Storage in the yolk platelets of low MW DNA produced by the regressing follicle cells

The present work was carried out to clarify the nature and origin of the yo lk DNA present in vitellogenic oocytes of the lizard Podarcis sicula. Morph ological and biochemical evidences indicate that it has an intrafollicular origin, from the apoptotic bodies resulting from follicle cells regression at the end of previtellogenesis. This conclusion is reinforced by the obser vation that the oocyte membrane, in in vitro experiments, is unpermeable to exogenous DNA. Biochemical evidences reveal that the yolk DNA has a tow (2 00bp) molecular weight and this suggests that it is produced by the endonuc leases typically involved in apoptotic DNA laddering. Indeed, immunocytoche mical analyses demonstrate that follicle cells contain significant amounts of DNAse I. In immunoblots, carried out during different periods of the ova rian cycle, the enzyme shows a MW of about 33, 66 or 100 kDa thus indicatin g that its activity in the follicle of Podarcis is modulated by dimerizatio n and/or binding to regulatory factors. (C) 2001 Wiley-Liss, Inc.