EVOLUTION OF ACETYLCHOLINESTERASE TRANSCRIPTS AND MOLECULAR-FORMS DURING DEVELOPMENT IN THE CENTRAL-NERVOUS-SYSTEM OF THE QUAIL

We studied the expression of acetylcholinesterase (AChE) in the nervou s system (cerebellum, optic lobes, and neuroretina) of the quail at di fferent stages of development, from embryonic day 10 (E10) to the adul t. Analyzing AChE mRNAs and AChE molecular forms, we observed variatio ns in the following: (a) production of multiple mRNA species (4.5 kb, 5.3 kb, and 6 kb); (b) translation and/or stability of the AChE protei n; (c) production of active and inactive AChE molecules; (d) productio n of amphiphilic and nonamphiphilic AChE forms; and (e) proportions of tetrameric G(4), dimeric G(2), and monomeric G(1) forms. The large tr anscripts present distinct temporal patterns and disappear in the adul t, which possesses only the 4.5-kb mRNA; these changes are unlikely to be related to those observed for the AChE protein, because all transc ripts seem to encode the same catalytic subunit (type T). In addition, the levels of mRNA and AChE are not correlated in the three regions, especially at the adult stage. The proportion of inactive AChE was fou nd to be markedly higher at the hatching period (E16) than at earlier stages (E10 and E13) or in the adult. The G(4) form is predominant alr eady at E10, and in the adult its proportion reaches 80% of the activi ty in the cerebellum and optic lobes, and 65-70% in the neuroretina. T his form is largely nonamphiphilic in embryonic tissues, but it become s progressively more amphiphilic with development. Thus, the different processing and maturation steps appear to be regulated in an independ ent manner and potentially correspond to physiologically adaptative me chanisms.