Project description:BACKGROUND: The Pacific oyster Crassostrea gigas (Mollusca, Lophotrochozoa) is an alternative and irregular protandrous hermaphrodite: most individuals mature first as males and then change sex several times. Little is known about genetic and phenotypic basis of sex differentiation in oysters, and little more about the molecular pathways regulating reproduction. We have recently developed and validated a microarray containing 31,918 oligomers (Dheilly et al., 2011) representing the oyster transcriptome. The application of this microarray to the study of mollusk gametogenesis should provide a better understanding of the key factors involved in sex differentiation and the regulation of oyster reproduction. METHODOLOGY/PRINCIPAL FINDINGS: Gene expression was studied in gonads of oysters cultured over a yearly reproductive cycle. Principal component analysis and hierarchical clustering showed a significant divergence in gene expression patterns of males and females coinciding with the start of gonial mitosis. ANOVA analysis of the data revealed 2,482 genes differentially expressed during the course of males and/or females gametogenesis. The expression of 434 genes could be localized in either germ cells or somatic cells of the gonad by comparing the transcriptome of female gonads to the transcriptome of stripped oocytes and somatic tissues. Analysis of the annotated genes revealed conserved molecular mechanisms between mollusks and mammals: genes involved in chromatin condensation, DNA replication and repair, mitosis and meiosis regulation, transcription, translation and apoptosis were expressed in both male and female gonads. Most interestingly, early expressed male-specific genes included bindin and a dpy-30 homolog and female-specific genes included foxL2, nanos homolog 3, a pancreatic lipase related protein, cd63 and vitellogenin. Further functional analyses are now required in order to investigate their role in sex differentiation in oysters. CONCLUSIONS/SIGNIFICANCE: This study allowed us to identify potential markers of early sex differentiation in the oyster C. gigas, an alternative hermaphrodite mollusk. We also provided new highly valuable information on genes specifically expressed by mature spermatozoids and mature oocytes.

Project description:Background The Pacific oyster Crassostrea gigas (Mollusca, Lophotrochozoa) is an alternative and irregular protandrous hermaphrodite. Little is known about the genetic and phenotypic bases of sex determinism in oysters, and little more about the molecular pathways regulating reproduction. We have recently developed and validated a microarray containing 31,918 oligomers (Dheilly et al., 2011) representing the oyster transcriptome. The application of this microarray to the study of mollusks gametogenesis should provide a better understanding of the key factors involved in sex differentiation and the regulation of oyster reproduction. Results Expression of the 31,918 ESTs was studied in gonads of oysters cultured along the French Atlantic coasts over a yearly reproductive cycle. Principal component analysis and hierarchical clustering first showed a significant divergence in gene expression patterns of males and females beginning when gonial mitosis started. Early expressed male-specific genes included bindin and female-specific genes included foxL2, a pancreatic lipase related protein, cd63 and vitellogenin. ANOVA analysis of the data further revealed 2482 genes differentially expressed during the course of males and/or females gametogenesis. The expression of 434 genes could be localized in either germ cells or somatic cells of the gonad by comparing the transcriptome of gonads to the transcriptomes of striped oocytes and somatic tissues. Analysis of the annotated genes revealed conserved molecular mechanisms between mollusks and mammals. Genes involved in chromatin condensation, DNA replication and repair, mitosis and meiosis regulation, transcription, translation and apoptosis were expressed in both male and female gonads. Additional lists of genes more specifically involved in either spermatogenesis (meiotic phase, in spermatozoids and mature sperm formation and in flagella structure and movement) or oogenesis (female sex differentiation, transcriptional regulation, cell cycle regulation and oocytes maturation) were also generated. Conclusions Our study provides novel insight into spermatogenesis and oogenesis in an alternative hermaphrodite bivalve, the Pacific oyster C. gigas. We identified genes opening new perspectives for functional studies of the signaling pathways implicated in gonad differentiation and development.

Project description:Background The Pacific oyster Crassostrea gigas (Mollusca, Lophotrochozoa) is an alternative and irregular protandrous hermaphrodite. Little is known about the genetic and phenotypic bases of sex determinism in oysters, and little more about the molecular pathways regulating reproduction. We have recently developed and validated a microarray containing 31,918 oligomers (Dheilly et al., 2011) representing the oyster transcriptome. The application of this microarray to the study of mollusks gametogenesis should provide a better understanding of the key factors involved in sex differentiation and the regulation of oyster reproduction. Results Expression of the 31,918 ESTs was studied in gonads of oysters cultured along the French Atlantic coasts over a yearly reproductive cycle. Principal component analysis and hierarchical clustering first showed a significant divergence in gene expression patterns of males and females beginning when gonial mitosis started. Early expressed male-specific genes included bindin and female-specific genes included foxL2, a pancreatic lipase related protein, cd63 and vitellogenin. ANOVA analysis of the data further revealed 2482 genes differentially expressed during the course of males and/or females gametogenesis. The expression of 434 genes could be localized in either germ cells or somatic cells of the gonad by comparing the transcriptome of gonads to the transcriptomes of striped oocytes and somatic tissues. Analysis of the annotated genes revealed conserved molecular mechanisms between mollusks and mammals. Genes involved in chromatin condensation, DNA replication and repair, mitosis and meiosis regulation, transcription, translation and apoptosis were expressed in both male and female gonads. Additional lists of genes more specifically involved in either spermatogenesis (meiotic phase, in spermatozoids and mature sperm formation and in flagella structure and movement) or oogenesis (female sex differentiation, transcriptional regulation, cell cycle regulation and oocytes maturation) were also generated. Conclusions Our study provides novel insight into spermatogenesis and oogenesis in an alternative hermaphrodite bivalve, the Pacific oyster C. gigas. We identified genes opening new perspectives for functional studies of the signaling pathways implicated in gonad differentiation and development. Individual gonad oysters were sampled in 3 sites: site 1 = Locmariaquer (Brittany, France), site 2 = Baie des Veys (Normandy, France), and site 3 = Argenton (Brittany, France). 8 undifferentiated stage 0 gonads from site 1 were processed. 4 individuals from site 1 were processed for each gonad developmental stage and sex: stage 1 male, stage 1 female, stage 2 male, stage 2 female, stage 3 male, and stage 3 female. Pools of stage 3 females were prepared with individuals from site 1 and site 2 for biological validation of the results. Striped gonads from stage 3 females were prepared for prediction of gene expression localization.

Dataset Information

SOHLHs Might Be Gametogenesis-Specific bHLH Transcriptional Regulation Factors in Crassostrea gigas.

Publications

SOHLHs Might Be Gametogenesis-Specific bHLH Transcriptional Regulation Factors in <i>Crassostrea gigas</i>.

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