Article révisé par les pairs
| Résumé : | Molecular embryology has made great advances in recent years: at present far more is known than 10 or 15 yr ago of the molecular organization of the genetic material, the structures of rDNA and the 'maturation' of the rRNAs, the biochemical role of the nucleolus, the influence of cytoplasmatic factors on genic activity, the metabolic inhibitors of unfertilized eggs, and the influence of hormones on oocytes, etc. Further progress is expected, and it seems likely that long known embryologic concepts, such as those of the functional organization of the embryo in different areas, the gradients and morphogenetic fields, regulation and induction, will be increasingly understood in molecular terms. Maybe the old philosophic discussions on the problems of preformation and pigenesis (Buffon, Spallanzani and others) may even finally be brought to an end: in molecular terminology preformation means the already preformed, stable, maternal mRNA: while epigenesis would bear on the newly formed, short lived mRNA which can only be formed in the nuclei of the embryo. Will molecular embryology also contribute to the solution of the major medical problems of humanity? The author believes so, at least in 2 important fields indicated by the slogans 'cancer' and 'ageing'. Malignancy means the absence of cell differentiation: cancer cells divide but do not differentiate. If it were possible, based on a more profound understanding of the molecular mechanisms of cell differentiation, to force cancer cells to differentiate, they would also lose their malignancy. Ageing begins very early and should therefore also deserve the interest of the molecular embryologists, who often talk of 'young' and 'old' blastulas (to which can be added that at any rate a blastula is already very old in comparison with an oocyte!). There are quite sensible grounds for the assumption that, from the molecular point of view, ageing is nothing but a slow accumulation of errors, as occasionally occur in protein biosynthesis (theory of Orgel), and that physiologic death is the result of a 'catastrophic' error of this kind. |
