Follicle-stimulating hormone receptor (FSHR) in Chinese alligator, Alligator sinensis: Molecular characterization, tissue distribution and mRNA expression changes during the female reproductive cycle

The 2039 A/G FSH receptor gene polymorphism influences glucose metabolism in healthy men

OBJECTIVE

To assess the role of c. 2039 A/G (p. Asp680Ser) (rs6166) and c. -29 G/A (rs1394205) follicle-stimulating hormone receptor (FSHR) gene single nucleotide polymorphisms (SNPs) in a cohort of healthy men.

METHODS

One-hundred twenty-seven healthy men underwent evaluation of the anthropometric parameters, assessment of metabolic and lipid profile, measurement FSH serum levels, and genotyping of both the aforementioned FSHR SNPs. Data grouped according to the FSHR rs6166 or rs1394205 genotypes underwent to statistical analysis.

MAIN RESULTS

The three groups of men for each FSHR SNP did not differ statistically significantly for body mass index and serum FSH levels. As for FSHR rs6166 SNP, glucose levels were significantly lower in men with the GG genotype compared with those with the AA genotype. Men with AG had lower insulin levels and HOMA index values compared with those carrying the genotype AA (p < 0.05). The GG group showed a negative correlation between serum FSH levels and insulin and between serum FSH levels and HOMA index (p < 0.05). In contrast, men grouped according to the FSHR rs1394205 genotype showed no significant difference in blood glucose, serum insulin levels, and HOMA index. The AG group showed a negative correlation between FSH insulin and between serum FSH levels and HOMA index (p < 0.05).

CONCLUSIONS

Men with the genotype GG of the FSHR rs6166 SNP have lower blood glucose levels than those with the AA genotype. Their FSH levels inversely correlated with insulin and HOMA index. In contrast, the genotype FSHR rs6166 A/G did not reveal any role of FSH on glucose metabolism in healthy men. The inverse relationship between FSH and insulin or HOMA index in the group with the genotype GG of the FSHR rs6166 SNP suggests a possible cross-talk between FSH and insulin.

Multi-omics analysis reveals that natural hibernation is crucial for oocyte maturation in the female Chinese alligator

BACKGROUND

Hibernation in an appropriate environment not only is important for the survival of hibernators in winter, but also is crucial for breeding in the following season for many hibernating species. However, the genetic and epigenetic mechanism underlying this process remain unclear. In the current study, we performed an integrative multi-omics analysis of gonads collected from Chinese alligators that overwintered in wild cave and artificial warmroom to explore transcriptomic and epigenomic alternations in these organs.

RESULTS

The data revealed that in the breeding season, female alligators were more strongly affected in terms of gene expression than males by non-hibernation because of overwintering in a warm room, especially for genes related to oocyte maturation, and this effect commenced in winter with the downregulation of STAR, which is the rate limiting factor of steroid biosynthesis. Further, miRNAs were found to play essential roles in this negative effect of overwintering in the warm room on hibernation. The upregulated miRNAs likely were responsible for the suppression of oocyte maturation in the breeding season. Finally, DNA methylome changes, especially hypomethylation, were found to play an important role in the alterations in ovarian function-related gene expression induced by non-hibernation.

CONCLUSIONS

Our study revealed the crucial role of hibernation quality for oocyte maturation in the Chinese alligator and the underlying genetic and epigenetic mechanisms, and highlights the importance of habitat, and especially, the overwintering site, in the conservation of not only the Chinese alligator, but also other endangered hibernators.

Molecular characterization and tissue expression profiles of prepro-vasoactive intestinal peptide in the Chinese alligator (Alligator sinensis) during the active and hibernating periods

The Chinese alligator (Alligator sinensis), a freshwater crocodilian endemic to China, is one of the most endangered crocodilian species; up to this date, very little is known about the endocrine regulation of its metabolic activities during different physiological states. In this study, we characterized the structure of the prepro-vasoactive intestinal peptide in Chinese alligator (prepro-caVIP) for the first time and examined its expression profiles in various tissues during the active and hibernating periods. The prepro-caVIP cDNA consists of a 221-bp 5'-untranslated region (UTR), a 606-bp complete coding region (CDS), and a 312-bp 3'-UTR, which encodes the 201-amino acid prepro-caVIP containing a 28-amino acid vasoactive intestinal peptide (VIP) and a 27-amino acid PHI (peptide histidine isoleucine). Multiple alignment analysis showed that VIP shares 100% identity with the given birds, reptiles, and African clawed frog, and 89% identity with mammals, 96% with fishes. Real-time quantitative PCR showed that the prepro-caVIP is widely expressed in all the examined tissues, and the expression level is significantly higher in small intestine, stomach, pancreas, lung, and skeletal muscle, whereas lower in heart, liver, spleen, kidney, ovary, and oviduct. During hibernation, the expression level of caVIP was significantly decreased in small intestine (P < 0.01), pancreas, and skeletal muscle (P < 0.05), whereas significantly increased in liver, spleen, and lung (P < 0.01). The wide distribution of caVIP and its differential expression changes in various tissues during hibernation implicated that it might play multiple effects in Chinese alligator and participate in the physiological adaptation of various organs in a paracrine and/or neurocrine manner.

Insulin-like growth factor I (IGF-I) in Chinese alligator, Alligator sinensis: Molecular characterization, tissue distribution and mRNA expression changes during the active and hibernating periods

The Chinese alligator Alligator sinensis is an endangered species endemic to China, up to date, little is known about the regulation of its growth and development. Insulin-like growth factor I (IGF-I) plays a vital role in regulating vertebrate growth and development. In this study, the full-length cDNA of IGF-I in Chinese alligator (caIGF-I) was obtained for the first time, it contains 890-bp nucleotides encoding a 153-amino acid precursor, the mature caIGF-I consists of 70 amino acids by cleaving the signal peptide and C-terminal extension (E domain). The caIGF-I contains all the features of IGF-I peptide with B, C, A, and D domains and the six conservative cysteine residues involved in the stable tertiary structure. Multiple alignment analysis showed that the amino acid sequence of caIGF-I shares high identity with American alligator Alligator mississippiensis (100%) and birds (95-97%). Phylogenetic tree analysis of the IGF-I amino acid sequences indicated that alligators cluster into the bird branch. Real-time quantitative PCR technique showed that caIGF-I is widely expressed in all the examined tissues with the highest expression level in liver, higher in pancreas and oviduct while lower in heart, spleen, lung, kidney, stomach, intestines, ovary and muscles. During hibernation, the caIGF-I expression level decreased significantly in liver, pancreas, oviduct and kidney, while did not significantly change in heart, spleen, lung, stomach, small intestine, ovary and muscles. The mRNA expression changes during the two periods implicate that caIGF-I might play an important role in the regulation of feeding and growth in the Chinese alligator.

Molecular cloning, characterization, tissue distribution and mRNA expression changes during the hibernation and reproductive periods of estrogen receptor alpha (ESR1) in Chinese alligator, Alligator sinensis

Chinese alligator, Alligator sinensis, is a critically endangered reptile species unique to China. Little is known about the mechanism of growth- and reproduction-related hormones gene expression in Chinese alligator. Estrogens play important roles in regulating multiple reproduction- and non-reproduction-related functions by binding to their corresponding receptors. Here, the full-length cDNA of estrogen receptor alpha (ERα/ESR1) was cloned and sequenced from Chinese alligator for the first time, which comprises 1764bp nucleotides and encodes a predicted protein of 587 amino acids. Phylogenetic analysis of ESR1 showed that crocodilians and turtles were the sister-group of birds. The results of real-time quantitative PCR indicated that the ESR1 mRNA was widely expressed in the brain and peripheral tissues. In the brain and pituitary gland, ESR1 was most highly transcribed in the cerebellum. But in other peripheral tissues, ESR1 mRNA expression level was the highest in the ovary. Compared with hibernation period, ESR1 mRNA expression levels were increased significantly in the reproductive period (P<0.05) in cerebellum, pituitary gland, liver, spleen, lung, kidney and ovary, while no significant change in other examined tissues (P>0.05). The ESR1 mRNA expression levels changes during the two periods of different tissues suggested that ESR1 might play an important role in mediation of estrogenic multiple reproductive effects in Chinese alligator. Furthermore, it was the first time to quantify ESR1 mRNA level in the brain of crocodilians, and the distribution and expression of ESR1 mRNA in the midbrain, cerebellum and medulla oblongata was also reported for the first time in reptiles.

Polymorphisms of the Ovine BMPR-IB, BMP-15 and FSHR and Their Associations with Litter Size in Two Chinese Indigenous Sheep Breeds

The Small Tailed Han sheep and Hu sheep are two prolific local sheep in China. In this study, the polymorphisms of BMPR-IB (Bone morphogenetic protein receptor IB), BMP-15 (Bone morphogenetic protein 15) and FSHR (follicle stimulating hormone receptor) were investigated to check whether they are associated with litter size in Small Tailed Han sheep and Hu sheep. Consequently, three polymorphisms, FecB mutation in BMPR-IB (c.746A>G), FecG mutation in BMP-15 (c.718C>T) and the mutation (g. 47C>T) in FSHR were found in the above two sheep breeds with a total number of 1630 individuals. The single marker association analysis showed that the three mutations were significantly associated with litter size. The ewes with genotype FecBB/FecBB and FecBB/FecB+ had 0.78 and 0.58 more lambs (p < 0.01) than those with genotype FecB+/FecB+, respectively. The heterozygous Han and Hu ewes with FecXG/FecX+ genotype showed 0.30 (p = 0.05) more lambs than those with the FecX+/FecX+ genotype. For FSHR gene, the ewes with genotype CC had 0.52 (p < 0.01) and 0.75 (p < 0.01) more lambs than those with genotypes TC and TT, respectively. Combined effect analyses indicated an extremely significant interaction (p < 0.01) between the random combinations of BMPR-IB, BMP-15 and FSHR genes on litter size. In addition, the Han and Hu ewes with BB/G+/CC genotype harbor the highest litter size among ewes analyzed in current study. In conclusion, BMPR-IB, BMP-15 and FSHR polymorphisms could be used as genetic markers in multi-gene pyramiding for improving litter size in sheep husbandry.