An IL-7 splicing-defect lymphopenia mouse model revealed by genome-wide mutagenesis.
Homeostasis of the hematopoietic system is tightly regulated by an array of cytokines that control proliferation, differentiation and apoptosis of various cell lineages. To identify genes that are essential for hematopoietic homeostasis, we screened C57BL/6 mice that had been genome-wide mutagenized by N-ethyl-N-nitrosourea (ENU) to produce altered blood cell composition. We identified a mutant mouse line with a drastic reduction in the number of T and B cell lineages in lymphatic tissues and peripheral blood, as well as severe atrophy of the thymus and lymph nodes. Genotyping with a genome-wide single nucleotide polymorphism (SNP) marker set mapped the mutant phenotype to chromosome 3A and subsequent direct DNA sequencing revealed a G-to-A point mutation in the splicing donor site of the third exon of the candidate gene for IL-7, a lymphocyte survival cytokine. Such mutation resulted in skipping of exon 3 and production of an internally truncated IL-7 (DeltaE3-IL7). Furthermore, using recombinant proteins produced in a baculoviral system, we demonstrated that DeltaE3-IL7 had no detectable anti-apoptotic activity even at a dose that was 30 times more than that required for a wild-type protein to manifest a full activity in a naïve T cell survival assay. Our data suggest that this mutant mouse line provides an alternative animal model for the study of severe combined immunodeficiency (SCID) syndrome in humans.
Huang
Hong-Wen
HW
Institute of Biomedical Sciences, Academia Sinica, Taipei, 11529, Taiwan.
Chiang
Yun-Jung
YJ
Hung
Shuen-Iu
SI
Li
Chung-Leung
CL
Yen
Jeffrey Jong-Young
JJ
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology; D002460:Cell Line; D019070:Cell Lineage; D004252:DNA Mutational Analysis; D004195:Disease Models, Animal; D005038:Ethylnitrosourea / Q000633:toxicity; D016678:Genome / Q000187:drug effects / Q000235:genetics; D015851:Interleukin-7 / Q000235:genetics*; D008231:Lymphopenia / Q000235:genetics*; D038041:Lymphopoiesis / Q000235:genetics*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D016296:Mutagenesis; D012326:RNA Splicing / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000166:cytology
D015851:Interleukin-7; D012333:RNA, Messenger; D005038:Ethylnitrosourea