Mice homozygous for the autosomal recessive mutation, SCID (SCID mice) are severely deficient in mature lymphocytes. Early B and T lineage-committed cells are clearly present in SCID lymphopoietic tissues, but are unable to differentiate into functional B and T lymphocytes. This developmental arrest is believed to reflect a defect in the system responsible for the recombination of V (variable), D (diversity) and J (joining) gene elements that code for immunoglobulin (Ig) and T cell receptor (TCR) variable regions. This proposal deals with two levels of complexity in the manifestation of the SCID defect. The first concerns whether V(D)J recombination in SCID cells is equally defective at all Ig and TCR loci. Since the recombination of V(D)J elements within and between different Ig and TCR loci follows an ordered developmental pattern, the applicant will test for possible differences in the effect of SCID (or expression of SCID) in lymphocytes representing distinct stages of early development. Different populations of lymphocytes will be analyzed for VDJ recombinase activity and V(D)J recombination, with emphasis on the frequency of recombination and the structure of the recombination junctions at different loci. The second level of complexity concerns the leaky SCID phenotype. This refers to SCID mice that develop a few clones of functional B and T cells and produce detectable serum Ig (Ig+); interestingly, leaky SCID mice with B or T cells only have not been observed. Dr. Bosma will test whether SCID leakiness reflects a low frequency of somatic reversion at the SCID locus, and also possibly, a low frequency of normal Ig and TCR gene rearrangement mediated by the defective SCID recombinase activity. He will also test to what extent the invariable presence of T cells in serum Ig+ SCID mice reflects T cell dependent growth requirements of B cells and/or somatic reversion before the commitment to the B and T cell lineages.
These aims will involve testing various cell lines from leaky SCID mice for reversion to normal x-irradiation sensitivity (increased radiosensitivity is a property of SCID cells), analyzing a large sample of B cell hybridomas and/or plasmacytomas from old leaky SCID mice for normal (or abnormal) rearrangement at the non-productive Ig alleles, and constructing athymic nude-SCID mice and chimeric SCID mice. The experiments outlined in this proposal should tell us more about the effect of SCID on early lymphocyte development. This is important for understanding the genetic control of both normal and abnormal lymphocyte differentiation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI013323-18
Application #
2059967
Study Section
Allergy and Immunology Study Section (ALY)
Project Start
1976-05-01
Project End
1995-07-31
Budget Start
1993-08-01
Budget End
1995-07-31
Support Year
18
Fiscal Year
1993
Total Cost
Indirect Cost
Name
Institute for Cancer Research
Department
Type
DUNS #
872612445
City
Philadelphia
State
PA
Country
United States
Zip Code
19111
Nakajima, P B; Menetski, J P; Roth, D B et al. (1995) V-D-J rearrangements at the T cell receptor delta locus in mouse thymocytes of the alpha beta lineage. Immunity 3:609-21
Chang, Y; Bosma, G C; Bosma, M J (1995) Development of B cells in scid mice with immunoglobulin transgenes: implications for the control of V(D)J recombination. Immunity 2:607-16
Fish, S M; Bosma, M J (1994) Abnormal deletions in the T-cell receptor delta locus of mouse thymocytes. Mol Cell Biol 14:4455-64
Kotloff, D B; Bosma, M J; Ruetsch, N R (1993) Scid mouse Pre-B cells with intracellular mu chains: analysis of recombinase activity and IgH gene rearrangements. Int Immunol 5:383-91
Kotloff, D B; Bosma, M J; Ruetsch, N R (1993) V(D)J recombination in peritoneal B cells of leaky scid mice. J Exp Med 178:1981-94
Roth, D B; Menetski, J P; Nakajima, P B et al. (1992) V(D)J recombination: broken DNA molecules with covalently sealed (hairpin) coding ends in scid mouse thymocytes. Cell 70:983-91
Roth, D B; Nakajima, P B; Menetski, J P et al. (1992) Double-strand breaks associated with V(D)J recombination at the TCR delta locus in murine thymocytes. Curr Top Microbiol Immunol 182:115-24
Bosma, M J (1992) B and T cell leakiness in the scid mouse mutant. Immunodefic Rev 3:261-76
Roth, D B; Nakajima, P B; Menetski, J P et al. (1992) V(D)J recombination in mouse thymocytes: double-strand breaks near T cell receptor delta rearrangement signals. Cell 69:41-53
Carroll, A M; Bosma, M J (1991) T-lymphocyte development in scid mice is arrested shortly after the initiation of T-cell receptor delta gene recombination. Genes Dev 5:1357-66

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