scholarly journals Novel PITX2 Mutations including a Mutation Causing an Unusual Ophthalmic Phenotype of Axenfeld-Rieger Syndrome

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Liqin Huang ◽  
Yong Meng ◽  
Xiangming Guo
Keyword(s):  
Genomic Dna ◽  
Anterior Segment ◽  
Dominant Negative ◽  
Chinese Patients ◽  
Dominant Negative Effect ◽  
Sequencing Analysis ◽  
Coding Region ◽  
Direct Dna Sequencing ◽  
Rieger Syndrome ◽  
Pitx2 Gene

Purpose. The aims of this study were to examine novel mutations in PITX2 and FOXC1 in Chinese patients with anterior segment dysgenesis (ASD) and to compare the clinical presentations of these mutations with previously reported associated phenotypes. Methods. Twenty-six unrelated patients with different forms of ASD were enrolled from our paediatric and genetic eye clinic. The ocular manifestations of both eyes of each patient were recorded. Genomic DNA was prepared from venous leukocytes. All coding exons of PITX2 and FOXC1 were amplified by polymerase chain reaction (PCR) from genomic DNA and subjected to direct DNA sequencing. Analysis of mutations in control subjects was performed by heteroduplex single-strand conformation polymorphism (SSCP) analysis. Results. Sequence analysis of the PITX2 gene revealed four mutations, including c.475_476delCT (P.L159VfsX39), c.64C > T (P.Q22X), c.296delG (P.R99PfsX56), and c.206G > A (P.R69H). The first three mutations were found to be novel. The c.475_476delCT (P.L159VfsX39) mutation, located at the 3′ end of the PITX2-coding region, was identified in a Chinese Axenfeld-Rieger syndrome (ARS) patient who presented with an unusual severe phenotype of bilateral aniridia. The clinical characteristics, including the severity and manifestations of the patient’s phenotype, were compared with reported PITX2-associated aniridia phenotypes of ARS in the literature. Conclusions. These results expand the mutation spectrum of the PITX2 gene in patients with ARS. The PITX2 gene may be responsible for a significant portion of ARS with additional systemic defects in the Chinese population. This is the first reported case of a mutation at the 3′ end of the PITX2-coding region extending the phenotypic consequences to bilateral aniridia. The traits of ARS could display tremendous variability in severity and manifestations due to the dominant-negative effect of PITX2. Our results further emphasize the importance of careful clinical and genetic analysis in determining mutation-disease associations and may lead to a better understanding of the role of PITX2 in ocular development.

A Missense Mutation (Tyr88 to Cys) in the Platelet Membrane Glycoprotein Ibβ Gene Affects GPIb/IX Complex Expression

2001 ◽  
Vol 86 (11) ◽  
pp. 1249-1256 ◽  
Author(s):  
Yumi Kurokawa ◽  
Takehiko Kamijo ◽  
Shinji Kunishima ◽  
Dermot Kenny ◽  
Kiyoshi Kitano ◽  
...  
Keyword(s):  
Missense Mutation ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Platelet Glycoprotein ◽  
Homozygous Mutation ◽  
Sequencing Analysis ◽  
Giant Platelets ◽  
Giant Platelet ◽  
Negative Effect ◽  
Dna Sequencing Analysis

SummaryThis study examined the molecular basis of a missense mutation of the platelet glycoprotein (GP) Ibβ gene in two families. In the propositus with a novel form of Bernard-Soulier syndrome (BSS) from Family I, only GPIbα was detectable in reduced amounts on platelet surfaces by flow cytometry. There were no GPIX or GPIbβ found by immunoblotting. DNA sequencing analysis showed a homozygous mutation in the GPIbβ gene which changed Tyr (TAC) to Cys (TGC) at residue 88. Her parents were heterozygous for Tyr88Cys in the GPIbβ gene. In transient transfection studies on 293T cells, both Tyr88Cys and Tyr88Ala mutations suppressed the expression of GPIb/IX complexes. In addition, Tyr88Cys GPIbβ mutation was found to exert a dominant negative effect on the GPIb expression.Five individuals from Family II, four of whom reported elsewhere as having giant platelet disorders with normal aggregation (BLOOD, 1997; 89: 2404) and one newly analyzed in this study, were heterozygous for Tyr88Cys in the GPIb gene. Microsatellite analysis of chromosome 22 showed a common haplotype in 8 of the individuals with Tyr88Cys mutations in Families I and II. Tyr88 in the GPIbβ gene plays a significant role in the GPIb/IX expression; the defect causes BSS in a homozygous form and possibly giant platelets in a heterozygous form.

scholarly journals Identification of a Rare and Potential Pathogenic MC4R Variant in a Brazilian Patient With Adulthood-Onset Severe Obesity

2020 ◽  
Vol 11 ◽  
Author(s):  
Kaio Cezar Rodrigues Salum ◽  
Guilherme Orofino de Souza ◽  
Gabriella de Medeiros Abreu ◽  
Mário Campos Junior ◽  
Fabiana Barzotto Kohlrausch ◽  
...  
Keyword(s):  
Body Weight ◽  
Severe Obesity ◽  
Rare Variants ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Loss Of Function ◽  
Coding Region ◽  
Childhood Onset ◽  
Brazilian Patient ◽  
Onset Group

BackgroundThe melanocortinergic pathway orchestrates the energy homeostasis and impairments in this system often lead to an increase in body weight. Rare variants in the melanocortin 4 receptor (MC4R) gene resulting in partial or complete loss of function have been described with autosomal co-dominant inheritance. These mutations are the most common cause of non-syndromic monogenic obesity. In this context, this study aimed to sequence the MC4R gene in a Brazilian cohort of adults with severe obesity.MethodsThis study included 163 unrelated probands with Body Mass Index (BMI) ≥ 35 kg/m2, stratified into three groups, according to the period of obesity onset. From the total sample, 25 patients were enrolled in the childhood-onset group (0–11 years), 19 patients in the adolescence/youth-onset group (12–21 years), and 119 patients in the adult-onset group (>21 years). Blood pressure, anthropometric and biochemical characteristics were obtained, and the MC4R coding region of each subject’s DNA was assessed using automated Sanger sequencing.ResultsSignificant anthropometric differences between the groups were observed. Higher body weight and BMI medians were found in patients with childhood-onset or adolescence/youth-onset when compared to the adulthood-onset obesity group. A total of five mutations were identified, including four missense variants: p.Ser36Thr, p.Val103Ile, p.Ala175Thr, and p.Ile251Leu. Additionally, we observed one synonymous variant (p.Ile198=). The p.Ala175Thr variant was identified in a female case with severe obesity and adulthood-onset. This variant was previously described as a partial loss-of-function mutation, in which the minor allele poses dominant-negative effect, probably resulting in reduced cAMP activity.ConclusionThis study showed a prevalence of common and rare variants in a cohort of Brazilian adults with severe obesity and candidates to bariatric surgery. We have identified a rare potentially pathogenic MC4R variant in a Brazilian patient with severe and adulthood-onset obesity.

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 Four novel mutations in the ALPL gene in Chinese patients with odonto, childhood, and adult hypophosphatasia

2018 ◽  
Vol 38 (4) ◽  
Author(s):  
Lijun Xu ◽  
Qianqian Pang ◽  
Yan Jiang ◽  
Ou Wang ◽  
Mei Li ◽  
...  
Keyword(s):  
Serum Alkaline Phosphatase ◽  
Gene Mutations ◽  
Dominant Negative ◽  
Chinese Patients ◽  
Dominant Negative Effect ◽  
Healthy Controls ◽  
Missense Mutations ◽  
Genetic Characteristics ◽  
Chinese Families ◽  
Negative Effect

Hypophosphatasia (HPP) is a rare inherited disorder characterized by defective bone and/or dental mineralization, and decreased serum alkaline phosphatase (ALP) activity. ALPL, the only gene related with HPP, encodes tissue non-specific ALP (TNSALP). Few studies were carried out in ALPL gene mutations in the Chinese population with HPP. The purpose of the present study is to elucidate the clinical and genetic characteristics of HPP in five unrelated Chinese families and two sporadic patients. Ten clinically diagnosed HPP patients from five unrelated Chinese families and two sporadic patients and fifty healthy controls were genetically investigated. All 12 exons and exon–intron boundaries of the ALPL gene were amplified by PCR and directly sequenced. The laboratory and radiological investigations were conducted simultaneously in these HPP ten patients. A 3D model of the TNSALP was used to predict the dominant negative effect of identified missense mutations. Three odonto, three childhood, and four adult types of HPP were clinically diagnosed. Ten mutations were identified in five unrelated Chinese families and two sporadic patients, including eight missense mutations and two frameshift mutations. Of which, four were novel: one frameshift mutation (p.R138Pfsx45); three missense mutations (p.C201R, p.V459A, p.C497S). No identical mutations and any other new ALPL mutations were found in unrelated 50 healthy controls. Our study demonstrated that the ALPL gene mutations are responsible for HPP in these Chinese families. These findings will be useful for clinicians to improve understanding of this heritable bone disorder.

scholarly journals Deletions of distant regulatory sequences upstream of zebrafish pitx2 result in a range of ocular phenotypes

2019 ◽  
Author(s):  
Eric Weh ◽  
Elena Sorokina ◽  
Kathryn Hendee ◽  
Doug B. Gould ◽  
Elena V. Semina
Keyword(s):  
Anterior Segment ◽  
Genomic Region ◽  
Upstream Region ◽  
Regulatory Sequences ◽  
Coding Region ◽  
Enhancer Activity ◽  
Anterior Segment Dysgenesis ◽  
Rieger Syndrome ◽  
Nearby Region ◽  
Vertebrate Eye

ABSTRACTDevelopment of the anterior segment of the vertebrate eye is a highly coordinated process. Genetic mutations in factors guiding this process result in Anterior Segment Dysgenesis (ASD), a spectrum of disorders affecting the iris, cornea, trabecular meshwork and/or other iridocorneal angle structures and associated with glaucoma. One of the first factors linked to ASD in humans was PITX2, a homeodomain containing transcription factor with a role in Axenfeld-Rieger syndrome (ARS). In addition to pathogenic alleles within the coding region of PITX2, deletions affecting the distant upstream region, but not PITX2 itself, have also been reported in ARS. Consistent with this, the distant upstream region was shown to contain multiple conserved elements (CE) with pitx2-related enhancer activity identified through studies in zebrafish. The two smallest human deletions reported to date encompass conserved elements 5-11 (ΔCE5-11) or 5-7 (ΔCE5-7). We previously reported the generation of ΔCE5-11 in zebrafish and we have now replicated the smallest deletion, ΔCE5-7, in the same model and studied the associated phenotype, expression, and DNA methylation profiles; we also performed further phenotypic examinations of the pitx2ΔCE5-11 fish. We show that the expression changes and phenotypes observed in the two lines are variable but that the severity generally correlates with the size of the deletion and the number of affected CEs; pitx2 promoter and a nearby region were hypermethylated in the pitx2ΔCE5-7 embryonic eyes. In addition, a subset of pitx2ΔCE5-11 animals were found to have a severe retinal phenotype suggesting that additional factors may modify the effects of this allele. These data provide further insight into functional sequences in the PITX2/pitx2 genomic region that coordinate PITX2/pitx2 expression during eye development and provide the basis for future studies into PITX2/pitx2 upstream regulators and modifiers.

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 Novel HAX1 Gene Mutation in a Vietnamese Boy with Severe Congenital Neutropenia

2018 ◽  
Vol 2018 ◽  
pp. 1-4
Author(s):  
Tham Thi Tran ◽  
Quang Van Vu ◽  
Taizo Wada ◽  
Akihiro Yachie ◽  
Huong Le Thi Minh ◽  
...  
Keyword(s):  
Early Onset ◽  
Bacterial Infections ◽  
Complete Blood Count ◽  
Hereditary Diseases ◽  
Severe Neutropenia ◽  
Sequencing Analysis ◽  
Severe Congenital Neutropenia ◽  
Congenital Neutropenia ◽  
Direct Dna Sequencing ◽  
Life Threatening

Severe congenital neutropenia (SCN) is a rare disease that involves a heterogeneous group of hereditary diseases. Mutations in the HAX1 gene can cause an autosomal recessive form of SCN-characterized low blood neutrophil count from birth, increased susceptibility to recurrent and life-threatening infections, and preleukemia predisposition. A 7-year-old boy was admitted due to life-threatening infections, mental retardation, and severe neutropenia. He had early-onset bacterial infections, and his serial complete blood count showed persistent severe neutropenia. One older sister and one older brother of the patient died at the age of 6 months and 5 months, respectively, because of severe infection. Bone marrow analysis revealed a maturation arrest at the promyelocyte/myelocyte stage with few mature neutrophils. In direct DNA sequencing analysis, we found a novel homozygous frameshift mutation (c.423_424insG, p.Gly143fs) in the HAX1 gene, confirming the diagnosis of SCN. The patient was successfully treated with granulocyte colony-stimulating factor (G-CSF) and antibiotics. A child with early-onset recurrent infections and neutropenia should be considered to be affected with SCN. Genetic analysis is useful to confirm diagnosis. Timely diagnosis and suitable treatment with G-CSF and antibiotics are important to prevent further complication.

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.

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