcript protein (UXT) exhibited high stability across various developmental stages, TBP and hydroxymethylbilane synthase (HMBS) were the most stably expressed genes in immature stages, and mitochondrial ribosomal protein L39 (MRPL39) and TBP exhibited the most stable expression across mature stages. This study provided suitable RGs for gene expression studies in yak testis development.

Abstract

Testis has an important function in male reproduction. Its development is regulated by a large number of genes. The real-time reserve transcriptase-quantitative polymerase chain reaction (RT-qPCR) is a useful tool to evaluate the gene expression levels. However, unsuitable reference genes (RGs) can cause the misinterpretation of gene expression levels. Unfortunately, the ideal RGs for yak testis development are yet to be studied. In this study, 13 commonly used RGs were selected to identify the most stable RGs in yak testis at four different developmental stages, including two immature stages (6 months and 18 months) and two mature stages (30 months and 6 years). This study used GeNorm, NormFinder, BestKeeper, ∆Ct, and RefFinder programs to evaluate the stability of 13 candidate genes. The results of RefFinder showed that the stabilities of TATA box-binding protein (TBP) and ubiquitously expressed transcript protein (UXT) were ranked the top two across all developmental stages. TBP and hydroxymethylbilane synthase (HMBS) were stably expressed in immature stages, while mitochondrial ribosomal protein L39 (MRPL39) and TBP had higher stability than other candidate genes in mature stages. This study provided valuable information for gene expression studies to assist further investigation on the molecular mechanisms in underlying yak testis development.

MiR-125b-2 Knockout in Testis Is Associated with Targeting to the PAP Gene, Mitochondrial Copy Number, and Impaired Sperm Quality

It has been reported that the miR-125 family plays an important role in regulating embryo development. However, the function of miR-125b-2 in spermatogenesis remains unknown. In this study, we used a model of miR-125b knockout (KO) mice to study the relationship between miR-125b-2 and spermatogenesis. Among the KO mice, the progeny test showed that the litter size decreased significantly (p = 0.0002) and the rate of non-parous females increased significantly from 10% to 38%. At the same time, the testosterone concentration increased significantly (p = 0.007), with a remarkable decrease for estradiol (p = 0.02). Moreover, the sperm count decreased obviously (p = 0.011) and the percentage of abnormal sperm increased significantly (p = 0.0002). The testicular transcriptome sequencing revealed that there were 173 up-regulated genes, including Papolb (PAP), and 151 down-regulated genes in KO mice compared with wild type (WT). The Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene ontology (GO) analysis showed that many of these genes were involved in sperm mitochondrial metabolism and other cellular biological processes. Meanwhile, the sperm mitochondria DNA (mtDNA) copy number increased significantly in the KO mice, but there were no changes observed in the mtDNA integrity and mutations of mt-Cytb, as well as the mt-ATP6 between the WT mice and KO mice. In the top 10 up-regulated genes, PAP, as a testis specific expressing gene, affect the process of spermatogenesis. Western blotting and the Luciferase assay validated that PAP was the target of miR-125b-5p. Intriguingly, we also found that both miR-125b and PAP were only highly expressed in the germ cells (GC) instead of in the Leydig cells (LC) and Sertoli cells (SC). Additionally, miR-125b-5p down regulated the secretion of testosterone in the TM3 cell by targeting PAP (p = 0.021). Our study firstly demonstrated that miR-125b-2 regulated testosterone secretion by directly targeting PAP, and increased the sperm mtDNA copy number to affect semen quality. The study indicated that miR-125b-2 had a positive influence on the reproductive performance of animals by regulating the expression of the PAP gene, and could be a potential drugs and diagnostic target for male infertility.