Analysis of illegitimate Notch1 and Bcl11b V(D)J deletion events during mouse development (P4400)

Abstract

Abstract Previously, others identified hotspots for deletional illegitimate V(D)J rearrangements in normal mouse thymus involving cryptic RSSs in Notch1 and Bcl11b, onco/tumor suppressor genes involved in T cell development. These deletions are associated with radiation-induced and other T cell malignancies. We are conducting expanded frequency and junctional analyses of deletions during mouse development to examine and compare age- and gender-specific detection and occurrence of these events. Deletions in thymus increase in frequency between fetal and neonatal stages, are seen through at least 7 months of age, and are found in spleen. Deletions are more frequent at Bcl11b than Notch1 as previously observed, but both genes show clonality of deletion bearing cells. Junctional processing analysis indicates that nucleotide loss is more frequent and extensive at Bcl11b than Notch1, thus P nucleotide insertions are more abundant in Notch1 junctions. N nucleotide insertions increase between fetal and juvenile stages, with recessed palindromes (Pr nucleotides) corresponding mostly to single-base additions consistent with normal TdT activity. An in depth age and gender junctional processing analysis is in progress as are determinations of postnatal inducibility of deletions using inducible RAG transgenic mice. We present our results in the context of similar studies of V(D)J deletions at the nonimmune HPRT locus and normal V(D)J recombination at antigen receptor loci.