scholarly journals The Heterozygous Disproportionate Micromelia (Dmm) Mouse: Morphological Changes in Fetal Cartilage Precede Postnatal Dwarfism and Compared With Lethal Homozygotes Can Explain the Mild Phenotype

2008 ◽  
Vol 56 (11) ◽  
pp. 1003-1011 ◽  
Author(s):  
Robert E. Seegmiller ◽  
Brandon D. Bomsta ◽  
Laura C. Bridgewater ◽  
Cindy M. Niederhauser ◽  
Carolina Montaño ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Coding Region ◽  
Transmission Microscopy ◽  
Mild Phenotype ◽  
Morphological Alterations ◽  
Rib Cartilage ◽  
Negative Effect ◽  
Reduced Rate

The disproportionate micromelia ( Dmm) mouse has a mutation in the C-propeptide coding region of the Co/2a1 gene that causes lethal dwarfism when homozygous ( Dmm/Dmm) but causes only mild dwarfism observable ∼1-week postpartum when heterozygous ( Dmm/+). The purpose of this study was 2-fold: first, to analyze and quantify morphological changes that precede the expression of mild dwarfism in Dmm/+ animals, and second, to compare morphological alterations between Dmm/+ and Dmm/Dmm fetal cartilage that may correlate with the marked skeletal differences between mild and lethal dwarfism. Light and electron transmission microscopy were used to visualize structure of chondrocytes and extracellular matrix (ECM) of fetal rib cartilage. Both Dmm/+ and Dmm/Dmm fetal rib cartilage had significantly larger chondrocytes, greater cell density, and less ECM per unit area than +/+ littermates. Quantitative RT-PCR showed a decrease in aggrecan mRNA in Dmm/+ vs +/+ cartilage. Furthermore, the cytoplasm of chondrocytes in Dmm/+ and Dmm/Dmm cartilage was occupied by significantly more distended rough endoplasmic reticulum (RER) compared with wild-type chondrocytes. Fibril diameters and packing densities of +/+ and Dmm/+ cartilage were similar, but Dmm/Dmm cartilage showed thinner, sparsely distributed fibrils. These findings support the prevailing hypothesis that a C-propeptide mutation could interrupt the normal assembly and secretion of Type II procollagen trimers, resulting in a buildup of proα1(II) chains in the RER and a reduced rate of matrix synthesis. Thus, intracellular entrapment of proα1(II) seems to be primarily responsible for the dominant-negative effect of the Dmm mutation in the expression of dwarfism.

scholarly journals Mice Null for Sox18 Are Viable and Display a Mild Coat Defect

2000 ◽  
Vol 20 (24) ◽  
pp. 9331-9336 ◽  
Author(s):  
David Pennisi ◽  
Josephine Bowles ◽  
Andras Nagy ◽  
George Muscat ◽  
Peter Koopman
Keyword(s):  
Vascular Endothelium ◽  
Point Mutations ◽  
Hair Follicles ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Mild Phenotype ◽  
Negative Effect ◽  
Cardiovascular Defects ◽  
Sox Proteins ◽  
Hair Shafts

ABSTRACT We have previously shown that Sox18 is expressed in developing vascular endothelium and hair follicles during mouse embryogenesis and that point mutations in Sox18 are the underlying cause of cardiovascular and hair follicle defects inragged (Ra) mice. Here we describe the analysis of Sox18 −/− mice produced by gene targeting. Despite the profound defects seen in Ra mice,Sox18 −/− mice have no obvious cardiovascular defects and only a mild coat defect with a reduced proportion of zigzag hairs. A reduction in the amount of pheomelanin pigmentation in hair shafts was also observed; later-forming hair follicles showed a reduced subapical pheomelanin band, giving Sox18 −/−mice a slightly darker appearance than Sox18 +/+and Sox18 +/− siblings.Sox18 −/− mice are viable and fertile and show no difference in the ability to thrive relative to littermates. Because of the mild effect of the mutation on the phenotype ofSox18 −/− mice, we conclude that the semidominant nature of the Ra mutations is due to atrans-dominant negative effect mediated by the mutant SOX18 proteins rather than haploinsufficiency as has been observed for otherSOX genes. Due to the similarity of SOX18 to other subgroup F SOX proteins, SOX7 and −17, and the overlap in expression of these genes, functional redundancy amongst these SOX proteins could also account for the mild phenotype of Sox18 −/−mice.

scholarly journals A Dominant Negative Effect of eth-1r, a Mutant Allele of the Neurospora crassa S-Adenosylmethionine Synthetase-Encoding Gene Conferring Resistance to the Methionine Toxic Analogue Ethionine

Genetics ◽  
1996 ◽  
Vol 144 (4) ◽  
pp. 1455-1462
Author(s):  
José L Barra ◽  
Mario R Mautino ◽  
Alberto L Rosa
Keyword(s):  
Neurospora Crassa ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Resistant Phenotype ◽  
Negative Effect ◽  
Encoding Gene ◽  
Adenosylmethionine Synthetase ◽  
Adomet Synthetase ◽  
Identical Gene

eth-1r a thermosensitive allele of the Neurospora crassa S-adenosylmethionine (AdoMet) synthetase gene that confers ethionine resistance, has been cloned and sequenced. Replacement of an aspartic amino acid residue (D48 → N48), perfectly conserved in prokaryotic, fungal and higher eukaryotic AdoMet synthetases, was found responsible for both thermosensitivity and ethionine resistance conferred by eth-1r. Gene fusion constructs, designed to overexpress eth-1r in vivo, render transformant cells resistant to ethionine. Dominance of ethionine resistance was further demonstrated in eth-1  +/eth-1r partial diploids carrying identical gene doses of both alleles. Heterozygous eth-1  +/eth-1r cells have, at the same time, both the thermotolerance conferred by eth-1  + and the ethionine-resistant phenotype conferred by eth-1r. AdoMet levels and AdoMet synthetase activities were dramatically decreased in heterozygous eth-1  +/eth-1r cells. We propose that this negative effect exerted by eth-1r results from the in vivo formation of heteromeric eth-1  +/eth-1r AdoMet synthetase molecules.

scholarly journals Restoration of Silencing in Saccharomyces cerevisiae by Tethering of a Novel Sir2-Interacting Protein, Esc8

Genetics ◽  
2002 ◽  
Vol 162 (2) ◽  
pp. 633-645 ◽  
Author(s):  
Guido Cuperus ◽  
David Shore
Keyword(s):  
Protein A ◽  
Dominant Negative ◽  
Class I ◽  
Dominant Negative Effect ◽  
Rna Pol Ii ◽  
Interacting Protein ◽  
Nucleosome Remodeling ◽  
Negative Effect ◽  
Close Homolog

Abstract We previously described two classes of SIR2 mutations specifically defective in either telomeric/HM silencing (class I) or rDNA silencing (class II) in S. cerevisiae. Here we report the identification of genes whose protein products, when either overexpressed or directly tethered to the locus in question, can establish silencing in SIR2 class I mutants. Elevated dosage of SCS2, previously implicated as a regulator of both inositol biosynthesis and telomeric silencing, suppressed the dominant-negative effect of a SIR2-143 mutation. In a genetic screen for proteins that restore silencing when tethered to a telomere, we isolated ESC2 and an uncharacterized gene, (YOL017w), which we call ESC8. Both Esc2p and Esc8p interact with Sir2p in two-hybrid assays, and the Esc8p-Sir2 interaction is detected in vitro. Interestingly, Esc8p has a single close homolog in yeast, the ISW1-complex factor Ioc3p, and has also been copurified with Isw1p, raising the possibility that Esc8p is a component of an Isw1p-containing nucleosome remodeling complex. Whereas esc2 and esc8 deletion mutants alone have only marginal silencing defects, cells lacking Isw1p show a strong silencing defect at HMR but not at telomeres. Finally, we show that Esc8p interacts with the Gal11 protein, a component of the RNA pol II mediator complex.

scholarly journals Dominant Negative Mutants Implicate STAT5 in Myeloid Cell Proliferation and Neutrophil Differentiation

Blood ◽  
1999 ◽  
Vol 93 (12) ◽  
pp. 4154-4166 ◽  
Author(s):  
Robert L. Ilaria ◽  
Robert G. Hawley ◽  
Richard A. Van Etten
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Cytokine Signaling ◽  
Transactivation Domain ◽  
Negative Effects ◽  
Murine Bone Marrow ◽  
Negative Effect

Abstract STAT5 is a member of the signal transducers and activation of transcription (STAT) family of latent transcription factors activated in a variety of cytokine signaling pathways. We introduced alanine substitution mutations in highly conserved regions of murine STAT5A and studied the mutants for dimerization, DNA binding, transactivation, and dominant negative effects on erythropoietin-induced STAT5-dependent transcriptional activation. The mutations included two near the amino-terminus (W255KR→AAA and R290QQ→AAA), two in the DNA-binding domain (E437E→AA and V466VV→AAA), and a carboxy-terminal truncation of STAT5A (STAT5A/▵53C) analogous to a naturally occurring isoform of rat STAT5B. All of the STAT mutant proteins were tyrosine phosphorylated by JAK2 and heterodimerized with STAT5B except for the WKR mutant, suggesting an important role for this region in STAT5 for stabilizing dimerization. The WKR, EE, and VVV mutants had no detectable DNA-binding activity, and the WKR and VVV mutants, but not EE, were defective in transcriptional induction. The VVV mutant had a moderate dominant negative effect on erythropoietin-induced STAT5 transcriptional activation, which was likely due to the formation of heterodimers that are defective in DNA binding. Interestingly, the WKR mutant had a potent dominant negative effect, comparable to the transactivation domain deletion mutant, ▵53C. Stable expression of either the WKR or ▵53C STAT5 mutants in the murine myeloid cytokine-dependent cell line 32D inhibited both interleukin-3–dependent proliferation and granulocyte colony-stimulating factor (G-CSF)–dependent differentiation, without induction of apoptosis. Expression of these mutants in primary murine bone marrow inhibited G-CSF–dependent granulocyte colony formation in vitro. These results demonstrate that mutations in distinct regions of STAT5 exert dominant negative effects on cytokine signaling, likely through different mechanisms, and suggest a role for STAT5 in proliferation and differentiation of myeloid cells.

scholarly journals Insight into the AcrAB-TolC Complex Assembly Process Learned from Competition Studies

Antibiotics ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 830
Author(s):  
Prasangi Rajapaksha ◽  
Isoiza Ojo ◽  
Ling Yang ◽  
Ankit Pandeya ◽  
Thilini Abeywansha ◽  
...  
Keyword(s):  
Efflux Pump ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Assembly Process ◽  
Multidrug Efflux ◽  
E Coli ◽  
Multidrug Efflux Pumps ◽  
Negative Effect ◽  
Dynamic Assembly ◽  
Pump Assembly

The RND family efflux pump AcrAB-TolC in E. coli and its homologs in other Gram-negative bacteria are major players in conferring multidrug resistance to the cells. While the structure of the pump complex has been elucidated with ever-increasing resolution through crystallography and Cryo-EM efforts, the dynamic assembly process remains poorly understood. Here, we tested the effect of overexpressing functionally defective pump components in wild type E. coli cells to probe the pump assembly process. Incorporation of a defective component is expected to reduce the efflux efficiency of the complex, leading to the so called “dominant negative” effect. Being one of the most intensively studied bacterial multidrug efflux pumps, many AcrA and AcrB mutations have been reported that disrupt efflux through different mechanisms. We examined five groups of AcrB and AcrA mutants, defective in different aspects of assembly and substrate efflux. We found that none of them demonstrated the expected dominant negative effect, even when expressed at concentrations many folds higher than their genomic counterpart. The assembly of the AcrAB-TolC complex appears to have a proof-read mechanism that effectively eliminated the formation of futile pump complex.

scholarly journals The Diagnostic Journey of a Patient with Prader–Willi-Like Syndrome and a Unique Homozygous SNURF-SNRPN Variant; Bio-Molecular Analysis and Review of the Literature

Genes ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 875
Author(s):  
Karlijn Pellikaan ◽  
Geeske M. van Woerden ◽  
Lotte Kleinendorst ◽  
Anna G. W. Rosenberg ◽  
Bernhard Horsthemke ◽  
...  
Keyword(s):  
Intellectual Disability ◽  
Single Nucleotide Polymorphism Array ◽  
Genetic Defect ◽  
Missense Variant ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Pituitary Hormone ◽  
Negative Effect

Prader–Willi syndrome (PWS) is a rare genetic condition characterized by hypotonia, intellectual disability, and hypothalamic dysfunction, causing pituitary hormone deficiencies and hyperphagia, ultimately leading to obesity. PWS is most often caused by the loss of expression of a cluster of genes on chromosome 15q11.2-13. Patients with Prader–Willi-like syndrome (PWLS) display features of the PWS phenotype without a classical PWS genetic defect. We describe a 46-year-old patient with PWLS, including hypotonia, intellectual disability, hyperphagia, and pituitary hormone deficiencies. Routine genetic tests for PWS were normal, but a homozygous missense variant NM_003097.3(SNRPN):c.193C>T, p.(Arg65Trp) was identified. Single nucleotide polymorphism array showed several large regions of homozygosity, caused by high-grade consanguinity between the parents. Our functional analysis, the ‘Pipeline for Rapid in silico, in vivo, in vitro Screening of Mutations’ (PRiSM) screen, showed that overexpression of SNRPN-p.Arg65Trp had a dominant negative effect, strongly suggesting pathogenicity. However, it could not be confirmed that the variant was responsible for the phenotype of the patient. In conclusion, we present a unique homozygous missense variant in SNURF-SNRPN in a patient with PWLS. We describe the diagnostic trajectory of this patient and the possible contributors to her phenotype in light of the current literature on the genotype–phenotype relationship in PWS.

Novel REST Truncation Mutations Causing Hereditary Gingival Fibromatosis

2021 ◽  
pp. 002203452199662
Author(s):  
J.T. Chen ◽  
C.H. Lin ◽  
H.W. Huang ◽  
Y.P. Wang ◽  
P.C. Kao ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Genetic Disorder ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Wild Type ◽  
Negative Effect ◽  
Localization Signal ◽  
Gingival Fibromatosis

Hereditary gingival fibromatosis (HGF) is a rare genetic disorder featured by nonsyndromic pathological overgrowth of gingiva. The excessive gingival tissues can cause dental, masticatory, and phonetic problems, which impose severe functional and esthetic burdens on affected individuals. Due to its high recurrent rate, patients with HGF have to undergo repeated surgical procedures of gingival resection, from childhood to adulthood, which significantly compromises their quality of life. Unraveling the genetic etiology and molecular pathogenesis of HGF not only gains insight into gingival physiology and homeostasis but also opens avenues for developing potential therapeutic strategies for this disorder. Recently, mutations in REST (OMIM *600571), encoding a transcription repressor, were reported to cause HGF (GINGF5; OMIM #617626) in 3 Turkish families. However, the functions of REST in gingival homeostasis and pathogenesis of REST-associated HGF remain largely unknown. In this study, we characterized 2 HGF families and identified 2 novel REST mutations, c.2449C>T (p.Arg817*) and c.2771_2793dup (p.Glu932Lysfs*3). All 5 mutations reported to date are nonsenses or frameshifts in the last exon of REST and would presumably truncate the protein. In vitro reporter gene assays demonstrated a partial or complete loss of repressor activity for these truncated RESTs. When coexpressed with the full-length protein, the truncated RESTs impaired the repressive ability of wild-type REST, suggesting a dominant negative effect. Immunofluorescent studies showed nuclear localization of overexpressed wild-type and truncated RESTs in vitro, indicating preservation of the nuclear localization signal in shortened proteins. Immunohistochemistry demonstrated a comparable pattern of ubiquitous REST expression in both epithelium and lamina propria of normal and HGF gingival tissues despite a reduced reactivity in HGF gingiva. Results of this study confirm the pathogenicity of REST truncation mutations occurring in the last exon causing HGF and suggest the pathosis is caused by an antimorphic (dominant negative) disease mechanism.

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