Résumé :
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The mammalian synemin is a very unique intermediate filament (IF) gene encoding three isoforms (H, M and L) achieved by alternative mRNA splicing, exon skipping and an open reading frame shift. Synemin is a desmin-related myopathies (DRM)-associated protein and an A-kinase anchoring protein (AKAP) playing an important role in assembling components of cytoskeleton. Synemin is present in various tissues: muscles, neuro-glial cells and lens. We demonstrated the presence of synemin M in 5 day embryos (E5) and that the expression of three synemin isoforms is spatially and temporally regulated. We have examined the expression profile of synemin isoforms in mouse pluripotent embryonic stem (ES) cells and during their neural differentiation induced by retinoic acid. Using RT-PCR, Western blotting and immunostaining, we show that synemin M is present at both mRNA and protein levels in undifferentiated ES cells, as early as the pluripotency factor Oct-3/4 and intermediate filament keratin 8. We have observed an obvious change of synemin M expression profile during the neural differentiation of ES cells. Synemin H was produced only in neural precursors when the neural differentiation started, concomitant with synemin M, nestin and glial fibrillary acidic protein. However, both synemin H and M were restricted to the progenitor line during the neural differentiation program. Our in vivo analysis also confirmed the expression of synemins H/M in multipotent neural stem cells in the adult brain subventricular zone, a neurogenic germinal niche of the mice. Taken together, the findings herein represent the first evidence that synemin M may be helpful to characterize ES cells, while synemin H could be a useful marker of early neural differentiation of stem cells. Collaboration: V. Moura-Neto, B.S. Paulsen, S.K. Rehen- Universidade Federal do Rio de Janeiro, Brasil This work was supported by grants no. 13607 from Association Franse contre les Myopathies (AFM) .
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