Publications by authors named "Boudjema Imarazene"

4 Publications

  • Page 1 of 1

Primordial Germ Cell Migration and Histological and Molecular Characterization of Gonadal Differentiation in Pachón Cavefish Astyanax mexicanus.

Sex Dev 2021 Mar 10:1-18. Epub 2021 Mar 10.

INRAE, Laboratoire de Physiologie et Génomique des poissons, Rennes, France,

The genetic regulatory network governing vertebrate gonadal differentiation appears less conserved than previously thought. Here, we investigated the gonadal development of Astyanax mexicanus Pachón cavefish by looking at primordial germ cells (PGCs) migration and proliferation, gonad histology, and gene expression patterns. We showed that PGCs are first detected at the 80% epiboly stage and then reach the gonadal primordium at 1 day post-fertilization (dpf). However, in contrast to the generally described absence of PGCs proliferation during their migration phase, PGCs number in cavefish doubles between early neurula and 8-9 somites stages. Combining both gonadal histology and vasa (germ cell marker) expression patterns, we observed that ovarian and testicular differentiation occurs around 65 dpf in females and 90 dpf in males, respectively, with an important inter-individual variability. The expression patterns of dmrt1, gsdf, and amh revealed a conserved predominant male expression during cavefish gonadal development, but none of the ovarian differentiation genes, i. e., foxl2a, cyp19a1a, and wnt4b displayed an early sexually dimorphic expression, and surprisingly all these genes exhibited predominant expression in adult testes. Altogether, our results lay the foundation for further research on sex determination and differentiation in A. mexicanus and contribute to the emerging picture that the vertebrate sex differentiation downstream regulatory network is less conserved than previously thought, at least in teleost fishes.
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http://dx.doi.org/10.1159/000513378DOI Listing
March 2021

RADSex: A computational workflow to study sex determination using restriction site-associated DNA sequencing data.

Mol Ecol Resour 2021 Feb 16. Epub 2021 Feb 16.

Physiological Chemistry, Biocenter, University of Wuerzburg, Wuerzburg, Germany.

The study of sex determination and sex chromosome organization in nonmodel species has long been technically challenging, but new sequencing methodologies now enable precise and high-throughput identification of sex-specific genomic sequences. In particular, restriction site-associated DNA sequencing (RAD-Seq) is being extensively applied to explore sex determination systems in many plant and animal species. However, software specifically designed to search for and visualize sex-biased markers using RAD-Seq data is lacking. Here, we present RADSex, a computational analysis workflow designed to study the genetic basis of sex determination using RAD-Seq data. RADSex is simple to use, requires few computational resources, makes no prior assumptions about the type of sex-determination system or structure of the sex locus, and offers convenient visualization through a dedicated R package. To demonstrate the functionality of RADSex, we re-analysed a published data set of Japanese medaka, Oryzias latipes, where we uncovered a previously unknown Y chromosome polymorphism. We then used RADSex to analyse new RAD-Seq data sets from 15 fish species spanning multiple taxonomic orders. We identified the sex determination system and sex-specific markers in six of these species, five of which had no known sex-markers prior to this study. We show that RADSex greatly facilitates the study of sex determination systems in nonmodel species thanks to its speed of analyses, low resource usage, ease of application and visualization options. Furthermore, our analysis of new data sets from 15 species provides new insights on sex determination in fish.
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http://dx.doi.org/10.1111/1755-0998.13360DOI Listing
February 2021

Eye Development in Embryo: What the Uncommon Gene Expression Profiles Tell Us about Eye Evolution.

Front Physiol 2017 24;8:613. Epub 2017 Aug 24.

UMR Biologie des Organismes et Ecosystèmes Aquatiques, Museum National d'Histoire Naturelle, Sorbonne Universités, Centre National de la Recherche Scientifique (CNRS 7208), Université Pierre et Marie Curie (UPMC), Université de Caen Normandie, Institut de Recherche Pour le Développement (IRD207), Université des AntillesParis, France.

In metazoans, there is a remarkable diversity of photosensitive structures; their shapes, physiology, optical properties, and development are different. To approach the evolution of photosensitive structures and visual function, cephalopods are particularly interesting organisms due to their most highly centralized nervous system and their camerular eyes which constitute a convergence with those of vertebrates. The eye morphogenesis in numerous metazoans is controlled mainly by a conserved Retinal Determination Gene Network (RDGN) including , and playing also key developmental roles in non-retinal structures and tissues of vertebrates and . Here we have identified and explored the role of in eye morphogenesis, and nervous structures controlling the visual function in . We compare that with the already shown expressions in eye development of and genes. is the pigment responsible for light sensitivity in metazoan, which correlate to correlate visual function and eye development. We studied expression during retina differentiation. By hybridization, we show that (1) all of the RDGN genes, including , are expressed in the eye area during the early developmental stages but they are not expressed in the retina, unlike , which could have a role in retina differentiation; (2) is expressed in the retina just before vision gets functional, from stage 23 to hatching. Our results evidence a role of , and in eye development. However, the gene network involved in the retinal photoreceptor differentiation remains to be determined. Moreover, for the first time, expression is shown in the embryonic retina of cuttlefish suggesting the evolutionary conservation of the role of in visual phototransduction within metazoans. These findings are correlated with the physiological and behavioral observations suggesting that is able to react to light stimuli from stage 25 of organogenesis on, as soon as the first retinal pigments appear.
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http://dx.doi.org/10.3389/fphys.2017.00613DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5573735PMC
August 2017

Pre-hatching fluoxetine-induced neurochemical, neurodevelopmental, and immunological changes in newly hatched cuttlefish.

Environ Sci Pollut Res Int 2016 Mar 14;23(6):5030-45. Epub 2015 May 14.

Normandie Université, CS F-14032, Caen, France.

Embryonic and early postembryonic development of the cuttlefish Sepia officinalis (a cephalopod mollusk) occurs in coastal waters, an environment subject to considerable pressure from xenobiotic pollutants such as pharmaceutical residues. Given the role of serotonin in brain development and its interaction with neurodevelopmental functions, this study focused on fluoxetine (FLX), a selective serotonin reuptake inhibitor (SSRI, antidepressant). The goal was to determine the effects of subchronic waterborne FLX exposure (1 and 10 μg L(-1)) during the last 15 days of embryonic development on neurochemical, neurodevelopmental, behavioral, and immunological endpoints at hatching. Our results showed for the first time that organic contaminants, such as FLX, could pass through the eggshell during embryonic development, leading to a substantial accumulation of this molecule in hatchlings. We also found that FLX embryonic exposure (1 and 10 μg L(-1)) (1) modulated dopaminergic but not serotonergic neurotransmission, (2) decreased cell proliferation in key brain structures for cognitive and visual processing, (3) did not induce a conspicuous change in camouflage quality, and (4) decreased lysozyme activity. In the long term, these alterations observed during a critical period of development may impair complex behaviors of the juvenile cuttlefish and thus lead to a decrease in their survival. Finally, we suggest a different mode of action by FLX between vertebrate and non-vertebrate species and raise questions regarding the vulnerability of early life stages of cuttlefish to the pharmaceutical contamination found in coastal waters.
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http://dx.doi.org/10.1007/s11356-015-4591-7DOI Listing
March 2016