Developmentally regulated mRNAs in mouse liver.

The mouse liver contains a group of 10--12 different tissue-specific mRNAs, each present at an average concentration of 12,000--15,000 copies per cell [Hastie, N. D. & Bishop, J. O. (1976) Cell 9, 761--774]. We have determined, by translation in vitro, that these mRNAs are developmentally regulated in the liver. We have also used specific cloned probes to quantitate the developmental time course of expression of five different abundant liver mRNAs. We have found that there are at least three periods during liver development when specific abundant mRNAs are first detectable: prior to 14 days postconception, at birth, and during the onset of sexual maturity. These results indicate that all the members of this mRNA group are not under common developmental regulation. One of the abundant liver mRNAs (p54 mRNA) increases more than 1000-fold in the liver 1 day before birth. We discuss factors that may be involved in the developmental regulation of expression of the genes encoding these mRNAs.