Concentrations of progesterone, follistatin, and follicle-stimulating hormone in peripheral plasma across the estrous cycle and pregnancy in merino ewes that are homozygous or noncarriers of the Booroola gene

A meta-analysis of mRNA expression profiling studies in sheep with different FecB genotypes

The FecB mutation in the sheep BMPRIB is strongly correlated with high ovulation traits but its mechanism remains unclear. This study explored differentially expressed genes (DEGs) and their associated molecular mechanisms that may be involved in FecB mutation-induced high ovulation from the perspective of the hypothalamic-pituitary-gonadal (HPG) axis by conducting a systematic review and meta-analysis. The PubMed, EMBASE, CNKI, WanFang, and CBM databases were searched for eligible articles published before August 2022, focusing on mRNA sequencing of different tissues in the HPG axis in sheep with different FecB genotypes. A total of 6555 DEGs were identified from the analysis of six published articles and experimental results from our laboratory. The DEGs were screened by vote-counting rank and robust rank aggregation. Among these, in the follicular phase, FKBP5, CDCA7 and CRABP1 were upregulated in the hypothalamus. INSM2 was upregulated, while LDB3 was downregulated in the pituitary. CLU, SERPINA14, PENK, INHA and STAR were upregulated, while FERMT2 and NPY1R were downregulated in the ovary. On the HPG axis, TAC1 was upregulated and NPNT was downregulated. Many DEGs were found in sheep with different FecB genotypes. The genes FKBP5, CDCA7, CRABP1, INSM2, LDB3, CLU, SERPINA14, PENK, INHA, STAR, FERMT2, NPY1R, TAC1 and NPNT, may be associated with FecB mutation-induced high ovulation in different tissues. These candidate genes will further improve the mechanism of multiple fertility traits induced by the FecB mutation from the perspective of the HPG axis.

Effects of FecB Mutation on Estrus, Ovulation, and Endocrine Characteristics in Small Tail Han Sheep

The Booroola fecundity gene (FecB) has a mutation that was found to increase the ovulation rate and litter size in Booroola Merino sheep. This mutation is also associated with the fecundity of small-tail han (STH) sheep, an important maternal breed used to produce hybrid offspring for mutton production in China. Previous research showed that the FecB gene affects reproduction in STH sheep, based on litter size records. However, the effects of this gene on estrus, ovulation, and endocrine characteristics in these sheep remain unclear. Here, we analyzed the traits mentioned earlier and compared them among the three FecB genotypes of STH ewes using estrus synchronization. Overall, 53 pluriparous ewes were selected from among 890 STH ewes and subjected to FecB genotyping for experiments to characterize estrous and ovulation rates. FecB heterozygous (+B) ewes presented an earlier onset of estrus (42.9 ± 2.2 h) and a shorter estrous cycle (17.2 ± 0.2 days) (P ≤ 0.05). The ovulation rates increased with the increasing copy number of the B allele (P ≤ 0.01). Ovulation time showed no significant differences among the three FecB genotypes. The serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone, estrogen (E2), and progesterone (P4) were measured in 19 of the ewes. Serum concentrations of E2 and FSH dramatically varied around the time of behavioral estrus. In FecB mutant homozygous (BB) ewes, E2 concentration had two peaks, which were higher (P ≤ 0.05) than those of ++ genotypes. FSH concentration of BB ewes was higher (P ≤ 0.05) than that of the ++ ewes just after estrus. The expression of the estrogen receptor 1 (ESR1) gene in the +B genotype was higher than in the other genotypes. Based on the data for the reproductive performance of STH ewes with the three FecB genotypes, our study suggests that the development of follicles in ewes with the B allele is dependent on the response to FSH regulated by E2 in the early stage. +B ewes, exhibiting moderate ovulation and litter size and a shorter estrous cycle, can be highly recommended in sheep crossbreeding systems for commercial mutton production. Moreover, this study provides useful information to conserve better and use the genetic resources of STH sheep in China.

Detection of mRNA Expression and Copy Number Variations Within the Goat Fec B Gene Associated With Litter Size

The Booroola fecundity (Fec ^B ) gene, as the first major fecundity gene identified in Booroola sheep, has attracted careful attention. So far, previous research have uncovered the Fec^B mutation (Q249R) as the main mutation by virtue of which sheep exhibits multiple lambing phenomena. This mutation is now being intensively studied and widely used. However, such effect of the Fec^B mutation has not been applied to goats, and similar types of the Fec ^B gene in goats still need to be studied. Thus, the current study attempted to verify potential mutations in the goat Fec ^B gene as well as investigate their functions related to fecundity. First, Fec ^B expression was investigated in six different goat tissues, and we found that Fec ^B expression was highest in the mammary gland, followed by the ovary. Next, the influence of the Fec ^B gene was analyzed from a new perspective, where five potential copy number variations (CNVs) (CNV1-5) within the Fec ^B gene were identified for the first time, and then their effects on litter size were measured. Our results point out that CNV3 (P = 3.44E-4) and CNV5 (P = 0.034) could significantly influence the litter size of goats. Identically, the combination genotype of CNV3 and CNV5 which consisted of their dominant genotypes was also significantly associated with goat litter size (P = 7.80E-5). Hence, CNV3 and CNV5 could serve as potential DNA molecular markers applied to DNA editing and DNA microarray. Additionally, the abovementioned study has laid a theoretical foundation for the detection of potential fertility-related quantitative trait loci within the goat Fec ^B gene.

Quantitative expression of mRNA encoding BMP/SMAD signalling genes in the ovaries of Booroola carrier and non-carrier GMM sheep

The GMM sheep is a carrier of Booroola fecundity (FecB) gene, which produces the twins and triplets in one lambing. The homozygous carrier GMM (FecB^BB ), non-carrier GMM and Malpura (FecB⁺⁺ ) ewes were synchronized by progesterone sponges, and the plasma progesterone concentration was measured by RIA. The results showed that the progesterone concentration did not differ significantly (p > .05) in homozygous carrier GMM (5.74 ± 1.2 ng/ml), non-carrier GMM (5.42 ± 1.4 ng/ml) and non-carrier Malpura ewes (5.67 ± 1.5 ng/ml). Further, quantitative expression of BMP factors/receptors and SMAD signalling genes were analysed in the ovaries of sheep by qRT-PCR. The study showed that the expression of BMP2 was slightly higher (p > .05) in carrier GMM than that of non-carrier GMM, but it was almost similar to Malpura ewes. Expression of BMP4 and BMP7 was significantly higher (p < .001; p < .05) in carrier GMM than that of non-carrier GMM and Malpura ewes. Although BMP6 expression was higher (p > .05) in carrier GMM than that of non-carrier GMM, but lower (p > .05) than the Malpura ewes. Expression of BMP15 (p < .05), GDF5 (p < .01) and GDF9 (p < .05) was significantly higher in carrier GMM than non-carrier GMM ewes. Surprisingly, BMPR1B expression was significantly higher (p < .001) in non-carrier GMM and Malpura than the carrier GMM ewes, while TGFβRI did not differ significantly (p > .05) among both GMM genotypes. On the other hand, expression of BMPR1A (p > .05) and BMPRII (p < .05) was higher in carrier GMM than the non-carrier GMM, but significantly lower (p < .001) than the Malpura ewes. It was interesting to note that the expression of SMAD1 (p > .05), SMAD2 (p < .001), SMAD3 (p < .05), SMAD4 (p < .001), SMAD5 (p < .001) and SMAD8 (p < .001) was lower in the carrier GMM than that of non-carrier GMM ewes. It is concluded that the FecB mutation alters the expression of BMPR1B and SMAD signalling genes in the ovaries of homozygous carrier GMM ewes.

Age-related expression of TGF beta family receptors in human cumulus oophorus cells

PURPOSE

During ovarian follicle growth, local cellular interactions are essential for oocyte quality acquisition and successful fertilization. While cumulus cells (CCs) nurture oocytes, they also deliver oocyte-secreted factors (OSFs) that activate receptors on CCs. We hypothesized that disturbance of those interactions contributes to age-related lower reproductive success in women submitted to assisted reproductive technology treatments.

METHODS

Women aged 27-48, without recognized personal reproductive disorder, were enrolled in the study and divided in <35- and ≥35-year-old groups. CCs collected upon follicle aspiration were processed for immunocytochemistry and RNA extraction. The expression patterns of OSF receptors BMPR2, ALK 4, ALK5, and activin receptor-like kinase (ALK6) were studied.

RESULTS

Independently of age, receptors were found mostly in the cell periphery. The quantitative assay revealed that in older women, BMPR2, ALK 4, and ALK6 were all significantly decreased, whereas ALK5 was slightly increased.

CONCLUSIONS

Female age imparts an effect on the expression of OSF receptors in CCs. The findings indicate that reproductive aging affects the local regulation of signaling pathways mediated by BMPR2, ALK6, and ALK4 receptor activation, suggesting their joint involvement.

Effect of temperature variation on hormonal concentration at various gestation stages in black Bengal goat

Aim:

The present study was conducted to evaluate the effect of risingtemperature on the metabolic as well as the reproductive performance of the black Bengal goat.

Materials and Methods:

A total 27 numbers of non-pregnant black Bengal goats of the same parity comprised the experimental animals. The selected goats were randomly assigned to 3 groups of 9 each, maintaining uniformity in body weight (average 14-18 kg). Goats in Group-I were kept between the temperature ranges of 35-40°C, in Group-II between 20°Cand 27°C, and Group-III were kept under loose housing system and serve as a control. Goats in all the groups were bred naturally. Blood was collected prior to feeding in the morning on the day 1 (estrus), 20, 45, 90, and 135, expected day of parturition and also 2 days after parturition from goats of all the three groups.

Results:

It was observed that the level of plasma estrogen decreased (p<0.05) up to day 45 of gestation, then after increased up to 135 days of gestation and was maximum on expected day of parturition which was significantly (p<0.05) higher than all the values. Plasma progesterone level increased from day 20 and was the highest on day 90 and then decreased significantly (p<0.05) on expected date of parturition. The luteinizing hormone value decreased significantly (p<0.05) on expected day of parturition and day 2 after parturition in all the groups. Follicle stimulating hormone concentration showed a significant (p<0.05) decrease from day 1 to 2 days after parturition in all the groups. The plasma triiodothyronine (T₃) level did not vary between and within the treatment groups at any stage of the experiment. The plasma thyroxine (T₄) level varied significantly (p<0.01) within and (p<0.05) between groups at all stages of reproduction. A significant (p<0.05) variation in plasma cortisol concentration in all the groups increased significantly until the day of parturition and dropped significantly (p<0.01) in 2 days after parturition in all the groups.

Conclusion:

The present experiment revealed that rise in temperature has no any deleterious effect on the metabolic as well as the reproductive hormonal concentrationat variousstages of gestation inblack Bengal goat.

Flow cytometric analysis of FSHR, BMRR1B, LHR and apoptosis in granulosa cells and ovulation rate in merino sheep

The aim of the present study was to determine the direct cause of the mutation-induced, increased ovulation rate in Booroola Merino (BB) sheep. Granulosa cells were removed from antral follicles before ovulation and post-ovulation from BB (n=5) and WT (n=12) Merino ewes. Direct immunofluorescence measurement of mature cell surface receptors using flow cytometry demonstrated a significant up-regulation of FSH receptor (FSHR), transforming growth factor beta type 1, bone morphogenetic protein receptor (BMPR1B), and LH receptor (LHR) in BB sheep. The increased density of FSHR and LHR provide novel evidence of a mechanism for increasing the number of follicles that are recruited during dominant follicle selection. The compounding increase in receptors with increasing follicle size maintained the multiple follicles and reduced the apoptosis, which contributed to a high ovulation rate in BB sheep. In addition, we report a mutation-independent mechanism of down-regulation to reduce receptor density of the leading dominant follicle in sheep. The suppression of receptor density coincides with the cessation of mitogenic growth and steroidogenic differentiation as part of the luteinization of the follicle. The BB mutation-induced attenuation of BMPR1B signaling led to an increased density of the FSHR and LHR and a concurrent reduction in apoptosis to increase the ovulation rate. The role of BMPs in receptor modulation is implicated in the development of multiple ovulations.

The impact of passive immunisation against BMPRIB and BMP4 on follicle development and ovulation in mice

The primordial follicle reserve is the corner stone of female fertility and determines the longevity and quality of reproduction. Complete depletion of this reserve will lead to primary infertility, and the key-limiting step of follicle depletion is the transition from primordial to primary follicles. It has been reported that this process is gonadotrophin-independent, but other conflicting reports are indicated otherwise and this discrepancy needs to be unequivocally clarified. The aim of this study was to investigate the role of bone morphogenetic proteins (BMPs) in the regulation of folliculogenesis in mice passively immunised against BMP receptor 1B (BMPRIB) and BMP4. While a stereological study revealed that the numbers of primordial follicles in immunised mice were significantly higher when compared with control animals, treatment with equine chorionic gonadotrophin showed no effect. In parallel, immunofluorescence microscopy revealed the presence of BMPRIB but not FSH receptor in primordial follicles. The number of primary follicles in immunised mice were also significantly increased when compared with control animals. After puberty, the rates of depletion of primordial and primary follicles were increased with age, particularly in treated animals; however, there was no significant difference between the treatment groups of the same age. Based on these results together with our previous reports in sheep and mice, we confirm that the attenuation of BMP signalling system can be an effective approach to sustain the primordial follicle reserve while promoting the development of growing follicles, ovulation and consequently overall female fertility.

Ovarian follicle development in Booroola sheep exhibiting impaired bone morphogenetic protein signalling pathway

The role of bone morphogenetic proteins (BMPs) in the regulation of ovarian function has been extensively investigated but the mechanism of regulation is not well understood. The aim of this study was to investigate the effect of mutation in the BMP receptor in Booroola sheep on the number of primordial follicles and rate of follicle recruitment in comparison with that in normal merino sheep in vivo. Whole sheep ovaries at the time of birth, 1.5 and 5 years old were collected and processed for the follicle quantification, using computerised stereological methods and statistical analyses. At birth, the total number of primordial follicles in Booroola sheep was significantly lower than in merino sheep. At 1.5 and 5 years, a reversed pattern in favour of Booroola ewes was seen with significantly more primordial follicles than merino. In parallel, the rate of primordial follicle recruitment to developing cohort was substantially lower in Booroola ewes with only 51 and 66% of primordial follicle consumption at 1.5 and 5 years respectively compared to 92 and 97% in merino ewes. On other hand, the mean numbers of developing primary follicles were smaller in Booroola sheep at the time of birth, yet, Booroola ewes possess more primary follicles than merino at 1.5 years. These findings suggest that attenuation of the intraovarian signalling pathway of BMPs may in fact be a successful means of rationalising follicle consumption, preventing unnecessary loss of follicles from the initial primordial follicle pool, hence increasing reproductive longevity and fertility.

Changes in ovarian follistatin levels during the oestrous cycle in sheep may serve as an intraovarian regulator

The expression and concentration of follistatin and activin change during oestrous cycle suggesting their involvement in the regulation of follicular development. The aim of this study was to determine the level, source and potential role of follistatin in the sheep ovary. Follistatin in ovarian venous blood, measured by radioimmunoassay, remained at its low level from follicular phase (day -1 and 0) to mid-luteal phase (days 11-13) phase but were significantly elevated during the late luteal phase (days 14 and 15) when corpora lutea underwent regression. Western blot analyses of follicular fluid at day 15 of the cycle showed two strong bands at 42 and 45 kDa and weakly stained bands at 39 and 31 kDa. At day 0, these bands became weaker and the 39 kDa band became undetectable. However, there were no differences in follistatin concentrations between ovaries with and without functional corpus luteum (CL) during the whole luteal phase. In addition, although the ovaries of Booroola ewes normally contain more corpora lutea than those of normal merino ewes, follistatin concentrations in both jugular and ovarian venous blood were similar in Booroola and normal merino ewes. It is concluded that the secretion of follistatin from the ovary is not related to the formation of CL or high ovulation rate of Booroola ewes. The elevation in follistatin concentration in follicular fluid and ovarian blood during late luteal phase may indicate a dual role of follistatin in the luteolysis of existing CL and development of new follicle cohort.

Changes in concentrations of follistatin in maternal plasma and foetal fluids during pregnancy and parturition in sheep

Studies have shown that follistatin may be involved in the regulation of ovarian development, pregnancy and parturition. The aim of the present study was to measure follistatin levels in maternal plasma and foetal fluids during pregnancy and parturition in sheep. Using a previously described follistatin radioimmunoassay, we found that follistatin in foetal plasma and allantoic fluid was higher in the female than in the male at days 50-75 of gestation. Follistatin concentrations in maternal plasma declined from -9 to -3h before the completion of lamb delivery, and increased from 21 to 39 h after parturition. These results suggest that follistatin may play a role in femaleness development, and that follistatin may be involved in the mechanism of normal parturition and in regulation of the tissue repair after parturition.

Seasonal variation of reproductive performance, foetal development and progesterone concentrations of sheep in the subtropics

The aim of the present study was to investigate the effect of breeding season [late spring (LSP) vs winter (WIN)] on reproductive performances, foetal development and progesterone (P(4)) concentrations of sheep in the subtropics. Ewes of Farafra breed were exposed for mating in LSP (n = 79) and WIN (n = 45). Ultrasonographic examinations were performed at days 25, 45 and 75 of mating to estimate the pregnancy rate, incidence of twinning and percentage of foetal losses. Foetal growth rate was determined at 10-day interval, and blood samples were taken on days 0 (oestrus), 8, 18 of oestrous cycle and on days 30, 45, 60 and 90 of pregnancy for P(4) analysis. The results showed that pregnancy and lambing rates were greater (p < 0.01) for ewes mated in LSP (93.7% and 92.4%) than for those mated in WIN (75.6% and 71.1%), respectively. There was no effect of season on the incidence of twinning (overall 19.1%) or the frequency of foetal losses (overall 7.3%). Transient reduction of placental size, foetal growth and P(4) concentration was observed following LSP matings. In conclusion, pregnancy and lambing rates were higher following LSP matings. Summer heat stress of the late spring mated ewes transiently interferes with foetal growth and P(4) concentrations.

d-Aspartate and reproductive activity in sheep

D-aspartic acid (D-Asp) has been isolated from neuroendocrine tissues of many invertebrates and vertebrates. Recently, it has been demonstrated that this D-amino acid may be converted to N-methyl-D-aspartic acid (NMDA), a neuromodulator associated with sexual activity. In this study, we determined D-Asp and NMDA concentrations in endocrine glands and other tissues in ewes after D-Asp administration and in controls. We also evaluated the effects of d-Asp administration on the reproductive activity of ewes by determining either progesterone concentrations or LH pulses in the presence or absence of estradiol benzoate. The pineal gland showed the highest natural content of D-Asp (1.47+/-0.22 micromol/g tissue), whereas the pituitary gland had the highest capability to store d-Asp, with a peak value (9.7+/-0.81 micromol/g tissue) 6 h after its administration. NMDA increased sharply 12 h following D-Asp administration, reaching values three times higher than the baseline in both the pituitary and brain. D-Asp was quickly adsorbed after subcutaneous administration, with a peak in plasma levels 2 h after administration and a return to baseline values after 6 h. D-Asp administration achieved a significant (P < 0.001) increase in LH values with respect to estradiol or estradiol + D-Asp treatments. d-Asp treatment once or twice a week did not successfully drive acyclic ewes into reproductive activity. In conclusion, the results obtained in this study demonstrated that D-Asp is endogenously present in sheep tissues and electively stored in endocrine glands and brain after its administration. NMDA and LH increase following D-Asp administration suggesting a role of this D-amino acid in the reproductive activity of sheep.

Activins, inhibins and follistatins in the large domestic species

The activins and inhibins are members of the transforming growth factor-beta (TGF-beta) superfamily and, along with follistatin, a high affinity binding protein of activin, form a group of interrelated factors originally isolated for their role in regulating the release of follicle-stimulating hormone (FSH). Knowledge of their function, particularly that of activin, has expanded since being originally isolated, such that they are now regarded as important paracrine regulators in many cellular systems. This review summarizes the biology of these proteins as has been established in the large domestic animals. While the majority of data relate to the pituitary, ovary, uterus/placenta and testis, consideration is also given to emerging roles in inflammatory processes and in non-reproductive tissues or systems.