Contribution of the Belgian school of embryology to the concept of neural induction by the organizer.

Abstract

Albert BRACHET, founder of the Brussels School of embryology, conducted delicate experiments in which he selectively destroyed zones of the grey crescent with heated needles. This allowed him to observe, in 1923, that the median region of the grey crescent of the blastula is a area of spontaneous differentiation and that this "primary self-differentiation centre" organizes the axial organs in anurans. It is thus fair to say that A. BRACHET contributed significantly to the emergence of the organizer concept. Albert DALCQ and Jean PASTEELS, successors of A. BRACHET, trying to solve the problem of the organizer's determination, proposed their famous quantitative theory of embryonic development resulting in the concept of morphogenetic potential, which increases with the CV concentration, a combination of a cortical constituent C and a vegetal substance V. Jean BRACHET, the younger son of A. BRACHET and one of the founding father of molecular biology and embryology, was soon convinced that the organizer owes its inducing power to a chemical substance. Being the first to suggest the role of RNA in protein synthesis, he first imagined that RNA could be the active substance in induction but became convinced afterwards that the inducer must have a proteic nature. His interest in the molecular aspects of induction stimulated research that was to make chemical embryology molecular.