scholarly journals Defining relative mutational difficulty to understand cancer formation and prevention

2019 ◽  
Author(s):  
Lin Shan ◽  
Jiao Yu ◽  
Zhengjin He ◽  
Shishuang Chen ◽  
Mingxian Liu ◽  
...  
Keyword(s):  
Human Cancer ◽  
Low Frequency ◽  
Dominant Negative ◽  
Missense Mutations ◽  
Nucleotide Change ◽  
P53 Mutations ◽  
Loss Of Function ◽  
Functional Importance ◽  
Negative Effects ◽  
Different Types

SummaryMost mutations in human cancer are low-frequency missense mutations, whose functional status remains hard to predict. Here we show that depending on the type of nucleotide change and the surrounding sequences, the tendency to generate each type of nucleotide mutations varies greatly, even by several hundred folds. Therefore, a cancer-promoting mutation may appear only in a small number of cancer cases, if the underlying nucleotide change is too difficult to generate. We propose a method that integrates both the original mutation counts and their relative mutational difficulty. Using this method, we can accurately predict the functionality of hundreds of low-frequency missense mutations in p53, PTEN and INK4A. Many loss-of-function p53 mutations with dominant negative effects were identified, and the functional importance of several regions in p53 structure were highlighted by this analysis. Furthermore, mutational difficulty analysis also points to potential means of cancer prevention. Our study not only established relative mutational difficulties for different types of mutations in human cancer, but also showed that by incorporating such parameter, we can bring new angles to understanding cancer formation and prevention.

scholarly journals Loss of mutant TP53 does not impair the sustained proliferation, survival or metastasis of diverse cancer cells

2020 ◽  
Author(s):  
Zilu Wang ◽  
François Vaillant ◽  
Catherine Chang ◽  
Chris Riffkin ◽  
Elizabeth Lieschke ◽  
...  
Keyword(s):  
Human Cancer ◽  
Hot Spot ◽  
Point Mutations ◽  
Chemotherapeutic Agents ◽  
Dominant Negative ◽  
Loss Of Function ◽  
Negative Effects ◽  
Substantial Impact ◽  
Human Cancer Cell Lines ◽  
Cellular Stresses

AbstractThe tumour suppressor TP53 is the most frequently mutated gene in human cancer and these aberrations confer poor chemotherapeutic responses1-3. Point mutations typically cluster in the DNA binding domain, with certain ‘hot-spot’ residues disproportionally represented1-4 These mutations abrogate binding of the TP53 transcription factor to DNA and thereby prevent upregulation of genes critical for tumour suppression (loss-of-function)1-3. Mutant TP53 is reported to additionally contribute to tumour development, sustained growth and metastasis not only through dominant-negative effects on wild-type TP535 but also through neomorphic gain-of-function (GOF) activities6. Understanding the contributions of these postulated attributes of mutant TP53 to the development and expansion of tumours will facilitate the design of rational therapeutic strategies. Here we used CRISPR/CAS9 to delete mutant TP53 in a panel of diverse human cancer cell lines. The loss of mutant TP53 expression had no impact on the survival, proliferative capacity or metabolic state of the tumour cells, nor did it sensitise them to cellular stresses and chemotherapeutic agents. These data suggest that putative GOF effects of mutant TP53 are not universally required for the sustained survival and proliferation of fully malignant cells. Therefore, therapeutic approaches that abrogate expression or function of mutant TP53 would not be expected to have substantial impact.

scholarly journals Lrrk regulates the dynamic profile of dendritic Golgi outposts through the golgin Lava lamp

2015 ◽  
Vol 210 (3) ◽  
pp. 471-483 ◽  
Author(s):  
Chin-Hsien Lin ◽  
Hsun Li ◽  
Yi-Nan Lee ◽  
Ying-Ju Cheng ◽  
Ruey-Meei Wu ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Kinase Activity ◽  
Dominant Negative ◽  
Dendritic Arbor ◽  
Leucine Rich Repeat ◽  
Loss Of Function ◽  
Negative Effects ◽  
Golgi Membranes ◽  
Prominent Component ◽  
Dynamic Profile

Constructing the dendritic arbor of neurons requires dynamic movements of Golgi outposts (GOPs), the prominent component in the dendritic secretory pathway. GOPs move toward dendritic ends (anterograde) or cell bodies (retrograde), whereas most of them remain stationary. Here, we show that Leucine-rich repeat kinase (Lrrk), the Drosophila melanogaster homologue of Parkinson’s disease–associated Lrrk2, regulates GOP dynamics in dendrites. Lrrk localized at stationary GOPs in dendrites and suppressed GOP movement. In Lrrk loss-of-function mutants, anterograde movement of GOPs was enhanced, whereas Lrrk overexpression increased the pool size of stationary GOPs. Lrrk interacted with the golgin Lava lamp and inhibited the interaction between Lva and dynein heavy chain, thus disrupting the recruitment of dynein to Golgi membranes. Whereas overexpression of kinase-dead Lrrk caused dominant-negative effects on GOP dynamics, overexpression of the human LRRK2 mutant G2019S with augmented kinase activity promoted retrograde movement. Our study reveals a pathogenic pathway for LRRK2 mutations causing dendrite degeneration.

scholarly journals p53 Mutants Have Selective Dominant-Negative Effects on Apoptosis but Not Growth Arrest in Human Cancer Cell Lines

2000 ◽  
Vol 20 (3) ◽  
pp. 770-778 ◽  
Author(s):  
Oscar N. Aurelio ◽  
Xiao-Tang Kong ◽  
Swati Gupta ◽  
Eric J. Stanbridge
Keyword(s):  
Human Cancer ◽  
Growth Arrest ◽  
Carcinoma Cells ◽  
Dominant Negative ◽  
Wild Type ◽  
Osteosarcoma Cells ◽  
Negative Effects ◽  
Human Cancer Cell Lines ◽  
Lung Carcinoma Cells ◽  
Apoptotic Pathways

ABSTRACT A bidirectional expression vector that allowed equal transcription of cloned wild-type and mutant p53 cDNAs from the same vector was developed. The vector was transfected into CaLu 6 lung carcinoma cells or Saos-2 osteosarcoma cells. All p53 mutants examined were recessive to wild-type p53 transactivation ofp21WAF1/CIP1 but dominant-negative for transactivation of Bax. An examination of effects on growth arrest and apoptotic pathways indicated that all mutants were recessive to wild type for growth arrest but only three of seven mutants were dominant negative for induction of apoptosis.

Revisiting Li-Fraumeni Syndrome From TP53 Mutation Carriers

2015 ◽  
Vol 33 (21) ◽  
pp. 2345-2352 ◽  
Author(s):  
Gaëlle Bougeard ◽  
Mariette Renaux-Petel ◽  
Jean-Michel Flaman ◽  
Camille Charbonnier ◽  
Pierre Fermey ◽  
...  
Keyword(s):  
Tp53 Mutation ◽  
Soft Tissue Sarcomas ◽  
Dominant Negative ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Li Fraumeni Syndrome ◽  
Tumor Onset ◽  
Mutation Carriers ◽  
The Mean ◽  
Li Fraumeni

Purpose The aim of the study was to update the description of Li-Fraumeni syndrome (LFS), a remarkable cancer predisposition characterized by extensive clinical heterogeneity. Patients and Methods From 1,730 French patients suggestive of LFS, we identified 415 mutation carriers in 214 families harboring 133 distinct TP53 alterations and updated their clinical presentation. Results The 322 affected carriers developed 552 tumors, and 43% had developed multiple malignancies. The mean age of first tumor onset was 24.9 years, 41% having developed a tumor by age 18. In childhood, the LFS tumor spectrum was characterized by osteosarcomas, adrenocortical carcinomas (ACC), CNS tumors, and soft tissue sarcomas (STS) observed in 30%, 27%, 26%, and 23% of the patients, respectively. In adults, the tumor distribution was characterized by the predominance of breast carcinomas observed in 79% of the females, and STS observed in 27% of the patients. The TP53 mutation detection rate in children presenting with ACC or choroid plexus carcinomas, and in females with breast cancer before age 31 years, without additional features indicative of LFS, was 45%, 42% and 6%, respectively. The mean age of tumor onset was statistically different (P < .05) between carriers harboring dominant-negative missense mutations (21.3 years) and those with all types of loss of function mutations (28.5 years) or genomic rearrangements (35.8 years). Affected children, except those with ACC, harbored mostly dominant-negative missense mutations. Conclusion The clinical gradient of the germline TP53 mutations, which should be validated by other studies, suggests that it might be appropriate to stratify the clinical management of LFS according to the class of the mutation.

scholarly journals A Novel Multi-Exon Deletion of PACS1 in a Three-Generation Pedigree: Supplements to PACS1 Neurodevelopmental Disorder Spectrum

2021 ◽  
Vol 12 ◽  
Author(s):  
Yuan Liu ◽  
Hongke Ding ◽  
Tizhen Yan ◽  
Ling Liu ◽  
Lihua Yu ◽  
...  
Keyword(s):  
Neurodevelopmental Disorder ◽  
Dominant Negative ◽  
Facial Features ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Pathogenic Variants ◽  
Cognitive Delay ◽  
Whole Exome ◽  
Before And After ◽  
Exon Deletion

PACS1 neurodevelopmental disorder (PACS1-NDD) is a category of rare disorder characterized by intellectual disability, speech delay, dysmorphic facial features, and developmental delay. Other various physical abnormalities of PACS1-NDD might involve all organs and systems. Notably, there were only two unique missense mutations [c.607C &gt; T (p.Arg203Trp) and c.608G &gt; A (p.Arg203Gln)] in PACS1 that had been identified as pathogenic variants for PACS1-NDD or Schuurs-Hoeijmakers syndrome (SHMS). Previous reports suggested that these common missense variants were likely to act through dominant-negative or gain-of-function effects manner. It is still uncertain whether the intragenic deletion or duplication in PACS1 will be disease-causing. By using whole-exome sequencing, we first identified a novel heterozygous multi-exon deletion covering exons 12–24 in PACS1 (NM_018026) in four individuals (two brothers and their father and grandfather) in a three-generation family. The younger brother was referred to our center prenatally and was evaluated before and after the birth. Unlike SHMS, no typical dysmorphic facial features, intellectual problems, and structural brain anomalies were observed among these four individuals. The brothers showed a mild hypermyotonia of their extremities at the age of 3 months old and recovered over time. Mild speech and cognitive delay were also noticed in the two brothers at the age of 13 and 27 months old, respectively. However, their father and grandfather showed normal language and cognitive competence. This study might supplement the spectrum of PACS1-NDD and demonstrates that the loss of function variation in PACS1 displays no contributions to the typical SHMS which is caused by the recurrent c.607C &gt; T (p.Arg203Trp) variant.

Drosophila transcription factor AP-2 in proboscis, leg and brain central complex development

Development ◽  
2001 ◽  
Vol 128 (8) ◽  
pp. 1239-1252 ◽  
Author(s):  
I. Monge ◽  
R. Krishnamurthy ◽  
D. Sims ◽  
F. Hirth ◽  
M. Spengler ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Dominant Negative ◽  
Central Complex ◽  
Missense Mutations ◽  
Leg Length ◽  
New Paradigm ◽  
Negative Effects ◽  
Wing Vein ◽  
Normal Length ◽  
Hypomorphic Alleles

We report loss- and gain-of-function analyses that identify essential roles in development for Drosophila transcription factor AP-2. A mutagenesis screen yielded 16 lethal point mutant alleles of dAP-2. Null mutants die as adults or late pupae with a reduced proboscis, severely shortened legs (~30% of normal length) lacking tarsal joints, and disruptions in the protocerebral central complex, a brain region critical for locomotion. Seven hypomorphic alleles constitute a phenotypic series yielding hemizygous adults with legs ranging from 40–95% of normal length. Hypomorphic alleles show additive effects with respect to leg length and viability; and several heteroallelic lines were established. Heteroallelic adults have moderately penetrant defects that include necrotic leg joints and ectopic growths (sometimes supernumerary antennae) invading medial eye territory. Several dAP-2 alleles with DNA binding domain missense mutations are null in hemizygotes but have dominant negative effects when paired with hypomorphic alleles. In wild-type leg primordia, dAP-2 is restricted to presumptive joints. Ectopic dAP-2 in leg discs can inhibit but not enhance leg elongation indicating that functions of dAP-2 in leg outgrowth are region restricted. In wing discs, ectopic dAP-2 cell autonomously transforms presumptive wing vein epithelium to ectopic sensory bristles, consistent with an instructive role in sensory organ development. These findings reveal multiple functions for dAP-2 during morphogenesis of feeding and locomotor appendages and their neural circuitry, and provide a new paradigm for understanding AP-2 family transcription factors.

scholarly journals Dominant-negative effects of human P/Q-type Ca2+ channel mutations associated with episodic ataxia type 2

2006 ◽  
Vol 290 (4) ◽  
pp. C1209-C1220 ◽  
Author(s):  
Chung-Jiuan Jeng ◽  
Yu-Ting Chen ◽  
Yi-Wen Chen ◽  
Chih-Yung Tang
Keyword(s):  
Dominant Negative ◽  
Episodic Ataxia ◽  
Molar Ratio ◽  
Loss Of Function ◽  
Negative Effects ◽  
Autosomal Dominant Disorder ◽  
Episodic Ataxia Type 2 ◽  
Episodic Ataxia Type ◽  
Suppression Effects

Episodic ataxia type 2 (EA2) is an inherited autosomal dominant disorder related to cerebellar dysfunction and is associated with mutations in the pore-forming α1A-subunits of human P/Q-type Ca2+ channels (Cav2.1 channels). The majority of EA2 mutations result in significant loss-of-function phenotypes. Whether EA2 mutants may display dominant-negative effects in human, however, remains controversial. To address this issue, five EA2 mutants in the long isoform of human α1A-subunits were expressed in Xenopus oocytes to explore their potential dominant-negative effects. Upon coexpressing the cRNA of α1A-WT with each α1A-mutant in molar ratios ranging from 1:1 to 1:10, the amplitude of Ba2+ currents through wild-type (WT)-Cav2.1 channels decreased significantly as the relative molar ratio of α1A-mutants increased, suggesting the presence of an α1A-mutant-specific suppression effect. When we coexpressed α1A-WT with proteins not known to interact with Cav2.1 channels, we observed no significant suppression effects. Furthermore, increasing the amount of auxiliary subunits resulted in partial reversal of the suppression effects in nonsense but not missense EA2 mutants. On the other hand, when we repeated the same coinjection experiments of α1A-WT and mutant using a splice variant of α1A-subunit that contained a considerably shorter COOH terminus (i.e., the short isoform), no significant dominant-negative effects were noted until we enhanced the relative molar ratio to 1:10. Altogether, these results indicate that for human WT-Cav2.1 channels comprising the long-α1A-subunit isoform, both missense and nonsense EA2 mutants indeed display prominent dominant-negative effects.

scholarly journals OP0314 DOCK8 MUTATIONS IN COVID-19 AND MIS-C CYTOKINE STORM SYNDROME

2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 192.1-192
Author(s):  
R. Cron ◽  
M. Zhang ◽  
D. Absher ◽  
J. Bridges ◽  
A. Schnell ◽  
...  
Keyword(s):  
Nk Cell ◽  
Foamy Virus ◽  
Dominant Negative ◽  
Target Cells ◽  
Missense Mutations ◽  
Cytokine Storm ◽  
Negative Effects ◽  
Research Support ◽  
Rare Mutations ◽  
Lytic Function

Background:We recently identified DOCK8 as a novel gene associated with cytokine storm syndrome (CSS)1. Heterozygous missense mutations in DOCK8 diminish NK cell lytic function and contribute to increased pro-inflammatory cytokine production (CSS). CSS is a potential complication of COVID-19 with severe consequences2. Children are at risk of a SARS-CoV-2 post-infectious CSS, multisystem inflammatory syndrome in children (MIS-C)3. Host genetic factors associated with COVID-19 CSS and MIS-C CSS are unknown.Objectives:The goals are to identify and functionally study rare mutations in DOCK8 in patients with SARS-CoV-2 COVID-19 and MIS-C.Methods:To date, 16 adult patients enrolled in a COVID-19 CSS clinical trial at UAB had whole genome sequencing. Four (25%) had rare heterozygous DOCK8 mutations (3 missense, 1 intronic). A COVID-19 CSS adult patient in Seattle also had a DOCK8 missense mutation. In addition, DOCK8 missense mutations were identified in five children (UAB & Northwell) hospitalized with MIS-C. DOCK8 mutations, or wild-type (WT) sequence controls, were introduced into human NK-92 cells by FOAMY virus transduction. WT and mutant DOCK8-expressing NK-92 cells were incubated with K562 target cells and compared for cytolysis and degranulation (CD107a).Results:One COVID-19 patient DOCK8 mutation (Gly523Arg) reduced NK cell degranulation by 30% and cytolysis by 23% (n=3) (Figure 1). Similar studies of 3 MIS-C patients with DOCK8 missense mutations (Arg899Trp, Ala2Thr, Pro687Leu) revealed up to 31% reduced NK cell degranulation and 48% reduction in cytolysis by 3 distinct mutations (n=3). Two-way ANOVA analysis revealed statistically significant (p<0.05) differences in NK cell degranulation and lysis for four unique DOCK8 mutations.Conclusion:Heterozygous DOCK8 missense mutations may contribute to severe COVID-19 and MIS-C CSS by partial dominant-negative effects yielding decreased NK cell cytolysis.References:[1]Schulert GS, Cron RQ. The genetics of macrophage activation syndrome. Genes Immun 2020:21:169-181.[2] Cron RQ, Chatham WW. The rheumatologist’s role in COVID-19. J Rheumatol 2020:47:639-642.[3]Reiff D, Mannion ML, Samuy N, Scalici P, Cron RQ. Distinguishing active pediatric COVID-19 from MIS-C. Pediatr Rheumatol Online J, in press.Disclosure of Interests:Randy Cron Consultant of: SOBI, Novartis, Pfizer, Sironax, Grant/research support from: SOBI, Mingce Zhang: None declared, Remy Cron: None declared, Devin Absher: None declared, John Bridges: None declared, Amanda Schnell: None declared, Pavan Bhatraju: None declared, Anshul Vagrecha: None declared, Shannon Lozinsky: None declared, Suchitra Acharya: None declared, Carolyn Levy: None declared, Winn Chatham Grant/research support from: SOBI.

scholarly journals Siah-1 N-Terminal RING Domain Is Required for Proteolysis Function, and C-Terminal Sequences Regulate Oligomerization and Binding to Target Proteins

1999 ◽  
Vol 19 (1) ◽  
pp. 724-732 ◽  
Author(s):  
Gang Hu ◽  
Eric R. Fearon
Keyword(s):  
Cell Fate ◽  
Point Mutations ◽  
Dominant Negative ◽  
Ring Domain ◽  
Dominant Negative Mutant ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Target Proteins ◽  
Proteasome Pathway ◽  
Seven In Absentia

ABSTRACT The Drosophila seven in absentia (sina) gene was initially discovered because its inactivation leads to R7 photoreceptor defects. Recent data indicate that Sina binds to the Sevenless pathway protein Phyllopod, and together they mediate degradation of Tramtrack, a transcriptional repressor of R7 cell fate. Independent studies have shown that Sina and its highly related mammalian homologues Siah-1 and Siah-2 bind to the DCC (deleted in colorectal cancer) protein and promote its proteolysis via the ubiquitin-proteasome pathway. To determine the roles of mammalian Siahs in proteolysis and their interactions with target proteins, we sought to define Siah-1 domains critical for regulation of DCC. Mutant Siah-1 proteins, harboring missense mutations in the carboxy (C)-terminal domain analogous to those present in Drosophila sinaloss-of-function alleles, failed to promote DCC degradation. Point mutations and deletion of the amino (N)-terminal RING finger domain of Siah-1 abrogated its ability to promote DCC proteolysis. In the course of defining Siah-1 sequences required for DCC degradation, we found that Siah-1 is itself rapidly degraded via the proteasome pathway, and RING domain mutations stabilized the Siah-1 protein. Siah-1 was found to oligomerize with itself and other Sina and Siah proteins via C-terminal sequences. Finally, evidence that endogenous Siah-1 regulates DCC proteolysis in cells was obtained through studies of an apparent dominant negative mutant of Siah-1, as well as via an antisense approach. The data indicate that the Siah-1 N-terminal RING domain is required for its proteolysis function, while the C-terminal sequences regulate oligomerization and binding to target proteins, such as DCC.

Mechanisms of I Ks suppression in LQT1 mutants

2000 ◽  
Vol 279 (6) ◽  
pp. H3003-H3011 ◽  
Author(s):  
Laura Bianchi ◽  
Silvia G. Priori ◽  
Carlo Napolitano ◽  
Krystyna A. Surewicz ◽  
Adrienne T. Dennis ◽  
...  
Keyword(s):  
Cell Surface ◽  
Dominant Negative ◽  
Delayed Rectifier ◽  
Poor Correlation ◽  
Type I ◽  
Missense Mutations ◽  
Wild Type ◽  
Negative Effects ◽  
Clinical Phenotypes ◽  
First Time

Mutations in the cardiac potassium ion channel gene KCNQ1 (voltage-gated K+ channel subtype KvLQT1) cause LQT1, the most common type of hereditary long Q-T syndrome. KvLQT1 mutations prolong Q-T by reducing the repolarizing cardiac current [slow delayed rectifier K+ current ( I Ks )], but, for reasons that are not well understood, the clinical phenotypes may vary considerably even for carriers of the same mutation, perhaps explaining the mode of inheritance. At present, only currents expressed by LQT1 mutants have been studied, and it is unknown whether abnormal subunits are transported to the cell surface. Here, we have examined for the first time trafficking of KvLQT1 mutations and correlated the results with the I Ks currents that were expressed. Two missense mutations, S225L and A300T, produced abnormal currents, and two others, Y281C and Y315C, produced no currents. However, all four KvLQT1 mutations were detected at the cell surface. S225L, Y281C, and Y315C produced dominant negative effects on wild-type I Ks current, whereas the mutant with the mildest dysfunction, A300T, did not. We examined trafficking of a severe insertion deletion mutant Δ544 and detected this protein at the cell surface as well. We compared the cellular and clinical phenotypes and found a poor correlation for the severely dysfunctional mutations.

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