Summary TCF 11, a human bZIP transcription factor, has recently been cloned, mapped and characterised in the laboratory of Professor Kolsto. We propose to discover the role of this novel transcription factor by studying its homologue in the mouse. Genomic and cDNA clones homologous to the human TCF11 gene will be isolated and characterised by screening the relevant mouse libraries. The mouse gene, TCfl I will be mapped by linkage analysis to see if it corresponses to any mouse mutations which are models of human genetic disease. Tcf11 expression will be examined in the adult mouse by analysis of Northern blots and throughout embryonic development by in situ hybridisation of Tcf11 RNA to whole mount embryos. The effects of null or over expression of Tcf11 will be studied by generating transgenic mice carrying null or multiple copies of the gene.