Translation and stability of ovalbumin messenger RNA injected into growing oocytes and fertilized ova of mice

Abstract

Growing mouse oocytes and fertilized ova were injected with chicken ovalbumin messenger RNA (mRNAov) and chicken conalbumin mRNA (mRNAcon) and cultured in vitro. Estimation of mRNAov and mRNAcon stability by hybridization of cDNAov and cDNAcon to extracted mRNA from injected oocytes and fertilized ova indicated a half-life of 147 and 366 h in the oocyte and 5 and 3 h in the fertilized ovum respectively. Stability of mRNAov was similar in the fertilized and unfertilized ovum. Oocytes injected with chicken ovalbumin mRNA were also labelled with [3H]leucine and ovalbumin synthesis was measured by immunoprecipitation. The amount of ovalbumin synthesized during the initial 7 h was less than during the period of 18-25 or 66-73 h postinjection. The greatest percentage of ovalbumin to total protein synthesis occurred between 66-73 h. Oocytes secreted 12% of the synthesized ovalbumin during each of the 7 h periods (0-7, 18-25 and 66-73 h) indicating a stable mechanism for secretion throughout the culture period. These studies demonstrate: a dramatic difference in stability of injected mRNA between the growing oocyte and the unfertilized or fertilized ovum, and a gradual increase in the translation of injected mRNA by the growing oocyte during in vitro culture.