It has become increasingly clear that certain genes, depending upon the time and nature of their expression, can regulate the somewhat opposed processes of both tumorigenesis and differentiation. The embryonal carcinoma (EC) cell system has proven to be of particular value in studies of these two processes as well as in evaluating their interrelatedness. Therefore, in an attempt to identify novel regulatory genes the applicant mutagenized an EC cell line via retroviral insertion and generated a mutant line that differs from EC cells in both tumorigenicity and differentiation. The applicant has shown that the mutation was created by a single insertion into a hemizygous site. Sequencing of both the immediate 5' and 3' flanking regions at this site has revealed open reading frames with no homology to any known mouse gene. This indicates that the mutant phenotypes may have arisen as a result of viral insertion into a novel mouse coding sequence. The applicant proposes to use further flanking sequence information, zoo blotting, CpG island analysis and exon trapping techniques to identify a transcription unit at or near this locus. This transcript will be used to isolate a full length cDNA clone and then compare and sequence the gene from both cDNA and genomic clones and examine the 5' regulatory region. The applicant will also analyze the functional consequences of expression of the transcript in cell transfectants and transgenic mice and determine the tissue and embryonic specific expression patterns. Finally, she will isolate and characterize specific proteins whose expression has been altered as a consequence of the gene disruption. The applicant believes that these studies will result in the identification of a novel mouse gene and contribute to our understanding of the molecular and cellular elements controlling both proliferation and differentiation.
