401
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Affiliation(s)
- Y Zhu
- Center for Developmental Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas, Texas 75390-9133, USA
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402
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Hiatt KK, Ingram DA, Zhang Y, Bollag G, Clapp DW. Neurofibromin GTPase-activating protein-related domains restore normal growth in Nf1-/- cells. J Biol Chem 2001; 276:7240-5. [PMID: 11080503 DOI: 10.1074/jbc.m009202200] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the Ras superfamily of signaling proteins modulate fundamental cellular processes by cycling between an active GTP-bound conformation and an inactive GDP-bound form. Neurofibromin, the protein product of the NF1 tumor suppressor gene, and p120GAP are GTPase-activating proteins (GAPs) for p21(Ras) (Ras) and negatively regulate output by accelerating GTP hydrolysis on Ras. Neurofibromin and p120GAP differ markedly outside of their conserved GAP-related domains (GRDs), and it is therefore unknown if the respective GRDs contribute functional specificity. To address this question, we expressed the GRDs of neurofibromin and p120GAP in primary cells from Nf1 mutant mice in vitro and in vivo. Here we show that expression of neurofibromin GRD, but not the p120GAP GRD, restores normal growth and cytokine signaling in three lineages of primary Nf1-deficient cells that have been implicated in the pathogenesis of neurofibromatosis type 1 (NF1). Furthermore, utilizing a GAP-inactive mutant NF1 GRD identified in a family with NF1, we demonstrate that growth restoration is a function of NF1 GRD GAP activity on p21(Ras). Thus, the GRDs of neurofibromin and p120GAP specify nonoverlapping functions in multiple primary cell types.
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Affiliation(s)
- K K Hiatt
- Herman B Wells Center for Pediatric Research, Departments of Microbiology/Immunology and Pediatrics, Indiana University School of Medicine, Indianapolis 46202, USA
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403
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Abstract
Neurofibromatosis type 1 (NF1) represents a major risk factor for development of malignancy, particularly malignant peripheral nerve sheath tumors (MPNST), optic gliomas, other gliomas, and leukemias. The oncologist will see NF1 patients referred for treatment of malignancy, and should be alert to the possibility of undiagnosed NF1 among patients with cancer. Brain tumors tend to have a more indolent course in NF1 than in the general population, and hence are best managed conservatively. MPNST, in contrast, do not respond to standard chemotherapy or radiation therapy. The most effective treatment of MPNST appears to be early diagnosis and surgery, but early diagnosis is hampered by frequent occurrence within preexisting large tumors, making new growth or change difficult to detect. New insights into pathogenesis now offer hope of development of specific methods of treatment with reduced toxicity and more precise molecular targeting. There is an urgent need, however, to develop methods to measure tumor growth and monitor outcomes, develop preclinical drug screening systems, and further explore the pathogenesis of the disorder to determine whether mechanisms other than Ras regulation may be important in pathogenesis.
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Affiliation(s)
- B R Korf
- Partners Center for Human Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
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404
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Affiliation(s)
- K Cichowski
- Genetics Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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405
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Dragatsis I, Zeitlin S. A method for the generation of conditional gene repair mutations in mice. Nucleic Acids Res 2001; 29:E10. [PMID: 11160912 PMCID: PMC30411 DOI: 10.1093/nar/29.3.e10] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Conditional gene repair mutations in the mouse can assist in cell lineage analyses and provide a valuable complement to conditional gene inactivation strategies. We present a method for the generation of conditional gene repair mutations that employs a loxP-flanked (floxed) selectable marker and transcriptional/translational stop cassette (neostop) located within the first intron of a target gene. In the absence of Cre recombinase, expression of the targeted allele is suppressed generating a null allele, while in the presence of Cre, excision of neostop restores expression to wild-type levels. To test this strategy, we have generated a conditional gene repair allele of the mouse Huntington's disease gene homolog (HDH:). Insertion of neostop within the HDH: intron 1 generated a null allele and mice homozygous for this allele resembled nullizygous HDH: mutants and died after embryonic day 8.5. In the presence of a cre transgene expressed ubiquitously early in development, excision of neostop restored HDH: expression and rescued the early embryonic lethality. A simple modification of this strategy that permits the generation of conventional gene knockout, conditional gene knockout and conditional gene repair alleles using one targeting construct is discussed.
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Affiliation(s)
- I Dragatsis
- Department of Genetics and Development and Department of Pathology, Columbia University, New York, NY 10032, USA
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406
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Muir D, Neubauer D, Lim IT, Yachnis AT, Wallace MR. Tumorigenic properties of neurofibromin-deficient neurofibroma Schwann cells. THE AMERICAN JOURNAL OF PATHOLOGY 2001; 158:501-13. [PMID: 11159187 PMCID: PMC1850316 DOI: 10.1016/s0002-9440(10)63992-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Dermal and plexiform neurofibromas are peripheral nerve sheath tumors that arise frequently in neurofibromatosis type 1. The goal of the present study was to examine the tumorigenic properties of neurofibromin-deficient human Schwann cells (SCs) that were found to represent a subset of SCs present in approximately half of the total neurofibromas examined. Highly enriched SC cultures were established from 10 dermal and eight plexiform neurofibromas by selective subculture using glial growth factor-2 and laminin. These cultures had low tumorigenic potential in classical in vitro assays yet several unique preneoplastic properties were frequently observed, including delayed senescence, a lack of density-limited growth, and a strong propensity to spontaneously form proliferative cell aggregates rich in extracellular matrix. Western blot analysis failed to detect full-length neurofibromin in any of the neurofibroma SC cultures, indicating that neurofibromin-deficient SCs had a substantial growth advantage. Immunohistochemical staining of the originating tumors showed the majority were comprised principally of neurofibromin-negative SCs, whereas the remainder contained both neurofibromin-negative and neurofibromin-positive SCs. Lastly, engraftment of neurofibromin-deficient SC cultures into the peripheral nerves of scid mice consistently produced persistent neurofibroma-like tumors with diffuse and often extensive intraneural growth. These findings indicate that neurofibromin-deficient SCs are involved in neurofibroma formation and, by selective subculture, provide a resource for the development of an in vivo model to further examine the role of these mutant SCs in neurofibroma histogenesis.
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Affiliation(s)
- D Muir
- Divisions of Neurology and Genetics, the Department of Pediatrics, University of Florida Brain Institute and College of Medicine, Gainesville, Florida 32610, USA.
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407
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Crabtree JS, Scacheri PC, Ward JM, Garrett-Beal L, Emmert-Buck MR, Edgemon KA, Lorang D, Libutti SK, Chandrasekharappa SC, Marx SJ, Spiegel AM, Collins FS. A mouse model of multiple endocrine neoplasia, type 1, develops multiple endocrine tumors. Proc Natl Acad Sci U S A 2001; 98:1118-23. [PMID: 11158604 PMCID: PMC14718 DOI: 10.1073/pnas.98.3.1118] [Citation(s) in RCA: 311] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant cancer syndrome, characterized primarily by multiple tumors in the parathyroid glands, endocrine pancreas, and anterior pituitary. Other tumors, including gastrinoma, carcinoid, adrenal cortical tumors, angiofibroma, collagenoma, and lipoma, also occur in some patients. Individuals with MEN1 almost always have loss-of-function mutations in the MEN1 gene on chromosome 11, and endocrine tumors arising in these patients usually show somatic loss of the remaining wild-type allele. To examine the role of MEN1 in tumor formation, a mouse model was generated through homologous recombination of the mouse homolog Men1. Homozygous mice die in utero at embryonic days 11.5-12.5, whereas heterozygous mice develop features remarkably similar to those of the human disorder. As early as 9 months, pancreatic islets show a range of lesions from hyperplasia to insulin-producing islet cell tumors, and parathyroid adenomas are also frequently observed. Larger, more numerous tumors involving pancreatic islets, parathyroids, thyroid, adrenal cortex, and pituitary are seen by 16 months. All of the tumors tested to date show loss of the wild-type Men1 allele, further supporting its role as a tumor suppressor gene.
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MESH Headings
- Adenoma/genetics
- Adenoma/pathology
- Animals
- Chromosome Mapping
- Chromosomes, Artificial, Bacterial
- Chromosomes, Human, Pair 11
- Crosses, Genetic
- Disease Models, Animal
- Exons
- Female
- Fetal Death
- Genes, Lethal
- Genes, Tumor Suppressor
- Homozygote
- Humans
- Hyperparathyroidism/genetics
- Hyperparathyroidism/pathology
- Islets of Langerhans/pathology
- Male
- Mice
- Mice, Inbred Strains
- Mice, Transgenic
- Multiple Endocrine Neoplasia Type 1/genetics
- Multiple Endocrine Neoplasia Type 1/pathology
- Neoplasm Proteins/genetics
- Pancreatic Neoplasms/genetics
- Pancreatic Neoplasms/pathology
- Parathyroid Neoplasms/genetics
- Parathyroid Neoplasms/pathology
- Phosphoglycerate Kinase/genetics
- Pregnancy
- Proto-Oncogene Proteins
- Recombination, Genetic
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Affiliation(s)
- J S Crabtree
- National Human Genome Research Institute, National Cancer Institute, and National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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408
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Epstein JA, Buck CA. Transcriptional regulation of cardiac development: implications for congenital heart disease and DiGeorge syndrome. Pediatr Res 2000; 48:717-24. [PMID: 11102536 DOI: 10.1203/00006450-200012000-00003] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In recent years, impressive advances have occurred in our understanding of transcriptional regulation of cardiac development. These insights have begun to elucidate the mystery of congenital heart disease at the molecular level. In addition, the molecular pathways emerging from the study of cardiac development are being applied to the understanding of adult cardiac disease. Preliminary results support the contention that a thorough understanding of molecular programs governing cardiac morphogenesis will provide important insights into the pathogenesis of human cardiac diseases. This review will focus on examples of transcription factors that play critical roles at various phases of cardiac development and their relevance to cardiac disease. This is an exciting and burgeoning area of investigation. It is not possible to be all-inclusive, and the reader will note important efforts in the areas of cardiomyocyte determination, left-right asymmetry, cardiac muscular dystrophies, electrophysiology and vascular disease are not covered. For a more complete discussion, the reader is referred to recent reviews including the excellent compilation of observations assembled by Harvey and Rosenthal (1).
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MESH Headings
- Abnormalities, Multiple/embryology
- Abnormalities, Multiple/genetics
- Animals
- Aorta/embryology
- Branchial Region/embryology
- Branchial Region/pathology
- Cell Lineage
- Cell Movement
- Chick Embryo
- Chromosomes, Human, Pair 22/genetics
- DiGeorge Syndrome/embryology
- DiGeorge Syndrome/genetics
- Fetal Heart/growth & development
- Fetal Heart/pathology
- Gene Expression Regulation, Developmental
- Genes
- Genes, Homeobox
- Gestational Age
- Heart Conduction System/cytology
- Heart Conduction System/embryology
- Heart Defects, Congenital/embryology
- Heart Defects, Congenital/genetics
- Heart Valves/embryology
- Homeodomain Proteins/physiology
- Humans
- Mice
- Mice, Mutant Strains
- Morphogenesis/genetics
- Neural Crest/cytology
- Sequence Deletion
- Transcription Factors/deficiency
- Transcription Factors/genetics
- Transcription Factors/physiology
- Transcription, Genetic
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Affiliation(s)
- J A Epstein
- Cardiovascular Division, Department of Medicine, University of Pennsylvania Health System, Philadelphia, PA 19104, USA
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409
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Lin AE, Birch PH, Korf BR, Tenconi R, Niimura M, Poyhonen M, Armfield Uhas K, Sigorini M, Virdis R, Romano C, Bonioli E, Wolkenstein P, Pivnick EK, Lawrence M, Friedman JM. Cardiovascular malformations and other cardiovascular abnormalities in neurofibromatosis 1. AMERICAN JOURNAL OF MEDICAL GENETICS 2000; 95:108-17. [PMID: 11078559 DOI: 10.1002/1096-8628(20001113)95:2<108::aid-ajmg4>3.0.co;2-0] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Although it is well recognized that a peripheral vasculopathy may occur in patients with neurofibromatosis 1 (NF1), it is unclear whether cardiovascular abnormalities are more common. We reviewed the frequency of cardiovascular abnormalities, in particular, cardiovascular malformations (CVMs), among 2322 patients with definite NF1 in the National Neurofibromatosis Foundation International Database from 1991-98. Cardiovascular malformations were reported in 54/2322 (2.3%) of the NF1 patients, only 4 of whom had Watson syndrome or NF1-Noonan syndrome. There was a predominance of Class II "flow" defects [Clark, 1995: Moss and Adams' Heart Disease in Infants, Children, and Adolescents Including the Fetus and Young Adult. p 60-70] (43/54, 80%) among the NF1 patients with CVMs. Pulmonic stenosis, that was present in 25 NF1 patients, and aortic coarctation, that occurred in 5, constitute much larger proportions of all CVMs than expected. Of interest was the paucity of Class I conotruncal defects (2 patients with tetralogy of Fallot), and the absence of atrioventricular canal, anomalous pulmonary venous return, complex single ventricle and laterality defects. Besides the 54 patients with CVMs, there were 27 patients with other cardiac abnormalities (16 with murmur, 5 with mitral valve prolapse, 1 with intracardiac tumor, and 5 with electrocardiogram abnormalities). No patient in this study had hypertrophic cardiomyopathy. There were 16 patients who had a peripheral vascular abnormality without an intracardiac CVM, plus an additional 4 patients among those with a CVM who also had a peripheral vascular abnormality.
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Affiliation(s)
- A E Lin
- Genetics and Teratology Unit, Pediatric Service, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
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410
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Holzenberger M, Lenzner C, Leneuve P, Zaoui R, Hamard G, Vaulont S, Bouc YL. Cre-mediated germline mosaicism: a method allowing rapid generation of several alleles of a target gene. Nucleic Acids Res 2000; 28:E92. [PMID: 11058142 PMCID: PMC113161 DOI: 10.1093/nar/28.21.e92] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2000] [Revised: 09/12/2000] [Accepted: 09/12/2000] [Indexed: 11/14/2022] Open
Abstract
Conditional gene targeting uses the insertion of expression cassettes for the selection of targeted embryonic stem cells. The presence of these cassettes in the final targeted chromosomal locus may affect the normal expression of the targeted gene and produce interesting knock down phenotypes. We show here that the selection cassette may then be selectively removed in vivo, using three appropriately positioned loxP sites in the targeted gene and the transgenic mouse EIIaCre. This strategy was applied to two different target genes and we demonstrated that it is reliable and reproducible. First, we generated double transgenic EIIaCre/loxP mice (F1) that showed variable degrees of mosaicism for partially CRE-recombined floxed alleles. Efficiency of EIIaCre at creating mosaicism was dependent on the target gene and on parental transmission of the transgene. The segregation of partially recombined alleles and EIIaCre transgene was obtained in the next generation using mosaic F1 males. Mosaic females were unsuitable for this purpose because they systematically generated complete excisions during oogenesis. Our strategy is applicable to other approaches based on three loxP sites. As this procedure allows generation of knock down (presence of neo), knockout (total exision of the loxP-flanked sequences) and floxed substrains (excision of the selection cassette) from a single, targeted germline mutation and in a single experiment, its use may become more widespread in conditional mutagenesis.
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Affiliation(s)
- M Holzenberger
- INSERM U515, Hôpital Saint-Antoine, 184 rue du Fbg St-Antoine, F-75571 Paris Cedex 12, France. France.
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411
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Sherman LS, Atit R, Rosenbaum T, Cox AD, Ratner N. Single cell Ras-GTP analysis reveals altered Ras activity in a subpopulation of neurofibroma Schwann cells but not fibroblasts. J Biol Chem 2000; 275:30740-5. [PMID: 10900196 PMCID: PMC3066458 DOI: 10.1074/jbc.m001702200] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neurofibromatosis type 1 (NF1) is a common genetic disorder characterized by multiple neurofibromas, peripheral nerve tumors containing mainly Schwann cells and fibroblasts. The NF1 gene encodes neurofibromin, a tumor suppressor postulated to function in part as a Ras GTPase-activating protein. The roles of different cell types and of elevated Ras-GTP in neurofibroma formation are unclear. To determine which neurofibroma cell type has altered Ras-GTP regulation, we developed an immunocytochemical assay for active, GTP-bound Ras. In NIH 3T3 cells, the assay detected overexpressed, constitutively activated K-, N-, and Ha-Ras and insulin-induced endogenous Ras-GTP. In dissociated neurofibroma cells from NF1 patients, Ras-GTP was elevated in Schwann cells but not fibroblasts. Twelve to 62% of tumor Schwann cells showed elevated Ras-GTP, unexpectedly revealing neurofibroma Schwann cell heterogeneity. Increased basal Ras-GTP did not correlate with increased cell proliferation. Normal human Schwann cells, however, did not demonstrate elevated basal Ras activity. Furthermore, compared with cells from wild type littermates, Ras-GTP was elevated in all mouse Nf1(-/-) Schwann cells but never in Nf1(-/-) mouse fibroblasts. Our results indicate that Ras activity is detectably increased in only some neurofibroma Schwann cells and suggest that neurofibromin is not an essential regulator of Ras activity in fibroblasts.
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Affiliation(s)
- Larry S. Sherman
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0521
| | - Radhika Atit
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0521
| | - Thorsten Rosenbaum
- Department of Neuropediatrics, Children’s Hospital, Heinrich-Heine-University, Dusseldorf, Germany
| | - Adrienne D. Cox
- Departments of Radiation Oncology and Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599-7512
| | - Nancy Ratner
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0521
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412
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Abstract
Cardiac muscle cells exhibit two related but distinct modes of growth that are highly regulated during development and disease. Cardiac myocytes rapidly proliferate during fetal life but exit the cell cycle irreversibly soon after birth, following which the predominant form of growth shifts from hyperplastic to hypertrophic. Much research has focused on identifying the candidate mitogens, hypertrophic agonists, and signaling pathways that mediate these processes in isolated cells. What drives the proliferative growth of embryonic myocardium in vivo and the mechanisms by which adult cardiac myocytes hypertrophy in vivo are less clear. Efforts to answer these questions have benefited from rapid progress made in techniques to manipulate the murine genome. Complementary technologies for gain- and loss-of-function now permit a mutational analysis of these growth control pathways in vivo in the intact heart. These studies have confirmed the importance of suspected pathways, have implicated unexpected pathways as well, and have led to new paradigms for the control of cardiac growth.
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Affiliation(s)
- W R MacLellan
- Department of Medicine, UCLA School of Medicine 90076, USA
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413
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Reilly KM, Loisel DA, Bronson RT, McLaughlin ME, Jacks T. Nf1;Trp53 mutant mice develop glioblastoma with evidence of strain-specific effects. Nat Genet 2000; 26:109-13. [PMID: 10973261 DOI: 10.1038/79075] [Citation(s) in RCA: 268] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Astrocytomas are the leading cause of brain cancer in humans. Because these tumours are highly infiltrative, current treatments that rely on targeting the tumour mass are often ineffective. A mouse model for astrocytoma would be a powerful tool for dissecting tumour progression and testing therapeutics. Mouse models of astrocytoma have been designed to express oncogenic proteins in astrocytes, but have had limited success due to low tumour penetrance or limited tumour progression. We present here a mouse model of astrocytomas involving mutation of two tumour-suppressor genes, Nf1 and Trp53. Humans with mutations in NF1 develop neurofibromatosis type I (NF1) and have increased risk of optic gliomas, astrocytomas and glioblastomas. The TP53 tumour suppressor is often mutated in a subset of astrocytomas that develop at a young age and progress slowly to glioblastoma (termed secondary glioblastomas, in contrast to primary glioblastomas that develop rapidly de novo). This mouse model shows a range of astrocytoma stages, from low-grade astrocytoma to glioblastoma multiforme, and may accurately model human secondary glioblastoma involving TP53 loss. This is the first reported mouse model of astrocytoma initiated by loss of tumour suppressors, rather than overexpression of transgenic oncogenes.
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Affiliation(s)
- K M Reilly
- Department of Biology and Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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414
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Rosenbaum T, Rosenbaum C, Winner U, Müller HW, Lenard HG, Hanemann CO. Long-term culture and characterization of human neurofibroma-derived Schwann cells. J Neurosci Res 2000; 61:524-32. [PMID: 10956422 DOI: 10.1002/1097-4547(20000901)61:5<524::aid-jnr7>3.0.co;2-z] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Neurofibromas are benign tumors arising from the peripheral nerve sheath and are a typical finding in neurofibromatosis type 1 (NF1). Schwann cells are the predominant cell type in neurofibromas and thus are supposed to play a major role in the pathogenesis of these tumors. It is not known, however, if NF1 mutations in Schwann cells result in an altered phenotype that subsequently leads to tumor formation. To characterize the biological properties of neurofibroma-derived Schwann cells we developed cell culture techniques that enabled us to isolate Schwann cells from neurofibromas and grow them in vitro for several weeks without significant fibroblast contamination. Neurofibroma-derived Schwann cells were characterized by altered morphology, heterogeneous growth behavior, and increased expression of the P0 antigen while several other features of normal human Schwann cells were retained. We conclude that neurofibroma-derived Schwann cells exhibit a distinct phenotype in vitro but that the observed abnormalities by themselves are insufficient to explain neurofibroma formation. Application of our improved culture conditions makes neurofibroma-derived Schwann cells readily available for further studies to define their role in tumorigenesis in neurofibromatosis type 1.
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Affiliation(s)
- T Rosenbaum
- Department of Neuropediatrics, Heinrich-Heine-University, Düsseldorf, Germany.
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415
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Abstract
The field of pediatric dermatology continues to be enriched by the insights offered through molecular genetics. For some genetic skin disorders, including neurofibromatosis, tuberous sclerosis complex, and several forms of epidermolysis bullosa, genetic research has resulted in an evolving understanding of the relationship between genotype and phenotype, with the ability to predict some of the features of these disorders on the basis of the genetic defect. However, widespread use of molecular genetics for diagnostic testing of these disorders has not been possible because of genetic heterogeneity, limited availability, and reduced sensitivity. The appropriate use of genetic services is emphasized in this, the molecular era.
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Affiliation(s)
- M A Parisi
- Department of Pediatrics, Children's Hospital and Regional Medical Center, Seattle, Washington, USA
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416
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Affiliation(s)
- L F Parada
- Center for Developmental Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., 75390-9133, Dallas, TX, USA.
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417
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Affiliation(s)
- W D Cook
- Bone Marrow Research Laboratories, Royal Melbourne Hospital, Melbourne, Victoria, Australia
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418
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Holzenberger M, Leneuve P, Hamard G, Ducos B, Perin L, Binoux M, Le Bouc Y. A targeted partial invalidation of the insulin-like growth factor I receptor gene in mice causes a postnatal growth deficit. Endocrinology 2000; 141:2557-66. [PMID: 10875258 DOI: 10.1210/endo.141.7.7550] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The insulin-like growth factor (IGF) system is a major regulator of somatic growth in vertebrates. Both ligands (IGF-I and IGF-II) signal via the same IGF receptor (IGF-IR). Classical IGF-IR invalidation is lethal at birth, so that conditional models are needed to study the postnatal role of this receptor. To establish a genetically inducible invalidation of IGF-IR, we targeted the IGF-IR gene using a construct that introduced a neomycin resistance cassette into intron 2, leaving the rest of the gene intact. This neomycin resistance cassette interfered with the processing of the primary transcript, resulting in there being 12% fewer IGF-binding sites at the cell surface in heterozygous mice and 41% fewer in homozygous mice. Hetero- and homozygous offspring grew more slowly than their wild-type littermates. This difference was noticeable from 4 weeks after birth and was significant from 5 weeks after birth in males. In females, the effect on postnatal growth of insertion of the neo cassette was not significant. In males, IGF-I levels increased moderately (+26%) but significantly, indicating effective feedback regulation of the IGF system. IGF-binding protein-4 (IGFBP-4) levels, estimated by Western ligand blotting, were low in homozygotes (-38%), whereas IGFBP-1, -2, and -3 levels were unaffected. In females, IGF-I and IGFBP-1, -2, -3, and -4 levels did not differ significantly among heterozygous, homozygous, and wild-type animals. We investigated the molecular mechanism involved and characterized two RNA-splicing events that could account for the decrease in IGF-IR. The phenotype of these mice developed exclusively postnatally, and body proportions were maintained. IGF-IRneo mice constitute a new model for human postnatal growth deficiency.
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419
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Tevosian SG, Deconinck AE, Tanaka M, Schinke M, Litovsky SH, Izumo S, Fujiwara Y, Orkin SH. FOG-2, a cofactor for GATA transcription factors, is essential for heart morphogenesis and development of coronary vessels from epicardium. Cell 2000; 101:729-39. [PMID: 10892744 DOI: 10.1016/s0092-8674(00)80885-5] [Citation(s) in RCA: 338] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We disrupted the FOG-2 gene in mice to define its requirement in vivo. FOG-2(-/-) embryos die at midgestation with a cardiac defect characterized by a thin ventricular myocardium, common atrioventricular canal, and the tetralogy of Fallot malformation. Remarkably, coronary vasculature is absent in FOG-2(-/-) hearts. Despite formation of an intact epicardial layer and expression of epicardium-specific genes, markers of cardiac vessel development (ICAM-2 and FLK-1) are not detected, indicative of failure to activate their expression and/or to initiate the epithelial to mesenchymal transformation of epicardial cells. Transgenic reexpression of FOG-2 in cardiomyocytes rescues the FOG-2(-/-) vascular phenotype, demonstrating that FOG-2 function in myocardium is required and sufficient for coronary vessel development. Our findings provide the molecular inroad into the induction of coronary vasculature by myocardium in the developing heart.
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Affiliation(s)
- S G Tevosian
- Division of Hematology-Oncology, Children's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts 02115, USA
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420
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Atit RP, Mitchell K, Nguyen L, Warshawsky D, Ratner N. The neurofibromatosis type 1 (Nf1) tumor suppressor is a modifier of carcinogen-induced pigmentation and papilloma formation in C57BL/6 mice. J Invest Dermatol 2000; 114:1093-100. [PMID: 10844550 PMCID: PMC2862652 DOI: 10.1046/j.1523-1747.2000.00994.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is increasing evidence implicating the human NF1 gene in epithelial carcinogenesis. To test if NF1 can play a part in skin tumor formation, we analyzed effects of the skin cancer initiator dimethylbenz-anthracene and/or the tumor promoter 12-O-tetradecanoyl-13-acetylphorbol on mice heterozygous for null mutations in Nf1 (Nf1+/-). Mice were on the C57BL/6 background, noted for resistance to chemical carcinogens. Nf1+/- mice (18 of 24) developed papillomas after treatment with dimethylbenzanthracene and 12-O-tetradecanoyl-13-acetylphorbol; papillomas did not develop in wild-type C57BL/6 mice nor Nf1+/- mice treated with 12-O-tetradecanoyl-13-acetylphorbol alone. All papillomas analyzed (six of six) had mutations in codon 61 of H-ras, demonstrating strong cooperation between the Nf1 GTPase activating protein for Ras, neurofibromin, and Ras-GTP. After exposure to 12-O-tetradecanoyl-13-acetylphorbol, Nf1+/- keratinocytes showed significant, sustained, increases in proliferation, implicating Nf1 in phorbol ester responsive pathways. Thus, Nf1 levels regulate the response of keratinocytes to 12-O-tetradecanoyl-13-acetylphorbol. Nf1+/- mice also showed a 2-fold increase in the development of pigmented skin patches stimulated by dimethylbenzanthracene; patches were characterized by hair follicles in anagen phase, implicating keratinocytes in the aberrant hyperpigmentation. Our results show that mutation in the Nf1 gene causes abnormal keratinocyte proliferation that can be revealed by environmental assaults such as carcinogen exposure. The data support a plausible role for NF1 mutation in human epithelial carcinogenesis.
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Affiliation(s)
- Radhika P. Atit
- Division of Molecular and Developmental Biology, Children’s Hospital Research Foundation, Cincinnati, Ohio, U.S.A
| | - Kent Mitchell
- Department of Environmental Health, University of Cincinnati, College of Medicine, Cincinnati, Ohio, U.S.A
| | - Lam Nguyen
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati, College of Medicine, Cincinnati, Ohio, U.S.A
| | - David Warshawsky
- Department of Environmental Health, University of Cincinnati, College of Medicine, Cincinnati, Ohio, U.S.A
| | - Nancy Ratner
- Division of Molecular and Developmental Biology, Children’s Hospital Research Foundation, Cincinnati, Ohio, U.S.A
- Department of Cell Biology, Neurobiology and Anatomy, University of Cincinnati, College of Medicine, Cincinnati, Ohio, U.S.A
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421
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422
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DeClue JE, Heffelfinger S, Benvenuto G, Ling B, Li S, Rui W, Vass WC, Viskochil D, Ratner N. Epidermal growth factor receptor expression in neurofibromatosis type 1-related tumors and NF1 animal models. J Clin Invest 2000; 105:1233-41. [PMID: 10791998 PMCID: PMC315438 DOI: 10.1172/jci7610] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
We have found that EGF-R expression is associated with the development of the Schwann cell-derived tumors characteristic of neurofibromatosis type 1 (NF1) and in animal models of this disease. This is surprising, because Schwann cells normally lack EGF-R and respond to ligands other than EGF. Nevertheless, immunoblotting, Northern analysis, and immunohistochemistry revealed that each of 3 malignant peripheral nerve sheath tumor (MPNST) cell lines from NF1 patients expressed the EGF-R, as did 7 of 7 other primary MPNSTs, a non-NF1 MPNST cell line, and the S100(+) cells from each of 9 benign neurofibromas. Furthermore, transformed derivatives of Schwann cells from NF1(-/-) mouse embryos also expressed the EGF-R. All of the cells or cell lines expressing EGF-R responded to EGF by activation of downstream signaling pathways. Thus, EGF-R expression may play an important role in NF1 tumorigenesis and Schwann cell transformation. Consistent with this hypothesis, growth of NF1 MPNST lines and the transformed NF1(-/-) mouse embryo Schwann cells was greatly stimulated by EGF in vitro and could be blocked by agents that antagonize EGF-R function.
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Affiliation(s)
- J E DeClue
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, Maryland 20892, USA.
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423
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Abstract
Despite tremendous technical improvements in neuroimaging and neurosurgery, the prognosis for patients with malignant astrocytoma remains devastating because of the underlying biology and growth characteristics of the tumor. However, our understanding of the molecular bases of these tumors has greatly increased due to study findings involving operative specimens, astrocytoma predisposing human syndromes, teratogen-induced animal and established human astrocytoma cell lines, and more recently transgenic mouse models. Appropriate small-animal models of spontaneously occurring astrocytomas, which replicate the growth and molecular characteristics found in human tumors, are essential to test the relevance and interactions of these molecular aberrations. In addition, it is hoped that relevant molecular targets will eventually be therapeutically exploited to improve patient outcomes. Appropriate animal models are also essential for testing these novel biological therapies, before they are brought to the clinic, requiring a large investment of time and money. In this paper, various astrocytoma models are discussed, with emphasis on transgenic mouse models that are of great interest to laboratory investigators.
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424
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Vogel KS, El-Afandi M, Parada LF. Neurofibromin negatively regulates neurotrophin signaling through p21ras in embryonic sensory neurons. Mol Cell Neurosci 2000; 15:398-407. [PMID: 10845775 DOI: 10.1006/mcne.2000.0836] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Embryonic sensory and sympathetic neurons that lack neurofibromin, the protein product of the neurofibromatosis type 1 (Nfl) gene, survive and extend neurites in the absence of neurotrophins. To determine whether neurofibromin negatively regulates neurotrophin signaling through its interaction with p21ras, we used Fab antibody fragments to block Ras function in DRG, trigeminal, nodose, and SCG neurons isolated from Nfl(-/-) and wild-type mouse embryos. We show that introduction of anti-Ras Fab fragments significantly reduces the ability of neurofibromin-deficient neurons to survive in the absence of neurotrophins. Moreover, addition of H-ras protein enhances the survival of Nfl(-/-), but not wild-type, DRG neurons. Our results are consistent with a major role for neurofibromin in modulating Trk signaling through p21ras during neuronal development.
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Affiliation(s)
- K S Vogel
- Center for Developmental Biology, University of Texas Southwestern Medical Center, Dallas 75235-9133, USA.
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425
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Borghesani PR, Alt FW, Bottaro A, Davidson L, Aksoy S, Rathbun GA, Roberts TM, Swat W, Segal RA, Gu Y. Abnormal development of Purkinje cells and lymphocytes in Atm mutant mice. Proc Natl Acad Sci U S A 2000; 97:3336-41. [PMID: 10716718 PMCID: PMC16240 DOI: 10.1073/pnas.97.7.3336] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Motor incoordination, immune deficiencies, and an increased risk of cancer are the characteristic features of the hereditary disease ataxia-telangiectasia (A-T), which is caused by mutations in the ATM gene. Through gene targeting, we have generated a line of Atm mutant mice, Atm(y/y) mice. In contrast to other Atm mutant mice, Atm(y/y) mice show a lower incidence of thymic lymphoma and survive beyond a few months of age. Atm(y/y) mice exhibit deficits in motor learning indicative of cerebellar dysfunction. Even though we found no gross cerebellar degeneration in older Atm(y/y) animals, ectopic and abnormally differentiated Purkinje cells were apparent in mutant mice of all ages. These findings establish that some neuropathological abnormalities seen in A-T patients also are present in Atm mutant mice. In addition, we report a previously unrecognized effect of Atm deficiency on development or maintenance of CD4(+)8(+) thymocytes. We discuss these findings in the context of the hypothesis that abnormal development of Purkinje cells and lymphocytes contributes to the pathogenesis of A-T.
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Affiliation(s)
- P R Borghesani
- Department of Pediatric Oncology and Division of Cellular and Molecular Biology, Dana-Farber Cancer Institute, Boston, MA 00115, USA
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426
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Abnormal development of Purkinje cells and lymphocytes in Atm mutant mice. Proc Natl Acad Sci U S A 2000. [PMID: 10716718 PMCID: PMC16240 DOI: 10.1073/pnas.050584897] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Motor incoordination, immune deficiencies, and an increased risk of cancer are the characteristic features of the hereditary disease ataxia-telangiectasia (A-T), which is caused by mutations in the ATM gene. Through gene targeting, we have generated a line of Atm mutant mice, Atm(y/y) mice. In contrast to other Atm mutant mice, Atm(y/y) mice show a lower incidence of thymic lymphoma and survive beyond a few months of age. Atm(y/y) mice exhibit deficits in motor learning indicative of cerebellar dysfunction. Even though we found no gross cerebellar degeneration in older Atm(y/y) animals, ectopic and abnormally differentiated Purkinje cells were apparent in mutant mice of all ages. These findings establish that some neuropathological abnormalities seen in A-T patients also are present in Atm mutant mice. In addition, we report a previously unrecognized effect of Atm deficiency on development or maintenance of CD4(+)8(+) thymocytes. We discuss these findings in the context of the hypothesis that abnormal development of Purkinje cells and lymphocytes contributes to the pathogenesis of A-T.
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427
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Abstract
Over the past two decades, the mouse has established itself as the primary organism in which to investigate the fundamental mechanisms of carcinogenesis and to model human neoplasia. The principal reason underlying such dominance almost certainly arises out of our ever increasing ability to manipulate the murine germline. Over the past 20 years we have moved from a position where animal models arose either spontaneously or were generated through exposure to carcinogen to a position in which it is possible to create and study precise mutations of choice. The most recent advances in inducible and conditional technologies now open the possibility for both temporal and tissue-specific gene manipulation. Each of these technological breakthroughs has facilitated significant steps forward in our understanding of the genetic basis of tumorigenesis. This review will highlight some of the major advances in the production and use of murine models of neoplasia over the last two decades.
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Affiliation(s)
- A R Clarke
- Cardiff School of Biosciences, Cardiff University, PO Box 911, Cardiff CF10 3US, UK.
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428
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Guo HF, Tong J, Hannan F, Luo L, Zhong Y. A neurofibromatosis-1-regulated pathway is required for learning in Drosophila. Nature 2000; 403:895-8. [PMID: 10706287 DOI: 10.1038/35002593] [Citation(s) in RCA: 217] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The tumour-suppressor gene Neurofibromatosis 1 (Nf1) encodes a Ras-specific GTPase activating protein (Ras-GAP). In addition to being involved in tumour formation, NF1 has been reported to cause learning defects in humans and Nf1 knockout mice. However, it remains to be determined whether the observed learning defect is secondary to abnormal development. The Drosophila NF1 protein is highly conserved, showing 60% identity of its 2,803 amino acids with human NF1 (ref. 12). Previous studies have suggested that Drosophila NF1 acts not only as a Ras-GAP but also as a possible regulator of the cAMP pathway that involves the rutabaga (rut)-encoded adenylyl cyclase. Because rut was isolated as a learning and short-term memory mutant, we have pursued the hypothesis that NF1 may affect learning through its control of the Rut-adenylyl cyclase/cAMP pathway. Here we show that NF1 affects learning and short-term memory independently of its developmental effects. We show that G-protein-activated adenylyl cyclase activity consists of NF1-independent and NF1-dependent components, and that the mechanism of the NF1-dependent activation of the Rut-adenylyl cyclase pathway is essential for mediating Drosophila learning and memory.
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Affiliation(s)
- H F Guo
- Cold Spring Harbor Laboratory, New York 11724, USA
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429
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430
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Silva AJ, Elgersma Y, Costa RM. Molecular and cellular mechanisms of cognitive function: implications for psychiatric disorders. Biol Psychiatry 2000; 47:200-9. [PMID: 10682217 DOI: 10.1016/s0006-3223(99)00294-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent studies on the molecular and cellular basis of learning and memory have brought us closer than ever to understanding the mechanisms of synaptic plasticity and their relevance to memory formation. Genetic approaches have played a central role in these new findings because the same mutant mice can be studied with molecular, cellular, circuit, and behavioral tools. Therefore, the results can be used to construct models that cut across levels of analytical complexity, forging connections from the biochemistry of the modified protein to the behavior of the mutant mice. These findings are not only improving our understanding of learning and memory, they are also enriching our understanding of cognitive disorders, such as neurofibromatosis type I. Mechanisms underlying long-term changes in synaptic function are likely to be at the heart of many cognitive and emotional processes in humans. Therefore, molecular and cellular insights into learning and memory undoubtedly will have a profound impact on the understanding and treatment of psychiatric disorders.
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Affiliation(s)
- A J Silva
- Department of Neurobiology, University of California Los Angeles 90095-1761, USA
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431
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Inhibition of juvenile myelomonocytic leukemia cell growth in vitro by farnesyltransferase inhibitors. Blood 2000. [DOI: 10.1182/blood.v95.2.639] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Juvenile myelomonocytic leukemia (JMML) is an early childhood disease for which there is no effective therapy. Therapy with 13-cis retinoic acid or low-dose chemotherapy can induce some responses, but neither mode is curative. Stem cell transplantation can produce lasting remissions but is hampered by high rates of relapse. The pathogenesis of JMML involves deregulated cytokine signal transduction through the Ras signaling pathway, with resultant selective hypersensitivity of JMML cells to granulocyte-macrophage colony-stimulating factor (GM-CSF). A JMML mouse model, achieved through homozygous deletion of the neurofibromatosis gene, confirmed the involvement of deregulated Ras in JMML pathogenesis. With this pathogenetic knowledge, mechanism-based treatments are now being developed and tested. Ras is critically dependent on a prenylation reaction for its signal transduction abilities. Farnesyltransferase inhibitors are compounds that were developed specifically to block the prenylation of Ras. Two of these compounds, L-739,749 and L-744,832, were tested for their ability to inhibit spontaneous JMML granulocyte-macrophage colony growth. Within a dose range of 1 to 10 μmol/L, each compound demonstrated dose-dependent inhibition of JMML colony growth. An age-matched patient with a different disease and GM-CSF–stimulated normal adult marrow cells also demonstrated dose-dependent inhibitory effects on colony growth, but they were far less sensitive to these compounds than JMML hematopoietic progenitors. Even if the addition of L-739,749 were delayed for 5 days, significant inhibitory effects would still show in JMML cultures. These results demonstrate that a putative Ras-blocking compound can have significant growth inhibitory effects in vitro, perhaps indicating a potential treatment for JMML.
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432
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Ingram DA, Yang FC, Travers JB, Wenning MJ, Hiatt K, New S, Hood A, Shannon K, Williams DA, Clapp DW. Genetic and biochemical evidence that haploinsufficiency of the Nf1 tumor suppressor gene modulates melanocyte and mast cell fates in vivo. J Exp Med 2000; 191:181-8. [PMID: 10620616 PMCID: PMC2195790 DOI: 10.1084/jem.191.1.181] [Citation(s) in RCA: 146] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/1999] [Accepted: 10/18/1999] [Indexed: 12/04/2022] Open
Abstract
Neurofibromatosis type 1 (NF1) is a common autosomal-dominant disorder characterized by cutaneous neurofibromas infiltrated with large numbers of mast cells, melanocyte hyperplasia, and a predisposition to develop malignant neoplasms. NF1 encodes a GTPase activating protein (GAP) for Ras. Consistent with Knudson's "two hit" model of tumor suppressor genes, leukemias and malignant solid tumors in NF1 patients frequently demonstrate somatic loss of the normal NF1 allele. However, the phenotypic and biochemical consequences of heterozygous inactivation of Nf1 are largely unknown. Recently neurofibromin, the protein encoded by NF1, was shown to negatively regulate Ras activity in Nf1-/- murine myeloid hematopoietic cells in vitro through the c-kit receptor tyrosine kinase (dominant white spotting, W). Since the W and Nf1 locus appear to function along a common developmental pathway, we generated mice with mutations at both loci to examine potential interactions in vivo. Here, we show that haploinsufficiency at Nf1 perturbs cell fates in mast cells in vivo, and partially rescues coat color and mast cell defects in W(41) mice. Haploinsufficiency at Nf1 also increased mast cell proliferation, survival, and colony formation in response to Steel factor, the ligand for c-kit. Furthermore, haploinsufficiency was associated with enhanced Ras-mitogen-activated protein kinase activity, a major downstream effector of Ras, via wild-type and mutant (W(41)) c-kit receptors. These observations identify a novel interaction between c-kit and neurofibromin in vivo, and offer experimental evidence that haploinsufficiency of Nf1 alters both cellular and biochemical phenotypes in two cell lineages that are affected in individuals with NF1. Collectively, these data support the emerging concept that heterozygous inactivation of tumor suppressor genes may have profound biological effects in multiple cell types.
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Affiliation(s)
- David A. Ingram
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Herman B.Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Feng-Chun Yang
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Herman B.Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Howard Hughes Medical Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Jeffrey B. Travers
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Herman B.Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Mary Jo Wenning
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Herman B.Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Kelly Hiatt
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Herman B.Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Sheryl New
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Herman B.Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Antoinette Hood
- Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Kevin Shannon
- Department of Pediatrics, University of California at San Francisco School of Medicine, San Francisco, California 94143
| | - David A. Williams
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Herman B.Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Howard Hughes Medical Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - D. Wade Clapp
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana 46202
- Herman B.Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana 46202
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433
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Birnbaum RA, O'Marcaigh A, Wardak Z, Zhang YY, Dranoff G, Jacks T, Clapp DW, Shannon KM. Nf1 and Gmcsf interact in myeloid leukemogenesis. Mol Cell 2000; 5:189-95. [PMID: 10678181 DOI: 10.1016/s1097-2765(00)80415-3] [Citation(s) in RCA: 118] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The NF1 tumor suppressor gene encodes neurofibromin, a GTPase-activating protein (GAP) for p21ras (Ras). Children with NF1 are predisposed to juvenile myelomonocytic leukemia (JMML). Some heterozygous Nf1 mutant mice develop a similar myeloproliferative disorder (MPD), and adoptive transfer of Nf1-deficient fetal liver cells consistently induces this MPD. Human JMML and murine Nf1-deficient cells are hypersensitive to granulocyte-macrophage colony-stimulating factor (GM-CSF) in methylcellulose cultures. We generated hematopoietic cells deficient in both Nf1 and Gmcsf to test whether GM-CSF is required to drive excessive proliferation of Nf1-/- cells in vivo. Here we show that GM-CSF play a central role in establishing and maintaining the MPD and that recipients engrafted with Nf1-/- Gmcsf-/- hematopoietic cells are hypersensitive to exogenous GM-CSF.
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Affiliation(s)
- R A Birnbaum
- Department of Pediatrics, University of California, San Francisco 94143-0519, USA
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434
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435
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Vogel KS, Klesse LJ, Velasco-Miguel S, Meyers K, Rushing EJ, Parada LF. Mouse tumor model for neurofibromatosis type 1. Science 1999; 286:2176-9. [PMID: 10591653 PMCID: PMC3079436 DOI: 10.1126/science.286.5447.2176] [Citation(s) in RCA: 296] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder characterized by increased incidence of benign and malignant tumors of neural crest origin. Mutations that activate the protooncogene ras, such as loss of Nf1, cooperate with inactivating mutations at the p53 tumor suppressor gene during malignant transformation. One hundred percent of mice harboring null Nf1 and p53 alleles in cis synergize to develop soft tissue sarcomas between 3 and 7 months of age. These sarcomas exhibit loss of heterozygosity at both gene loci and express phenotypic traits characteristic of neural crest derivatives and human NF1 malignancies.
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Affiliation(s)
- Kristine S. Vogel
- Center for Developmental Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75235–9133, USA
| | - Laura J. Klesse
- Center for Developmental Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75235–9133, USA
| | - Susana Velasco-Miguel
- Center for Developmental Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75235–9133, USA
| | - Kimberly Meyers
- Center for Developmental Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75235–9133, USA
| | - Elizabeth J. Rushing
- Department of Pathology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75235–9133, USA
| | - Luis F. Parada
- Center for Developmental Biology, University of Texas Southwestern Medical Center, 6000 Harry Hines Blvd., Dallas, TX 75235–9133, USA
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436
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Cichowski K, Shih TS, Schmitt E, Santiago S, Reilly K, McLaughlin ME, Bronson RT, Jacks T. Mouse models of tumor development in neurofibromatosis type 1. Science 1999; 286:2172-6. [PMID: 10591652 DOI: 10.1126/science.286.5447.2172] [Citation(s) in RCA: 376] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Neurofibromatosis type 1 (NF1) is a prevalent familial cancer syndrome resulting from germ line mutations in the NF1 tumor suppressor gene. Hallmark features of the disease are the development of benign peripheral nerve sheath tumors (neurofibromas), which can progress to malignancy. Unlike humans, mice that are heterozygous for a mutation in Nf1 do not develop neurofibromas. However, as described here, chimeric mice composed in part of Nf1-/- cells do, which demonstrates that loss of the wild-type Nf1 allele is rate-limiting in tumor formation. In addition, mice that carry linked germ line mutations in Nf1 and p53 develop malignant peripheral nerve sheath tumors (MPNSTs), which supports a cooperative and causal role for p53 mutations in MPNST development. These two mouse models provide the means to address fundamental aspects of disease development and to test therapeutic strategies.
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Affiliation(s)
- K Cichowski
- Department of Biology and Center for Cancer Research and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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437
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Inoue H, Noumi T, Nagata M, Murakami H, Kanazawa H. Targeted disruption of the gene encoding the proteolipid subunit of mouse vacuolar H(+)-ATPase leads to early embryonic lethality. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1413:130-8. [PMID: 10556625 DOI: 10.1016/s0005-2728(99)00096-1] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Vacuolar H(+)-ATPase (V-ATPase) is responsible for acidification of intracellular compartments in eukaryotic cells. Its 16-kDa subunit (proteolipid, PL16) plays a central role in V-ATPase function, forming the principal channel via which protons are translocated. To elucidate physiological roles of V-ATPase in mammalian cell function and embryogenesis, we attempted to generate a PL16 null mutant mouse by gene-targeting. Mice heterozygous (PL16(+/-)) for the proteolipid mutation were intercrossed and their offspring were classified according to genotype. There were no homozygous (PL16(-/-)) pups among 69 neonates examined, but a few PL16(-/-) embryos were found during the pre-implantation stages of embryonic development, up to day 3.5 post-coitum. These results suggested that PL16 (and hence V-ATPase) may play an essential role in cell proliferation and viability during early embryogenesis. PL16(+/-) mice were indistinguishable from their wild-type littermates and displayed no discernible abnormalities, although the PL16 mRNA level in PL16(+/-) mice decreased to about one-half of wild-type levels.
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Affiliation(s)
- H Inoue
- Department of Biological Science, Graduate School of Science, Osaka University, Machikaneyama-cho 1-16, Toyonaka city, Osaka, Japan
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438
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Affiliation(s)
- F O Smith
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, USA
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439
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Abstract
Tumor suppressor genes have a diversity of functions, but they have in common the property of inhibiting neoplastic transformation. When they become inactivated, a constraint is removed that allows cells to grow inappropriately. Mutations in these genes are now thought to be the initiating events in most cancers. The first tumor suppressor gene was discovered through its role in retinoblastoma, and many other tumor suppressor genes also have important ophthalmic manifestations. The first group of tumor suppressor genes to be discussed are those involved in retinoblastoma and uveal melanoma. These are among the most frequently mutated genes in human cancer and are key regulators of growth and homeostasis. The second group of genes is associated with specific hereditary tumor syndromes with ophthalmic manifestations. These genes function in a variety of molecular pathways and are associated with neoplastic and non-neoplastic abnormalities in restricted tissue distributions. Research on tumor suppressor genes continues to shed light on the molecular pathophysiology of ophthalmic tumors and will increasingly yield diagnostic and therapeutic applications.
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Affiliation(s)
- J W Harbour
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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440
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Abstract
Oncogenic RAS alleles encode proteins that accumulate in the guanosine triphosphate (GTP)-bound state. Because post-translational processing of Ras by farnesyltransferase is essential for biologic function, inhibitors of this enzyme have been developed as rational cancer therapeutics. We have investigated farnesyltransferase inhibitor (FTI) L-744,832 in an in vivo murine model of myeloid leukemia that is associated with inactivation of the Nf1 tumor suppressor gene.Nf1 encodes a GTPase activating protein for Ras, andNf1-deficient (Nf1−/−) hematopoietic cells show hyperactive Ras signaling through the mitogen-activated protein (MAP) kinase pathway. L-744,832 inhibited H-Ras prenylation in cell lines and in primary hematopoietic cells and abrogated the in vitro growth of myeloid progenitor colonies in response to granulocyte-macrophage colony-stimulating factor (GM-CSF). This FTI also partially blocked GM-CSF–induced MAP kinase activation, but did not reduce constitutively elevated levels of MAP kinase activity in primaryNf1−/− cells. Injection of a single dose of 40 or 80 mg/kg of L-744,832 increased the amount of unprocessed H-Ras in bone marrow cells, but had no detectable effect on N-Ras. Adoptive transfer ofNf1−/− hematopoietic cells into irradiated mice induces a myeloproliferative disorder that did not respond to L-744,832 treatment. We speculate that the lack of efficacy in this model is due to the resistance of N-Ras and K-Ras processing to inhibition by this FTI.
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441
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Winnier GE, Kume T, Deng K, Rogers R, Bundy J, Raines C, Walter MA, Hogan BL, Conway SJ. Roles for the winged helix transcription factors MF1 and MFH1 in cardiovascular development revealed by nonallelic noncomplementation of null alleles. Dev Biol 1999; 213:418-31. [PMID: 10479458 DOI: 10.1006/dbio.1999.9382] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The murine Mf1 and Mfh1 genes have overlapping patterns of expression in the embryo and encode forkhead/winged helix transcription factors with virtually identical DNA binding domains. Previous studies have shown that Mfh1 null mutants have severe cardiovascular defects, including interruptions and coarctations of the aortic arch and ventricular septal defects (Iida et al., Development 124, 4627-4638, 1997). Here, we show that Mf1(lacZ) homozygous null mutants also have a similar spectrum of cardiovascular abnormalities. Moreover, most embryos doubly heterozygous for Mfh1(tm1) and Mf1(lacZ) die before birth with interruptions and coarctations of the aortic arch, dysgenesis of the aortic and pulmonary valves, ventricular septal defects, and other cardiac anomalies. This nonallelic noncomplementation and the similar patterns of expression of the two genes in the mesenchyme and endothelial cells of the branchial arches, outflow tract, and heart suggest that Mf1 and Mfh1 play interactive roles in the morphogenesis of the cardiovascular system. Implications for the development of human congenital heart defects are discussed.
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Affiliation(s)
- G E Winnier
- Howard Hughes Medical Institute, Vanderbilt University Medical Center, Nashville, Tennessee, 37232-2175, USA
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442
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Affiliation(s)
- J F Moley
- Department of Surgery, Washington University School of Medicine, St Louis, Missouri, USA
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443
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Gutmann DH, Loehr A, Zhang Y, Kim J, Henkemeyer M, Cashen A. Haploinsufficiency for the neurofibromatosis 1 (NF1) tumor suppressor results in increased astrocyte proliferation. Oncogene 1999; 18:4450-9. [PMID: 10442636 DOI: 10.1038/sj.onc.1202829] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Individuals affected with neurofibromatosis 1 (NF1) harbor increased numbers of GFAP-immunoreactive cerebral astrocytes and develop astrocytomas that can lead to blindness and death. Mice heterozygous for a targeted Nf1 mutation (Nf1+/-) were employed as a model for the human disease to evaluate the hypothesis that reduced NF1 protein (neurofibromin) expression may confer a growth advantage for astrocytes, such that inactivation of only one NF1 allele is sufficient for abnormal astrocyte proliferation. Here, we report that Nf17+/- mice have increased numbers of cerebral astrocytes and increased astrocyte proliferation compared to wild-type littermates. Intriguingly, primary Nf1+/- astrocyte cultures failed to demonstrate a cell-autonomous growth advantage unless they were cocultured with C17 neuronal cells. This C17 neuronal cell-induced Nf1+/- increase in proliferation was blocked by MEK inhibition (PD98059), suggesting a p21-ras-dependent effect. Furthermore, mice heterozygous for a targeted mutation in another GAP molecule, p120-GAP, demonstrated no increases in cerebral astrocyte number. These findings suggest that reduced NF1 expression results in a cell context-dependent increase in astrocyte proliferation that may be sufficient for the development of astrocytic growth abnormalities in patients with NF1.
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Affiliation(s)
- D H Gutmann
- Department of Neurology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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444
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Lakkis MM, Golden JA, O'Shea KS, Epstein JA. Neurofibromin deficiency in mice causes exencephaly and is a modifier for Splotch neural tube defects. Dev Biol 1999; 212:80-92. [PMID: 10419687 DOI: 10.1006/dbio.1999.9327] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Neural tube defects are common and serious human congenital anomalies. These malformations have a multifactorial etiology and can be reproduced in mouse models by mutations of numerous individual genes and by perturbation of multiple environmental factors. The identification of specific genetic interactions affecting neural tube closure will facilitate our understanding of molecular pathways regulating normal neural development and will enhance our ability to predict and modify the incidence of spina bifida and other neural tube defects. Here, we report a genetic interaction between Nf1, encoding the intracellular signal transduction protein neurofibromin, and Pax3, a transcription factor gene mutated in the Splotch mouse. Both Pax3 and Nf1 are important for the development of neural crest-derived structures and the central nervous system. Splotch is an established model of folate-sensitive neural tube defects, and homozygous mutant embryos develop spina bifida and sometimes exencephaly. Neural development is grossly normal in heterozygotes and neural tube defects are not seen. In contrast, we found a low incidence of neural tube defects in heterozygous Splotch mice that also harbored a mutation in one Nf1 allele. All compound homozygotes had severe neural tube defects and died earlier in embryogenesis than either Nf1(-/-) or Sp(-/-) embryos. We also report occasional exencephaly in Nf1(-/-) mice and identify more subtle CNS abnormalities in normal-appearing Nf1(-/-) embryos. Though other genetic loci and environmental factors affect the incidence of neural tube defects in Splotch mice, these results establish Nf1 as the first known gene to act as a modifier of neural tube defects in Splotch.
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Affiliation(s)
- M M Lakkis
- Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, 19104, USA
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445
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Mechtersheimer G, Ota�o-Joos M, Ohl S, Benner A, Lehnert T, Willeke F, M�ller P, Otto HF, Lichter P, Joos S. Analysis of chromosomal imbalances in sporadic and NF1-associated peripheral nerve sheath tumors by comparative genomic hybridization. Genes Chromosomes Cancer 1999. [DOI: 10.1002/(sici)1098-2264(199908)25:4<362::aid-gcc8>3.0.co;2-q] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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446
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Yu W, Sipowicz MA, Haines DC, Birely L, Diwan BA, Riggs CW, Kasprzak KS, Anderson LM. Preconception urethane or chromium(III) treatment of male mice: multiple neoplastic and non-neoplastic changes in offspring. Toxicol Appl Pharmacol 1999; 158:161-76. [PMID: 10406931 DOI: 10.1006/taap.1999.8692] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Increase in neoplasia in offspring after preconception exposure of parents presents puzzling features such as high frequency of effects and lack of Mendelian inheritance. The present study examined the hypothesis that preconception carcinogenesis involves an increase in the rate of occurrence of neoplasms with a spontaneous incidence. Male NIH Swiss mice (12 per group) were exposed 2 weeks before mating (once, ip) to urethane (1.5 g/kg) or chromium(III) chloride (1 mmol/kg). Offspring (48-78/sex/group) were examined for all grossly apparent changes when moribund or at natural death, followed by histopathological diagnosis and statistical analysis. Significant exposure-related changes occurred in multiple organs. Ten to 20 percent of offspring showed changes related to paternal exposure, including at least one sired by most treated males. Pheochromocytomas occurred in both male and female offspring after both treatments, with none in controls. These neoplasms are rare in mice and suggest endocrine dysfunction as a component of preconception carcinogenesis. This was supported by increases in thyroid follicular cell and Harderian gland tumors, ovarian cysts, and uterine abnormalities. Lung tumors were increased in female offspring only. Effects seen in offspring only after paternal urethane exposure were an increase in preneoplasia/neoplasia in the glandular stomach (males) and in females, increased lymphoma but decreased incidence of histiocytic sarcoma. Increases in incidence of male reproductive gland tumors and of renal non-neoplastic lesions occurred only after chromium exposure. Thus, preconception exposure of fathers to toxicants had a significant impact on both neoplastic and non-neoplastic changes in almost all tissues in which these lesions often occur naturally during the aging process.
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Affiliation(s)
- W Yu
- Division of Basic Sciences, National Cancer Institute, Frederick, Maryland, 21702, USA
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447
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Abstract
Abstract
Therapy-related acute myeloid leukemia and myelodysplastic syndrome (t-AML and MDS) are severe late complications of treatment with genotoxic chemotherapeutic agents. Children with neurofibromatosis type 1 (NF1) are predisposed to malignant myeloid disorders that are associated with inactivation of the NF1 tumor suppressor gene in the leukemic clone. Recent clinical data suggest that NF1 might be also associated with an increased risk of t-AML after treatment with alkyating agents. To test this hypothesis, we administered cyclophosphamide or etoposide to cohorts of wild-type and heterozygousNf1 knockout mice. Cyclophosphamide exposure cooperated strongly with heterozygous inactivation of Nf1 in myeloid leukemogenesis, while etoposide did not. Somatic loss of the normalNf1 allele correlated with clinical disease and was more common in 129/Sv mice than in 129/Sv × C57BL/6 animals. Leukemic cells showing loss of heterozygosity at Nf1 retained a structural allele on each chromosome 11 homolog. These studies establish a novel in vivo model of alkylator-induced myeloid malignancy that will facilitate mechanistic and translational studies.
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448
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Abstract
Therapy-related acute myeloid leukemia and myelodysplastic syndrome (t-AML and MDS) are severe late complications of treatment with genotoxic chemotherapeutic agents. Children with neurofibromatosis type 1 (NF1) are predisposed to malignant myeloid disorders that are associated with inactivation of the NF1 tumor suppressor gene in the leukemic clone. Recent clinical data suggest that NF1 might be also associated with an increased risk of t-AML after treatment with alkyating agents. To test this hypothesis, we administered cyclophosphamide or etoposide to cohorts of wild-type and heterozygousNf1 knockout mice. Cyclophosphamide exposure cooperated strongly with heterozygous inactivation of Nf1 in myeloid leukemogenesis, while etoposide did not. Somatic loss of the normalNf1 allele correlated with clinical disease and was more common in 129/Sv mice than in 129/Sv × C57BL/6 animals. Leukemic cells showing loss of heterozygosity at Nf1 retained a structural allele on each chromosome 11 homolog. These studies establish a novel in vivo model of alkylator-induced myeloid malignancy that will facilitate mechanistic and translational studies.
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449
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Rosenbaum T, Engelbrecht V, Krölls W, van Dorsten FA, Hoehn-Berlage M, Lenard HG. MRI abnormalities in neurofibromatosis type 1 (NF1): a study of men and mice. Brain Dev 1999; 21:268-73. [PMID: 10392751 DOI: 10.1016/s0387-7604(99)00024-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Hyperintense lesions on T2-weighted MR images of the brain, predominantly located in the basal ganglia, the brainstem and cerebellum, are a frequent finding in patients with neurofibromatosis type 1. Nature and significance of these lesions are still unknown so that the term 'unidentified bright objects' (UBOs) has been introduced to allow an unbiased description. We analyzed brain MRI scans of 31 children with definite diagnosis of neurofibromatosis type 1 according to the NIH criteria. High-intensity lesions on T2-weighted images were present in 86% of the patients. They did not correlate to other MRI findings such as optic pathway gliomas and were not indicative of intellectual impairment. Additionally, brain MR imaging of Nf1 knockout mice was performed to find out if similar abnormalities are present in this animal model. A total of 9 Nf1 knockout mice was examined on a dedicated animal MRI scanner at 4.7 Tesla but no evidence of high-signal intensity lesions on T2-weighted images was found. Therefore, the Nf1 mouse model seems to be unhelpful in providing further insights into the histological basis of hyperintense MRI abnormalities in NF1 patients.
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Affiliation(s)
- T Rosenbaum
- Department of Neuropediatrics, Children's Hospital, Heinrich-Heine-University, Düsseldorf, Germany.
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450
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Li J, Liu KC, Jin F, Lu MM, Epstein JA. Transgenic rescue of congenital heart disease and spina bifida in Splotch mice. Development 1999; 126:2495-503. [PMID: 10226008 DOI: 10.1242/dev.126.11.2495] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pax3-deficient Splotch mice display neural tube defects and an array of neural crest related abnormalities including defects in the cardiac outflow tract, dorsal root ganglia and pigmentation. Pax3 is expressed in neural crest cells that emerge from the dorsal neural tube. Pax3 is also expressed in the somites, through which neural crest cells migrate, where it is required for hypaxial muscle development. Homozygous mutant Splotch embryos die by embryonic day 14. We have utilized the proximal 1.6 kb Pax3 promoter and upstream regulatory elements to engineer transgenic mice reproducing endogenous Pax3 expression in neural tube and neural crest, but not the somite. Over expression of Pax3 in these tissues reveals no discernible phenotype. Breeding of transgenic mice onto a Splotch background demonstrates that neural tube and neural crest expression of Pax3 is sufficient to rescue neural tube closure, cardiac development and other neural crest related defects. Transgenic Splotch mice survive until birth at which time they succumb to respiratory failure secondary to absence of a muscular diaphragm. Limb muscles are also absent. These results indicate that regulatory elements sufficient for functional expression of Pax3 required for cardiac development and neural tube closure are contained within the region 1.6 kb upstream of the Pax3 transcriptional start site. In addition, the single Pax3 isoform used for this transgene is sufficient to execute these developmental processes. Although the extracellular matrix and the environment of the somites through which neural crest migrates is known to influence neural crest behavior, our results indicate that Pax3-deficient somites are capable of supporting proper neural crest migration and function suggesting a cell autonomous role for Pax3 in neural crest.
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Affiliation(s)
- J Li
- Cardiovascular Division, Department of Medicine, Department of Cell and Developmental Biology and the Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
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