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M Schlissel

Publications and source records attributed to M Schlissel.

9 recordsLinked to original sources
PubMed1997

Both E12 and E47 allow commitment to the B cell lineage.

The E2A gene products, E12 and E47, are required for proper B cell development. Mice lacking the E2A gene products generate only a very small number of B220+ cells, which lack immunoglobulin DJ(H) rearrangements. We have now generated mice expressing either E12 or E47. B cell development in mice expressing E12 but lacking E47 is perturbed at the pro-B cell stage, and these mice lack IgM+B220+ B cells in both bone marrow and spleen. IgM+B220+ B cells can be detected, albeit at significantly reduced levels, in the bone marrow and spleen of mice lacking E12. Ectopic expression of both E12 and E47 in a null mutant background shows that E12 and E47 act in concert to promote B lineage development. Taken together, the data indicate that both E12 and E47 allow commitment to the B cell lineage and act synergistically to promote B lymphocyte maturation.

Animals↗
PubMed1996

Mutations in the p53 and SCID genes cooperate in tumorigenesis.

DNA damage can cause mutations that contribute to cellular transformation and tumorigenesis. The p53 tumor suppressor acts to protect the organism from DNA damage by inducing either G1 arrest to facilitate DNA repair or by activating physiological cell death (apoptosis). Consistent with this critical function of p53, mice lacking p53 are predisposed to developing tumors, particularly lymphoma. The severe combined immune deficiency (scid) focus encodes the catalytic subunit of DNA protein kinase (DNA-PKcs), a protein complex that has a role in the cellular response to DNA damage. Cells from scid mice are hypersensitive to radiation and scid lymphocytes fail to develop from precursors because they are unable to properly join DNA-coding ends during antigen receptor gene rearrangement. We examined the combined effect of loss of p53 and loss of DNA-PKcs on lymphocyte development and tumorigenesis by generating p53-/- scid mice. Our data demonstrate that loss of p53 promotes T-cell development in scid mice but does not noticeably affect B lymphopoiesis. Moreover, scid cells are able to induce p53 protein expression and activate G1 arrest or apoptosis in response to ionizing radiation, indicating that DNA-PKcs is not essential for these responses to DNA damage. Furthermore, p53-/- scid double mutant mice develop lymphoma earlier than p53-/- littermates, demonstrating that loss of these two genes can cooperate in tumorigenesis. Collectively, these results provide evidence for an unsuspected role of p53 as a checkpoint regulator in early T-cell development and demonstrate that loss of an additional component of the cellular response to DNA damage can cooperate with loss of p53 in lymphomagenesis.

Animals↗
PubMed1996

Surface blebs on apoptotic cells are sites of enhanced procoagulant activity: implications for coagulation events and antigenic spread in systemic lupus erythematosus.

The restriction of phosphatidylserine (PtdSer) to the inner surface of the plasma membrane bilayer is lost early during apoptosis. Since PtdSer is a potent surface procoagulant, and since there is an increased incidence of coagulation events in patients with systemic lupus erythematosus (SLE) who have anti-phospholipid antibodies, we addressed whether apoptotic cells are procoagulant and whether anti-phospholipid antibodies influence this. Apoptotic HeLa cells, human endothelial cells, and a murine pre-B-cell line were markedly procoagulant in a modified Russell viper venom assay. This procoagulant effect was entirely abolished by addition of the PtdSer-binding protein, annexin V, confirming that it was PtdSer-dependent. The procoagulant effect was also abolished by addition of IgG purified from the plasma of three patients with anti-phospholipid antibody syndrome, but not IgG from normal controls. Confocal microscopy of apoptotic cells stained with fluorescein-isothiocyanate-conjugated-annexin V demonstrated (Ca2+)-dependent binding to the surface of membrane blebs o apoptotic cells, but not to intracellular membranes. Recent data indicate that the surface blebs of apoptotic cells constitute an important immunogenic particle in SLE. We propose that the PtdSer exposed on the outside of these blebs can induce the production of anti-phospholipid antibodies, which might also enhance the immunogenicity of the bleb contents. When apoptosis occurs in a microenvironment in direct contact with circulating plasma, the unique procoagulant consequences of the apoptotic surface may additionally be expressed. This might explain the increased incidence of pathological intravascular coagulation events that occur in some lupus patients who have anti-phospholipid antibodies.

Animals↗
PubMed1993

Double-strand signal sequence breaks in V(D)J recombination are blunt, 5'-phosphorylated, RAG-dependent, and cell cycle regulated.

Immunoglobulin and T-cell receptor genes are assembled during lymphocyte development by a novel, highly regulated series of gene rearrangement reactions known as V(D)J recombination. All rearranging loci are flanked by conserved heptamer-nonamer recombination signal sequences. Gene rearrangement results in the imprecise fusion of coding sequences and the precise fusion of signal sequences. DNA molecules with double-stranded breaks near signal sequences have been detected in cells undergoing V(D)J recombination of the TCR delta locus. We have devised a ligation-mediated PCR assay that detects broken-ended molecules in purified genomic DNA. Using this assay we found that DNA breaks occurring precisely at the signal sequence-coding sequence junction are a general feature of V(D)J recombination, appearing in association with each type of rearranging immunoglobulin gene segment. We show that a significant fraction of these broken ends are blunt and 5'-phosphorylated. In addition, detection of these broken-ended signal sequences is dependent on the activity of RAG-1 and RAG-2, and is restricted to the G0/G1 phase of the cell cycle. The pattern of broken-ended molecules detected in cells at various stages of development reflects the activity of the V(D)J recombinase at different loci during B- and T-cell development.

Aging↗
PubMed1992

The purification of B-cell precursors from mouse fetal liver.

Lymphocyte progenitor cells isolated on sequential days of gestation from mouse fetal liver represent distinct stages in B cell development. We have utilized polymerase chain reaction (PCR)-based assays to detect immunoglobulin (Ig) gene rearrangement and flow cytometry to assay cell surface markers following fractionation based on the differential expression of the B cell-specific phosphatase CD45 (B220). The purification of B220+ cells from day 17 fetal liver resulted in a 10-fold enrichment of cells which had undergone gene rearrangement events. We have also shown that day 13 fetal liver cells activate successive Ig gene rearrangements during short-term culture in the presence of fetal calf serum (FCS), interleukin-3 (IL3), and interleukin-7 (IL7). However, partially purified lymphocyte precursors fail to activate Ig gene rearrangement in culture unless they are cultured in the presence of a stromal cell line.

Animals↗
PubMed1991

Helix-loop-helix transcription factor E47 activates germ-line immunoglobulin heavy-chain gene transcription and rearrangement in a pre-T-cell line.

E47 is a helix-loop-helix transcription factor that binds to sites in the immunoglobulin heavy-chain and kappa light-chain gene enhancers. Other proteins of this type are involved in cell-type determination. A possible role for E47 in B-cell development was tested by overexpressing a cDNA encoding E47 in the pre-T-cell line 2017. We found a dramatic activation of a germ-line heavy-chain gene transcript in these stable transfectants and an equally large induction of immunoglobulin D-to-J rearrangement, the first recognized step in B-cell development. Germ-line kappa light-chain gene transcription and rearrangement were unaffected, but transcription of the recombination-activating genes RAG-1 and RAG-2 and the lymphoid-specific transcription factor Oct-2 was increased. These T cells did not transcribe their rearranged DJ alleles, however, and failed to progress to the next stage of heavy-chain gene assembly, V-to-DJ rearrangement. Because transcription factor E47 can induce pre-T cells to carry out events of B-cell differentiation, it may be a crucial determinant of the earliest stages of B-cell development.

Animals↗
PubMed1983

Purified RNA polymerase III accurately and efficiently terminates transcription of 5S RNA genes.

RNA polymerase III was purified to about 90% homogeneity from ovarian tissue of Xenopus laevis. The enzyme accurately initiates and terminates transcription of 5S RNA synthesis in isolated nuclei, but not when naked 5S DNA is used as a template. A sensitive hybridization technique was used to demonstrate that the purified polymerase, even when supplemented with a transcription factor that binds specifically to the 5S RNA gene internal control region, is unable to initiate synthesis at the start site of the 5S RNA gene. However, the polymerase alone terminates transcription at precisely the same site that is recognized in vivo and in complete transcription extracts. The purified polymerase distinguishes between weak and strong terminator sequences with the same relative efficiency as the enzyme in complete extracts. We conclude that the pure enzyme can recognize the simple consensus sequence found at the end of genes transcribed by RNA polymerase III.

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