The Journal of Experimental Medicine
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Published online 10 July 2000.
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© The Rockefeller University Press, 0022-1007/2000/7/171/ $5.00
The Journal of Experimental Medicine, Volume 192, Number 2, July 17, 2000 171-182


Original Article

Ras Mediates Effector Pathways Responsible for Pre-B Cell Survival, Which Is Essential for the Developmental Progression to the Late Pre-B Cell Stage

Hitoshi Nagaokaa, Yoshimasa Takahashia, Reiko Hayashid, Tohru Nakamuraa,e, Kumiko Ishiia, Junichiro Matsudab, Atsuo Ogurab, Yumiko Shirakataf, Hajime Karasuyamag, Tetsuo Sudoh, Shin-Ichi Nishikawai, Takeshi Tsubataj, Tsuguo Mizuochie, Toshihiko Asanoc, Hitoshi Sakanod, and Toshitada Takemoria
a Department of Immunology, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
b Department of Veterinary Science, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
c Division of Experimental Animal Research, National Institute of Infectious Diseases, Tokyo 162-8640, Japan
d Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
e Laboratory of Biomedical Chemistry, Department of Applied Chemistry, Tokai University, Kanagawa 259-1292, Japan
f Department of Gene Research, The Cancer Institute, Japanese Foundation for Cancer Research, Tokyo 170-8455, Japan
g Department of Immunology, The Tokyo Metropolitan Institute of Medical Science, Tokyo 113-8613, Japan
h Toray Basic Research Laboratories, Kanagawa-ken 259-1192, Japan
i Department of Molecular Genetics, Graduate School of Medicine, Kyoto University, Kyoto 606-8507, Japan
j Department of Immunology, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan

Correspondence to: Toshitada Takemori, Department of Immunology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-Ku, Tokyo 162-8640, Japan. Tel:81-3-5285-1156 Fax:81-3-5285-1156 E-mail:ttoshi{at}nih.go.jp.

Ras is essential for the transition from early B cell precursors to the pro-B stage, and is considered to be involved in the signal cascade mediated by pre-B cell antigen receptors. To examine the role of p21ras in the late stage of B cell differentiation, we established transgenic mice (TG) expressing a dominant-inhibitory mutant of Ha-ras (Asn-17 Ha-ras) in B lineage cells at high levels after the early B cell precursor stage. Expression of p21Asn-17 Ha-ras was associated with a prominent reduction in the number of late pre-B cells, but had little effect on proliferation of early pre-B cells. Inhibition of p21ras activity markedly reduced the life span of pre-B cells, due, at least in part, to downregulation of the expression of an antiapoptotic protein, Bcl-xL. Thus, the apparent role for p21ras activity in pre-B cell survival may explain the decreased numbers of late pre-B cells in Asn-17 Ha-ras TG. Consistent with this possibility, overexpression of Bcl-2 in Asn-17 Ha-ras TG reversed the reduction in the number of late pre-B cells undergoing immunoglobulin light chain gene (IgL) rearrangement and progressing to immature B cells. These results suggest that p21ras mediates effector pathways responsible for pre-B cell survival, which is essential for progression to the late pre-B and immature B stages.

Key Words: B cell development, life span, immunoglobulin gene rearrangement, Bcl-xL, Bcl-2


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