Early gametogenesis in the Pacific oyster: new insights using stem cell and mitotic markers

Type Article
Date 2017-11
Language English
Author(s) Cavelier Patricia1, 2, Cau Julien1, 3, Morin Nathalie1, 4, Delsert Claude1, 4, 5
Affiliation(s) 1 : Univ Montpellier, F-34095 Montpellier, France.
2 : CNRS, UMR 5535, IGMM, F-34293 Montpellier, France.
3 : CNRS, UPR 1142, IGH, F-34396 Montpellier, France.
4 : CNRS, UMR5237, CRBM, F-34293 Montpellier, France.
5 : 3AS Ifremer, F-34250 Palavas Les Flots, France.
Source Journal Of Experimental Biology (0022-0949) (Company Of Biologists Ltd), 2017-11 , Vol. 220 , N. 21 , P. 3988-3996
DOI 10.1242/jeb.167734
WOS© Times Cited 2
Keyword(s) Germline cells, Cell cycle, Reproduction, Bivalve, Marine invertebrates
Abstract While our knowledge of bivalve gametogenesis has progressed in recent times, more molecular markers are needed in order to develop tissue imaging. Here, we identified stem cell and mitotic markers to further characterize oyster early gametogenesis, mainly through immunofluorescence microscopy. Intense alkaline phosphatase activity, a non-specific marker for stem cells, was detected on the outer edge of the gonad ducts at the post-spawning stage, suggesting an abundance of undifferentiated cells very early during the sexual cycle. This observation was confirmed using an antibody against Sox2, a transcription factor specific for stem or germline cells, which labeled cells in the gonad duct inner mass and ciliated epithelium early during the initial oyster sexual cycle. Moreover, Vasa, a cytoplasmic marker for germline cells, was also detected in the gonad acini and duct cells, thus confirming that germline cells were abundant early on. In addition, the binding of the minichromosome maintenance MCM6 protein to chromatin indicated the gonad acini and duct cells were engaged in the cell cycle. DNA replication was indeed confirmed by an abundant in vivo incorporation of BrdU into the duct cell chromatin. Finally, proliferation of acini and duct cells was demonstrated by the chromatin-bound Ser10-phosphorylated histone H3, a mitotic marker. The markers for the cell cycle and mitosis used here thus indicate that acini and duct cells were already actively dividing early during the oyster sexual cycle. In addition, together with the stem cell markers, these data reveal that the epithelium delimiting the duct outer edge contains a dynamic population of undifferentiated cells.
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