Structural modifications of non-mammalian gonadotropin-releasing hormone (GnRH) isoforms: design of novel GnRH analogues

Generation of cynomolgus monkey fetuses with intracytoplasmic sperm injection based on the MII-stage oocytes acquired by personalized superovulation protocol

Background

Mature oocytes at the metaphase II status (MII-stage oocytes) played an important role in assisted reproductive technology in non-human primates.

Objectives

In order to improve the proportion of MII-stage oocytes retrieval, three different superovulation protocols were performed on 24 female cynomolgus monkeys.

Methods

All the monkeys received once-daily injection of follicle-stimulating hormone (25 international unit [IU]) on day 3 of the menstruation, 3-day intervals, twice daily for 8–12 days until the time of human chorionic gonadotropin (1,500 IU) injection, on the 14–17th day of menstruation collecting oocytes. The difference between protocol I and protocol II was that 0.1 mg the gonadotropin-releasing hormone agonist was injected on day 1 of the menstruation, while the difference between personalized superovulation protocol and protocol II was that oocytes could be collected on the 14–17th day of menstrual cycle according to the length of each monkey.

Results

The total number of oocytes harvested using the personalized superovulation protocol was much higher than that using protocol I (p < 0.05), and the proportion of MII-stage oocytes was significantly greater than that from either superovulation protocol I or II (p < 0.001 and p < 0.01 respectively), while the proportion of immature oocytes at the germinal vesicle was less than that from superovulation protocol I (p < 0.05).

Conclusions

The personalized superovulation protocol could increase the rate of MII-stage oocytes acquired, and successfully develop into embryos after intracytoplasmic sperm injection, and eventually generated fetus.

Systems approaches to genomic and epigenetic inter-regulation of peptide hormones in stress and reproduction

The evolution of the organismal stress response and fertility are two of the most important aspects that drive the fitness of a species. However, the integrated regulation of the hypothalamic pituitary adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes has been traditionally thwarted by the complexity of these systems. Pepidergic signalling systems have emerged as critical integrating systems for stress and reproduction. Current high throughput systems approaches are now providing a detailed understanding of peptide signalling in stress and reproduction. These approaches were dependent upon a long history of discovery aimed at the structural characterization of the associated molecular components. The combination of comparative genomics, microarray and epigenetic studies has led not only to a much greater understanding of the integration of stress and reproduction but also to the discovery of novel physiological systems. Recent epigenomic approaches have similarly yielded a new level of complexity in the interaction of these physiological systems. Together, such studies have provided a greater understanding of the effects of stress and reproduction.

Dopamine D1 receptor blockage potentiates AMPA-stimulated luteinising hormone release in the goldfish

Previous microarray analyses of the goldfish hypothalamus led us to hypothesise that dopamine could potentially inhibit the excitatory effects of glutamate on luteinising hormone (LH). Post-spawning female goldfish were pre-treated (-4.5 h) with either saline (C; control), SCH 23390 (S; D(1) -receptor antagonist) or sulpiride (L; D(2) -receptor antagonist), followed by an i.p. injection, at -0.5 h, of saline or the glutamate agonist AMPA (A, SA or LA). Blood, hypothalamus and telencephalon tissues were collected. Serum LH was not affected in the S, L, A, or LA groups relative to control as determined by radioimmunoassay. The SA group, however, showed a 289% (P<0.0005) increase in serum LH compared to either treatment alone or control. Real-time reverse transcriptase-polymerase chain reaction identified the mRNAs for ionotropic (Gria2a, Gria4) glutamate receptor subunits, activin βa, isotocin, and cGnRH-II as being significantly affected by some of the treatments. The same experiment conducted with sexually-regressed female fish showed a very different LH profile, indicating that this mechanism is seasonally-dependent. We also show that i.p. injection of 1 μg/g isotocin was able to increase LH levels by 167% in sexually regressed female fish relative to controls. Taken together, these results demonstrate that blockage of the D(1) receptor primes post-spawning goldfish for AMPA-stimulated LH release, and provides further insights into the central regulation of reproduction.

Sequence of two gonadotropin releasing hormones from tunicate suggest an important role of conformation in receptor activation

The primary structure of two forms of gonadotropin releasing hormone (GnRH) from tunicate (Chelyosoma productum) have been determined based on mass spectrometric and chemical sequence analyses. The peptides, tunicate GnRH-I and -II, contain features unprecedented in vertebrate GnRH. Tunicate GnRH-I contains a putative salt bridge between Asp5 and Lys8. A GnRH analog containing a lactam bridge between Asp5 and Lys8 was found to increase release of estradiol compared with that of the native tunicate GnRH-I and -II. Tunicate GnRH-II contains a cysteine residue and was isolated as a dimeric peptide. These motifs suggest that the conformation plays an important role in receptor activation.