Constitutive expression of terminal deoxynucleotidyl transferase in transgenic mice is sufficient for N region diversity to occur at any Ig locus throughout B cell differentiation.
N region diversity in Ag receptors is a developmentally regulated process in B and T cells that correlates with the differential expression of terminal deoxynucleotidyl transferase (TdT). Absent in fetal and newborn mice, TdT expression is restricted to early T and pro-B cells in adults. To extend the TdT expression pattern throughout B cell ontogenesis, we generated transgenic mice carrying a TdT cDNA under the regulatory elements of the N-myc gene and the IgH enhancer. High expression was observed in secondary lymphoid organs consistent with TdT activity beyond the pre-B cell stage. This suggests that TdT transgene expression is not down-regulated as is the endogenous gene. Unlike normal mice, extensive N region diversity was found in rearranged lambda light chain genes of adult transgenic animals. Therefore, expression of TdT appears sufficient for N region diversity to occur at any Ig locus. More importantly, expression of the transgene takes place during fetal development. As a consequence, the potential fetal B cell repertoire is modified as both rearranged heavy and light chain genes now show N region additions. Constitutive expression of TdT throughout B cell differentiation does not therefore appear deleterious and suggests that TdT is recruited only to participate in the V(D)J recombination process.
Bentolila
L A
LA
Unit of Genetics and Developmental Biochemistry, National Center for Scientific Research, Paris, France.
Wu
G E
GE
Nourrit
F
F
Fanton d'Andon
M
M
Rougeon
F
F
Doyen
N
N
D000818:Animals; D000916:Antibody Diversity / Q000235:genetics*; D001402:B-Lymphocytes / Q000201:enzymology / Q000276:immunology*; D001482:Base Composition; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D004253:DNA Nucleotidylexotransferase / Q000096:biosynthesis*; D015321:Gene Rearrangement / Q000276:immunology*; D007147:Immunoglobulin Light Chains / Q000235:genetics; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection
D007147:Immunoglobulin Light Chains; D007135:Immunoglobulin Variable Region; D004253:DNA Nucleotidylexotransferase