cGnRH II involvement in pyriform cell apoptosis

Immunolocalization of activin and inhibin at different stages of follicular development in the lizard Sceloporus torquatus

The activins and inhibins are glycoproteins with a role in the follicular development of vertebrates, that are found in follicular fluid and somatic follicular cells, with a different pattern among taxa. The principal function of activin (Act) is to modulate the follicle-stimulating hormone (FSH) synthesis and secretion, whereas inhibin (Inh) downregulates it. Both factors are modulators of intraovarian follicular recruitment, oocyte maturation, cell proliferation, and steroidogenic activity. Our aim was to characterize the immunolocalization of Act and Inh in the ovarian follicles during the reproductive cycle of the lizard Sceloporus torquatus. Act was detected in the granulosa cells and oocyte cortex in the different stages of follicular development. On the other hand, we identified Inh in the oocyte cortex and the cytoplasm of pyriform and small cells of previtellogenic follicles. Also, we found immunoreactivity in the oocyte cortex, theca, and small cells of vitellogenic and preovulatory follicles. Our data provide evidence that Act and Inh have changes related to the stage of follicular development. This dynamic appears to be conserved among vertebrates and is fundamental to ensure an adequate follicular development in this specie.

Glyphosate Interference in Follicular Organization in the Wall Lizard Podarcis siculus

Glyphosate (Gly) is a broad-spectrum herbicide widely used thanks to its high efficiency and low toxicity. However, evidence exists of its toxic effects on non-target organisms. Among these, the animals inhabiting agricultural fields are particularly threatened. Recent studies demonstrated that exposure to Gly markedly affected the morphophysiology of the liver and testis of the Italian field lizard Podarcis siculus. The present study aimed to investigate the effects of the herbicide on the female reproductive system of this lizard in order to have a full picture of Gly-induced reproductive impairment. The animals were exposed to 0.05 and 0.5 μg/kg of pure Gly by gavage for 3 weeks. The results demonstrated that Gly, at both doses tested, profoundly interfered with ovarian function. It induced germ cells' recruitment and altered follicular anatomy by anticipating apoptotic regression of the pyriform cells. It also induced thecal fibrosis and affected oocyte cytoplasm and zona pellucida organizations. At the functional levels, Gly stimulated the synthesis of estrogen receptors, suggesting a serious endocrine-disrupting effect. Overall, the follicular alterations, combined with those found at the level of the seminiferous tubules in males, suggest serious damage to the reproductive fitness of these non-target organisms, which over time could lead to a decline in survival.

Spring and Fall recrudescence in Podarcis siculus ovaries: A role for progesterone

In the lacertid Podarcis siculus the reproductive cycle is typically biphasic, with alternate recrudescence (Spring and Fall) and resting (Summer and Winter) phases. This study aimed to shed some light on the role exerted by progesterone during the two recrudescence periods; to this purpose, exogenous progesterone was administered intraperitoneally and the effects on oogonial proliferation, oocyte recruitment, and follicle cells apoptosis were determined. The presence and distribution of progesterone receptors was also investigated by immunohistochemistry and western blotting. Results indicate that progesterone would play different roles and follow different route of action in the two recrudescence periods thus confirming the complexity of the mechanisms controlling oogenesis in this species of vertebrate.

Alternative splicing of GnRH2 and GnRH2-associated peptide plays roles in gonadal differentiation of the rice field eel, Monopterus albus

The rice field eel, Monopterus albus, is a protogynous hermaphrodite fish, in which the gonads are initially female ovaries which then transform into male testes. The exact mechanisms governing sex reversal in the rice field eel are unknown. In this study, a novel alternative splicing variant of GnRH2 (GnRH2-SV), retaining the second intron, was discovered in the gonad of the rice field eel. Compared to GnRH2, GnRH2-SV may give rise to a novel truncated GnRH2-associated peptide (New GAP2). The normal transcript of GnRH2 was primarily expressed in the brain, and could also be detected in the liver, spleen, ovary, and testis. However, GnRH2-SV was only expressed in the ovary and testis. During sex reversal, GnRH2 expression levels increased significantly at late stages; however, expression levels of GnRH2-SV were lower in ovary than in ovotestis and testis. We also examined the effect of three peptides (GnRHa, GAP2, and New GAP2) on gonadal sex differentiation during the third stage of ovarian development of the rice field eel. Compared to the control group, the expression of amh increased significantly following incubation with each of the three peptides. However, only New GAP2 stimulated the expression of sox9a1 mRNA in vitro. After intraperitoneal injection of GAP2, the expression of amh, foxl2, and cyp19a1a increased significantly after 12 h; the concentration of serum 11-KT was also significantly increased at the 12 h time point. Treatment with New GAP2 significantly increased the expression of amh, dmrt1a, and sox9a1, and also increased the concentration of serum 11-KT. After treated with GnRHa, the expression of amh, dmrt1a, sox9a1, cyp19a1a, and foxl2 increased significantly, as did the level of serum E2. These results indicated that both GAP2 and New GAP2 play a crucial role in inducing expression changes of sex-differentiation related genes, and may be involved in the gonadal development and sex reversal in the rice field eel.

Expression of caspase 3 in ovarian follicle cells of the lizard Podarcis sicula

In this study, our aim was to determine whether caspase 3 plays a role, during previtellogenesis, in the ovarian follicular epithelium of the lizard Podarcis sicula. We investigated the presence and localization of proform and active caspase 3 by enzyme assay, Western blotting and immunocytochemistry. In parallel, a fragment of caspase 3 was cloned for the first time in this species, sequenced and used for in situ hybridization to localize messengers and analysed by a phylogenetic survey to shed light on its homology with reptilian caspases. Results demonstrated that: (1) the follicle cells expressed a caspase of the 3/7 group and the mRNA for caspase 3 was transcribed in the stem phase and was completely translated during cell differentiation; (2) the proform protein was stored during the differentiated (nurse) stage and activated at the end of previtellogenesis provoking the degeneration of cells; (3) the predicted protein sequence, although partial, had a strong similarity with the known reptilian caspases 3. The epithelial cells of the ovarian follicle, therefore, do not employ caspase 3 during the nurse stage but, instead, prepare for apoptosis long before the process actually begins. The relevance of this strategy is discussed.