Early nuclear modifications related to cellular activation: from histology to molecular cytopathology (1967-1997)

The nuclear chromatin structure and function are altered as soon as the first steps of cellular activation induced by membrane stimulation. Different studies carried on lymphatic tissues as well as isolated cell suspensions (lympho-monocytes) demonstrate that an early and transitory chromatin dispersion, visualised by nuclear refringency (1967), is related to the genome derepression allowing DNA transcription mecanism. This is linked to the expression of c-fos proto-oncogene and that of specific proteins synthesis This occurs before c myc expression and could play a role in the regulation of surface antigens expression. Independent from the induction of cell proliferation, but related to cell differentiation, the early and transitory chromatin dispersion as well as the influence of c-fos related to proteic system activator (AP(1)) is discussed in referring to recent studies (1997), as well as the regulation factors of the chromatin filament structure.