Studies in the Alt laboratory broadly focus on the areas of developmental immunology and cancer. Studies aimed at defining molecular aspects of lymphocyte differentiation focus on the mechanism and control of V(D)J recombination, the mechanism and control of immunoglobulin heavy chain class switch recombination, and elucidation of signaling pathways that effect early B and T cell differentiation. Studies in other areas include elucidation of mechanisms of DNA double strand break repair and studies of the function of the Myc family of cellular oncogenes. The approaches employed by the laboratory range from basic molecular genetics and biochemistry to gene-targeted mutation and the generation of novel animal-based approaches and models. In the latter context, the laboratory has generated numerous mutant mouse lines including models for diseases ranging from immunodeficiencies to cancer. Some of the most recent work focuses on the interplay between site-directed recombination, DNA end-joining, and cell cycle/cell death pathways in lymphogenesis, neurogenesis, genomic stability, and cancer.