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Gustafson JA, Park SS, Cunningham ML. Calvarial osteoblast gene expression in patients with craniosynostosis leads to novel polygenic mouse model. PLoS One 2019; 14:e0221402. [PMID: 31442251 PMCID: PMC6707563 DOI: 10.1371/journal.pone.0221402] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 08/06/2019] [Indexed: 12/21/2022] Open
Abstract
Craniosynostosis is the premature fusion of the sutures of the calvaria and is principally designated as being either syndromic (demonstrating characteristic extracranial malformations) or non-syndromic. While many forms of syndromic craniosynostosis are known to be caused by specific mutations, the genetic etiology of non-syndromic, single-suture craniosynostosis (SSC) is poorly understood. Based on the low recurrence rate (4-7%) and the fact that recurrent mutations have not been identified for most cases of SSC, we propose that some cases of isolated, single suture craniosynostosis may be polygenic. Previous work in our lab identified a disproportionately high number of rare and novel gain-of-function IGF1R variants in patients with SSC as compared to controls. Building upon this result, we used expression array data from calvarial osteoblasts isolated from infants with and without SSC to ascertain correlations between high IGF1 expression and expression of other osteogenic genes of interest. We identified a positive correlation between increased expression of IGF1 and RUNX2, a gene known to cause SSC with increased gene dosage. Subsequent phosphorylation assays revealed that osteoblast cell lines from cases with high IGF1 expression demonstrated inhibition of GSK3β, a serine/threonine kinase known to inhibit RUNX2, thus activating osteogenesis through the IRS1-mediated Akt pathway. With these findings, we have utilized established mouse strains to examine a novel model of polygenic inheritance (a phenotype influenced by more than one gene) of SSC. Compound heterozygous mice with selective disinhibition of RUNX2 and either overexpression of IGF1 or loss of function of GSK3β demonstrated an increase in the frequency and severity of synostosis as compared to mice with the RUNX2 disinhibition alone. These polygenic mouse models reinforce, in-vivo, that the combination of activation of the IGF1 pathway and disinhibition of the RUNX2 pathway leads to an increased risk of developing craniosynostosis and serves as a model of human SSC.
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Affiliation(s)
- Jonas A. Gustafson
- Seattle Children’s Research Institute, Center for Developmental Biology and Regenerative Medicine, Seattle, Washington, United States of America
| | - Sarah S. Park
- Seattle Children’s Research Institute, Center for Developmental Biology and Regenerative Medicine, Seattle, Washington, United States of America
| | - Michael L. Cunningham
- Seattle Children’s Research Institute, Center for Developmental Biology and Regenerative Medicine, Seattle, Washington, United States of America
- Seattle Children’s Hospital Craniofacial Center, Seattle, Washington, United States of America
- University of Washington, Department of Pediatrics, Seattle, Washington, United States of America
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Optimizing Genomic Methods for Mapping and Identification of Candidate Variants in ENU Mutagenesis Screens Using Inbred Mice. G3-GENES GENOMES GENETICS 2018; 8:401-409. [PMID: 29208648 PMCID: PMC5919724 DOI: 10.1534/g3.117.300292] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Positional cloning of ENU-induced mutations has traditionally relied on analysis of polymorphic variation between two strains. In contrast, the application of whole-genome sequencing (WGS) has enabled gene discovery in mutant lines maintained on an inbred genetic background. This approach utilizes genetic variation derived from ENU-induced variants for mapping and reduces the likelihood of phenotypic variation, making it an ideal method for genetic modifier screening. Here, we describe the results of such a screen, wherein we determined the minimal number of mutant genomic DNA samples to include in our analyses and improved the sensitivity of our screen by individually barcoding each genomic DNA library. We present several unique cases to illustrate this approach's efficacy, including the discovery of two distinct mutations that generate essentially identical mutant phenotypes, the ascertainment of a non-ENU-induced candidate variant through homozygosity mapping, and an approach for the identification of putative dominant genetic modifiers.
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Shi Y, Tu Y, Mecham RP, Bassnett S. Ocular phenotype of Fbn2-null mice. Invest Ophthalmol Vis Sci 2013; 54:7163-73. [PMID: 24130178 DOI: 10.1167/iovs.13-12687] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Fibrillin-2 (Fbn2) is the dominant fibrillin isoform expressed during development of the mouse eye. To test its role in morphogenesis, we examined the ocular phenotype of Fbn2(-/-) mice. METHODS Ocular morphology was assessed by confocal microscopy using antibodies against microfibril components. RESULTS Fbn2(-/-) mice had a high incidence of anterior segment dysgenesis. The iris was the most commonly affected tissue. Complete iridal coloboma was present in 37% of eyes. Dyscoria, corectopia and pseudopolycoria were also common (43% combined incidence). In wild-type (WT) mice, fibrillin-2-rich microfibrils are prominent in the pupillary membrane (PM) during development. In Fbn2-null mice, the absence of Fbn2 was partially compensated for by increased expression of fibrillin-1, although the resulting PM microfibrils were disorganized, compared with WTs. In colobomatous adult Fbn2(-/-) eyes, the PM failed to regress normally, especially beneath the notched region of the iris. Segments of the ciliary body were hypoplastic, and zonular fibers, although relatively plentiful, were unevenly distributed around the lens equator. In regions where the zonular fibers were particularly disturbed, the synchronous differentiation of the underlying lens fiber cells was affected. CONCLUSIONS Fbn2 has an indispensable role in ocular morphogenesis in mice. The high incidence of iris coloboma in Fbn2-null animals implies a previously unsuspected role in optic fissure closure. The observation that fiber cell differentiation was disturbed in Fbn2(-/-) mice raises the possibility that the attachment of zonular fibers to the lens surface may help specify the equatorial margin of the lens epithelium.
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Affiliation(s)
- Yanrong Shi
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri
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Homozygous nonsense mutations in TWIST2 cause Setleis syndrome. Am J Hum Genet 2010; 87:289-96. [PMID: 20691403 DOI: 10.1016/j.ajhg.2010.07.009] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 07/14/2010] [Accepted: 07/15/2010] [Indexed: 12/20/2022] Open
Abstract
The focal facial dermal dysplasias (FFDDs) are a group of inherited developmental disorders in which the characteristic diagnostic feature is bitemporal scar-like lesions that resemble forceps marks. To date, the genetic defects underlying these ectodermal dysplasias have not been determined. To identify the gene defect causing autosomal-recessive Setleis syndrome (type III FFDD), homozygosity mapping was performed with genomic DNAs from five affected individuals and 26 members of the consanguineous Puerto Rican (PR) family originally described by Setleis and colleagues. Microsatellites D2S1397 and D2S2968 were homozygous in all affected individuals, mapping the disease locus to 2q37.3. Haplotype analyses of additional markers in the PR family and a consanguineous Arab family further limited the disease locus to approximately 3 Mb between D2S2949 and D2S2253. Of the 29 candidate genes in this region, the bHLH transcription factor, TWIST2, was initially sequenced on the basis of its known involvement in murine facial development. Homozygous TWIST2 nonsense mutations, c.324C>T and c.486C>T, were identified in the affected members of the Arab and PR families, respectively. Characterization of the expressed mutant proteins, p.Q65X and p.Q119X, by electrophoretic mobility shift assays and immunoblot analyses indicated that they were truncated and unstable. Notably, Setleis syndrome patients and Twist2 knockout mice have similar facial features, indicating the gene's conserved role in mammalian development. Although human TWIST2 and TWIST1 encode highly homologous bHLH transcription factors, the finding that TWIST2 recessive mutations cause an FFDD and dominant TWIST1 mutations cause Saethre-Chotzen craniocynostosis suggests that they function independently in skin and bone development.
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ENU mutagenesis reveals a novel phenotype of reduced limb strength in mice lacking fibrillin 2. PLoS One 2010; 5:e9137. [PMID: 20161761 PMCID: PMC2817753 DOI: 10.1371/journal.pone.0009137] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 01/25/2010] [Indexed: 01/14/2023] Open
Abstract
Background Fibrillins 1 (FBN1) and 2 (FBN2) are components of microfibrils, microfilaments that are present in many connective tissues, either alone or in association with elastin. Marfan's syndrome and congenital contractural arachnodactyly (CCA) result from dominant mutations in the genes FBN1 and FBN2 respectively. Patients with both conditions often present with specific muscle atrophy or weakness, yet this has not been reported in the mouse models. In the case of Fbn1, this is due to perinatal lethality of the homozygous null mice making measurements of strength difficult. In the case of Fbn2, four different mutant alleles have been described in the mouse and in all cases syndactyly was reported as the defining phenotypic feature of homozygotes. Methodology/Principal Findings As part of a large-scale N-ethyl-N-nitrosourea (ENU) mutagenesis screen, we identified a mouse mutant, Mariusz, which exhibited muscle weakness along with hindlimb syndactyly. We identified an amber nonsense mutation in Fbn2 in this mouse mutant. Examination of a previously characterised Fbn2-null mutant, Fbn2fp, identified a similar muscle weakness phenotype. The two Fbn2 mutant alleles complement each other confirming that the weakness is the result of a lack of Fbn2 activity. Skeletal muscle from mutants proved to be abnormal with higher than average numbers of fibres with centrally placed nuclei, an indicator that there are some regenerating muscle fibres. Physiological tests indicated that the mutant muscle produces significantly less maximal force, possibly as a result of the muscles being relatively smaller in Mariusz mice. Conclusions These findings indicate that Fbn2 is involved in integrity of structures required for strength in limb movement. As human patients with mutations in the fibrillin genes FBN1 and FBN2 often present with muscle weakness and atrophy as a symptom, Fbn2-null mice will be a useful model for examining this aspect of the disease process further.
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Abstract
Unraveling the function of the mammalian genome relies heavily on analyses of the laboratory mouse. Because of its powerful genetics and available technologies to manipulate the genome, plus its developmental and physiological similarities to humans, it has become a goal to generate mutations in all mouse genes and analyze the phenotypic consequences. Gene targeting in embryonic stem (ES) cells is the method of choice for making null mutations in known genes of interest. However, forward genetics approaches, in which mutations are produced randomly throughout the genome, has the advantage of producing alleles of varying severity both within known genes, in non-coding regulatory elements, or in other unannotated functional elements. Such forward genetic mutation screens in mice have typically involved treating male mice with N-ethyl-N-nitrosourea (ENU), followed by three generations of breeding to render potential recessive mutations homozygous, at which time phenotype screens can be performed. An alternative strategy for randomly mutagenizing the mouse genome is by chemical treatment of ES cells. This enables the use of multiple alternative chemicals with different mutational spectra, can reduce breeding to two generations, and impart a higher mutational load. Furthermore, ES cell mutagenesis can be used to create banks of clones that can be screened for point mutations in genes of interest, and to conduct forward genetic screens in vitro to detect potential phenotypes prior to generation of mice. In this chapter, we provide a detailed protocol for mutagenizing ES cells with the point mutagen ethylmethanesulfonate (EMS).
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Affiliation(s)
- Robert Munroe
- College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
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Chen YT, Akinwunmi PO, Deng JM, Tam OH, Behringer RR. Generation of a Twist1 conditional null allele in the mouse. Genesis 2007; 45:588-92. [PMID: 17868088 DOI: 10.1002/dvg.20332] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Twist1 is the mouse ortholog of TWIST1, the human gene mutated in Saethre-Chotzen syndrome. Previously, a Twist1 null allele was generated by gene targeting in mouse embryonic stem cells. Twist1 heterozygous mice develop polydactyly and a craniofacial phenotype similar to Saethre-Chotzen patients. Mice homozygous for the Twist1 null allele die around embryonic day 11.5 (E11.5) with cranial neural tube closure and vascular defects, hindering in vivo studies of Twist1 function at later stages of development. Here, we report the generation of a Twist1 conditional null allele in mice that functions like a wild-type allele but can be converted to a null allele upon Cre-mediated recombination.
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Affiliation(s)
- You-Tzung Chen
- Department of Molecular Genetics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA
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Robinson PN, Arteaga-Solis E, Baldock C, Collod-Béroud G, Booms P, De Paepe A, Dietz HC, Guo G, Handford PA, Judge DP, Kielty CM, Loeys B, Milewicz DM, Ney A, Ramirez F, Reinhardt DP, Tiedemann K, Whiteman P, Godfrey M. The molecular genetics of Marfan syndrome and related disorders. J Med Genet 2006; 43:769-87. [PMID: 16571647 PMCID: PMC2563177 DOI: 10.1136/jmg.2005.039669] [Citation(s) in RCA: 276] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Marfan syndrome (MFS), a relatively common autosomal dominant hereditary disorder of connective tissue with prominent manifestations in the skeletal, ocular, and cardiovascular systems, is caused by mutations in the gene for fibrillin-1 (FBN1). The leading cause of premature death in untreated individuals with MFS is acute aortic dissection, which often follows a period of progressive dilatation of the ascending aorta. Recent research on the molecular physiology of fibrillin and the pathophysiology of MFS and related disorders has changed our understanding of this disorder by demonstrating changes in growth factor signalling and in matrix-cell interactions. The purpose of this review is to provide a comprehensive overview of recent advances in the molecular biology of fibrillin and fibrillin-rich microfibrils. Mutations in FBN1 and other genes found in MFS and related disorders will be discussed, and novel concepts concerning the complex and multiple mechanisms of the pathogenesis of MFS will be explained.
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Affiliation(s)
- P N Robinson
- Institute of Medical Genetics, Charité University Hospital, Humboldt University, Augustenburger Platz 1, 13353 Berlin, Germany.
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Michaud EJ, Culiat CT, Klebig ML, Barker PE, Cain KT, Carpenter DJ, Easter LL, Foster CM, Gardner AW, Guo ZY, Houser KJ, Hughes LA, Kerley MK, Liu Z, Olszewski RE, Pinn I, Shaw GD, Shinpock SG, Wymore AM, Rinchik EM, Johnson DK. Efficient gene-driven germ-line point mutagenesis of C57BL/6J mice. BMC Genomics 2005; 6:164. [PMID: 16300676 PMCID: PMC1325271 DOI: 10.1186/1471-2164-6-164] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2005] [Accepted: 11/21/2005] [Indexed: 11/24/2022] Open
Abstract
Background Analysis of an allelic series of point mutations in a gene, generated by N-ethyl-N-nitrosourea (ENU) mutagenesis, is a valuable method for discovering the full scope of its biological function. Here we present an efficient gene-driven approach for identifying ENU-induced point mutations in any gene in C57BL/6J mice. The advantage of such an approach is that it allows one to select any gene of interest in the mouse genome and to go directly from DNA sequence to mutant mice. Results We produced the Cryopreserved Mutant Mouse Bank (CMMB), which is an archive of DNA, cDNA, tissues, and sperm from 4,000 G1 male offspring of ENU-treated C57BL/6J males mated to untreated C57BL/6J females. Each mouse in the CMMB carries a large number of random heterozygous point mutations throughout the genome. High-throughput Temperature Gradient Capillary Electrophoresis (TGCE) was employed to perform a 32-Mbp sequence-driven screen for mutations in 38 PCR amplicons from 11 genes in DNA and/or cDNA from the CMMB mice. DNA sequence analysis of heteroduplex-forming amplicons identified by TGCE revealed 22 mutations in 10 genes for an overall mutation frequency of 1 in 1.45 Mbp. All 22 mutations are single base pair substitutions, and nine of them (41%) result in nonconservative amino acid substitutions. Intracytoplasmic sperm injection (ICSI) of cryopreserved spermatozoa into B6D2F1 or C57BL/6J ova was used to recover mutant mice for nine of the mutations to date. Conclusions The inbred C57BL/6J CMMB, together with TGCE mutation screening and ICSI for the recovery of mutant mice, represents a valuable gene-driven approach for the functional annotation of the mammalian genome and for the generation of mouse models of human genetic diseases. The ability of ENU to induce mutations that cause various types of changes in proteins will provide additional insights into the functions of mammalian proteins that may not be detectable by knockout mutations.
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Affiliation(s)
- Edward J Michaud
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
- The University of Tennessee-Oak Ridge National Laboratory Graduate School of Genome Science and Technology, Oak Ridge, TN 37830, USA
| | - Cymbeline T Culiat
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
- The University of Tennessee-Oak Ridge National Laboratory Graduate School of Genome Science and Technology, Oak Ridge, TN 37830, USA
| | - Mitchell L Klebig
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
- The University of Tennessee-Oak Ridge National Laboratory Graduate School of Genome Science and Technology, Oak Ridge, TN 37830, USA
- Department of Biochemistry, Cellular, and Molecular Biology, The University of Tennessee, Knoxville, TN 37996, USA
| | - Paul E Barker
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - KT Cain
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Debra J Carpenter
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Lori L Easter
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Carmen M Foster
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Alysyn W Gardner
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - ZY Guo
- SpectruMedix, 2124 Old Gatesburg Road, State College, PA 16803, USA
| | - Kay J Houser
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Lori A Hughes
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Marilyn K Kerley
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Zhaowei Liu
- SpectruMedix, 2124 Old Gatesburg Road, State College, PA 16803, USA
| | - Robert E Olszewski
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Irina Pinn
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Ginger D Shaw
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Sarah G Shinpock
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Ann M Wymore
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
| | - Eugene M Rinchik
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
- The University of Tennessee-Oak Ridge National Laboratory Graduate School of Genome Science and Technology, Oak Ridge, TN 37830, USA
- Department of Biochemistry, Cellular, and Molecular Biology, The University of Tennessee, Knoxville, TN 37996, USA
- Taconic, 273 Hover Avenue, Germantown, NY 12526, USA
| | - Dabney K Johnson
- Life Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831, USA
- The University of Tennessee-Oak Ridge National Laboratory Graduate School of Genome Science and Technology, Oak Ridge, TN 37830, USA
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Munroe RJ, Ackerman SL, Schimenti JC. Genomewide two-generation screens for recessive mutations by ES cell mutagenesis. Mamm Genome 2005; 15:960-5. [PMID: 15599554 DOI: 10.1007/s00335-004-2406-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Accepted: 08/24/2004] [Indexed: 10/24/2022]
Abstract
Forward genetic mutation screens in mice are typically begun by mutagenizing the germline of male mice with N-ethyl-N-nitrosourea (ENU). Genomewide recessive mutations transmitted by these males can be rendered homozygous after three generations of breeding, at which time phenotype screens can be performed. An alternative strategy for randomly mutagenizing the mouse genome is by chemical treatment of embryonic stem (ES) cells. Here we demonstrate the feasibility of performing genome-wide mutation screens with only two generations of breeding. Mice potentially homozygous for mutations were obtained by crossing chimeras derived from ethylmethane sulfonate (EMS)-mutagenized ES cells to their daughters, or by intercrossing offspring of chimeras. This strategy was possible because chimeras transmit variations of the same mutagenized diploid genome, whereas ENU-treated males transmit numerous unrelated genomes. This also results in a doubling of screenable mutations in a pedigree compared to germline ENU mutagenesis. Coupled with the flexibility to treat ES cells with a variety of potent mutagens and the ease of producing distributable, quality-controlled, long-term supplies of cells in a single experiment, this strategy offers a number of advantages for conducting forward genetic screens in mice.
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Blanc I, Bach A, Lallemand Y, Perrin-Schmitt F, Guénet JL, Robert B. A new mouse limb mutation identifies a Twist allele that requires interacting loci on chromosome 4 for its phenotypic expression. Mamm Genome 2004; 14:797-804. [PMID: 14724733 DOI: 10.1007/s00335-003-2284-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2003] [Accepted: 07/18/2003] [Indexed: 10/26/2022]
Abstract
Pluridigite ( Pdt) is a semi-dominant mutation obtained after a mutagenesis experiment with ethyl-nitroso-urea (ENU). The mutant exhibits abnormal skeletal pattern formation characterized by the formation of extra digits (polydactyly) in the preaxial (anterior) part of the hindlimbs. The phenotype shows incomplete penetrance, depending on the genetic background. In an F2 cross with C57BL/6, the phenotype could not be associated with a single locus. Strong linkage was observed with markers located on Chromosome (Chr) 12, in a 2-cM interval between D12Mit136 and D12Mit153. This region contains the Twist gene, and we show that the [Pdt] phenotype is dependent upon a new allele of Twist. We further identified that the whole Chr 4 is associated with the [Pdt] phenotype. The Pluridigite phenotype thus results from the combination of a Twist mutant allele and at least two additional loci.
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Affiliation(s)
- Isabelle Blanc
- Unité Postulante de Génétique Moléculaire de la Morphogenèse, URA CNRS 2578, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France
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12
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Brouha B, Meischl C, Ostertag E, de Boer M, Zhang Y, Neijens H, Roos D, Kazazian HH. Evidence consistent with human L1 retrotransposition in maternal meiosis I. Am J Hum Genet 2002; 71:327-36. [PMID: 12094329 PMCID: PMC379165 DOI: 10.1086/341722] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2002] [Accepted: 05/10/2002] [Indexed: 11/04/2022] Open
Abstract
We have used a unique polymorphic 3' transduction to show that a human L1, or LINE-1 (long interspersed nucleotide element-1), retrotransposition event most likely occurred in the maternal primary oocyte during meiosis I. We characterized a truncated L1 retrotransposon with a 3' transduction that was inserted, in a Dutch male patient, into the X-linked gene CYBB, thereby causing chronic granulomatous disease. We used the unique flanking sequence to localize the precursor L1 locus, LRE3, to chromosome 2q24.1. In a cell culture assay, the retrotransposition frequency of LRE3 is greater than that for any other element that has been tested to date. The patient's mother had two LRE3 alleles that differed slightly in the 3'-flanking genomic DNA. The patient had a single LRE3 allele that was identical to one of the maternal alleles; however, the patient's insertion matched the maternal LRE3 allele that he did not inherit. Other data indicate that there is only a small chance that the father (unavailable for analysis) carries the precursor LRE3 allele. In addition, paternal origin of the insertion would have required that an LRE3 mRNA transcribed before meiosis II be carried separately from its precursor LRE3 allele in the fertilizing sperm. Since the mother carries a potential precursor allele and the insertion was on the patient's maternal X chromosome, it is highly likely that the insertion originated during maternal meiosis I.
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Affiliation(s)
- Brook Brouha
- Department of Genetics, University of Pennsylvania School of Medicine, 475 Clinical Research Building, 415 Curie Boulevard, Philadelphia, PA 19104, USA
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Abstract
L1 retrotransposons comprise 17% of the human genome. Although most L1s are inactive, some elements remain capable of retrotransposition. L1 elements have a long evolutionary history dating to the beginnings of eukaryotic existence. Although many aspects of their retrotransposition mechanism remain poorly understood, they likely integrate into genomic DNA by a process called target primed reverse transcription. L1s have shaped mammalian genomes through a number of mechanisms. First, they have greatly expanded the genome both by their own retrotransposition and by providing the machinery necessary for the retrotransposition of other mobile elements, such as Alus. Second, they have shuffled non-L1 sequence throughout the genome by a process termed transduction. Third, they have affected gene expression by a number of mechanisms. For instance, they occasionally insert into genes and cause disease both in humans and in mice. L1 elements have proven useful as phylogenetic markers and may find other practical applications in gene discovery following insertional mutagenesis in mice and in the delivery of therapeutic genes.
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Affiliation(s)
- E M Ostertag
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
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