P Leder's research while affiliated with Harvard Medical School and other places

Publications (175)

Article
Full-text available
Oncogenesis is a progressive process often involving collaboration between various oncogenes and tumor suppressors. To identify those genes that collaborate with oncogenic ras, we took advantage of the Tg.AC transgenic mouse, a line that harbors the v-Ha-ras transgene and spontaneously develops an array of malignant tumors. By crossing Tg.AC mice o...
Article
beta-Catenin, an oncogene, and P53, a tumor suppressor, are common targets of mutation in human cancers. It has been observed that P53 is often inactivated in tumors involving beta-catenin activation. In an attempt to model this situation in vivo, we crossed the previously characterized MMTV-DeltaN-beta-catenin mouse with the P53 knockout mouse. Fe...
Article
Full-text available
Werner syndrome is an autosomal recessive disorder characterized by genomic instability and by the premature onset of a number of age-related diseases, including malignancy. To assess a potential collaboration between p21 or p53 cell cycle regulators and Wrn proteins, Wrn mutant mice were created and mated with p21 or p53 null mice to generate doub...
Article
Full-text available
Heregulin (HRG) is a member of the neuregulin family of ligands that have been shown to interact with and activate erbB receptors. A transgenic mouse model in which full-length HRG is overexpressed has proven that this protein can induce carcinomas in the murine mammary gland. These tumors display a high level of apoptosis, which appears to be medi...
Article
Excerpt Successful cell duplication requires accurate replication of the genome and its equal segregation to progenycells. The fidelity of these processes is ensured in part bycell cycle checkpoints, which monitor the genome andtrigger cell cycle arrest or initiate apoptosis in response todamage or errors in the ordering of cell cycle events(Hartwe...
Article
Full-text available
An unusual clinical finding in ataxia-telangiectasia, a human disorder caused by mutations in atm, is exquisite sensitivity to gamma irradiation. By contrast, homozygous deletion of p53 is marked by radiation resistance in certain tissue compartments. Previous studies (A. J. Levine, Cell, 88: 323-331, 1997) have shown that, in vitro, p53-deficient...
Article
FGFR2 is a membrane-spanning tyrosine kinase that serves as a high affinity receptor for several members of the fibroblast growth factor (FGF) family. To explore functions of FGF/FGFR2 signals in development, we have mutated FGFR2 by deleting the entire immunoglobin-like domain III of the receptor. We showed that murine FGFR2 is essential for chori...
Article
Full-text available
Ataxia-telangiectasia and Li-Fraumeni syndrome, pleiotropic disorders caused by mutations in the genes atm and p53, share a marked increase in cancer rates. A number of studies have argued for an interaction between these two genes (for comprehensive reviews, see M. S. Meyn, Cancer Res., 55: 5991-6001, 1995, and M. F. Lavin and Y. Shiloh, Annu. Rev...
Article
We have developed a differential display screening approach to identify mesoderm-specific genes, relying upon the differentiation of embryonic stem (ES) cells in vitro. Using this strategy, we have isolated a novel murine gene that encodes a secreted molecule containing a variant epidermal growth factor-like (EGF) motif. We named this gene Cryptic,...
Article
The kinetics of solitary mammary tumor formation in transgenic mice bearing the MMTV-int-2 (fgf3) fusion gene suggest that several genetic events are required for tumorigenesis. In an effort to identify elements that could contribute to this oncogenic process, we used differential display PCR to identify gene products that are strongly and specific...
Article
Full-text available
Ectopic activation of the TAL-1 gene in T lymphocytes occurs in the majority of cases of human T cell acute lymphoblastic leukemia (T-ALL), yet experiments to date have failed to demonstrate a direct transforming capability for tal-1. The tal-1 gene product is a serine phosphoprotein and basic helix-loop-helix (bHLH) transcription factor known to r...
Article
Full-text available
With use of the yeast two-hybrid system, the proteins RIP and FADD/MORT1 have been shown to interact with the "death domain" of the Fas receptor. Both of these proteins induce apoptosis in mammalian cells. Using receptor fusion constructs, we provide evidence that the self-association of the death domain of RIP by itself is sufficient to elicit apo...
Article
Neu differentiation factor (NDF), a member of the neuregulin family of ligands of erbB receptors, induces both differentiative and mitogenic effects on cultured human mammary epithelial cells. Since members of the epidermal growth factor receptor family, including Neu/erbB2, have been implicated in mammary carcinoma, we wished to know whether a pot...
Article
The formins, proteins involved in murine limb and kidney development, contain a proline-rich region that matches consensus sequences for Src homology 3 (SH3) ligands. To identify proteins that interact with formins, we used this proline-rich region to screen mouse limb bud expression libraries for formin binding proteins (FBPs). As expected, we fou...
Article
The protein-tyrosine phosphatase epsilon (PTP epsilon) is a transmembranal, receptor-type protein that possesses two phosphatase catalytic domains characteristic of transmembranal phosphatases. Here we demonstrate the existence of a nontransmembranal isoform of PTP epsilon, PTP epsilon-cytoplasmic. PTP epsilon-cytoplasmic and the transmembranal iso...
Article
We have isolated genomic and cDNA clones of Brca1, a mouse homolog of the recently cloned breast cancer-associated gene, BRCA1. Brca1 encodes an 1812-amino-acid protein with a conserved zinc finger domain and significant homology to the human protein. Brca1 maps to Chromosome 11 within a region of conserved synteny with human chromosome 17, consist...
Article
Transgenic mice that overexpress v-Ha-ras, c-myc, c-neu or int-2 proto-oncogenes in the mammary epithelium develop breast tumors with morphologies that are characteristic of each initiating oncogene, Since these morphological differences reflect distinctive patterns of tumor-specific gene expression, the identification of the products of these gene...
Article
Guinea pig eotaxin is a recently described member of the Cys-Cys family of chemokines and is involved in a guinea pig model of asthma. To determine whether eotaxin is a distinctive member of this family and to understand its physiologic role, we have cloned the mouse eotaxin gene and determined its structure and aspects of its biologic function. Th...
Article
IP-10 is a member of the chemokine family of cytokines and is induced in a variety of cells in response to interferon gamma and lipopolysaccharide. The self-aggregation common to many chemokines, including IP-10, has hindered the identification of a specific IP-10 receptor. Using an IP-10 alkaline phosphatase fusion protein that fortuitously blocks...
Article
A number of properties of the cancer-related genes c-myc and p53 suggest that they might collaborate to induce tumorigenesis. To test this notion, we produced doubly heterozygotic mice bearing disrupted p53 alleles and a fusion transgene consisting of the mouse mammary tumor virus (MMTV) LTR and the oncogene c-myc. Mice bearing both the MMT/c-myc t...
Article
Parental genomic imprinting refers to the phenomenon by which alleles behave differently depending on the sex of the parent from which they are inherited. In the case of the murine transgene RSVIgmyc, imprinting is manifest in two ways: differential DNA methylation and differential expression. In inbred FVB/N mice, a transgene inherited from a male...
Article
To study oncogenesis in the erythroid lineage, we have generated transgenic mice carrying the human c-MYC proto-oncogene under the control of mouse GATA-1 regulatory sequences. Six transgenic lines expressed the transgene and displayed a clear oncogenic phenotype. Of these, five developed an early onset, rapidly progressive erythroleukemia that res...
Article
Eotaxin is a member of the C-C family of chemokines and is related during antigen challenge in a guinea pig model of allergic airway inflammation (asthma). Consistent with its putative role in eosinophilic inflammation, eotaxin induces the selective infiltration of eosinophils when injected into the lung and skin. Using a guinea pig lung cDNA libra...
Article
Full-text available
The thymic lesion of the nude mouse causes a profound block in T cell development. The failure of most T cells to mature in nude mice is likely to reflect a requirement for signals elaborated in the normal thymus. Interleukin 7 (IL-7), a lymphokine that is normally expressed in the thymus and has been implicated in T cell maturation, might be centr...
Article
Transgenic mice harboring the int-2/Fgf-3 protooncogene under transcriptional control of the mouse mammary tumor virus (MMTV) promoter/enhancer exhibit a dramatic, benign hyperplasia of the mammary gland. In one int-2 transgenic line (TG.NX), this growth disturbance is evoked by pregnancy and regresses after parturition. Regression of hyperplastic...
Article
We have previously shown that each of four activated oncogenes (c-myc, neu, ras, and int-2) can serve as transgenic initiators of morphologically distinct adenocarcinomas of the murine mammary gland. Since abnormalities of these oncogenes are found frequently in human breast cancers, such differences are of particular interest. Thus, the distinctiv...
Article
We have explored the role of fibroblast growth factor receptor 1 (FGFR-1) in early embryonic development using three experimental systems: genetically deficient mice, in vitro blastocyst culture, and FGFR-1-deficient embryonic stem cells. Using these systems, we demonstrate that FGFR-1 is required for proper embryonic cell proliferation and for the...
Article
Full-text available
Leukemia inhibitory factor (LIF) is a cytokine involved in embryonic and hematopoietic development. To investigate the effects of LIF on the lymphoid system, we generated a line of transgenic mice that expresses diffusible LIF protein specifically in T cells. These mice display two categories of phenotype that were not previously attributed to LIF...
Article
The human interleukin 4 receptor (hIL-4R) is a member of a superfamily of cytokine receptors defined by conserved features of their extracellular domains. The intracellular domains of the hIL-4R and of other members of this family lack any recognizable enzymatic motifs, though ligand-dependent tyrosine phosphorylation of these receptors has been ob...
Article
The limb deformity locus (ld) on mouse chromosome 2 is required for the normal development of the limbs and kidney. Five recessive ld mutants have been described, all of which result in shortened limbs, oligosyndactyly, fusion of the long bones of the upper and lower limbs, and renal agenesis. The limb phenotype is completely penetrant in all anima...
Article
Full-text available
The murine myeloproliferative leukemia virus has previously been shown to contain a fragment of the coding region of the c-mpl gene, a member of the cytokine receptor superfamily. We have isolated cDNA and genomic clones encoding murine c-mpl and localized the c-mpl gene to mouse chromosome 4. Since some members of this superfamily function by tran...
Article
B-less mice express a human immunoglobulin (Ig) lambda transgene that induces a severe deficiency of both immature pre-B and mature B lymphocytes. To understand this perturbation in B lymphopoiesis, we have devised a sensitive limiting dilution polymerase chain reaction assay that quantitates specific Ig rearrangements and thus quantitates B lineag...
Article
Full-text available
Mutations at the mouse limb deformity (ld) locus result in defects of growth and patterning of the limb and kidney during embryonic development. The gene responsible for this phenotype is large and complex, with the capacity to generate a number of alternatively spliced messenger RNA transcripts encoding nuclear protein isoforms called "formins." W...
Article
Full-text available
A transgenic mouse strain with the zeta-globin promoter and the vHa-ras oncogene develops an array of mesenchymal and epithelial neoplasms described here. The predominate mesenchymal tumors were dermal spindle cell tumors, which resembled malignant fibrous histiocytomas found in humans. They were associated with hepatosplenomegaly and developed ben...
Article
Full-text available
To investigate the role of interleukin 7 (IL-7) in the development of the lymphoid system, we have generated two lines of transgenic mice carrying an IL-7 cDNA fused to an immunoglobulin heavy chain promoter and enhancer. This transgene is expressed in the bone marrow, lymph nodes, spleen, thymus, and skin provoking a perturbation of T cell develop...
Article
We have used a subtraction/coexpression strategy involving two different tumors derived from c-myc-bearing transgenic mice to identify a gene that is a target for c-Myc regulation. The gene, expressed in certain embryonic and adult tissues and in several (but not all) c-myc-based tumors, bears a functional c-Myc-binding sequence located 3' to its t...
Article
Murine erythropoiesis begins with the formation of primitive red blood cells in the blood islands of the embryonic yolk sac on day 7.5 of gestation. By analogy to human erythropoiesis, it has been thought that there is a gradual switch from the exclusive expression of the embryonic alpha-like globin (zeta) to the mature adult form (alpha) in these...
Article
The human T-cell leukemia virus type 1 (HTLV-I) is associated with adult CD4+ T-cell leukemia (ATL) and tropical spastic paraparesis (TSP). In as much as only a small percentage of individuals infected with HTLV-I develop either disease, we set out to model a genetic partner for this virus in an effort to understand and possibly reproduce its patho...
Article
Among its many activities, leukemia inhibitory factor (LIF) can maintain embryonic stem cell monolayers in a pluripotent undifferentiated state. Presuming that this might reflect its physiologic role during embryogenesis, we have examined LIF expression in the embryonic environment by RNase protection assays and have determined its in vitro effect...
Article
Full-text available
The heparin-binding growth factors include a family of seven structurally related proteins that can potentially interact with four known high affinity receptors. We have cloned the murine homologues of fibroblast growth factor receptors 1 and 3 (mFR1 and mFR3). To define the ligand specificity of these receptors, we have characterized their binding...
Article
The heparin-binding growth factors include a family of seven structurally related proteins that can potentially interact with four known high affinity receptors. We have cloned the murine homologues of fibroblast growth factor receptors 1 and 3 (mFR1 and mFR3). To define the ligand specificity of these receptors, we have characterized their binding...
Article
Full-text available
Interleukin 4 (IL-4) is a potent, pleiotropic lymphokine that affects a variety of cells, especially those of hematopoietic origin. Although murine and human IL-4 are homologous proteins, they display a species specificity in which murine IL-4 acts only upon mouse cells, and human IL-4 only upon human cells. We have used a mutagenesis strategy to d...
Article
Full-text available
We have created several transgenic mouse strains that bear the human lambda light chain gene driven by its own promoter and a mouse immunoglobulin heavy chain enhancer. The transgene is expressed in many tissues, with particularly high levels of expression in the bone marrow, thymus, spleen, and lymph nodes. One of these transgenic lines, B-less, d...
Article
Heparin is required for the binding of basic fibroblast growth factor (bFGF) to high-affinity receptors on cells deficient in cell surface heparan sulfate proteoglycan. So that this heparin requirement could be evaluated in the absence of other cell surface molecules, we designed a simple assay based on a genetically engineered soluble form of muri...
Article
Full-text available
The Wnt-1 and int-2 proto-oncogenes are transcriptionally activated by mouse mammary tumor virus insertion mutations in virus-induced tumors and encode secretory glycoproteins. To determine whether these two genes can cooperate during carcinogenesis, we have crossed two previously characterized lines of transgenic mice to obtain bitransgenic animal...
Article
Full-text available
The formins constitute a set of protein isoforms encoded by the alternatively spliced transcripts arising from the limb deformity (ld) locus of the mouse. Mutations in this locus disrupt formation of the anteroposterior axis of the embryonic limb. Although ld transcripts are widely expressed during embryogenesis, we have identified a novel transcri...
Article
The Wnt-1 and int-2 proto-oncogenes are transcriptionally activated by mouse mammary tumor virus insertion mutations in virus-induced tumors and encode secretory glycoproteins. To determine whether these two genes can cooperate during carcinogenesis, we have crossed two previously characterized lines of transgenic mice to obtain bitransgenic animal...
Article
Heparin is required for the binding of basic fibroblast growth factor (bFGF) to high-affinity receptors on cells deficient in cell surface heparan sulfate proteoglycan. So that this heparin requirement could be evaluated in the absence of other cell surface molecules, we designed a simple assay based on a genetically engineered soluble form of muri...
Article
We have analyzed mice expressing IL-4 as a transgene, and found that expression of this lymphokine has profound effects on B cell function. B cells from transgenic mice exhibit phenotypic changes, including an increase in size and elevated expression of class II MHC. IL-4 increases the quantity of IgE produced by transgenic-derived B cells in respo...
Article
The hypothesis that oncogenes influence tumor phenotype was tested by examining slides from 607 mammary tumors from 407 transgenic mice bearing the ras, myc, and/or neu oncogenes. Most tumors (91%) had patterns (phenotypes) that could not be classified by Dunn's standard nomenclature. The nonstandard tumors were described as eosinophilic small cell...
Article
Neurons are postmitotic for the adult life of animals. Tumors rarely, if ever, arise from neurons in the adult, although they do from other cells from the same lineage, such as the neuroendocrine C cells of the thyroid. We have found that 2 kb of the calcitonin gene-related peptide (CGRP)/calcitonin gene suffices to target expression to CGRP-contai...
Article
Full-text available
Membrane-bound immunoglobulin (mIg) is the antigen receptor on B lymphocytes mediating early events in antigen presentation and signal transduction. Wild-type human mIgM constructs transfected into the murine B-cell lymphoma A20 are expressed as transmembrane proteins with antigen presentation and signaling functions comparable to the endogenous mI...
Article
The murine limb deformity (ld) locus resides on mouse chromosome 2 and gives rise to a recessively inherited, characteristic limb deformity/renal aplasia phenotype. In this locus in the mouse, a gene, termed the "formin" gene, has been identified which encodes an array of differentially processed transcripts in both adult and embryonic tissues. A s...
Article
We have developed a binary transgenic system that activates an otherwise silent transgene in the progeny of a simple genetic cross. The system consists of two types of transgenic mouse strains, targets and transactivators. A target strain bears a transgene controlled by yeast regulatory sequences (UAS) that respond only to the yeast transcriptional...
Article
Experimental carcinogenesis has led to a concept that defines two discrete stages in the development of skin tumors: (i) initiation, which is accomplished by using a mutagen that presumably activates a protooncogene, and (ii) promotion, which is a reversible process brought about most commonly by repeated application of phorbol esters. We have crea...
Article
Full-text available
In an effort to identify widely active positive regulatory elements, we have examined the action of the cytomegalovirus enhancer-promoter in transgenic mice. These elements activated expression in 24 of 28 tissues tested. The greatest expression was observed in the heart, kidney, brain, and testis. Maximum expression further localized to specific c...
Article
In an effort to identify widely active positive regulatory elements, we have examined the action of the cytomegalovirus enhancer-promoter in transgenic mice. These elements activated expression in 24 of 28 tissues tested. The greatest expression was observed in the heart, kidney, brain, and testis. Maximum expression further localized to specific c...
Article
The induction of mammary tumors by mouse mammary tumor virus (MMTV) is thought to occur through proviral activation of one or more cellular genes. One of these, int-2, encodes a 27 kd protein which exhibits striking homology to the basic fibroblast growth factor family. To assess directly the role of the int-2 protein in cell proliferation, we have...
Article
We have used a cDNA probe for the human IgE receptor alpha chain to determine the chromosomal location for the human gene. A combination of Southern blot analysis of panels of somatic-cell hybrid DNAs and chromosomal in situ hybridization has localized the gene to the long arm of chromosome 1 at q21-q23. With this cDNA probe, we have also identifie...
Article
Full-text available
To gain insight into the role of the limb deformity (ld) gene in limb morphogenesis, we examined the morphologic details of early embryonic limb formation in the mutant ld/ld mouse. Initial morphological differences between wild-type and homozygous ld embryos are apparent during early gestational day 10, a time period during which anteroposterior l...
Article
Full-text available
This present review focuses on spontaneous neoplasms occurring in transgenic mice carrying and expressing activated cellular oncogenes. The historical development of transgenic mice as in vivo disease models is briefly traced, followed by a brief description of the actual technology in such systems. Additional emphasis is placed on the concept of t...
Article
We have isolated and characterized the gene coding for the alpha subunit of the rat mast cell high affinity IgE receptor. The gene comprises five exons and four introns and spans approximately 6.6 kilobases. The leader sequence is encoded by two exons, the second of which is only 21 base pairs long. The third and fourth exons each code for repeatin...
Article
Full-text available
We have isolated and characterized the gene coding for the α subunit of the rat mast cell high affinity IgE receptor. The gene comprises five exons and four introns and spans approximately 6.6 kilobases. The leader sequence is encoded by two exons, the second of which is only 21 base pairs long. The third and fourth exons each code for repeating im...
Article
Full-text available
The rat mast cell protease gene, RMCP II, is specifically expressed in the mucosal subclass of rat mast cells. We show here that the 5'-flanking region of this gene contains a mast cell-specific enhancer that directs preferential expression of a linked reporter gene (human growth hormone) transfected into rat basophilic leukemia cells. A DNA fragme...