An intensive examination of the role of gene expression in chicken erythropoiesis is proposed. Both primitive (embryonic) and definitive red cell differentiation will be studied. We have isolated and analyzed the structure of the seven chicken globin genes. Further studies on these genes will concentrate on in vitro mutagenesis of these genes. Deletion mutants will be generated from both ends of the genes. These deletions will also be recombined in vitro to generate linker substitution mutants. Chimeric genes will also be generated by in vitro recombination between globin genes and promoter regions of other genes (histone, c-src) and vice-versa. The mutants so generated will be examined for expression in SV40 vectors (COS or HeLa cells), and by microinjection and/or cotransformation with selectable genes. Other red cell-expressed genes such as the H5 histone gene(s) and carbonic anhydrase genes will also be studied. These genes are presently being isolated and their expression and chromatin structure will be examined in chick red cells. Other erythroid-expressed genes have been isolated by genomic recombinant DNA cloning and are also being isolated by cDNA cloning. The structure and expression of these genes wll also be examined to obtain a more complete picture of the program of gene expression during erythropoiesis. We also hope to isolate and study a globin gene which diverged from the higher vertebrate globin line prior to the Alpha-Beta divergence. Cell lines transformed by tsAEV will be examined for their suitability as in vitro analogues of erythropoiesis. Immunological reagents which allow the identification and isolation of chicken erythroid precursor cells will be prepared and characterized.