Cloning of total mRNA populations from adult and embryonic mice

Total clone banks of cDNAs synthesized from poly(A)-RNA obtained from three stages of the developing mouse were constructed. The stages chosen were 13-day-old embryo, neonatal, and fully grown adult. To have as complete a bank as possible, large numbers of individual clones were generated ~400,000 for the 13th day embryo and neonatal mouse and ~610,000 for the adult bank. In each case the clone bank was constructed by inserting double stranded cDNA into the PstI site of pBR322 by the “G-C tailing” method. Sequences cloned in this way could be separated from the plasmid host DNA by treatment of the resultant total chimeric plasmid population with PstI. Aliquots of the cloned cDNA material were labeled with ³²P by “nick translation” using Escherichia coli DNA polymerase I for the preparation of hybridization probes. Back-hybridization of these probes to the total clone banks allowed the determination of the sequence diversity among the above three very different developmental stages. The use of such clone banks should allow the identification of developmental stage specific mRNAs.