Regulation of ovarian folliculogenesis by IGF and BMP system in domestic animals

Nutrition, Growth, and Age at Puberty in Heifers

Puberty onset and age at first calving have a critical impact on livestock production for good reproductive efficiency of the herd and to reduce the duration of the non-productive stage of the growing heifer. Besides genetic factors, sexual maturation is also affected by environmental factors, such as nutrition, which can account for up to 20% of the observed variability. The rate of body weight gain during growth is considered the main variable influencing the age at puberty, dependent on planes of nutrition in growing animals during the prepubertal-to-pregnancy stage. This paper reviews current knowledge concerning nutrition management and attainment of puberty in heifers, considering the relevance of some indicators such as body measurements and hormones strictly linked to the growth and puberty process. Puberty onset is dependent on the acquisition of adequate subcutaneous adipose tissue mass, as it is the main source of the hormone leptin. Until a certain level, body condition score and age at puberty are negatively correlated, but beyond that, for fatter animals, such correlation is gradually lost. Age at puberty in heifers was reported to be negatively related to IGF-1. Future research should be planned considering the need to standardize the experimental animals and conditions.

Dynamic Expression Profile of Follicles at Different Stages in High- and Low-Production Laying Hens

Improving the efficiency of hens and extending the egg-laying cycle require maintaining high egg production in the later stages. The ovarian follicles, as the primary functional units for ovarian development and oocyte maturation, play a crucial role in regulating the continuous ovulation of hens. The egg production rate of laying hens is mostly affected by proper follicle growth and ovulation in the ovaries. The objective of this study was to identify the key genes and signaling pathways involved in the development of ovarian follicles in Taihang hens through transcriptome screening. In this study, RNA sequencing was used to compare and analyze the transcriptomes of ovarian follicles at four developmental stages: small white follicles (SWF), small yellow follicles (SYF), F5 follicles, and F2 follicles, from two groups: the high continual production group (H-Group) and the low continual production group (L-Group). A total of 24 cDNA libraries were constructed, and significant differential expression of 96, 199, 591, and 314 mRNAs was detected in the SWF, SYF, F5, and F2 follicles of the H and L groups, respectively. Based on the results of GO and KEGG enrichment analyses, each stage of follicle growth possesses distinct molecular genetic features, which have important effects on follicle development and significantly promote the formation of continuous production traits through the biosynthesis of steroid hormones, cytokine-cytokine receptor interaction, and neuroactive ligand-receptor interaction. Additionally, through STEM analysis, we identified 59 DEGs, including ZP4, KCNH1, IGFs, HMGA2, and CDH1, potentially associated with follicular development within four significant modules. This study represents the first transcriptome investigation of follicles in hens with high and low egg-producing characteristics at four crucial developmental stages. These findings provide important molecular evidence for understanding the regulation of follicular development and its variations.

Insulin-like growth factor (IGF) performance in ovarian function and applications in reproductive biotechnologies

The role of the insulin-like growth factor (IGF) system has attracted close attention. The activity of IGF binding proteins (IGFBPs) within the ovary has not been fully elucidated to date. These proteins bind to IGF with an equal, or greater, affinity than to the IGF1 receptor, thus being in the main position to regulate IGF signalling, in addition to extending the half-life of IGFs within the bloodstream and promoting IGF storage in specific tissue niches. IGF1 has an important part in cell proliferation, differentiation and apoptosis. Considering the importance of IGFs in oocyte maturation, this review sought to elucidate aspects including: IGF production mechanisms; constituent members of their family and their respective functions; the role that these factors play during folliculogenesis, together with their functions during oocyte maturation and apoptosis, and their performance during luteal development. This review also explores the role of IGFs in biotechnological applications, focusing specifically on animal genetic gain.

The role of insulin-like growth factor 2 mRNA binding proteins in female reproductive pathophysiology

Insulin-like growth factor 2 (IGF2) mRNA binding proteins (IMPs) family belongs to a highly conserved family of RNA-binding proteins (RBPs) and is responsible for regulating RNA processing including localization, translation and stability. Mammalian IMPs (IMP1-3) take part in development, metabolism and tumorigenesis, where they are believed to play a major role in cell growth, metabolism, migration and invasion. IMPs have been identified that are expressed in ovary, placenta and embryo. The up-to-date evidence suggest that IMPs are involved in folliculogenesis, oocyte maturation, embryogenesis, implantation, and placentation. The dysregulation of IMPs not only contributes to carcinogenesis but also disturbs the female reproduction, and may participate in the pathogenesis of reproductive diseases and obstetric syndromes, such as polycystic ovary syndrome (PCOS), pre-eclampsia (PE), gestational diabetes mellitus (GDM) and gynecological tumors. In this review, we summarize the role of IMPs in female reproductive pathophysiology, and hope to provide new insights into the identification of potential therapeutic targets.

Forecasting early onset diminished ovarian reserve for young reproductive age women

PURPOSE

To investigate the biological networks associated with DOR in young women and the subsequent molecular impact on preimplantation embryos.

METHODS

Whole peripheral blood was collected from patients: young women presenting with diminished ovarian reserve (DOR) and age-matched young women with normal ovarian reserve. Maternal exome sequencing was performed on the NovaSEQ 6000 and sequencing validation was completed using Taqman® SNP Genotyping Assays. Blastocyst global methylome and transcriptome sequencing were also analyzed.

RESULTS

Exome sequencing revealed 730 significant DNA variants observed exclusively in the young DOR patients. Bioinformatic analysis revealed a significant impact to the Glucocorticoid receptor (GR) signaling pathway and each young DOR female had an average of 6.2 deleterious DNA variants within this pathway. Additional stratification based on patient age resulted in a cut-off at 31 years for young DOR discrimination. Embryonic global methylome sequencing resulted in only a very small number of total CpG sites with methylation alterations (1,775; 0.015% of total) in the DOR group. Additionally, there was no co-localization between these limited number of altered CpG sites and significant variants, genes, or pathways. RNA sequencing also resulted in no biologically significant transcription changes between DOR blastocysts and controls.

CONCLUSION

GR signaling DNA variants were observed in women with early-onset DOR potentially compromising oocyte production and quality. However, no significant downstream effects on biological processes appear to impact the resulting blastocyst. The ability to forecast premature DOR for young women may allow for earlier identification and clinical intervention for this patient population.

New Anti-Müllerian Hormone Target Genes Involved in Granulosa Cell Survival in Women With Polycystic Ovary Syndrome

PURPOSE

A protective effect of anti-Müllerian hormone (AMH) on follicle atresia was recently demonstrated using long-term treatments, but this effect has never been supported by mechanistic studies. This work aimed to gain an insight into the mechanism of action of AMH on follicle atresia and on how this could account for the increased follicle pool observed in women with polycystic ovary syndrome (PCOS).

METHODS

In vivo and in vitro experiments were performed to study the effects of AMH on follicle atresia and on the proliferation and apoptosis of granulosa cells (GCs). RNA-sequencing was carried out to identify new AMH target genes in GCs. The expression of some of these genes in GCs from control and PCOS women was compared using microfluidic real time quantitative RT-PCR.

RESULTS

A short-term AMH treatment prevented follicle atresia in prepubertal mice. Consistent with this result, AMH inhibited apoptosis and promoted proliferation of different models of GCs. Moreover, integrative biology analyses of 965 AMH target genes identified in 1 of these GC models, confirmed that AMH had initiated a gene expression program favoring cell survival and proliferation. Finally, on 43 genes selected among the most up- and down-regulated AMH targets, 8 were up-regulated in GCs isolated from PCOS women, of which 5 are involved in cell survival.

MAIN CONCLUSIONS

Our results provide for the first time cellular and molecular evidence that AMH protects follicles from atresia by controlling GC survival and suggest that AMH could participate in the increased follicle pool of PCOS patients.

Discovery of single nucleotide polymorphisms in bone morphogenetic protein (BMP) genes of goats by double digest restriction-site associated DNA sequencing

Context Two native goat breeds from Kerala, Malabari and Attappady Black, differ significantly in prolificacy (i.e. no. of kids born/kidding). Prolificacy is an important economic trait and the subject of genetic research showing that bone morphogenetic protein (BMP) genes have a significant effect. Double digest restriction-site associated DNA sequencing (ddRADseq) is a highly efficient and low cost technology for high density discovery of single nucleotide polymorphisms (SNPs), which could serve as predictive markers for animal breeding programs. Aims The study was aimed at discovering SNPs in BMP genes that affect prolificacy, using ddRADseq followed by validation of selected SNP. Methods Blood DNA samples of 10 highly prolific Malabari and 10 less prolific Attappady Black goats were pooled by group and subjected to ddRADseq. SNPs observed in BMP genes were investigated and compared between groups. A validation study was done for the c.614–32789C>T variant in 100 Malabari and 50 Attappady Black goats by using PCR-RFLP. Key results In total, 6333 variants were identified by ddRADseq. Three variants were identified in BMP genes, which included two intronic variants c.614–32789C>T and c.490+6793T>C, in genes BMP6 and BMP5 and a downstream gene variant near the BMPR1B gene. According to ddRADseq data, variants in BMP5 and BMP6 differed in allelic distribution between Malabari and Attappady Black goats. For c.490+6793T>C in BMP5, the CC genotype was predominant in the highly prolific Malabari whereas TC was present in the Attappady Black group. The variant c.614–32789C>T in BMP6 was genotyped as TC in Malabari and CC in Attappady Black goats by ddRADseq. This variant was predicted to have an effect on splicing, according to the tool SplicePort. On the basis of bioinformatics analysis and the role of BMP6 gene in follicular dynamics, the variant in BMP6 was selected for further validation studies. All three genotypes were identified by PCR-RFLP; the C allele was the rare allele in the population with an allele frequency of 0.36. Presence of both alleles C and T and the three genotypes CC, TC and TT in this larger population substantiated the robustness of ddRADseq technique. Conclusions The technique discovered high confidence SNPs, which could be used for further validation and association studies to develop markers for selection of animals and for genetic improvement of this complex trait. Implications Techniques such as ddRADseq provide a large number of SNPs, and investigation of those polymorphisms found across the genome will help to identify new loci affecting traits of interest. This, in turn, will aid in exploring genetically complex traits in a faster and cheaper manner.

Progesterone dose during synchronization treatment alters luteinizing hormone receptor and steroidogenic enzyme mRNA abundances in granulosa cells of Nellore heifers

The objective was to investigate effects of progesterone (P₄) dose on abundance of luteinizing hormone receptor (LHCGR), aromatase (CYP19A1), 3β-hydroxysteroid dehydrogenase (HSD3B1), and other steroidogenic mRNA transcripts in granulosa cells from dominant follicles. Nellore heifers were assigned to one of six groups: new, first-use controlled internal drug release device (CIDR1) inserted for 5 days (Large-P₄-dose-D5; n = 7) or 6 days (Large-P₄-dose-D6; n = 8), prostaglandin (PG)F_2α administered on D0 and 1 previously-used CIDR (CIDR3) inserted for 5 days (Small- P₄-dose-D5; n = 8) or 6 days (Small-P₄-dose-D6; n = 8), CIDR1 inserted on D0 and removed plus PGF_2α on D5 (Large-P₄-dose-proestrus (PE); n = 7), and CIDR3 and PGF_2α on D0 and 1, CIDR3 removed plus PGF_2α on D5 (Small-P₄-dose-PE; n = 7). Duration of P₄ treatment (D5 compared to D6) affected abundances of CYP19A1 mRNA transcripts, with there being greater abundances on D6 than D5 (P ≤ 0.05). Heifers treated with the large dose of P₄ had a smaller dominant follicle, less serum and intra-follicular estradiol (E₂) concentrations (P ≤ 0.05) and lesser LHCGR, CYP19A1, and HSD3B1 transcript abundances (P ≤ 0.05). Heifers treated to induce PE had a larger follicle diameter (P = 0.09), greater intra-follicular E₂ concentrations and larger abundances of CYP19A1 mRNA transcript (P ≤ 0.05) than heifers of the D6 group. Overall, treatment with larger doses of P₄ resulted in lesser abundances of LHCGR, HSD3B1, and CYP19A1 mRNA transcripts; thus, potentially leading to development of smaller dominant follicles and lesser E₂ concentrations.

Molecular and cellular effects of insulin-like growth factor-1 and LongR3-IGF-1 on in vitro maturation of bovine oocytes: comparative study

Addition effects of insulin-like growth factor-1 (IGF-1) and its synthetic analogue insulin-like growth factor-1 recombinant-3 (LongR3-IGF-1) after in vitro maturation (IVM) of cattle cumulus-oocyte complexes (COCs) were compared and evaluated on meiotic progression, apoptosis and profile genes of oocyte competence (GDF9, BMP15, BAX, BCL2, OOSP1, IGFBP2, IGBFP4 and IGFBP5), and their respective cumulus cells (AREG, EGFR, FSHR, COX2, BAX, BCL2, IGFBP2, IGFBP4 and IGFBP5). The 739 COCs (n = 10 pools) of bovine ovaries were collected, selected and matured with IGF-1 (100 ng/mL), LongR3-IGF-1 (100 ng/mL), and in two control groups with 0.1% polyvinyl alcohol (PVA) or 10% fetal bovine serum (FBS), for 22-24 h. The statistical analysis was performed by a linear mixed effects model, ANOVA and Tukey tests. There was no statistical difference between experimental groups taken into account the meiotic progression and apoptosis (P > 0.05). Nevertheless, there were statistical differences (P ≤ 0.05) among FBS, IGF-1 and LongR3-IGF-1 groups for IGFBP4 gene expression, and among PVA, IGF-1 and LongR3-IGF-1 for COX2 gene expression in cumulus cells. Moreover, statistical difference was found for BCL2 gene expression between IGF-1, FBS and PVA groups and for IGFBP4 gene expression between LongR3-IGF-1, PVA and FBS in oocytes. There was no statistical difference between experimental groups for other genes evaluated. These results showed a good performance of IVM of bovine oocytes in the presence of LongR3-IGF-1 and the possibility of replacement of IGF-1 and FBS.

Plasma IGF1 and 17β-Estradiol Concentrations During the Follicular Wave in Llamas

The aim of this study was to characterize the temporal association between follicular waves and circulating concentrations of 17β-estradiol (E2) and IGF1 in llamas. Follicular waves could be clearly divided in three phases: growth, plateau and regression; with a mean duration of 18.8 ± 0.32 days. All follicular waves showed overlapping, so that as one dominant follicle was regressing, another one was growing. E2 plasma concentration showed a wavelike pattern, similar to that followed by the dominant follicle; reaching its maximum concentration at the end of the growth phase and decreasing at the end of the plateau phase. IGF1 also showed variations during the follicular wave. It tended to increase during the growth phase and decreased toward Days 14 and 16. IGF1 reached its maximum concentration before E2 did (5 ± 0.8 vs. 7.2 ± 0.5 days after wave emergence) and before the maximum follicular diameter was attained (10.2 ± 0.46 days after wave emergence). Both hormones started to rise again in coincidence with the development of a new follicular wave. The observed profiles allow to suggest that IGF1 could have a role on folliculogenesis and ovarian steroideogenesis in llamas, as reported for other species.

Indel variants within the PRL and GHR genes associated with sheep litter size

Growth hormone and prolactin belong to the class of peptide hormones that have a wide range of regulatory functions. In this study, polymorphisms of growth hormone receptor (GHR) and prolactin (PRL) genes were analysed as candidate genes, which are responsible for the litter size in Australian White (AUW) sheep. According to the statistical analyses results, the polymorphism information content (PIC) values of the PRL-P1-ins-23 bp, GHR-P2-del-23 bp and GHR-P8-del-23 bp were 0.371, 0.366 and 0.375, respectively, which indicates the high genetic polymorphism in AUW sheep. Moreover, all indel loci are not conformed to the HWE (p < .05). Further, our findings revealed that the PRL-P1-ins-23 bp polymorphism in the ovine PRL gene was significantly related to the first parity litter size (p = .001) and the DD genotype displaying the highest genotypic mean. Meanwhile, the GHR-P2-del-23 bp and GHR-P8-23 bp indels in the ovine GHR gene were significantly correlated with first parity litter size (p < .05), and the individuals with the genotype II showed significantly higher litter size than others. Collectively, these results demonstrated that our findings could be useful for future sheep breeding strategies based on the molecular-assisted selection (MAS).

Relationship between plasma concentrations of IGF-I and clinical endometritis, and response to progesterone synchrony in dairy cows during early lactation

The first aim of this study was to evaluate the relationship between the concentrations of plasma insulin-like growth factor-I (IGF-I) in the transition period and the incidence of clinical endometritis postpartum. The second aim was to evaluate the relationship between the concentration of plasma IGF-I in the transition period and the estrous synchrony response and pregnancy rate to a controlled internal drug release (CIDR) protocol. A total of 402 dairy cows, 250 multiparous and 152 primiparous, were enrolled. A blood sample was taken from all cows 2 and 1 wk precalving and wk 1, 3, 4, and 5 postcalving for subsequent analysis of IGF-I. Vaginal discharge score as a measurement of uterine health was recorded in wk 3, 4, and 5 postcalving. Estrous cycles of all cows were synchronized on ≥37 d in milk (mean = 59; range 37-93) using an 8-d CIDR protocol. All cows were scanned at 32 to 35 d after insemination to confirm pregnancy. Data were analyzed using Proc Mixed and Proc Logistic models in SAS (version 9.3; SAS Institute Inc., Cary, NC). Plasma IGF-I concentrations were significantly greater in the primiparous cows than in the multiparous cows, both before and after calving, and were therefore analyzed separately. In multiparous cows plasma IGF-I concentrations postcalving were significantly lower among cows with uterine infection than in those without infection, and multiparous cows with a plasma IGF-I concentration less than 40 ng/mL 1 wk after calving were 3 times more likely to suffer from a uterine infection 4 to 5 weeks postcalving (odds ratio 2.8; 95% confidence interval 1.0-7.6). Plasma IGF-I concentrations were significantly greater after calving in the 121 primiparous cows that exhibited estrus post-CIDR protocol (mean 125 ng/mL) than in the 25 primiparous cows that did not respond (mean 95 ng/mL). Multiparous cows with greater plasma IGF-I concentrations postcalving had a significantly greater chance of conceiving (mean plasma IGF-I concentration of conceiving cows = 86 ng/mL; nonconceiving = 70 ng/mL). These results show an association between greater concentrations of plasma IGF-I postcalving and response to CIDR protocol in primiparous animals (mean plasma IGF-I concentration of responders = 116 ng/mL; nonresponders = 95 ng/mL). In contrast no association was detected between concentrations of plasma IGF-I in relation to the response to the CIDR protocol in multiparous cows. In conclusion, changes in circulating concentrations of plasma IGF-I early postpartum may help predict reproductive status of dairy cows.

Genome-Wide Association Analysis Reveals Key Genes Responsible for Egg Production of Lion Head Goose

The lion head goose is one of the most important agricultural resources in China; however, its breeding process is relatively slow. In the present study, a genome-wide association study was performed for the genetic selection of egg production characters in lion head geese. We detected 30 single-nucleotide polymorphisms located in or near 30 genes that might be associated with egg production character, and quantitative real-time polymerase chain reaction was used to verify their expression level in lion head geese. The results showed that the expression levels of CRTC1 (encoding CREB-regulated transcription coactivator 1), FAAH2 (encoding fatty acid amide hydrolase 2), GPC3 (encoding glypican 3), and SERPINC1 (encoding serpin family C member 1) in high egg production population were significantly lower than those in the low egg production populations (*P < 0.05). The expression levels of CLPB (encoding caseinolytic peptidase B protein homolog), GNA12 (encoding guanine nucleotide-binding protein subunit alpha-12), and ZMAT5 (encoding zinc finger, matrin type 5) in the high egg production population were significantly higher than those in the low egg production populations (*P < 0.05). The expression of BMP4 (encoding bone morphogenetic protein 4), FRMPD3 (encoding FERM and PDZ domain containing 3), LIF (encoding leukemia inhibitory factor), and NFYC (encoding nuclear transcription factor Y subunit gamma) in the high egg production population were very significantly lower than those in the low egg production population (**P < 0.01). Our findings provide an insight into the economic traits of lion head goose. These candidate genes might be valuable for future breeding improvement.

Whole-genome sequence analysis reveals candidate genomic footprints and genes associated with reproductive traits in Thoroughbred horse

The primary objective of most horse breeding operations was to maximize reproductive efficiency and minimize the cost of producing live foals. Here, we compared individual horses from the Thoroughbred population (n = 17), known as a horse breed with poor reproductive performance, with other six horse populations (n = 28), to detect genomic signatures of positive selection underlying of reproductive traits. A number of protein-coding genes with significant (p-value <.01) higher F_ST values (616 genes) and a lower value for nucleotide diversity (π) (310 genes) were identified. The results of our study revealed some candidate genes such as IGFBP2, IGFBP5, GDF9, BRINP3 and GRID1 are possibly associated with functions influencing reproductive traits. These genes may have been under selection due to their essential roles in reproduction performance in horses. The candidate selected genes identified in this work should be of great interest for future research into genetic architecture of traits relevant to horse breeding programmes.

Plasma Protein Comparison between Dairy Cows with Inactive Ovaries and Estrus

To screen differentially expressed proteins in the blood dairy cows with inactive ovaries caused by a negative energy balance and to determine the roles of the identified proteins in the development of inactive ovaries.Holstein cows at 14 to 21 days postpartum in an intensive dairy farm were examined for their energy balance (EB) status by blood β-hydroxybutyrate (BHBA) and assigned to the inactive ovary (IO) group (n = 50) and the normal oestrus control (CON) group (n = 50) at 60 to 90 days postpartum by means of the oestrus manifestation, rectal examination and B-ultrasound examination. Fourteen differentially expressed proteins from 61 proteins in the plasma of dairy cows with IOs were identified by iTRAQ/LC-MS/MS and GO, KEGG, and PATHWAY analysis. Eleven expressed proteins were upregulated, and 3 expressed proteins were downregulated. Among the 10 differentially expressed proteins verified by Western blot or ELISA, the relative expression levels of ALDOB, IGFBP2, ITIH3 and LDHB in mixed samples and single samples were consistent with the proteomic protein results. PKM2, GPX3, ALDOB, RBP4 and AHSG were significantly different between the two groups (P < 0.05); APOA4 and SPAM1 were not significantly different (P > 0.05) but were still downregulated in the ovarian resting group. This study confirmed that 14 plasma differential proteins in the inactive ovaries of postpartum dairy cows were associated with follicular development, and these findings provide a foundation for further research on the mechanism and prevention of inactive ovaries in dairy cows.

Leptin and IGF1 receptors in alpaca (Vicugna pacos) ovaries

Folliculogenesis and ovulation are regulated by gonadotrophins and other factors such as Insulin like growth factor 1 (IGF1) and leptin. In various species the presence of IGF1 receptor (IGF1R) and leptin receptor (ObR) has been detected in the ovary, but not in the alpaca. Thus, the aim of the present study was to evaluate the presence of these receptors in this tissue and analyze if the presence of these receptors in the ovary is related to the presence of a corpus luteum (CL) and if abundances, as determined by immunostaining intensity vary with follicle size. The IGF1R and ObR were identified in primary and secondary follicles, granulosa and theca interna cells of tertiary follicles and in CL. There were greater abundances of IGF1R in granulosa cells of tertiary follicles of ovaries without compared with those with CL. In both groups, the immunostaining of granulosa cells was greater than in theca interna cells. The abundance of ObR was greater in primary and secondary follicles, and theca interna cells of tertiary follicles in ovaries with than those without CL. Immunostaining of granulosa cells was greater than theca interna cells only in ovaries without CL. There were no differences in the abundance of ObR and IGF1R between primary and secondary follicles and granulosa cells of tertiary follicles, neither in ovaries with or without CL. The abundance of IGF1R was not correlated with abundance of ObR neither in ovaries with or without CL. These results indicate a possible role for IGF and leptin in ovarian function. Furthermore, these receptors could be regulated by ovarian steroid hormones because abundance of these receptors in ovaries varies depending on whether there is a CL present in the ovary.

Effect of bST administration on plasma concentrations of IGF-I and follicular dynamics and ovulation during the interovulatory cycle of sheep and goats

This study used a comparative approach to gather clinical information to assess the effect of bovine somatotropin (bST) on follicular dynamics and ovulation in sheep and goats during an interovulatory cycle. The performance of general markers of ovarian function and specific features of follicular dynamics obtained by daily ultrasonography (US) were used to assess the hypothesis that bST, associated with supraphysiological levels of IGF-I, was able to disrupt the follicular dynamics and ovulation in Highlander ewes and Saanen goats. In Exp 1, 15 ewes and 14 goats were estrous-synchronized (P₄-6 days + PGFα d-6) and then allocated to a bST-treated group (50 and 100 mg, Lactotropin^®; n = 5 females each) and to an untreated control group (5 ewes and 4 goats) to assess the activity of bST through plasma IGF-I (RIA). In Exp 2, 12 animals from each species were synchronized. At day 6, they were divided into a bST-group (100 mg in sheep and 50 mg in goats, n = 6 each) and an untreated control group (n = 6 each). Starting at day 6 and up to 22 days after ovulation in sheep and 25 days in goats, each female was subjected to daily US (10 mHz probe) to assess follicular and luteal (CL) dynamics and ovulation. This included assessments of both general ovarian features and specific follicular wave features. Our results showed that bST increased plasma IGF-I by day 3 (p < 0.01) when compared to the control group. Moreover, these concentrations were maintained for at least 10 days in sheep and 10 days in goats before returning to pre-treatment concentrations. Increases in IGF-I after bST doses were similar in terms of a daily and total amount (P > 0.10). Results from Exp.2 indicate that in sheep, bST administration had a subtle inhibitory effect on follicular function. However, bST in goats had a stronger influence, extending the interovulatory cycle (P = 0,034), increasing the number of follicular waves during the period (P = 0.003), and reducing the functional potential of large follicles as measured by their lower follicular diameter (P = 0.02), duration of the follicle waves (P = 0.02), and persistence of follicles after reaching their maximum diameters (P = 0.04). In addition, untreated sheep and goats shared common patterns of terminal follicular development and ovulations characterized by overlapping between follicular waves and ovulations of follicles from different waves, features not seen in cattle.

Does the bone morphogenetic protein 7 inhibit oocyte maturation by autocrine/paracrine in mud crab?

A bone morphogenetic protein ligand (BMP7) and its two receptors (BMPRIB and BMPRII) were recently cloned and characterized in the mud crab, Scylla paramamosain. However specific functions of BMP7 and the mechanistic pathways regulating its function are largely unidentified. In the present study, we separated oocytes and follicle cells from the ovarian explants of S. paramamosain. Subsequent analysis using semi-quantitative PCR demonstrated that the mRNA of Sp-BMP7 was exclusively expressed in follicle cells while Sp-BMPRs were expressed in both oocytes and follicle cells. In vitro experiments further showed that the mRNA and protein levels of Cyclin B increased but Sp-BMP7 declined in 17α, 20β-Dihydroxyprogesterone (DHP)-induced oocytes. Furthermore, the inhibitory effects of Sp-BMP7 were not affected by the elimination of the contact/gap junction-mediated communication between oocytes and follicle cells. Our data indicate that BMP7 may play a role in the suppression of DHP-induced oocyte maturation by affecting autocrine/paracrine pathways in S. paramamosain.

Oral propylene glycol modifies follicular fluid and gene expression profiles in cumulus-oocyte complexes and embryos in feed-restricted heifers

Dietary supplementation with propylene glycol (PG) increases in vitro production of high-quality embryos in feed-restricted heifers. The aim of the present study was to evaluate the effects of PG in feed-restricted heifers on follicular fluid insulin and insulin-like growth factor (IGF) 1 concentrations, expression of IGF system genes in oocytes and cumulus cells and the expression of selected genes in blastocysts. Feed-restricted (R) heifers were drenched with water or PG during induced oestrous cycles (400mL of PG or water/drench, daily drenching at 1600 hours for the first 9 days of the oestrous cycle). Ovum pick-up (OPU) was performed after superovulation to produce in vitro embryos and without superovulation to recover oocytes, cumulus cells and follicular fluid. OPU was also performed in a control group (not feed restricted and no drenching). Follicular fluid IGF1 concentrations were reduced by R, and PG restored IGF1 concentrations to those seen in the control group. In cumulus cells, expression of IGF1, IGF1 receptor (IGF1R) and IGF binding protein 4 (IGFBP4) was decreased in the R group, and fully (IGF1 and IGF1R) or partially (IGFBP4) restored to control levels by PG. Blastocyst perilipin 2 (PLIN2; also known as adipophilin), Bcl-2-associated X protein (BAX), SCL2A1 (facilitated glucose/fructose transporter GLUT1), aquaporin 3 (AQP3), DNA (cytosine-5)-methyltransferase 3A (DNMT3A) and heat shock 70-kDa protein 9 (HSPA9B) expression were decreased in R heifers; PG restored the expression of the last four genes to control levels. In conclusion, these results suggest that, during follicular growth, PG exerts epigenetic regulatory effects on gene expression in blastocyst stage embryos.

The Mechanism of Melatonin and Its Receptor MT2 Involved in the Development of Bovine Granulosa Cells

Ovarian granulosa cells (GCs) are a critical approach to investigate the mechanism of gene regulation during folliculogenesis. The objective of this study was to investigate the role of MT2 in bovine GCs, and assess whether MT2 silencing affected GCs response to melatonin. We found that MT2 silencing significantly decreased the secretion of progesterone and estradiol, and increased the concentration of inhibin B and activin B. To further reveal the regulatory mechanism of MT2 silencing on steroids synthesis, it was found that the expression of CYP19A1 and CYP11A1 enzymes (steroid hormone synthesis) were down-regulated, while genes related to hormonal synthesis (StAR, RUNX2, INHA and INHBB) were up-regulated without affecting the expression of INHBA, suggesting that MT2 silencing may regulate hormone abundance. Furthermore, MT2 silencing significantly increased the expression of TGFBR3 and BMP6, and decreased the expression of LHR and DNMT1A without significant difference in the expression of FSHR and EGFR. In addition, MT2 silencing didn’t affect the effect of melatonin on increasing the expression of DNMT1A, EGFR, INHBA and LHR, and progesterone level, or decreasing INHA, TGFBR3 and StAR expression, and production of inhibin B. Moreover, MT2 silencing could disrupt the role of melatonin in decreasing the FSHR, INHBB and BMP6 expression, and activin B secretion. In conclusion, these results reveal that melatonin and MT2 are essential regulator of bovine GCs function by modulating reproduction-related genes expression, hormones secretion and other regulators of folliculogenesis.

Whole-genome analysis of structural variations between Xiang pigs with larger litter sizes and those with smaller litter sizes

To gain a better knowledge of structural variations (SVs) in Xiang pig, we used next-generation sequencing to analyze the Xiang pigs with larger (XL) or smaller litter sizes (XS). Our analysis yielded 28,040 putative SVs in the Xiang pig. These SVs distributed throughout all of chromosomes. Some functional regions including exons and untranslated regions were less varied than introns and intergenic regions. We detected 4637 and 4119 specific SVs, which contained 1697 and 1582 genes in XL and XS group, respectively. These genes were mainly enriched in the well-known pathways involved in development and reproduction processes. Population validation was carried out on 50 SVs candidates using PCR method in 144 Xiang pig crowds. All of 50 SVs were confirmed by PCR method and 14 SVs were associated with the litter size of Xiang pigs. These results may be helpful for the elucidation of growth and reproduction regulation in Xiang pig.

GATA Regulation and Function During the Ovarian Life Cycle

GATA4 and GATA6 are the sole GATA factors expressed in the ovary during embryonic development and adulthood. Up today, GATA4 and GATA6 are the only transcription factors that have been conditionally deleted during ovarian development and at each major stage of follicle maturation. The evidence from these transgenic mice revealed that GATA4 and GATA6 are crucial for follicles assembly, granulosa cell differentiation, postnatal follicle growth, and luteinization. Thus, conditional knockdown of both factors in the granulosa cells at any stage of development leads to female infertility. GATA targets impacting female reproduction include genes involved in steroidogenesis, hormone signaling, ovarian hormones, extracellular matrix organization, and apoptosis/cell division.

Metabolic Effects of FecB Gene on Follicular Fluid and Ovarian Vein Serum in Sheep (Ovis aries)

The FecB gene has been discovered as an important gene in sheep for its high relationship with the ovulation rate, but its regulatory mechanism remains unknown. In the present study, liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) techniques were adopted to detect the metabolic effects of FecB gene in follicular fluid (FF) and ovarian vein serum (OVS) in Small Tail Han (STH) sheep. ANOVA and random forest statistical methods were employed for the identification of important metabolic pathways and biomarkers. Changes in amino acid metabolism, redox environment, and energy metabolism were observed in FF from the three FecB genotype STH ewes. Principal component analysis (PCA) and hierarchical clustering analysis (HCA) showed that metabolic effects of FecB gene are more pronounced in FF than in OVS. Therefore, the difference of the metabolic profile in FF is also affected by the FecB genotypes. In Spearman correlation analysis, key metabolites (e.g., glucose 6-phosphate, glucose 1-phosphate, aspartate, asparagine, glutathione oxidized (GSSG), cysteine-glutathione disulfide, γ-glutamylglutamine, and 2-hydrosybutyrate) in ovine FF samples showed a significant correlation with the ovulation rate. Our findings will help to explain the metabolic mechanism of high prolificacy ewes and benefit fertility identification.

Potential Functions of IGFBP-2 for Ovarian Folliculogenesis and Steroidogenesis

Ovarian follicles, as transient structural and functional complexes with the oocyte and the associated cells, determine the female reproductive cycle and thus fertility. Ovarian function is subject to the strict control of hormones and growth factors and thus regulated by auto-, para-, and endocrine mechanisms but influenced also by endogenous factors. During the waves of follicular growth and development, one follicle (monoovulatory) or a limited number of them (polyovulatory) are selected under hypothalamic-gonadal control for maturation until ovulation, resulting in the fertile oocyte. Subordinate follicles inevitably enter different stages of atresia. A number of studies have observed species-specific alterations of IGFBP-2 levels during the phases of growth and development or selection and atresia of follicles. IGFBP-2 is thus probably involved in the process of follicle growth, differentiation, and degeneration. This may occur on the levels of IGF-dependent and -independent growth control but also due to the control of steroidogenesis, e.g., via induction of aromatase expression. In mice, IGFBP-2 delayed reproductive development most probably by IGF-independent mechanisms. Because reproductive development is closely linked to the control of life- or health-span and energy metabolism, we feel that the time is right now to resume research on the effects of IGFBP-2 in the ovarian follicular compartment.

Transcriptional profiling of porcine granulosa cells exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a toxic man-made chemical compound contaminating the environment. An exposure of living organisms to TCDD may result in numerous disorders, including reproductive pathologies. The aim of the current study was to examine the effects of TCDD on the transcriptome of porcine granulosa cell line AVG-16. By employing next-generation sequencing (NGS) we aimed to identify genes potentially involved in the mechanism of TCDD action and toxicity in porcine granulosa cells. The AVG-16 cells were treated with TCDD (100 nM) for 3, 12 or 24 h, and afterwards total cellular RNA was isolated and sequenced. In TCDD-treated cells we identified 141 differentially expressed genes (DEGs; p_adjusted < 0.05 and log2 fold change ≥1.0). The DEGs were assigned to GO term, covering biological processes, molecular functions and cellular components. Due to the large number of genes with altered expression, in the current study we analyzed only the genes involved in follicular growth, development and functioning. The obtained results showed that TCDD may affect ovarian follicle fate by influencing granulosa cell cycle, proliferation and DNA repair. The demonstrated over-time changes in the quantity and quality of genes being affected by TCDD treatment showed that the effects of TCDD on granulosa cells changed dramatically between 3-, 12- and 24-h of cell culture. This finding indicate that timing of gene expression measurement is critical for drawing correct conclusions on detailed relationships between the TCDD-affected genes and resulting intracellular processes. These conclusions have to be confirmed and extended by research involving proteomic and functional studies.

Expressão do mRNA para IGF-2 em oócitos e células do cumulus extraídos de folículos antrais e pré-antrais de ovelhas nativas do Estado de Pernambuco

RESUMO: Objetivou-se avaliar a expressão do mRNA para o gene do fator de crescimento IGF-2 em oócitos e células do cumulus de ovelhas em diferentes estágios do desenvolvimento folicular. Os folículos classificados morfologicamente como antrais (terciários e pré-ovulatórios) foram aspirados manualmente para obtenção dos oócitos e células do cumulus. Os folículos pré-antrais (secundários) foram extraídos do córtex ovariano, por microdissecção, e os oócitos retirados. Nos dois grupos, os oócitos foram desnudados e agrupados em “pools” de dez células cada (Grupo A, n=10; Grupo B, n=10) e dez amostras com grupos de células do cumulus (Grupo A1, n=10, B1, n=10). O mRNA foi extraído e convertido em cDNA utilizando a técnica da RT-PCR, utilizando Oligo DT randômico para o mRNA. A análise da expressão confirmou a expressão gênica para IGF-2 nos grupos de oócitos e células do cumulus. Houve um aumento da expressão relativa do mRNA para IGF-2 nos grupos de oócitos durante a fase mais tardia do desenvolvimento folicular e as diferenças foram consideradas significantes (p<0,05). Não houve variação significante da expressão de IGF2 entre os grupos de células do cumulus. Conclui-se que o fator de crescimento IGF-2 tem níveis mais elevados de expressão em oócitos ovinos, na segunda fase do desenvolvimento folicular, mas expressão semelhante em células do cumulus durante as fases estudadas do desenvolvimento folicular.

Systemic and intrafollicular components of follicle selection in mares

Mares are superb models for study of follicle selection owing to similarities between mares and women in relative follicle diameters at specific events during the follicular wave and follicle accessibility for experimental sampling and manipulation. Usually, only 1 major follicular wave with a dominant follicle (DF) greater than 30 mm develops during the 22 to 24 d of the equine estrous cycle and is termed the primary or ovulatory wave. A major secondary wave occasionally (25%) develops early in the cycle. Follicles of the primary wave emerge at 6 mm on day 10 or 11 (day 0 = ovulation). The 2 largest follicles begin to deviate in diameter on day 16 when the future DF and largest subordinate follicle (SF) are 23 mm and 20 mm, respectively. The deviation process begins the day before diameter deviation as indicated in the future DF but not in the future SF by (1) increase in prominence of an anechoic layer and vascular perfusion of the wall and (2) increase in follicular-fluid concentrations of IGF1, vascular endothelial growth factor, estradiol, and inhibin-A. A systemic component of the deviation process is represented by suppression of circulating FSH from secretion of inhibin and estradiol from the developing DF. Production of inhibin is stimulated by IGF1 and LH, and estradiol is stimulated by LH and not by IGF1 in mares. A local intrafollicular component involves the production of IGF1, which apparently increases the responsiveness of the future DF to FSH. The roles of the IGF system have been well studied in mares, but the effect of IGF1 on increasing the sensitivity of the follicle cells to FSH is based primarily on studies in other species. The greater response of the future DF than the SF to the low concentrations of FSH is the essence of selection. During the common growth phase that precedes deviation, diameter of the 2 largest follicles increases in parallel on average when normalized to emergence or retrospectively to deviation. Study of individual waves indicates that (1) the 2 follicles change ranks (relative diameters) during the common growth phase in about 30% of primary waves and (2) after ablation of 1, 2, or 3 of the largest follicles at the expected beginning of deviation, the next largest retained follicle becomes the DF indicating that several follicles have the capacity for dominance; therefore, it is proposed that the deviation process represents the entire mechanism of follicle selection in mares.

The theory of follicle selection in cattle

Selection of the dominant follicle (DF) during a follicular wave is manifested by diameter deviation or continued growth rate of the largest follicle (F1) and decreased growth rate of the next largest follicle (F2) when F1 reaches about 8.5 mm in cattle. The process of deviation in the future DF begins about 12 h before diameter deviation and involves an F1 increase in granulosa LH receptors and estradiol and maintenance of intrafollicular free insulin-like growth factor 1 (IGF1). Thereby, only F1 is developmentally prepared to use the declining FSH in the wave-stimulating FSH surge and to respond to a transient increase in LH to become the DF. A follicle that emerges first may maintain an F1 ranking and become the DF by being first to reach a critical developmental stage. However, an early size advantage is not a requisite component of the deviation process as indicated by (1) F1 and F2 may switch diameter rankings during a common growth phase that precedes diameter deviation owing to intraovarian factors that affect growth of individual follicles; (2) any follicle that reaches 5 mm regardless of diameter ranking may become a DF unless it is selected against during deviation; (3) a subordinate follicle may become dominant if the DF is ablated; (4) when F1 is ablated at 8.5 mm, the next largest follicle that is greater than 7.0 mm or the first follicle to subsequently reach 7.0 mm becomes the DF; (5) after ablation of F1 at 8.5 mm, IGF1 and estradiol increase in the intrafollicular fluid of F2 beginning at 6 h, and F2 grows to 8.5 mm in 12 h to become the DF. These considerations indicate that selection of a DF or partitioning into a DF and subordinate follicles is not initiated before the end of the common growth phase. That is, the deviation process represents the entire follicle selection mechanism.

Involvement of PAPP-A and IGFR1 in Cystic Ovarian Disease in Cattle

Cystic ovarian disease (COD) is one of the main causes of infertility in dairy cattle. It has been shown that intra-ovarian factors, such as members of the insulin-like growth factor (IGF) system, may contribute to follicular persistence. The bioavailability of IGF to initiate its response by binding to specific receptors (IGFRs) depends on interactions with related compounds, such as pregnancy-associated plasma protein A (PAPP-A). The aim of this study was to determine IGFR1 and PAPP-A expression both in follicles at different stages of development and in cysts, to evaluate the roles in the etiopathogenesis of COD in cattle. The mRNA expression of PAPP-A was higher in granulosa cells of large tertiary follicles than in cysts, whereas the protein PAPP-A present in the follicular fluid from these follicles showed no differences. Although no PAPP-A mRNA expression was detected in smaller tertiary follicles, in their follicular fluid, this protease was detected in lesser concentration than in cysts. The mRNA expression of IGFR1 was lower in granulosa cells from cystic follicles than in those from tertiary ones. However, the protein expression of this receptor presented the highest levels in cystic structures, probably to increase the possibility of IGF response. The data obtained would indicate that animals with COD have an altered regulation of the IGF system in the ovary, which could be involved in the pathogenesis of this disease in cattle.

Molecular mechanisms of enhancing porcine granulosa cell proliferation and function by treatment in vitro with anti-inhibin alpha subunit antibody

BACKGROUND

This study was conducted to clarify the effect of the inhibiting action of inhibin on porcine granulosa cell proliferation and function, and to investigate the underlying intracellular regulatory molecular mechanisms.

METHODS

Porcine granulosa cells were cultured in vitro, and were treated with an anti-inhibin alpha subunit antibody, with or without co-treatment of follicle-stimulating hormone (FSH) in the culture medium.

RESULTS

Treatment with anti-inhibin alpha subunit antibody led to a significant increase in estradiol (E2) secretion and cell proliferation. Anti-inhibin alpha subunit antibody worked synergistically with FSH at low concentrations (25 microg/mL) to stimulate E2 secretion, but attenuated FSH action at high concentrations (50 microg/mL). Immunoneutralization of inhibin bioactivity increased FOXL2, Smad3, and PKA phosphorylation, and mRNA expression of the transcription factors CEBP and c-FOS. The expression of genes encoding gonadotropin receptors, FSHR and LHR, and of those involved in steroidogenesis, as well as IGFs and IGFBPs, the cell cycle progression factors cyclinD1 and cyclinD2, and the anti-apoptosis and anti-atresia factors Bcl2, TIMP, and ADAMTS were upregulated following anti-inhibin alpha-subunit treatment. Treatment with anti-inhibin alpha subunit down regulated expression of the pro-apoptotic gene encoding caspase3. Although expression of the pro-angiogenesis genes FN1, FGF2, and VEGF was upregulated, expression of the angiogenesis-inhibiting factor THBS1 was downregulated following anti-inhibin alpha subunit treatment.

CONCLUSIONS

These results suggest that immunoneutralization of inhibin bioactivity, through augmentation of the activin and gonadotropin receptor signaling pathways and regulation of gene expression, permits the development of healthy and viable granulosa cells. These molecular mechanisms help to explain the enhanced ovarian follicular development observed following inhibin immunization in animal models.

The effects of intravenous, glucose versus saline on ovarian follicles and their levels of some mediators of insulin signalling

BACKGROUND

A short-term increase in food intake and specifically dietary energy can stimulate folliculogenesis and increase ovulation rate in ewes. The mechanism appears to involve the insulin-glucose metabolic system and its interaction with FSH signalling pathways in the granulosa cells of ovarian follicles. This experiment was designed to investigate the interaction between these two systems in the granulosa cells of ovarian follicles.

METHODS

Thirty six Ile-de-France ewes were used in this controlled experiment to study the effects of intravenous glucose on folliculogenesis. Eighteen ewes were infused with glucose (10 mM/h for 72 h) from day 8 of the oestrous cycle, while the others (controls) received saline. Ovaries were collected when the infusions ended (luteal phase) or 30 h later and after a luteolytic dose of a PGF2α analogue (follicular phase). Follicles were dissected and granulosa cells and follicular fluid harvested. The blood concentrations of glucose, insulin, oestradiol and FSH were monitored over the experiment. The levels of Aromatase P450 and of the phosphorylated and non-phosphorylated forms of Akt, AMPK and ERK in granulosa cells and the concentration of oestradiol in follicular fluid, were determined.

RESULTS

Glucose increased the circulating concentration of glucose (P < 0.05) and insulin (P < 0.05). It also increased the total number of follicles >1.0 mm in diameter (P < 0.05) and small (P < 0.05) follicles (>1.0 to 2.0 mm in diameter) but not medium (>2.0 to 3.5 mm in diameter) or large (>3.5 mm in diameter) follicles. Glucose decreased circulating oestradiol (P < 0.05) but not that of FSH or progesterone. Glucose reduced aromatase P450 (P < 0.05) and decreased the phosphorylation of Akt (P < 0.05), ERK (P < 0.05) and AMPK (P < 0.05) in granulosa cells from oestrogenic follicles. The level of Aromatase P450 was greatest in large oestrogenic follicles and the phosphorylation of Akt (P < 0.05), ERK (P < 0.05) and AMPK (P < 0.05) was lower in small follicles compared to medium and large follicles.

CONCLUSIONS

These data suggest that the effect of glucose in small follicles is a direct action of glucose that increases the number of small follicles while the effect of glucose in oestrogenic follicles is an indirect insulin-mediated action.

Hormonal composition of follicular fluid from abnormal follicular structures in mares

The objective was to characterise the hormonal composition of follicular fluid from mares with distinct anovulatory-cystic follicles. Follicular fluid was aspirated from six mares that presented with cystic follicles and from pre-ovulatory follicles of five normal mares (controls). Differences in progesterone, oestradiol, testosterone, IGF-I and IGF binding were analysed using Fisher's exact test. There were greater (P < 0.03) follicular fluid oestradiol concentrations in normal follicles and the testosterone concentration of the cystic fluid was greater (P < 0.05) than that of the normal fluid. There also was a greater (P < 0.03) percentage of IGF-I binding and lower (P < 0.02) IGF-I concentrations in the fluid collected from the cystic structures compared with the fluid from normal follicles. Despite the limited number of animals, the fact that fluid aspirated from cystic follicles had higher testosterone and lower oestradiol concentrations could be of diagnostic value when a practitioner wants to distinguish between a cystic and non-cystic persistent follicle. The research reported here also indicates a likely role for the IGF system in the pathogenesis of the development and maintenance of anovulatory follicular structures in mare ovaries.

Influence of Insulin-like Growth Factor I (IGF-I) on the survival and the in vitro development of caprine preantral follicles

The aim of this study was to investigate the effects of the insulin-like growth factor -I (IGF-I) on survival, activation (transition from primordial to primary follicles) and growth of caprine preantral follicles cultured in vitro. Fragments of ovarian cortex were cultured for one and seven days in the absence or presence of IGF-I (0, 50 and 100ng/ml). The non-cultured and cultured tissues were processed and analyzed by histology and transmission electron microscopy. The culture for one day in a medium with 100ng/ml of IGF-I showed 86.7% of morphologically normal follicles. These results were similar (P>0.05) to the percentage of normal follicles found in the control (96.7%). It was also found that this medium increased the percentage of follicular activation (developing follicles) with one day of culture. The oocyte and follicular diameters remained similar to the control by culturing for one day in a medium containing 100ng/ml of IGF-I. The ultrastructural analysis did not confirm the integrity of the follicular fragments in a medium containing IGF-I (100ng/ml) after one and seven days of culture. In conclusion, this study demonstrated that the addition of 100 ng/ml of IGF-I in the culture medium enables the development of preantral follicles of goats with one day of culture. However, it is not sufficient to maintain the follicular integrity and the follicular survival rate after seven days of culture.

The effect of nutrition and metabolic status on the development of follicles, oocytes and embryos in ruminants

The impact of nutrition and energy reserves on the fertility of ruminants has been extensively described. However, the metabolic factors and the molecular mechanisms involved in the interactions between nutrition and ovarian function are still poorly understood. These factors could be hormonal (either reproductive and/or metabolic) and/or dietary and metabolic (glucose, amino acids and fatty acids). In this review, we briefly summarize the impact of those nutrients (fatty acids, glucose and amino acids) and metabolic hormones (insulin/IGF-I, growth hormone, T3/4, ghrelin, apelin and the adipokines (leptin, adiponectin and resistin)) implicated in the development of ovarian follicles, oocytes and embryos in ruminants. We then discuss the current hypotheses on the mechanisms of action of these factors on ovarian function. We particularly describe the role of some energy sensors including adenosine monophosphate-activated kinase and peroxisome proliferator-activated receptors in the ovarian cells.

Transcriptome profiling of granulosa cells from bovine ovarian follicles during atresia

Background

The major function of the ovary is to produce oocytes for fertilisation. Oocytes mature in follicles surrounded by nurturing granulosa cells and all are enclosed by a basal lamina. During growth, granulosa cells replicate and a large fluid-filled cavity (the antrum) develops in the centre. Only follicles that have enlarged to over 10 mm can ovulate in cows. In mammals, the number of primordial follicles far exceeds the numbers that ever ovulate and atresia or regression of follicles is a mechanism to regulate the number of oocytes ovulated and to contribute to the timing of ovulation. To better understand the molecular basis of follicular atresia, we undertook transcriptome profiling of granulosa cells from healthy (n = 10) and atretic (n = 5) bovine follicles at early antral stages (< 5 mm).

Results

Principal Component Analysis (PCA) and hierarchical classification of the signal intensity plots for the arrays showed primary clustering into two groups, healthy and atretic. These analyses and size-frequency plots of coefficients of variation of signal intensities revealed that the healthy follicles were more heterogeneous. Examining the differentially-expressed genes the most significantly affected functions in atretic follicles were cell death, organ development, tissue development and embryonic development. The overall processes influenced by transcription factor gene TP53 were predicted to be activated, whereas those of MYC were inhibited on the basis of known interactions with the genes in our dataset. The top ranked canonical pathway contained signalling molecules common to various inflammatory/fibrotic pathways such as the transforming growth factor-β and tumour necrosis factor-α pathways. The two most significant networks also reflect this pattern of tissue remodelling/fibrosis gene expression. These networks also contain molecules which are present in the canonical pathways of hepatic fibrosis/hepatic stellate cell activation and transforming growth factor-β signalling and were up regulated.

Conclusions

Small healthy antral follicles, which have a number of growth outcomes, exhibit greater variability in gene expression, particularly in genes associated with cell division and other growth-related functions. Atresia, on the other hand, not only involves cell death but clearly is an active process similar to wound healing.

GATA4 and GATA6 silencing in ovarian granulosa cells affects levels of mRNAs involved in steroidogenesis, extracellular structure organization, IGF-I activity, and apoptosis

Knockdown of the transcription factors GATA4 and GATA6 in granulosa cells (GCs) impairs folliculogenesis and induces infertility. To investigate the pathways and genes regulated by these factors, we performed microarray analyses on wild-type GCs or GCs lacking GATA4, GATA6, or GATA4/6 (G4(gcko), G6(gcko), and G4/6(gcko)) after in vivo treatment with equine chorionic gonadotropin. GATA4 deletion affected a greater number of genes than GATA6, which correlates with the subfertility observed in G4(gcko) mice and the normal reproductive function found in G6(gcko) animals. An even greater number of genes were affected by the deletion of both factors. Moreover, the expression of FSH receptor, LH receptor, inhibin α and β, versican, pregnancy-associated plasma protein A, and the regulatory unit 2b of protein kinase A, which are known to be crucial for ovarian function, was greatly affected in double GATA4 and GATA6 knockouts when compared with single GATA-deficient animals. This suggests that GATA4 and GATA6 functionally compensate for each other in the regulation of key ovarian genes. Functional enrichment revealed that ovulation, growth, intracellular signaling, extracellular structure organization, gonadotropin and growth factor actions, and steroidogenesis were significantly regulated in G4/6(gcko) mice. The results of this analysis were confirmed using quantitative polymerase chain reaction, immunohistochemical, and biological assays. Treatment of GCs with cAMP/IGF-I, to bypass FSH and IGF-I signaling defects, revealed that most of the affected genes are direct targets of GATA4/6. The diversity of pathways affected by the knockdown of GATA underscores the important role of these factors in the regulation of GC function.

The highly prolific phenotype of Lacaune sheep is associated with an ectopic expression of the B4GALNT2 gene within the ovary

Prolific sheep have proven to be a valuable model to identify genes and mutations implicated in female fertility. In the Lacaune sheep breed, large variation in litter size is genetically determined by the segregation of a fecundity major gene influencing ovulation rate, named FecL and its prolific allele FecL(L) . Our previous work localized FecL on sheep chromosome 11 within a locus of 1.1 Mb encompassing 20 genes. With the aim to identify the FecL gene, we developed a high throughput sequencing strategy of long-range PCR fragments spanning the locus of FecL(L) carrier and non-carrier ewes. Resulting informative markers defined a new 194.6 kb minimal interval. The reduced FecL locus contained only two genes, insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) and beta-1,4-N-acetyl-galactosaminyl transferase 2 (B4GALNT2), and we identified two SNP in complete linkage disequilibrium with FecL(L) . B4GALNT2 appeared as the best positional and expressional candidate for FecL, since it showed an ectopic expression in the ovarian follicles of FecL(L) /FecL(L) ewes at mRNA and protein levels. In FecL(L) carrier ewes only, B4GALNT2 transferase activity was localized in granulosa cells and specifically glycosylated proteins were detected in granulosa cell extracts and follicular fluids. The identification of these glycoproteins by mass spectrometry revealed at least 10 proteins, including inhibin alpha and betaA subunits, as potential targets of B4GALNT2 activity. Specific ovarian protein glycosylation by B4GALNT2 is proposed as a new mechanism of ovulation rate regulation in sheep, and could contribute to open new fields of investigation to understand female infertility pathogenesis.

Role of insulin-like growth factor-I and follicular fluid from ovarian follicles with different diameters on porcine oocyte maturation and fertilization in vitro

The objective of this study was to determine the effects of insulin-like growth factor-I (IGF-I) (0, 60, 120, 180, and 240 ng/mL) and follicular fluid (FF) derived from 2 to 5 and 6 to 10 mm diameter follicles (SpFFs and LpFFs, respectively) added during in vitro maturation (IVM) of porcine oocytes on nuclear maturation and IVF. Cumulus-oocyte complexes (COCs) were matured in NCSU-37 medium supplemented with SpFFs or LpFFs and various IGF-I concentrations. The COCs were cultured for 44 hours, and then fertilized in vitro. Maturation and IVF results were recorded 18 hours after insemination. The IVM (%) was higher (P < 0.05) in the COCs matured in LpFFs than with SpFFs when 0 (90.0 ± 6.9 vs. 76.3 ± 10.7) or 60 ng/mL IGF-I (92.0 ± 8.1 vs. 81.8 ± 10.2) was added. In SpFFs media, there was a quadratic relationship (P < 0.01) between IGF-I concentration and IVM (peak results at IGF-I = 129 ng/mL). However, when the COCs were matured with LpFFs, there was a decreasing linear effect between IGF-I concentration and IVM. At all concentrations of IGF-I, the percentage of degenerated oocytes was higher in COCs matured in SpFFs than in LpFFs. Penetration (%) did not differ (P > 0.05) between COCs matured with SpFFs or LpFFs when 60 (66.8 ± 9.4 vs. 72.7 ± 11.3) or 180 ng/mL of IGF-I (75.7 ± 10.4 vs. 73.8 ± 13.2) were used. Monospermy (%) was similar between SpFFs and LpFFs only with addition of 120 ng/mL IGF-I. The IVF performance (%) did not differ between COCs matured with SpFFs or LpFFs when IGF-I concentrations of 120 (28.5 ± 8.8 vs. 38.5 ± 8.3) and 180 ng/mL (24.3 ± 10.2 vs. 30.12 ± 8.2) were used. There was no effect of IGF-I concentration or of FF type on the number of penetrated sperm per oocyte and on male pronuclear formation. For COCs matured with SpFFs, there was a quadratic relationship between IGF-I concentration and penetration, monospermy, and IVF performance (peak results at IGF-I = 179, 122, and 135 ng/mL, respectively). Thus, on the basis of the observed quadratic relationships, we inferred that when using SpFFs, the addition of IGF-I (122-179 ng/mL) to the IVM medium produced results similar to those obtained with LpFFs without adding IGF-I. In conclusion, the addition of IGF-I to the IVM medium supplemented with SpFFs increased maturation and improved IVF results. Alternatively, IGF-I had no effect on IVM or IVF when used with LpFFs.

Expression levels of mRNA for insulin-like growth factors 1 and 2, IGF receptors and IGF binding proteins in in vivo and in vitro grown bovine follicles

This study investigated mRNA levels for insulin-like growth factors (IGFs) IGF1 (IGF-I) and IGF2 (IGF-II), IGF receptors (IGF1R and IGF2R), and binding proteins (IGFBP-1, IGFBP-2. IGFBP-3, IGFBP-4, IGFBP-5 and IGFBP-6) in bovine follicles of 0.2, 0.5 or 1.0 mm in diameter. mRNA expression levels in in vitro cultured follicles that reached approximately 0.5 mm were compared with that of in vivo grown follicles. IGF1R and IGF2R expression levels in 0.5 mm in vivo follicles were higher than in 1.0 or 0.2 mm follicles, respectively. IGFBP-1, IGFBP-2. IGFBP-3, IGFBP-4, IGFBP-5 and IGFBP-6 showed variable expression in the follicular size classes analyzed. In vitro grown follicles had significantly reduced expression levels for IGF1, IGF1R, IGFBP-3, IGFBP-5 and IGFBP-6 mRNA when compared with 0.2 mm follicles, but, when compared with in vivo grown follicles (0.5 mm), only IGFBP-1, IGFBP-2, IGFBP-3 and IGFBP-6 showed a reduction in their expression. In conclusion, IGFs, their receptors and IGFBPs showed variable expression of mRNA levels in the follicular size classes analyzed.