6 DNA damage-induced p53 downregulates expression of RAG1 | 153 Previously, we have shown that endogenous DNA damage emanating from RAG1/2 activity could trigger a similar regulatory response as provoked by g-irradiation7. To study the effect of RAG1/2-dependent DNA damage on Foxp1 expression we made use of pre-B cell cultures from Rag1-/- mice, where the developmental block imposed by Rag1 deficiency is rescued by the transgenic expression of a functionally rearranged VH81x IgH m chain14. We observed that in in vitro cultured primary bone marrow B-cell progenitor cells prompted to undergo Igl recombination by IL7 and Flt3L withdrawal, Foxp1 mRNA levels were approximately 2-fold higher in Rag1-/- VH81x primary bone marrow as compared to their RAG-proficient counterparts (1.61-fold higher Foxp1 levels, p<0.05, on day 1 following IL7/ Flt3L withdrawal in Rag1-/- VH81x vs Rag1+/+ VH81x; and 1.59-fold higher Foxp1 levels, p<0.05, on day 3 after IL7/Flt3L withdrawal in Rag1-/- VH81x versus Rag1+/+ VH81x) (Figure 1I-J).
RkJQdWJsaXNoZXIy MTk4NDMw