Expression profiling of rainbow trout testis development identifies evolutionary conserved genes involved in spermatogenesis.

Chantier qualité GAInternational audienceBACKGROUND: Spermatogenesis is a late developmental process that involves a coordinated expression program in germ cells and a permanent communication between the testicular somatic cells and the germ-line. Current knowledge regarding molecular factors driving male germ cell proliferation and differentiation in vertebrates is still limited and mainly based on existing data from rodents and human. Fish with a marked reproductive cycle and a germ cell development in synchronous cysts have proven to be choice models to study precise stages of the spermatogenetic development and the germ cell-somatic cell communication network. In this study we used 9K cDNA microarrays to investigate the expression profiles underlying testis maturation during the male reproductive cycle of the trout, Oncorhynchus mykiss. RESULTS: Using total testis samples at various developmental stages and isolated spermatogonia, spermatocytes and spermatids, 3379 differentially expressed trout cDNAs were identified and their gene activation or repression patterns throughout the reproductive cycle were reported. We also performed a tissue-profiling analysis and highlighted many genes for which expression signals were restricted to the testes or gonads from both sexes. The search for orthologous genes in genome-sequenced fish species and the use of their mammalian orthologs allowed us to provide accurate annotations for trout cDNAs. The analysis of the GeneOntology terms therefore validated and broadened our interpretation of expression clusters by highlighting enriched functions that are consistent with known sequential events during male gametogenesis. Furthermore, we compared expression profiles of trout and mouse orthologs and identified a complement of genes for which expression during spermatogenesis was maintained throughout evolution. CONCLUSION: A comprehensive study of gene expression and associated functions during testis maturation and germ cell differentiation in the rainbow trout is presented. The study identifies new pathways involved during spermatogonia self-renewal or rapid proliferation, meiosis and gamete differentiation, in fish and potentially in all vertebrates. It also provides the necessary basis to further investigate the hormonal and molecular networks that trigger puberty and annual testicular recrudescence in seasonally breeding species

Développement des techniques de greffes de cellules souches germinale au service des productionspiscicoles : la réalité rejoint-elle la science-fiction ?

Session : ReproductionDéveloppement des techniques de greffes de cellules souches germinale au service des productionspiscicoles : la réalité rejoint-elle la science-fiction ? . 6. Journées de la Recherche Filière Piscicol

Bilan du séquençage d'une collection de "gènes exprimés" chez la truite arc-en-ciel <em>Oncorhynchus mykiss</em>

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Bilan du séquençage d'une collection de "gènes exprimés" chez la truite arc-en-ciel <em>Oncorhynchus mykiss</em>

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En quête des cellules souches de la gamétogenèse

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En quête des cellules souches de la gamétogenèse

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A promoter fragment of the sycp1 gene is sufficient to drive transgene expression in male and female meiotic germ cells in zebrafish.

International audienceThe synaptonemal complex protein 1 (Sycp1) is required for the formation of crossovers that occurs during the meiotic prophase. The tissue and cell-specific expression pattern of the Sycp1 protein have been studied in mammals and fish, but data on the corresponding transcript remain scarce. In this report, we described for the first time in zebrafish the tissue- and cell-specific expression pattern of the sycp1 gene. In ovary, the expression of the sycp1 transcript was restricted to the early primary oocytes. In testis, the sycp1 transcript was observed in primary spermatocytes in agreement with a previous report describing the localization of the Sycp1 protein in those cells. Unexpectedly, sycp1 transcript expression remained high in spermatids. To gain insight on the genomic region responsible for the sycp1 gene expression pattern, we generated four independent Dr_sycp1:eGFP transgenic zebrafish lines carrying the -1482/+338 gene fragment fused to the enhanced green fluorescent protein reporter gene. We demonstrate that this promoter fragment contains the information required for the cell-specific expression of the endogenous sycp1 gene in males and in females. However, the GFP protein and its associated fluorescence persist in spermatozoa and maturing oocytes. The Dr_sycp1:eGFP zebrafish lines have the potential to be valuable models to trace meiosis onset in zebrafish and constitute the first transgenic lines expressing the GFP reporter protein only in the male meiotic and postmeiotic cells in fish

Differential expression patterns of three aromatase genes and of four estrogen receptors genes in the testes of trout (Oncorhynchus mykiss)

Part of this work was presented at the 7th International Symposium on Fish Endocrinology, Buenos Aires, ArgentinaEstrogens are implicated in male gonad function, although their physiological roles remain uncertain. In the present study, we take advantage of the original model of spatio-temporal organization of trout spermatogenesis to revisit the synthesis and action sites of estrogens in fish testis. Within this system, somatic cell and germ cell development are synchronized due to a strict seasonal spermatogenetic cycle and the cystic organization of gonads. We evaluated the expression patterns and regulation of 3 aromatase isoforms (cyp19a, cyp19b-I, and cyp19b-II) and 4 estrogen receptors (esr1a, esr1b, esr2a, and esr2b) by quantitative reverse-transcriptase PCR during testicular maturation and in isolated germ cell populations. Our data demonstrated a reciprocal relationship between cyp19a and cyp19b (I and II) expression during testicular development (cyp19a decreased while cyp19b increased with maturation). Furthermore, cyp19b is significantly expressed in late germ cells. At the protein level, aromatase was immunohistochemically identified in interstitial tissue and in germ cells. Remarkable elevation of esr1a and esr2a was observed during the final stage of spermiation, while esr1b was expressed in an early stage of spermatogenetic development. Estrogen implants reduced testicular cyp19a transcript abundance while up-regulating cyp19b levels whereas androgens up-regulated testicular esr1a, esr2a, and esr2b. Together, the distinct spatio-temporal expression profiles and regulation of aromatases and estrogen receptors suggest that estrogens have discrete physiological functions during an early step of spermatogenesis and in the final stages of germ-cell maturation and/or excretion. This article is protected by copyright. All rights reserved

Investigation on two putative androgen-responsive genes expressed in the gonads of teleostean fish species

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Two-way selection for muscle lipid content modifies puberty and gametogenesis in rainbow trout

National audienceThe aim of the present work was to compare the reproductive characteristics of males and females from two divergent lines of spring-spawning rainbow trout, selected for high (fat line, FL) or low (lean line, LL) muscle lipid content. Muscular lipid content influences precocious puberty in I year-old males and in 2 year-old females, as well as the kinetics of gametogenesis. The relationship between the different phases of gametogenesis and fat reserves are discussed