Characterization of the melatonin receptor gene MT1 in mouflon (Ovis Gmelini Musimon) and its relationship with reproductive activity

Polymorphism of the MTNR1A Melatonin Receptor Gene in Goat Breeds of Northern Italy

Melatonin receptor MT1, encoded by the MTNR1A gene, is the main one involved in the seasonal regulation of reproductive activity. A correlation between this gene polymorphism and reproductive performance has been demonstrated in sheep. To date, no data about MTNR1A gene polymorphism are available regarding Italian goat breeds other than the Sarda goat. This study aimed to detect any PCR-RFLP polymorphic sites of MTNR1A using MnlI and RsaI enzymes in Northern Italian goat breeds, which are characterized by a pronounced reproductive seasonality. One-hundred-eight adult female goats belonging to four different breeds were included in the study (i.e., Frisa Valtellinese, n = 29; Orobica, n = 23; Lariana, n = 29; Camosciata delle Alpi, n = 27). Blood was sampled from each goat. Genomic DNA was extracted from each sample and the main part of exon II of MTNR1A gene was amplified by PCR and digested with MnlI and RsaI enzymes. Unexpectedly, none of the fragments were found to be polymorphic. The absence of polymorphism may be linked to the macro group of goat breeds that evolved during human migrations. Breeds of the Alpine-European strain would appear to show no polymorphism, as confirmed by our study, whereas breeds belonging to the Mediterranean-African or Asian-Middle Eastern strains do.

Expression and distribution of MTNR1A in the hypothalamus-pituitary-gonadal axis of Tibetan sheep during the estrous cycle

The melatonin 1A receptor (MTNR1A) is a membrane receptor distributed across the mammalian gonadal axis-associated membrane. Melatonin (MT) can specifically bind with MTNR1A on the cell membrane and regulates mammalian reproductive activities. However, the role of MTNR1A in regulating the reproductive physiological activities of sheep in the Tibetan Plateau remains unclear. In this study, the MT content in Tibetan sheep blood during the estrous cycle was detected by ELISA. The distribution of MTNR1A in the hypothalamus-pituitary-gonadal axis (HPGA) was analyzed by immunohistochemistry and immunofluorescence. Western blot and qRT-PCR were used to detect dynamic changes of MTNR1A mRNA and protein expression, and the protein distributions in the HPGA. The results showed that the average secretion level of MT in Tibetan sheep blood was highest occurred during diestrus and the lowest during proestrus. Additionally, the secretion of MT at night was significantly higher than during the day. The immunopositive products of MTNR1A were primarily distributed around the glial cells in the dorsal hypothalamic nucleus region, chromophobe cells, and eosinophilic cytoplasm in the pituitary gland, follicular granular layer, follicular adventitia, tubal mucosa, cilia, endometrium, interstices, and glands in the uterus. The expression trends of MTNR1A mRNA and proteins in the HPGA during the estrous cycle were the same. The relative expression levels of MTNR1A mRNA and proteins in the hypothalamus and ovaries were the highest during proestrus and the lowest during metestrus; the highest during diestrus in the pituitary and oviducts; the highest during metestrus in the uterus. Collectively, the differences in the secretion of MT in Tibetan sheep blood and the expression of MTNR1A in HPGA suggest that they may be affected by steroid hormone secretion during the estrous cycle of Tibetan sheep, which has a potential impact on the regulation of animal estrous cycle.

MTNR1A gene polymorphisms and reproductive recovery after seasonal anoestrus in different Mediterranean sheep breeds

The aims of this study were 1) to investigate the effect of MTNR1A gene polymorphisms on reproductive performance in ewes of one Italian and two Slovenian dairy sheep breeds (Sarda, Istrian Premenka and Boska, respectively) which were located at different latitudes, and 2) to highlight if the different season of the male placement with females that was utilized in the different breeding systems in Sardinia (Italy) and Slovenia resulted in different effects of these polymorphisms on reproductive functions. Reproductively mature ewes (n = 100) from each breed were utilized to conduct the study. To evaluate the reproductive efficiency, lambing dates and number of lambs born were recorded per ewe; additionally, the duration in days from ram placement with ewes to lambing (DRPEL), litter size and the fertility rate were determined based on lambing dates. In each breed, there were eight nucleotide variations within the MTNR1A gene exon II, two of which (g.17355358 and g.17355171), respectively, resulted in a valine to isoleucine, and alanine to aspartic acid substitution, in amino acid sequence. The SNPs at position g.17355452 and g.17355458 were determined to have effects on reproductive performance. Genotypes C/C and C/T at g.17355452 in Bovska and Sarda and genotype A/A at g.17355458 in Istrian Pramenka were associated with a greater fertility and a lesser duration in days from ram placement with ewes to lambing. These findings confirmed that the nucleotide sequences of the MTNR1A gene could affect reproductive functions of Mediterranean sheep.

Detection of Polymorphisms in the MTNR1A Gene and Their Association with Reproductive Performance in Awassi Ewes

Simple Summary

The purpose of the study was to explore the influence of MTNR1A gene polymorphisms on the reproductive performance in Awassi sheep, which is an important and widespread breed in developing Mediterranean countries. A total of 31 SNPs was detected, 5 of which caused amino acid changes. Two of the found SNPs were found to be totally linked and associated with an advanced reproductive recovery in ewes carrying the C allele. The obtained results could be useful for improving reproductive management in developing Mediterranean areas.

Abstract

The economy in Mediterranean areas is tightly linked to the evolution of the sheep-farming system; therefore, improvement in ewe’s reproductive performance is essential in the developing countries of this area. MTNR1A is the gene coding for Melatonin receptor 1 (MT1), and it is considered to be involved in the reproductive activity in sheep. The aims of this study were: (1) identifying the polymorphisms from the entire MTNR1A coding region and promoter in Lebanese Awassi sheep flocks, and (2) investigating the association between the found polymorphisms and the reproductive performance, assessed as lambing rate, litter size, and days to lambing (DTL). The study was conducted in two districts of Lebanon, where 165 lactating ewes, aged 5.2 ± 1.5 years, with body condition score (BCS) 3.3 ± 0.4, were chosen and exposed to adult and fertile rams. From 150 to 220 days after ram introduction, lambing dates and litter sizes were registered. This study provided the entire coding region of the MTNR1A receptor gene in the Awassi sheep breed. Thirty-one single nucleotide polymorphisms (SNPs) were detected, five of which were missense mutations. The H2, H3, and H4 haplotypes were associated with lower DTL (p < 0.05), as well as the SNPs rs430181568 and rs40738822721, named from now on SNP20 and SNP21, respectively. These SNPs were totally linked and can be considered as a single marker. The ewes carrying the C allele at both these polymorphic sites advanced their reproductive recovery (p < 0.05). These results are essential for improving reproductive management and obtaining advanced lambing in Awassi ewes.

Polymorphisms of the melatonin receptor 1A (MTNR1A) gene influence the age at first mating in autumn-born ram-lambs and sexual activity of adult rams in spring

The aim of this study was to determine whether polymorphisms of the melatonin receptor 1A (MTNR1A) gene influence the age at first mating in autumn-born ram-lambs and influence the out-of-season sexual activity of adult rams. In experiment 1, 24 Rasa Aragonesa ram-lambs born in September were genotyped for their RsaI and MnlI allelic variants of the MTNR1A gene, and the date of their first mounting with ejaculation after a period of semen collection training was documented. In experiment 2, the reproductive behavior, testicle size, and plasma testosterone concentrations of 18 adult rams (6 rams for each RsaI genotype) were recorded at the beginning (March) and end (May) of the seasonal anestrus. The number of days of training to achieve the first mating with ejaculation in T/T (C/C: 85.17 ± 12.08 C/T: 86.60 ± 18.87; T/T; 26.50 ± 24.50 d; P < 0.05), and G/G ram-lambs (G/G: 51.57 ± 14.99; A/G: 95.58 ± 10.95 d; P < 0.05) was significantly fewer than it was in the other genotypes. Likewise, for the RsaI genotype, 55% of the vulva-sniffing (P < 0.001), 48% of the approaches (P < 0.01), 48% of the mountings (P < 0.05) and 49% total activities (P < 0.001) were performed by T/T rams in March, and 50% of the sexual events in May (P < 0.001). For the Mnll variant, G/G rams performed a significantly (P < 0.001) larger proportion of the vulva-sniffing (41%), approaches (46%) and total activities (40%) in March, and 52% of the vulva-sniffing (P < 0.001), 43%, of the approaches (P < 0.001), 46% of the mountings (P < 0.05), and 47% of the total activities (P < 0.001) in May. Scrotal circumference, testicular volume, and plasma testosterone concentrations did not differ significantly among genotypes. Results confirmed that the polymorphisms of the MTNR1A gene sequence can influence reproductive performance in young and adult rams. Autumn-born ram-lambs that carried the T/T or G/G genotype had an advanced ability to reproduce, and T/T or G/G adult rams exhibited the most intense reproductive behavior. Genotyping might be a useful procedure for identifying the correct and rational use of rams in modern sheep farming.

Melatonin transport into mitochondria

Melatonin is a well-known, nighttime-produced indole found in bacteria, eukaryotic unicellulars, animals or vascular plants. In vertebrates, melatonin is the major product of the pineal gland, which accounts for its increase in serum during the dark phase, but it is also produced by many other organs and cell types. Such a wide distribution is consistent with its multiple and well-described functions which include from the circadian regulation and adaptation to seasonal variations to immunomodulatory and oncostatic actions in different types of tumors. The discovery of its antioxidant properties in the early 1990s opened a new field of potential protective functions in multiple tissues. A special mention should be made regarding the nervous system, where the indole is considered a major neuroprotector. Furthermore, mitochondria appear as one of the most important targets for the indole's protective actions. Melatonin's mechanisms of action vary from the direct molecular interaction with free radicals (free radical scavenger) to the binding to membrane (MLT1A and MLT1B) or nuclear receptors (RZR/RORα). Receptor binding has been associated with some, but not all of the indole functions reported to date. Recently, two new mechanisms of cellular uptake involving the facilitative glucose transporters GLUT/SLC2A and the proton-driven oligopeptide transporter PEPT1/2 have been reported. Here we discuss the potential importance that these newly discovered transport systems could have in determining the actions of melatonin, particularly in the mitochondria. We also argue the relative importance of passive diffusion vs active transport in different parts of the cell.

MT3 melatonin binding site, MT1 and MT2 melatonin receptors are present in oocyte, but only MT1 is present in bovine blastocyst produced in vitro

BACKGROUND

Melatonin inclusion into in vitro oocyte maturation (IVM) protocols has been suggested because it possesses a powerful free radical scavenger capability that improves the quality of the oocyte used in in vitro embryo production (IVP). The aim of our study was to investigate the presence of melatonin membrane receptors (MT1and MT2) and MT3, which is the melatonin binding site of NQO2 enzyme, in both oocytes and hatched blastocysts to consider an additional subcellular mechanism responsible for the effects of melatonin on IVP.

METHODS

The presence of the high affinity melatonin receptors was investigated through an autoradiographic binding assay, using the non-permeable ligand [125I]-iodomelatonin (17 pM) in embryos. The kind of melatonin site was investigated in oocytes and embryos by immunocytochemistry. In vitro fertilized bovine embryos produced from in vitro maturated oocytes supplemented with melatonin (0.0001 to 1000 nM) were analysed to determine their cleavage and blastocyst formation rates.

RESULTS

The [125I]-iodomelatonin (17 pM) binding in blastocysts was blocked by pre-incubation with melatonin (30000 nM), showing the presence of the high affinity melatonin receptors. MT1, MT2 and NQO2 immunoreactivity was observed in oocytes. MT1 immunoreactivity was observed in hatched blastocysts, however MT2 and NQO2 were not observed in this embryonic stage. Melatonin (pM) triggered significant difference in both cleavage and blastocysts formation rates.

CONCLUSIONS

The high affinity MT1 melatonin receptor must be taking part in IVM events; furthermore it is the first melatonin receptor to appear during bovine embryo development in vitro.

A polymorphism at the melatonin receptor 1A (MTNR1A) gene in Sarda ewes affects fertility after AI in the spring

The effect of MTNR1A gene polymorphisms on the fertility rate after AI in Sarda sheep was evaluated in 600 lactating adult ewes. Genomic DNA was subjected to amplification of the MTNR1A gene exon II. Amplicons were digested with restriction endonuclease MnlI. Ten samples from each genotype were sequenced. A polymorphism was detected (A612G) and ewes were determined to be +/+, +/- or -/- for the allele. Allelic frequency was 0.77 for the+allele and 0.23 for the - allele. The frequency of the +/+, +/- and -/- genotypes was 68, 19 and 13%, respectively. On 16 May 2009, 60 ewes from each genotype group were synchronised using intravaginal sponges containing 40 mg fluorogestone acetate for 14 days. At sponge removal, the ewes were administered 350 IU pregnant mare's serum gonadotropin and were then inseminated, 54-56 h later, with 400 × 10(6) spermatozoa. Pregnancies were confirmed 50 days after AI using transabdominal ultrasonography. Lambing dates and the number of newborn lambs were recorded within 155 days after AI. Conception and lambing rate were higher for ewes with the +/+ and +/- genotypes compared with those with the -/- genotype (P<0.01). In conclusion, there was a positive correlation between MTNR1A allele polymorphisms the reproductive response following synchronisation and AI in the spring.