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I R Kirsch

Publications and source records attributed to I R Kirsch.

At least 37 records · Page 2Linked to original sources
PubMed1997

The absolute number of trans-rearrangements between the TCRG and TCRB loci is predictive of lymphoma risk: a severe combined immune deficiency (SCID) murine model.

Pilot studies in human populations have demonstrated a correlation between the level of antigen receptor trans-rearrangements and risk (at the population level) of lymphoid malignancy. Irradiation of newborn severe combined immune deficiency mice results in an increased risk of subsequent development of thymic lymphoma (100% of mice so irradiated are dead of thymic lymphoma by 20 weeks of age). We, therefore, assayed the occurrence of trans-rearrangements in this well-controlled mouse mutant system and found a 50-100-fold increase in the absolute number of TCRGV-TCRBJ trans-rearrangements compared to unirradiated littermates (and a comparable fold increase over age-matched BALB/c mice) at 2 weeks following irradiation. We also found a marked disproportion in generating trans-rearrangements versus intralocus rearrangements in the severe combined immune deficiency system compared to BALB/c, independent of irradiation. The trans-rearrangements noted were polyclonal in nature. These data, again, suggest that the absolute level of antigen receptor trans-rearrangements may serve as a biomarker of lymphoma risk.

Animals↗
PubMed1997

Lymphocyte-specific genomic instability and risk of lymphoid malignancy.

Genetic instability is a force that links evolution, development and cancer. We have developed a quantifiable assay for a particular kind of lymphocyte-specific genetic instability (antigen receptor trans-rearrangements) mediated by the V(D)J recombinase complex. We find that the level of this type of instability correlates (at the population level) with risk for lymphoid malignancy. We have developed a murine model for this measure of instability to allow a more refined analysis of the genetic and environmental factors that sum to define population cancer risk.

Animals↗
PubMed1997

Hypogonadism and obesity in mice with a targeted deletion of the Nhlh2 gene.

The family of basic helix-loop-helix (bHLH) genes comprises transcription factors involved in many aspects of growth and development. We have previously described two bHLH transcription factors, Nhlh1 and Nhlh2 (originally named NSCL1 and NSCL2). The nucleotide and predicted protein sequences of Nhlh1 and Nhlh2 are homologous within their bHLH domain where there are only three conservative amino acid differences. During murine embryogenesis, Nhlh1 and Nhlh2 share an overlapping but distinct pattern of expression in the developing nervous system. To improve our understanding of the role of these genes during neurogenesis, we have generated mice containing targeted deletions of both genes and here describe our results for Nhlh2. Loss of Nhlh2 results in a disruption of the hypothalamic-pituitary axis in mice. Male Nhlh2-/- mice are microphallic, hypogonadal and infertile with alterations in circulating gonadotropins, a defect in spermatogenesis and a loss of instinctual male sexual behaviour. Female Nhlh2-/- mice reared alone are hypogonadal, but when reared in the presence of males, their ovaries and uteri develop normally and they are fertile. Both male and female homozygotes exhibit progressive adult-onset obesity. Nhlh2 is expressed in the ventral-medial and lateral hypothalamus, Rathke's pouch and in the anterior lobe of the adult pituitary. Our results support a role for Nhlh2 in the onset of puberty and the regulation of body weight metabolism.

Animals↗
PubMed1997

Trans-rearrangements and the risk of lymphoid malignancy.

BACKGROUND: Antigen receptor 'trans-rearrangements' occur in all individuals and represent a particular type of genetic instability whose mechanism, V(D)J recombination, is the same as that required for the development of a normal immune response. DESIGN: We have measured the level of trans-rearrangements in a variety of populations characterized by increased risk for the development of lymphoid malignancy. The human populations studied include those with an inherited predisposition to lymphomagenesis (ataxia-telangiectasia patients), as well as populations at increased risk because of an occupational (agriculture workers) or iatrogenic (Hodgkin's disease patients) exposure. In addition, we have developed a mouse model for the more controlled analysis of these events. RESULTS: There is a correlation between the absolute number of trans-rearrangements (as a population mean or median) and risk of lymphoma, whether that risk is based on an inherited predisposition or acquired exposure. CONCLUSION: This assay may serve as an easily measurable biomarker of lymphoma risk. If so, it is more than a fortuitous biomarker since the same mechanism responsible for the formation of trans-rearrangement is, at least in part, responsible for the majority of presumably 'malevolent' translocations associated with the transformation of lymphocytes.

Agricultural Workers' Diseases↗
PubMed1997

Expression of the SIL gene is correlated with growth induction and cellular proliferation.

The SIL gene was discovered at the site of a cancer-associated interstitial deletion in which its promoter assumed the regulation of a second gene, SCL. The human SIL gene encodes a 1287-amino acid cytosolic protein that has been found to be highly conserved in the mouse. SIL is expressed in proliferating cells and is down-regulated when cellular proliferation ceases because of serum starvation, contact inhibition, or induction of terminal differentiation. SIL is induced within 1 h of stimulation by 20% serum in growth-arrested 3T3 cells. This induction is independent of protein synthesis because "superinduction" is observed in the presence of the protein synthesis inhibitor cyclohexamide. Thus, SIL is an immediate-early gene. Upon release from serum starvation of 3T3 fibroblasts, SIL mRNA and protein levels display a biphasic pattern during the first cell cycle. In contrast, in exponentially growing EL4 lymphoblasts, SIL mRNA is stable throughout the cell cycle, whereas SIL protein accumulates into G2 phase and then falls precipitously at the completion of the cell cycle. This pattern of cell cycle expression suggests that SIL may play an important role in cellular growth and proliferation.

Animals↗
PubMed1996

Opposing effects of the basic helix-loop-helix transcription factor SCL on erythroid and monocytic differentiation.

The SCL gene (also called Tal-1 or TCL5) was identified because of its association with chromosomal translocations in childhood T-cell lymphoid leukemias. SCL codes for a basic helix-loop-helix (bHLH) factor that can function as a transcriptional activator or repressor. In the adult, SCL expression is restricted to hematopoietic cells and tissues, but its function in the process of lineage commitment is unknown. The present study was designed to address the role of SCL in hematopoietic cell differentiation. SCL expression was determined in primary hematopoietic cells through the screening of cDNA samples obtained by reverse transcription-polymerase chain reaction (RT-PCR) from single cells at different stages of differentiation. SCL RNA expression was highest in bipotential and committed erythroid precursors and diminished with subsequent maturation to proerythroblasts and normoblasts. In contrast, SCL mRNA was low to undetectable in precursors of granulocytes and monocytes and their maturing progeny. The same pattern of expression was observed after erythroid or monocytic differentiation of a bipotent cell line, TF-1, in that SCL mRNA levels remained elevated during erythroid differentiation and were downregulated with monocytic differentiation. Accordingly, TF-1 was chosen as a model to investigate the functional significance of this divergent pattern of SCL expression in the two lineages. Four independent clones stably transfected with an SCL expression vector exhibited enhanced spontaneous and delta-aminolevulinic acid-induced erythroid differentiation as measured by glycophorin expression and hemoglobinization, consistent with the view that SCL is a positive regulator of erythroid differentiation. Furthermore, constitutive SCL expression interfered with monocytic differentiation, as assessed by the generation of adherent cells and the expression of Fc gamma RII in response to TPA. These results suggest that the downregulation of SCL may be required for monocytic differentiation.

Adult↗
PubMed1996

Transrearrangements as biomarkers for risk of lymphoid malignancy.

In this chapter we describe an assay for lymphocyte specific antigen receptor transrearrangements mediated by the V(D)J recombinase complex. Such transrearrangements occur in all normal individuals, are capable of increasing the immune repertoire and can be viewed as a readily available baseline measure of a type of genetic instability. In human and murine systems, the absolute number of some of these transrearrangements correlates at the population level with risk for the development of lymphoid malignancy.

Animals↗
PubMed1995

Cloning and characterization of TCTA, a gene located at the site of a t(1;3) translocation.

We have cloned and characterized a novel gene at the site of a t(1;3)(p34;p21) translocation breakpoint in T-cell acute lymphoblastic leukemia. A cDNA for this gene, for which we propose the designation TCTA (T-cell leukemia translocation-associated gene), has been cloned. TCTA mRNA is expressed ubiquitously in normal tissues, with the highest levels of expression seen in the kidney. The TCTA gene is conserved throughout evolution in organisms ranging from Drosophila to humans. A short open reading frame encodes a predicted M(r) 12,000 protein without strong homology to any previously reported proteins. Of note, genomic Southern blots demonstrated a reduced TCTA signal in three of four small cell lung cancer cell lines tested, suggesting loss of one of the two copies of the gene.

Amino Acid Sequence↗
PubMed1995

Detection of very-rare-copy DNA in 0.2-ml dried human blood blots.

A nested PCR assay for chromosome 7 inversions (as identified by the presence of T-cell receptor trans-rearrangements) can detect as rare a frequency as 1 copy in 300,000 leukocytes. To identify such rare occurrences from dried blood blots, the most conveniently obtained and stored samples for field population studies, demands a DNA extraction method that will provide both high quality and high yield. We have satisfied this requirement by extracting proteins and other components directly from the minced filter with phenol, before extracting the DNA with Chelex-water. This provides a near maximal yield of denatured DNA of sufficient quality to detect these translocations with a sensitivity equivalent to that of DNA purified from whole blood samples. Blots stored 6 months worked as well as fresh blots. In addition, we present a method for obtaining native DNA from the dried blots, although at a much lower yield. The successful use of blood blots to detect such rare events signals the feasibility of large-scale field studies involving diagnostic molecular epidemiology.

Chromosomes, Human, Pair 7↗
PubMed1995

Genetic instability in patients with Hodgkin's disease undergoing chemotherapy.

We have studied the effect of chemotherapy on the level of a particular kind of genetic instability in patients with Hodgkin's disease. The particular type of genetic instability assayed is exemplified by trans-rearrangements between two (rather than within one) T cell antigen receptor. 16 patients were studied during their course of treatment. Presentation samples were available for 13 of these patients; 9 of them showed an increase in the level of trans-rearrangements during their exposure to chemotherapeutic agents (P < 0.043). All patients for whom posttherapy samples were available (10 out of 16) showed a return to baseline levels of trans-rearrangements 1-5 mo after completion of therapy (P < 0.03). Thus, this assay appears to be a marker for the "destabilizing" effects of certain chemotherapeutic agents.

Adult↗
PubMed1994

V(D)J recombination and ataxia-telangiectasia: a review.

I review one aspect of the A-T phenotype, the remarkable and fascinating increase of lymphocytes carrying chromosomal aberrations caused by V(D)J site-specific recombination. The review is organized to first present the facts of V(D)J recombination and the findings in this regard in A-T patients. Other populations that demonstrate similar increases in such chromosomal aberrations are then presented and a hypothesis is offered as to the basis and relevance of these increases vis-à-vis A-T. The contribution of V(D)J recombination to the clonal proliferations and frank lymphoid malignancies seen in A-T patients is briefly discussed. I conclude with some speculative comments extending the observations presented into a more global consideration of a possible function of an A-T gene.

Ataxia Telangiectasia↗
PubMed1993

MTCP-1: a novel gene on the human chromosome Xq28 translocated to the T cell receptor alpha/delta locus in mature T cell proliferations.

T-cell lymphoproliferative diseases are often associated with recurrent chromosomal translocations involving T cell receptor genes (TCR) and genes that are thought to play a role in the pathogenesis of these diseases. Whereas numerous such genes have already been identified in acute T cell leukemias, no candidate gene has yet been identified to play a role in the heterogeneous group of T cell proliferations with a mature phenotype. We here report the molecular cloning of two examples of the rare but recurrent t(X;14) translocation. The first translocation was associated with a benign clonal proliferation in an ataxia telangiectasia patient and the second with a T cell prolymphocytic leukemia. Both translocations implicated the TCR alpha/delta locus and a common breakpoint region on chromosome Xq28. A previously unidentified gene, abnormally transcribed in both T cell proliferations, was characterized in the immediate proximity of the breakpoints. This Xq28 gene has no homology with known sequences, uses a complex alternative splicing pattern and demonstrates two short open reading frames. This gene, named MTCP-1 (Mature T Cell Proliferation-1) is the first candidate gene potentially involved in the leukemogenic process of mature T cell proliferations.

Alternative Splicing↗
PubMed1992

Disruption of the SCL gene by a t(1;3) translocation in a patient with T cell acute lymphoblastic leukemia.

SCL gene disruptions are the most common chromosomal abnormality associated with the development of T cell acute lymphoblastic leukemia (ALL). Such disruptions can be the result of t(1;14) and t(1;7) translocations, as well as a cytogenetically undetectable interstitial deletion of chromosome 1. We present here a case of T cell ALL with a t(1;3)(p34;p21) translocation that also disrupts the SCL locus and leads to dysregulated SCL gene expression. This translocation, similar to previously reported SCL gene disruptions, appears to have been mediated, at least in part, by the V(D)J recombinase complex, since cryptic heptamer recognition sequences, as well as nontemplated N region nucleotide addition, are present at the breakpoints. The t(1;3) also disrupts a region on chromosome 3 characterized by alternating purine and pyrimidine residues, which can form a Z-DNA structure, reported to be prone to recombination events. A previously undescribed, evolutionarily conserved transcript unit is detected within 8 kb of the breakpoint on chromosome 3. This report extends the spectrum of recognized SCL translocations associated with T cell ALL, and underscores the contention that dysregulated SCL expression may be a causal event in T cell ALL.

Adolescent↗
PubMed1992

A comparative structural characterization of the human NSCL-1 and NSCL-2 genes. Two basic helix-loop-helix genes expressed in the developing nervous system.

Human cDNA clones for NSCL-1 and NSCL-2, two basic domain helix-loop-helix (bHLH) genes expressed predominantly in the developing nervous system, were obtained from a fetal brain cDNA library. The full-length transcripts and the genomic structures were determined. The cDNAs for the two genes encode predicted proteins of similar size (133 and 135 amino acids for NSCL-1 and NSCL-2, respectively) and structure. The carboxyl-terminal 75 amino acids of the two proteins contain the bHLH motif and differ from each other by only three conservative amino acid changes, while the amino-terminal portions are markedly divergent from each other. In addition to the similar protein structure, the genes have a similar genomic organization, suggesting a close evolutionary relationship. The 5'-regulatory regions of the two genes share some features (i.e. potential TATA, CCAAT, and GATA binding sites) but also differ significantly in their G+C content. NSCL-1 is relatively G+C-rich (63%) in the sequences upstream of transcription initiation and has multiple potential binding sites for transcription factors that bind to G+C-rich sequences (e.g. AP-2). NSCL-2 is relatively A+T-rich (63%) in this region and has a potential binding site for AP1. Studies of expression in normal tissues demonstrated expression of NSCL-1 and NSCL-2 in the developing central and peripheral nervous system, most likely in developing neurons. Additional Northern analysis studies in cell lines revealed expression of these genes in some cell lines derived from tumors with neural or neuroendocrine features such as neuroblastoma, PNET, and small cell lung cancer. NSCL-1 is expressed in a larger number of these cell lines. The differences in expression may parallel differences in developmental regulation.

Amino Acid Sequence↗
PubMed1992

A measure of genomic instability and its relevance to lymphomagenesis.

A recent pilot study that we performed on 12 individuals who are involved in the cultivation and processing of grains and legumes suggests to us that we may have in hand a relatively quick, inexpensive, and highly sensitive assay that identifies individuals at increased risk for the development of lymphoid malignancy. The generation of this assay evolved from our interest in the causes and consequences of lymphocyte-specific chromosomal aberration.

Chromosome Aberrations↗
PubMed1992

Disruption of the SCL locus in T-lymphoid malignancies correlates with commitment to the T-cell receptor alpha beta lineage.

The SCL/tal-1 gene on chromosome 1 is disrupted in up to 30% of immature T-cell malignancies, thus representing the most commonly recognized chromosomal abnormality in this disorder. Abnormalities of the gene occur rarely by chromosomal translocation into the T-cell receptor (TCR) delta locus and commonly by a site-specific 95-kb deletion, SIL-SCL (tald). Analysis of the SIL-SCL deletion by Southern blotting and polymerase chain reaction (PCR) in a series of 52 immature T-cell malignancies showed a type A deletion in 21% of cases, but no type B deletions. The type A deletion correlated with malignancies of the TCR alpha beta lineage, either on the basis of TCR alpha beta expression or bilateral TCR delta deletion. Fifty percent (5 of 10) of TCR alpha beta-expressing cells demonstrated the abnormality, whereas 0% (0 of 11) of TCR gamma delta-expressing cells did so. Six of eight SIL-SCL type A cases had undergone bilateral delta deletion, whereas only one of 31 cases with an apparently normal SCL gene had done so. These data demonstrate an association between SCL disruption and TCR alpha beta lineage differentiation and suggest that the SIL-SCL deletion occurs at the same stage of ontogeny as TCR delta deletion.

Adolescent↗