GnRH Receptor Gene Research Articles

Discovery and computational exploration of SNPs in GNRHR gene and their influence on protein structure and function in Indian goat breeds

This study focuses on identifying functional single nucleotide polymorphisms (SNPs) within the gonadotropin-releasing hormone receptor (GNRHR) gene and conducting subsequent in-silico analysis of their effects on protein structure and function in two distinct South Indian goat breeds, namely Attapady Black (n = 120) and Malabari goats (n = 180), known for their divergent prolificacy traits. Utilizing a DNA pool sequencing assay, ten SNPs were uncovered in the study population: c.-1129T>G, c.-1069A>G, c.-978A>C, c.-605A>G, c.-33A>G, c.-29T>G, c.48G>A, c.75G>A, c.209T>G, and c.*212A>G. Notably, two polymorphisms, c.-1129T>G and c.-33A>G, were novel. Additionally, two polymorphisms, c.-33A>G and c.-978A>C, were exclusive to Malabari goats. Analysis of upstream variants revealed modifications to transcription factor and micro-RNA (miRNA) binding sites, suggesting potential alterations in GNRHR expression. Of particular significance was the non-synonymous exonic variant at c.209T>G locus, resulting in methionine to arginine substitution at the 70th position within the first intracellular loop of the receptor protein. This amino acid change may have implications for the functional dynamics of the receptor as GnRHR intracellular loops are involved in G protein coupling thereby facilitation of downstream signalling pathways. The identified SNPs and their in-silico impact analysis contribute to our understanding of the molecular mechanisms underlying reproductive traits in these goat populations, with implications for future breeding strategies and genomic selection programs.

Diplotype-based assessment of GNRHR gene polymorphisms and their role in determining litter size at birth in the Malabari goat population of South India

The Gonadotropin Releasing Hormone Receptor (GNRHR) gene, a key regulator of the hypothalamo-pituitary-gonadal axis, plays a pivotal role in modulating reproductive potential in mammals by influencing the release of gonadotropins. In this study, we conducted a comprehensive population genetic analysis of haplotypes and diplotypes of the GNRHR and explored their association with litter size at birth in the prolific Malabari goat breed of South India. Utilizing PCR-single strand conformation polymorphism (SSCP) and PCR-sequencing-based typing (SBT) techniques, we genotyped 185 Malabari goats for diplotypes encompassing specific single nucleotide polymorphisms (SNPs) at c.–33A>G, c.–29 T>G, c.48 G>A, c.75 G>A, and c.209 T>G loci of the GNRHR gene. The PCR-SSCP and PCR-SBT revealed the presence of seven diplotypes and six haplotypes within the study population. Our results, as determined by ordinal logistic regression analysis, demonstrated a highly significant (p<0.01) influence of GNRHR diplotypes on litter size at birth up to the third parity, with a significant (p<0.05) effect observed in the fourth parity in Malabari goats. Specifically, the odds of multiple births were found to be 53.3% and 80.7% higher for AGAGG/ATGGT diplotypes compared to AGAGG/AGAGG diplotypes in the first and second parity, respectively. Furthermore, the odds ratio analysis highlighted a higher percentage of multiple births in AGAGG/AGAAG diplotypes during the third and fourth parities compared to other diplotypes in Malabari goats. Collectively, our findings suggest that heterozygote diplotypes confer a reproductive advantage over homozygous diplotypes for litter size at birth in the Malabari goat breed.

Expression and localization of HPG axis-related genes in Carassius auratus with different ploidy.

In the Dongting water system, the Carassius auratus (Crucian carp) complex is characterized by the coexistence of diploid forms (2n=100, 2nCC) and polyploidy forms. The diploid (2nCC) and triploid C.auratus (3n=150, 3nCC) had the same fertility levels, reaching sexual maturity at one year. The nucleotide sequence, gene expression, methylation, and immunofluorescence of the gonadotropin releasing hormone 2(Gnrh2), Gonadotropin hormone beta(Gthβ), and Gonadotropin-releasing hormone receptor(Gthr) genes pivotal genes of the hypothalamic-pituitary-gonadal (HPG) axis were analyzed. The analysis results indicated that Gnrh2, follicle-stimulating hormone receptor(Fshr), and Lethal hybrid rescue(Lhr) genes increased the copy number and distinct structural differentiation in 3nCC compared to that in 2nCC. The transcript levels of HPG axis genes in 3nCC were higher than 2nCC (P<0.05), which could promote the production and secretion of sex steroid hormones conducive to the gonadal development of 3nCC. Meanwhile, the DNA methylation levels in the promoter regions of the HPG axis genes were lower in 3nCC than in 2nCC. These results suggested that methylation of the promoter region had a potential regulatory effect on gene expression after triploidization. Immunofluorescence showed that the localization of the Fshβ, Lhβ, and Fshr genes between 3nCC and 2nCC remained unchanged, ensuring the normal expression of these genes at the corresponding sites after triploidization. Relevant research results provide cell and molecular biology evidence for normal reproductive activities such as gonad development and gamete maturation in triploid C. auratus, and contribute to further understanding of the genetic basis for fertility restoration in triploid C. auratus.

Investigation of subfertility in the female Nsmf knockout mouse

To study if a pituitary or ovarian defect contributes to subfertility of the female Nsmf knockout (KO) mouse, an animal model of the hypogonadotropic hypogonadism gene NSMF. Analysis of hypothalamic, pituitary and ovarian gene expression at baseline, serum gonadotropin levels before and after gonadotropin-releasing hormone (GnRH) stimulation, ovarian response and implantation after superovulation, gonadotropin effects after ovariectomy, and ovarian NSMF protein expression. University research laboratory. None; mice were used. Gonadotropin-releasing hormone stimulation, superovulation, and ovariectomy in separate experiments. Gene expression in the hypothalamus, pituitary, and ovary; ovarian response and implantation after superovulation; serum gonadotropins after GnRH stimulation and ovariectomy; Western blot to measure ovarian NSMF expression. We found increased hypothalamic Kiss1, Gnrh1, and Jak2 mRNA expression in female Nsmf KO vs. wild type (WT) mice. However, pituitary gonadotropin, and GnRH receptor gene expression was not affected, and serum gonadotropin levels were normal. Gonadotropins increased after ovariectomy for both groups. Baseline Kiss1, Fshr, Prkaca, Prkar1a, and Gdf9 ovarian mRNA expression was increased and Cyp19a1 expression was decreased in Nsmf KO mice, while superovulated Nsmf KO mice had reduced ovarian Kiss1r, Prkar1a, and Fshr mRNA expression, 50% less oocytes, and normal implantation. Western blot demonstrated NSMF protein expression in the ovary of WT mice. Altered hypothalamic and ovarian gene expression was demonstrated in female Nsmf KO mice. It is possible that increased hypothalamic Gnrh1 and Kiss1 mRNA expression could compensate for reduced NSMF enabling a normal pituitary gonadotropin response. Impaired superovulation response, altered ovarian gene expression, and decreased number of oocytes indicate ovarian dysfunction, but a uterine factor cannot be excluded. These findings provide an anatomic basis for future mechanistic studies of subfertility in female Nsmf KO mice.

A corazonin G protein-coupled receptor gene in the tick Ixodes scapularis yields two splice variants, each coding for a specific corazonin receptor

We have identified a corazonin G protein-coupled receptor (GPCR) gene in the tick Ixodes scapularis, which likely plays a central role in the physiology and behavior of this ectoparasite. This receptor gene is unusually large (1.133 Mb) and yields two corazonin (CRZ) receptor splice variants, where nearly half of the coding regions are exchanged: CRZ-Ra (containing exon 2, exon 3, and exon 4 of the gene) and CRZ-Rb (containing exon 1, exon 3, and exon 4 of the gene). CRZ-Ra codes for a GPCR with a canonical DRF sequence at the border of the third transmembrane helix and the second intracellular loop. The positively-charged R residue from the DRF sequence is important for coupling of G proteins after activation of a GPCR. CRZ-Rb, in contrast, codes for a GPCR with an unusual DQL sequence at this position, still retaining a negatively-charged D residue, but lacking a positively-charged R residue, suggesting different G protein coupling. Another difference between the two splice variants is that exon 2 from CRZ-Ra codes for an N-terminal signal sequence. Normally, GPCRs do not have N-terminal signal sequences, although a few mammalian GPCRs have. In the tick CRZ-Ra, the signal sequence probably assists with inserting the receptor correctly into the RER membrane. We stably transfected Chinese Hamster Ovary cells with each of the two splice variants and carried out bioluminescence bioassays that also included the use of the human promiscuous G protein G16. CRZ-Ra turned out to be selective for I. scapularis corazonin (EC50 = 10−8 M) and could not be activated by related neuropeptides like adipokinetic hormone (AKH) and AKH/corazonin-related peptide (ACP). Similarly, also CRZ-Rb could only be activated by corazonin, although about 4-fold higher concentrations were needed to activate it (EC50 = 4 x 10−8 M). The genomic organization of the tick corazonin GPCR gene is similar to that of the insect AKH and ACP receptor genes. This similar genomic organization can also be found in the human gonadotropin-releasing hormone (GnRH) receptor gene, confirming previous conclusions that the corazonin, AKH, and ACP receptor genes are the true arthropod orthologues of the human GnRH receptor gene.

Female-specific pituitary gonadotrope dysregulation in mice with chronic focal epilepsy

Gonadotropin hormone release from the anterior pituitary is critical to regulating reproductive endocrine function. Clinical evidence has documented that people with epilepsy display altered levels of gonadotropin hormones, both acutely following seizures and chronically. Despite this relationship, pituitary function remains a largely understudied avenue in preclinical epilepsy research. Recently, we showed that females in the intrahippocampal kainic acid (IHKA) mouse model of temporal lobe epilepsy displayed changes in pituitary expression of gonadotropin hormone and gonadotropin-releasing hormone (GnRH) receptor genes. Circulating gonadotropin hormone levels, however, have yet to be measured in an animal model of epilepsy. Here, we evaluated the circulating levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), GnRH receptor (Gnrhr) gene expression, and sensitivity to exogenous GnRH in IHKA males and females. Although no changes in overall dynamics of pulsatile patterns of LH release were found in IHKA mice of either sex, estrus vs. diestrus changes in basal and mean LH levels were larger in IHKA females with prolonged, disrupted estrous cycles. In addition, IHKA females displayed increased pituitary sensitivity to GnRH and higher Gnrhr expression. The hypersensitivity to GnRH was observed on diestrus, but not estrus. Chronic seizure severity was not found to be correlated with LH parameters, and FSH levels were unchanged in IHKA mice. These results indicate that although there are changes in pituitary gene expression and sensitivity to GnRH in IHKA females, there may also be compensatory mechanisms that aid in maintaining gonadotropin release in the state of chronic epilepsy in this model.

Association of Gonadotropin-Releasing Hormone Receptor (GnRHR) gene (c.18085 T&gt;G) and litter size in Ettawa crossbreed goat

In the present study, the association of Gonadotropin-Releasing Hormone Receptor gene (GnRHR) and litter size were investigated using the PCR-RFLP method as a genetic marker candidate for litter size in 35 individuals from Ettawa crossbreed goats. This research has two steps conducted in the laboratory and in the field. Data on litter size and blood samples were collected from the field. In the laboratory was carried out DNA isolation, amplification, and restriction. Molecular analysis of DNA isolation were precise, the enzyme Msp1 (C*CGG) with a product length of 706 bp was used for amplification and restriction analysis, releaved TT genotype in GnRHR gene fragment. In the exon 3 of chromosome 6, the single nucleotide polymorphism (SNP) c.18085 T&gt;G was found. Ettawa crossbreed goat in calculations using the hardy-weinberg law, insignificant results are obtained because the value is more than &gt; 0.05 (db; 1) = 0.50. The genotypes and allele frequencies found in the Ettawa Crossbreed Goat GnRHR genes are monomorphic and the GnRHR gene did not associate with litter size. The conclusion is that GnRHR exon 3 gene (SNP) c.18085 T&gt;G did not associate with litter size and can not be used as a genetic marker on Ettawa crossbred goats.

GNRHR-related central hypogonadism with spontaneous recovery – case report

BackgroundCongenital hypogonadotropic hypogonadism (CHH) is a clinically and genetically heterogeneous disease characterized by absent or incomplete puberty and infertility. Clinical characteristics are secondary to insufficient gonadotropin secretion, caused by deficient gonadotropin-releasing hormone (GnRH) production, secretion, or action. Loss-of-function variants of the gonadotropin-releasing hormone receptor (GNRHR) are associated with CHH without anosmia. CHH was previously considered a permanent condition, but in the past two decades, cases of spontaneous recovery of CHH have been reported. The reversal of hypogonadism in CHH is currently unpredictable, and can happen unnoticed.Case presentationThe male proband was diagnosed with CHH due to compound heterozygosity for two previously reported pathogenic missense variants in the GNRHR gene, NM_000406.2:c.416G > A (NP_000397.1:p.Arg139His) and c.785G > A (p.Arg262Gln) at 16 years of age. In addition to arrested partial puberty, he had a low testosterone level, gonadotropins in the range of early puberty, and a normal inhibin B level. A therapy with increasing doses of intramuscular testosterone undecanoate was received for 2.5 years, while there was no change in testicular volume. At the age of 19 years, testosterone supplementation was interrupted. During the next two years, he had spontaneous pubertal development to achieve a testicular volume of 20 mL, with normal adult levels of gonadotropins and testosterone.ConclusionsGenetic diagnostics can help discriminate congenital hypogonadotropic hypogonadism, deserving therapeutic intervention, from the self-limited constitutional delay of growth and puberty (CDGP). Patients with GNRHR associated hypogonadism can experience spontaneous recovery of the hypothalamic-pituitary–gonadal axis. Spontaneous testis enlargement in patients with central hypogonadism not taking gonadotropins or pulsatile GnRH therapy can indicate recovery of hypogonadism.

Impact of One-Week Administration of Dihydrotestosterone in Rat Anterior Pituitary Gland.

Hyperandrogenism causes dysfunction of the hypothalamic–pituitary–gonadal (HPG) axis in reproductive women. In this study, we examined the effects of dihydrotestosterone (DHT) on characteristic changes in rat anterior pituitary gland samples. DHT was administered to ovary-intact 6-week postnatal female rats for 7 days, after which the anterior pituitary glands were examined and compared with those in control rats. Estrous cyclicity was not drastically disrupted by DHT treatment. Common gonadotropin α subunit (Cga), luteinizing hormone β subunit (Lhb), and follicle-stimulating hormone (FSH) β subunit (Fshb) gene expression levels were not modulated by DHT treatment, while prolactin (Prl) gene expression was significantly repressed by DHT. Gonadotropin-releasing hormone (GnRH) receptor (Gnrh-r) gene expression was significantly inhibited by DHT, whereas pituitary adenylate cyclase-activating polypeptide (PACAP) receptor (Pca1-r) gene expression was increased by DHT. Gene expression levels of the receptors encoded by thyrotropin-releasing hormone (Trh-r) and kisspeptin (Kiss1-r) genes were unchanged. Expression of inhibin α subunit (Inha) and activin βA subunits (Actba) within the pituitary was inhibited by DHT treatment, while activin B subunit (Actbb) and follistatin (Fst) gene expression was unchanged by DHT. In mouse pituitary gonadotroph LβT2 cells, DHT did not modulate the gene expression of Gnrh-r, but it inhibited the expression of Inha and Actba subunits within the LβT2 cells. In rat prolactin-producing GH3 cells, DHT did not modulate prolactin gene expression, but it increased Pac1-r gene expression. The present observations suggest that DHT directly or indirectly affects the anterior pituitary gland and induces characteristic changes in hormone-producing cells.

A novel compound variant in GNRHR causing congenital idiopathic hypogonadotropic hypogonadism in a young male Korean patient.

Idiopathic hypogonadotropic hypogonadism (IHH) is a disease that shows symptoms of no or incomplete sexual maturation after 18 years old. The mutation of gonadotropin releasing hormone receptor gene (GNRHR) has been reported as the cause in 16% of total IHH patients. An 18-year-old adolescent was referred to endocrinology department for hypogonadism. He was born with cryptorchidism, had small testes at the age of 7 years, and showed low testosterone levels. Management of his hypogonadism was delayed due to his uncontrolled nephrotic syndrome. There were no abnormal findings on the brain MRI; atrophied testes discovered on his pelvis MRI; low levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone were observed. In the HCG simulation test, testosterone levels showed no significant increase, rising from 1.11 to 1.15 ng/dL. The patient harbored a novel compound heterozygous variant of c.514G>A (p.Gly172Arg) and c.113G>A (p.Arg38Gln) in the GNRHR gene. Here, we report a case of new GNRHR compound variant c.514G>A (p.Gly172Arg) and c.113G>A (p.Arg38Gln) in a Korean adolescent for hypogonadotropic hypogonadism.

NOVEL ASSOCIATION BETWEEN GnRHR GENE AND GROWTH TRAITS IN AWASSI AND KARAKUL SHEEP

This study was conducted to investigate the association of the Gonadotropin-Releasing Hormone Receptor (GnRHR) gene with growth traits in Awassi (n= 123) and Karakul (n= 78) sheep. Starting from the birth-day to 12 months of age, several growth traits were investigated, namely body weight and length, wither and rump height, chest, and abdominal circumferences. Four fragments were designed to amplify three exons of GnRHR gene, P1 and P2 for exon 1, P3 for exon 2, and P4 for exon 3. The polymorphisms in these amplicons were analyzed by single-strand conformation polymorphism (SSCP) method. Genotypic and allele frequency of GnRHR gene were computed after sequence alignment. The results detected two different SSCP banding patterns GG and GA for both P2 and P3 amplicons, and two novel mutations were observed in GA genotype of P2 and P3 amplicons respectively, p.N87= and p.L242F. The identified p.N87= exhibited no relationship with all measured growth traits, while p.L242F showed significant association with the body weight, length, and abdominal circumference in month-6 and month-9. This association was increasingly observed in month-12 with all growth traits, in which individuals with GA genotype exhibited higher growth traits measurements than individuals with GG genotype (P &lt; 0.01). In conclusion, the detected polymorphism of GnRHR gene exon-2 may be useful in marker-assisted selection for growth traits in Awassi and Karakul breeds. This study is the first one to describe the effect of GnRHR polymorphisms on growth traits, which confirm the potential usefulness of this gene in marker-assisted selection in sheep.

NOVEL ASSOCIATION BETWEEN GnRHR GENE AND GROWTH TRAITS IN AWASSI AND KARAKUL SHEEP: GnRHR genetic polymorphism in sheep

This study was conducted to investigate the association of the Gonadotropin-Releasing Hormone Receptor (GnRHR) gene with growth traits in Awassi (n= 123) and Karakul (n= 78) sheep. Starting from the birth-day to 12 months of age, several growth traits were investigated, namely body weight and length, wither and rump height, chest, and abdominal circumferences. Four fragments were designed to amplify three exons of GnRHR gene, P1 and P2 for exon 1, P3 for exon 2, and P4 for exon 3. The polymorphisms in these amplicons were analyzed by single-strand conformation polymorphism (SSCP) method. Genotypic and allele frequency of GnRHR gene were computed after sequence alignment. The results detected two different SSCP banding patterns GG and GA for both P2 and P3 amplicons, and two novel mutations were observed in GA genotype of P2 and P3 amplicons respectively, p.N87= and p.L242F. The identified p.N87= exhibited no relationship with all measured growth traits, while p.L242F showed significant association with the body weight, length, and abdominal circumference in month-6 and month-9. This association was increasingly observed in month-12 with all growth traits, in which individuals with GA genotype exhibited higher growth traits measurements than individuals with GG genotype (P < 0.01). In conclusion, the detected polymorphism of GnRHR gene exon-2 may be useful in marker-assisted selection for growth traits in Awassi and Karakul breeds. This study is the first one to describe the effect of GnRHR polymorphisms on growth traits, which confirm the potential usefulness of this gene in marker-assisted selection in sheep.

Effective accumulative temperature affects gonadal maturation by controlling expression of GnRH, GnRH receptor, serotonin receptor and APGWamide gene in Pacific abalone, Haliotis discus hannai during broodstock conditioning in hatcheries.

Water temperature is a crucial environmental factor that influences reproductive function of abalone. Broodstock conditioning exposed to effective accumulative temperature (EAT) is a common practice in abalone hatcheries. To understand the molecular mechanism underlying the regulation of gonadal maturation and reproduction of Haliotis discus hannai exposed to EAT and induced spawning period, changes in expression of neuroendocrine genes encoding two gonadotropin releasing hormone (Hdh-GnRH, GnRH-like peptide), GnRH receptor (HdhGnRH-R), serotonin receptor (5-HTHdh) and Hdh-APGWamide in neural ganglia and gonadal tissues were examined. Gonadosomatic index (GSI) was significantly increased with increasing EAT °C-days. Expression levels of Hdh-GnRH, GnRH-like peptide, HdhGnRH-R, 5-HTHdh and Hdh-APGWamide mRNA were significantly increased with increasing EAT °C-days in ganglion (where the gene synthesized) and gonadal tissues. The significant increase in mRNA expression of each examined gene started from EAT 500 to 750°C-days, reached an initial peak at 1000°C-days, suggesting gonadal maturation started from the onset of EAT and slowly continued until 750°C-days, then at 1000°C-days reached to initial peak developmental period. The maturation reached to spawning state at 1000°C-days and peaked at 1500°C-days. Hdh-GnRH showed significantly higher mRNA expression in pleuropedal ganglion and branchial ganglion, whereas GnRH like peptide showed higher expression in cerebral ganglion, and HdhGnRH-R, 5-HTHdh and Hdh-APGWamide showed higher expression in pleuropedal ganglion. All genes were expressed higher at higher EAT °C-days. During induced spawning period, higher mRNA expression of examined genes was observed at the time of spawning; however, a sharp decrease occurred after spawning, suggesting that these genes are involved in spawning activities. Taken together, these results indicate that an increase of EAT °C-days can increase expression of neuroendocrine genes and enhance gonadal maturation. Besides all these genes are involved in the process of spawning induction, and increase of GSI has a positive correlation with the increase of gene expression.

Thermal Stress Affects Gonadal Maturation by Regulating GnRH, GnRH Receptor, APGWamide, and Serotonin Receptor Gene Expression in Male Pacific Abalone, Haliotis discus hannai During Breeding Season

Temperature has crucial effects on gonadal development and reproduction of abalone. To understand the impact of thermal stress on molecular and physiological processes triggering the regulation of reproduction, changes in the mRNA expression of neuroendocrine genes encoding two abalone gonadotropin-releasing hormone (Hdh-GnRH, Hdh-GnRH-like peptide), GnRH receptor (Hdh-GnRH-R), Hdh-APGWamide, serotonin receptor (5-HThdh), and a heat shock protein HSP70 were examined in ganglia and testis of male Pacific abalone (Haliotis discus hannai). Abalone were exposed to low water temperature (LWT) and high water temperature (HWT) in early and peak breeding seasons for 7 days. Then, gonadosomatic index (GSI) was calculated, relative gene expression was measured by qRT-PCR, and levels of testosterone in hemolymph were also measured by ELISA during the peak breeding season. GSI did not show any significant changes during the early breeding season. However, it was significantly decreased in LWT- or HWT-exposed abalone compared to the normal water temperature (NWT) group during the peak breeding season. In the early breeding season, changes of mRNA expression of all five genes were significant between LWT and HWT groups on day-7. In the peak breeding season, compared to the NWT group, the mRNA expressions of different genes were significantly decreased in different tissues both in LWT and HWT groups of abalone, such as Hdh-GnRH-like peptide in the cerebral ganglion (CG) and testis; Hdh-GnRH in the pleuropedal ganglion (PPG) and branchial ganglion (BG); Hdh-GnRH-R in the CG, PPG, and testis; and Hdh-APGWamide in the PPG and testis. Interestingly, the expression of 5-HThdh was significantly increased in the HWT group but decreased in the LWT group. Expression of HSP70 was significantly increased in the testis after exposure to HWT. Hemolymph levels of testosterone were significantly decreased in the HWT group compared to those in the NWT group. Altogether, these results denote that thermal stress has a repressive effect on gonadal maturation and reproduction by regulating the expression of Hdh-GnRH-like peptide, Hdh-GnRH, Hdh-GnRH-R, Hdh-APGWamide, 5-HThdh, and HSP70 genes and levels of hemolymph testosterone.

GnRH-Related Neurohormones in the Fruit Fly Drosophila melanogaster.

Genomic and phylogenetic analyses of various invertebrate phyla revealed the existence of genes that are evolutionarily related to the vertebrate’s decapeptide gonadotropin-releasing hormone (GnRH) and the GnRH receptor genes. Upon the characterization of these gene products, encoding peptides and putative receptors, GnRH-related peptides and their G-protein coupled receptors have been identified. These include the adipokinetic hormone (AKH) and corazonin (CRZ) in insects and their cognate receptors that pair to form bioactive signaling systems, which network with additional neurotransmitters/hormones (e.g., octopamine and ecdysone). Multiple studies in the past 30 years have identified many aspects of the biology of these peptides that are similar in size to GnRH and function as neurohormones. This review briefly describes the main activities of these two neurohormones and their receptors in the fruit fly Drosophila melanogaster. The similarities and differences between Drosophila AKH/CRZ and mammalian GnRH signaling systems are discussed. Of note, while GnRH has a key role in reproduction, AKH and CRZ show pleiotropic activities in the adult fly, primarily in metabolism and stress responses. From a protein evolution standpoint, the GnRH/AKH/CRZ family nicely demonstrates the developmental process of neuropeptide signaling systems emerging from a putative common ancestor and leading to divergent activities in distal phyla.

Effects of the dominance hierarchy on social interactions, cortisol level, HPG-axis activities and reproductive success in the golden cuttlefish Sepia esculenta

Dominance hierarchies are ubiquitous among group-living animals and markedly affect growth performance, metabolism, agonistic interactions, and stress-related physiology in vertebrates. However, few studies have investigated the effects of dominance hierarchies on the hypothalamic-pituitary-gonadal (HPG) axis and reproduction, especially in cephalopods. In this study, we employed an economically important cephalopod, the golden cuttlefish Sepia esculenta, as the target animal. Adopting the classical paired design, we first identified the formation of a dominance hierarchy and then investigated its effects on social interactions, cortisol level, HPG-axis activities (as indicated by the concentrations of gonadotrophin-releasing hormone (GnRH) and estradiol and the mRNA abundances of gnrh and estrogen receptor (er) genes), and reproductive success (determined by parentage analysis using polymorphic microsatellite loci) during the reproductive period. In general, dominant individuals presented significantly higher frequencies of aggressive behaviors (categorized as attack, chase, displace and threaten behaviors) and reproductive behaviors (designated mating events for males and spawning events for females), lower cortisol concentrations, higher HPG-axis activities, and higher reproductive success than subordinate individuals (all P < 0.05). Strong correlations between the frequencies of reproductive behaviors and reproductive success and among cortisol levels, HPG-axis activities and reproductive success were observed. However, no significant differences between dominant and subordinate individuals in body weight, dorsal mantle length or dorsal mantle width were detected. These results clearly show that dominance hierarchies occur in golden cuttlefish and provide the first evidence that such hierarchies significantly affect stress physiology, HPG-axis activities, and reproductive success in cephalopods. In the aquaculture and artificial reproduction of golden cuttlefish, we suggest that measures be adopted to decrease or eliminate harmful agonistic interactions and the subsequent physiological stress caused by dominance hierarchies to increase the reproductive efficiency.

Morphological Evidence for Functional Crosstalk Between Multiple GnRH Systems in the Male Tilapia, Oreochromis niloticus.

Gonadotropin-releasing hormone (GnRH) is a reproductive neuropeptide, which controls vertebrate reproduction. In most vertebrates, there are more than two GnRH orthologs in the brain. In cichlid fish, the Nile tilapia (Oreochromis niloticus), GnRH1 is the primary hypophysiotropic hormone, while GnRH2 and GnRH3 are non-hypophysiotropic but neuromodulatory in function. Hypophysiotropic GnRH neurons are thought to inter-communicate, while it remains unknown if hypophysiotropic and non-hypophysiotropic GnRH systems communicate with each other. In the present study, we examined interrelationship between three GnRH types using specific antibodies raised against their respective GnRH associated peptide (GAP) sequence. Double-immunofluorescence labeling coupled with confocal microscopy revealed that in sexually mature males, GnRH-GAP1-immunoreactive (-ir) processes are in proximities of GnRH-GAP3-ir cell somata in the terminal nerve, while GnRH-GAP1-ir cell somata were also accompanied by GnRH-GAP3-ir processes in the preoptic area. However, such interaction was not seen in immature males. Further, there was no interaction between GnRH-GAP2 and GnRH-GAP1 or GnRH-GAP3 neurons. Single cell gene expression analysis revealed co-expression of multiple GnRH receptor genes (gnrhr1 and gnrhr2) in three GnRH-GAP cell types. In mature males, high levels of gnrhr2 mRNA were expressed in GnRH-GAP1-ir cells. In immature males, gnrhr1 and gnrhr2 mRNAs are highly expressed in GnRH-GAP3-ir cells. These results suggest heterologous interactions between the three GnRH-GAP cell types and their potential functional interaction during different reproductive stages.

Mammary gland-specific regulation of GNRH and GNRH-receptor gene expression is likely part of a local autoregulatory system in female vizcachas (Rodentia: Chinchillidae)

In addition to key mammotrophic hormones such as the pituitary prolactin (PRL) and the ovarian steroids progesterone and estradiol, there are local factors that modulate the tissue dynamics of the mammary glands during pregnancy and lactation. By immunohistochemistry and RT-PCR, we found local transcription and translation of gonadotropin-releasing hormone (GNRH), GNRH receptor (GNRHR), PRL and PRL receptor (PRLR) in mammary glands of adult vizcachas during pregnancy and lactation. Both GNRH and GNRHR showed a lag between protein expression and gene transcription throughout the gestational period: while the highest transcription levels of these genes were recorded at early-pregnancy, the epithelial immunoexpressions of both showed their maximum during lactation. RIA results corroborated the presence of GNRH in mammary glands at all the analyzed stages and confirmed the maximum amount of this peptide in the lactating group. Significant amounts of GNRH were detected in milk samples as well. Conversely, PRL and PRLR shared similar protein and gene expression profiles, all exhibiting maximum values during lactation. GNRH peptide content in mammary glands of females with sulpiride-induced hyperprolactinemia (HP) was significantly lower than that of control females (CT). Although PRL mRNA levels remained unchanged, there was a marked increase in theα-lactalbumin (LALBA) transcription in mammary glands of HP- vs CT-females. These results suggest that after targeting mammary glands, PRL stimulates the expression of milk protein genes, but also, tempers the local expression of GNRH. Mammary gland-explantssupplemented with a GNRH analogue (GN-explants) had no differences in terms of PRLR orLALBA transcription levels compared to CT-explants, so the mammary PRLR signaling would not appear to be modulated by GNRH. Yet, mRNA expression levels of both GNRH and the GNRHR-downstream factor, EGR1, were significantly higher in GN-explants compared to that of CT which would point to a GNRH-positive feedback mechanism. In summary, the local coupled expression of GNRH, GNRHR and EGR1 in the mammary gland throughout pregnancy of vizcachas, the PRL-dependent mammary GNRH secretion as well as the GNRH positive feedback on its own transcription suggest an autocrine-paracrine regulatory mechanism and propose an active role for GNRH in mammary gland tissue remodeling.

GnRH(1-5), a metabolite of gonadotropin-releasing hormone, enhances luteinizing hormone release via activation of kisspeptin neurons in female rats.

Accumulating evidence suggests that kisspeptin neurons in the arcuate nucleus (ARC), which coexpress neurokinin B and dynorphin, are involved in gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) pulse generation, while the anteroventral periventricular nucleus (AVPV) kisspeptin neurons are responsible for GnRH/LH surge generation. The present study aims to examine whether GnRH(1-5), a GnRH metabolite, regulates LH release via kisspeptin neurons. GnRH(1-5) was intracerebroventricularly injected to ovariectomized and estrogen-treated Wistar-Imamichi female rats. Immediately after the central GnRH(1-5) administration at 2 nmol, plasma LH concentration increased, resulting in significantly higher levels of the area under the curve and baseline of plasma LH concentrations compared to vehicle-injected controls. On the other hand, in Kiss1 knockout rats, GnRH(1-5) administration failed to affect LH secretion, suggesting that the facilitatory effect of GnRH(1-5) on LH release is mediated by kisspeptin neurons. Double in situ hybridization (ISH) for Kiss1 and Gpr101, a GnRH(1-5) receptor gene, revealed that few Kiss1-expressing cells coexpress Gpr101 in both ARC and AVPV. On the other hand, double ISH for Gpr101 and Slc17a6, a glutamatergic marker gene, revealed that 29.2% of ARC Gpr101-expressing cells coexpress Slc17a6. Further, most of the AVPV and ARC Kiss1-expressing cells coexpress Grin1, a gene encoding a subunit of NMDA receptor. Taken together, these results suggest that the GnRH(1-5)-GPR101 signaling facilitates LH release via indirect activation of kisspeptin neurons and that glutamatergic neurons may mediate the signaling. This provides a new aspect of kisspeptin- and GnRH-neuronal communication with the presence of stimulation from GnRH to kisspeptin neurons in female rats.

Divergent expression patterns of pituitary gonadotropin subunit and GnRH receptor genes to continuous GnRH in vitro and in vivo

Continuous, as opposed to pulsatile, delivery of hypothalamic gonadotropin-releasing hormone (GnRH) leads to a marked decrease in secretion of pituitary gonadotropins LH and FSH and impairment of reproductive function. Here we studied the expression profile of gonadotropin subunit and GnRH receptor genes in rat pituitary in vitro and in vivo to clarify their expression profiles in the absence and continuous presence of GnRH. Culturing of pituitary cells in GnRH-free conditions downregulated Fshb, Cga, and Gnrhr expression, whereas continuous treatment with GnRH agonists upregulated Cga expression progressively and Gnrhr and Fshb expression transiently, accompanied by a prolonged blockade of Fshb but not Gnrhr expression. In contrast, Lhb expression was relatively insensitive to loss of endogenous GnRH and continuous treatment with GnRH, probably reflecting the status of Egr1 and Nr5a1 expression. Similar patterns of responses were observed in vivo after administration of a GnRH agonist. However, continuous treatment with GnRH stimulated LH secretion in vitro and in vivo, leading to decrease in LH cell content despite high basal Lhb expression. These data suggest that blockade of Fshb expression and depletion of the LH secretory pool are two major factors accounting for weakening of the gonadotroph secretory function during continuous GnRH treatment.