Cyp19a1 (Aromatase) Expression in the Xenopus Brain at Different Developmental Stages

Abstract

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Cytochrome P450 aromatase (P450arom; aromatase) is a microsomal enzyme involved in the production of endogeneous sex steroids by converting testosterone into oestradiol. Aromatase is the product of the cyp19a1 gene and plays a crucial role in the sexual differentiation of the brain and in the regulation of reproductive functions. In the brain of mammals and birds, expression of cyp19a1 has been demonstrated in neuronal populations of the telencephalon and diencephalon. By contrast, a wealth of evidence established that, in teleost fishes, aromatase expression in the brain is restricted to radial glial cells. The present study investigated the precise neuroanatomical distribution of cyp19a1 mRNA during brain development in Xenopus laevis (late embryonic to juvenile stages). For this purpose, we used in situ hybridisation alone or combined with the detection of a proliferative (proliferating cell nuclear antigen), glial (brain lipid binding protein, Vimentin) or neuronal (acetylated tubulin; HuC/D; NeurobTubulin) markers. We provide evidence that cyp19a1 expression in the brain is initiated from the very early larval stage and remains strongly detected until the juvenile and adult stages. At all stages analysed, we found the highest expression of cyp19a1 in the preoptic area and the hypothalamus compared to the rest of the brain. In these two brain regions, cyp19a1-positive cells were never detected in the ventricular layers. Indeed, no co-labelling could be observed with radial glial (brain lipid binding protein, Vimentin) or dividing progenitors (proliferating cell nuclear antigen) markers. By contrast, cyp19a1-positive cells perfectly matched with the distribution of postmitotic neurones as shown by the use of specific markers (HuC/D, acetylated tubulin and NeurobTubulin). These data suggest that, similar to that found in other tetrapods, aromatase in the brain of amphibians is found in post-mitotic neurones and not in radial glia as reported in teleosts.

Steroid modulation of neurogenesis: Focus on radial glial cells in zebrafish

“…The radial identity of cells expressing aromatase has been attested in fish and now, it appears clearly that in these species, RGCs are the primary source of aromatase in the brain [64,71,72,78] while in mammals and birds, aromatase expression is confined to neurons under normal physiological conditions [79,80]. Data recently obtained in our laboratory demonstrated that in amphibian, aromatase expression is restricted to neurons during development as in adulthood [81]. In adult zebrafish, we did not observe sexual dimorphism in the expression of AroB (transcripts and protein) while in medaka, females exhibit a stronger periventricular expression in several regions, in particular the optic tectum [73].…”

Pattern of Neurogenesis and Identification of Neuronal Progenitor Subtypes during Pallial Development in Xenopus laevis

“…In Xenopus , RGc were observed using vimentin and BLBP as specific markers at late developmental stages (D’Amico et al, 2011) and the location of the labeled cells was used to define the vz (Coumailleau and Kah, 2014; Domínguez et al, 2015). The simultaneous observation of DAPI and BLBP allowed us to identify the radial organization in the pallium of Xenopus .…”

5‐hydroxymethylcytosine marks postmitotic neural cells in the adult and developing vertebrate central nervous system

“…On the next day, brains were taken out and fixed at 48C in 4% PFA, in order to be entirely processed for paraffin inclusion. Larvae and juvenile Xenopus were obtained, staged, and sacrificed as previously described (Coumailleau and Kah, 2014).…”