Rapid in vivo analysis of mutant forms of the LAT adaptor using Pax5-Lat double-deficient pro-B cells

Following injection into recombinase-activating gene-deficient (Rag1(-/-)) mice, pro-B cells lacking the Pax5 transcription factor (Pax5(-/-)) develop into most major hematopoietic lineages, with the notable exception of B cells. We assessed whether Pax5(-/-) pro-B cells that were also rendered deficient for the linker for activation of T cells (LAT), an adaptor essential for T cell receptor signaling, can be used for the rapid in vivo analysis of mutant forms of LAT. We showed that Pax5(-/-) Lat(-/-) pro-B cell lines can be infected with recombinant retroviruses expressing a LAT cDNA and sorted for the expression of LAT. When injected into Rag1(-/-) mice, they restore normal intrathymic T cell development and give rise to functional peripheral T cells. Considering that the handling of Pax5(-/-) pro-B cell lines is easier than that of bone marrow hematopoietic precursors, we used them for the rapid functional analysis of a novel Lat allelic series. When compared to knock-in and transgenic approaches, a major advantage of our Pax5(-/-) pro-B cell-based experimental approach consists in the production of mice bearing a given mutation within 2-3 months. Therefore, it constitutes a powerful first-line screen for mutations worth fastidious knock-in approaches.