The accumulation of the maternal pool of histone H1A during oogenesis in Xenopus laevis.

The accumulation of the maternal pool of histone H1A in Xenopus laevis oocytes was measured by the use of a semi-quantitative immunoradiographic method. This method implies the size-fractionation of total basic protein extracts from oocytes on a polyacrylamide gel, blotting of the proteins to diazotized paper and detection of histone proteins on the blots with the aid of antibodies to histone H1A and of [125I]protein A. It is shown that the maternal H1A pool that is present in fully-grown oocytes is accumulated very early in oogenesis, mainly in early vitellogenic oocytes. Stage III oocytes (Dumont, 1972) already contain approximately 80% of the final amount of H1A that is found in mature oocytes. The minimum amount of histone H1A estimated to be present in mature oocytes is 8-10 ng.