Browsing by Subject "Mutation"

Now showing 1 - 10 of 22
  • Thumbnail Image
    Item
    Bannayan Ruvalcaba Riley Syndrome
    (American College of Gastroenterology, 2014-01) Sagi, Sashidhar V.; Ballard, Darren D.; Marks, Rebecca A.; Dunn, Katie R.; Kahi, Charles J.; Department of Medicine, IU School of Medicine
    A 63-year-old male with history of prostate cancer treated with radiation presented for a colonoscopy for small volume hematochezia. The colonoscopy revealed numerous polyps, which were found to be ganglioneuromas on histological examination. He was referred to medical genetics with suspicion for hamartomatous polyposis syndrome and was found to have a mutation in the PTEN gene. Based on this and suggestive clinical findings, he was diagnosed with Bannayan Ruvalcaba Riley syndrome.
  • Thumbnail Image
    Item
    Beyond Tryptophan Synthase: Identification of Genes That Contribute to Chlamydia trachomatis Survival during Gamma Interferon-Induced Persistence and Reactivation
    (American Society for Microbiology, 2016-09-19) Muramatsu, Matthew K.; Brothwell, Julie A.; Steinman, Barry D.; Putman, Timothy E.; Rockey, Daniel D.; Nelson, David E.; Department of Microbiology & Immunology, IU School of Medicine
    Chlamydia trachomatis can enter a viable but nonculturable state in vitro termed persistence. A common feature of C. trachomatis persistence models is that reticulate bodies fail to divide and make few infectious progeny until the persistence-inducing stressor is removed. One model of persistence that has relevance to human disease involves tryptophan limitation mediated by the host enzyme indoleamine 2,3-dioxygenase, which converts l-tryptophan to N-formylkynurenine. Genital C. trachomatis strains can counter tryptophan limitation because they encode a tryptophan-synthesizing enzyme. Tryptophan synthase is the only enzyme that has been confirmed to play a role in interferon gamma (IFN-γ)-induced persistence, although profound changes in chlamydial physiology and gene expression occur in the presence of persistence-inducing stressors. Thus, we screened a population of mutagenized C. trachomatis strains for mutants that failed to reactivate from IFN-γ-induced persistence. Six mutants were identified, and the mutations linked to the persistence phenotype in three of these were successfully mapped. One mutant had a missense mutation in tryptophan synthase; however, this mutant behaved differently from previously described synthase null mutants. Two hypothetical genes of unknown function, ctl0225 and ctl0694, were also identified and may be involved in amino acid transport and DNA damage repair, respectively. Our results indicate that C. trachomatis utilizes functionally diverse genes to mediate survival during and reactivation from persistence in HeLa cells.
  • Thumbnail Image
    Item
    The Current Landscape of Genetic Testing in Cardiovascular Malformations: Opportunities and Challenges
    (Frontiers, 2016-07-25) Landis, Benjamin J.; Ware, Stephanie M.; Department of Pediatrics, IU School of Medicine
    Human cardiovascular malformations (CVMs) frequently have a genetic contribution. Through the application of novel technologies, such as next-generation sequencing, DNA sequence variants associated with CVMs are being identified at a rapid pace. While clinicians are now able to offer testing with NGS gene panels or whole exome sequencing to any patient with a CVM, the interpretation of genetic variation remains problematic. Variable phenotypic expression, reduced penetrance, inconsistent phenotyping methods, and the lack of high-throughput functional testing of variants contribute to these challenges. This article elaborates critical issues that impact the decision to broadly implement clinical molecular genetic testing in CVMs. Major benefits of testing include establishing a genetic diagnosis, facilitating cost-effective screening of family members who may have subclinical disease, predicting recurrence risk in offsprings, enabling early diagnosis and anticipatory management of CV and non-CV disease phenotypes, predicting long-term outcomes, and facilitating the development of novel therapies aimed at disease improvement or prevention. Limitations include financial cost, psychosocial cost, and ambiguity of interpretation of results. Multiplex families and patients with syndromic features are two groups where disease causation could potentially be firmly established. However, these account for the minority of the overall CVM population, and there is increasing recognition that genotypes previously associated with syndromes also exist in patients who lack non-CV findings. In all circumstances, ongoing dialog between cardiologists and clinical geneticists will be needed to accurately interpret genetic testing and improve these patients' health. This may be most effectively implemented by the creation and support of CV genetics services at centers committed to pursuing testing for patients.
  • Thumbnail Image
    Item
    Early severe coronary heart disease and ischemic heart failure in homozygous familial hypercholesterolemia: A case report
    (Wolters Kluwer Health, 2018-10) Kuang, Hongyu; Zhou, Xue; Li, Li; Yi, Qijian; Shou, Weinian; Lu, Tiewei; Pediatrics, School of Medicine
    RATIONALE: Familial hypercholesterolemia (FH) is a common inherited cause of coronary heart disease (CHD) and premature death in an early age. Nevertheless, an ischemic heart failure (IHF) associated with FH seems to be rare, and an early diagnosis and therapy could influence the prognosis. PATIENT CONCERNS: In this 13-year-old girl, multiple xanthomas began to develop from the first day of birth. Until June, 2017, she was admitted to our center due to edema, oliguria, and dyspnea during exertion, which was attributed to a recent respiratory infection. DIAGNOSIS: Homozygous FH (HoFH), CHD, and IHF. INTERVENTIONS: The patient has been treated with statin, ezetimibe, aspirin, and traditional heart failure (HF) medications. In addition, the beta-blocker was simultaneously administered. OUTCOMES: Genotypes of this proband indicated homozygous mutations of low-density lipoprotein receptor (LDLR) and some co-segregated mutations, such as von Willebrand factor (VWF) and fibroblast growth factor receptors. At 6-month follow-up, we found a decreased level of plasma lipid profile, in addition to a significant improvement in 6-minute walk distance and functional class. Echocardiography indicated nonsignificant improvements in the structure and function of the heart. LESSONS: This case report indicates that HoFH can lead to dramatically progressive endothelial damages and ventricular remodeling, severe atherosclerosis, even IHF. Genetic outcomes indicate IHF with HoFH could possibly result from LDLR mutations and some co-segregated mutations influencing endothelial function and cardiovascular remodeling. In a short-term follow-up, a combination of statins, ezetimibe, aspirin, and traditional HF agents is safe and effective for IHF with HoFH, and there is a need for further identification of drugs to ameliorate endothelial function and cardiovascular remodeling which may play an important role in long-term treatment.
  • Thumbnail Image
    Item
    Genetic strategies to detect genes involved in alcoholism and alcohol-related traits
    (The National Institute on Alcohol Abuse and Alcoholism, 2002) Dick, Danielle M.; Foroud, Tatiana; Medical and Molecular Genetics, School of Medicine
    Researchers are using a variety of sophisticated approaches to identify genes that contribute to the development of alcoholism in humans or influence other alcohol-related traits. These strategies include linkage approaches, which can identify broad chromosomal regions that are likely to contain genes predisposing to the disorder, and association approaches, which test the association between a particular marker allele and a specific outcome. Animal studies using diverse strategies can also help identify genes or DNA regions that influence alcohol-related traits in humans. The results of these analyses are likely to have implications for fields such as genetic counseling, gene therapy, and pharmacogenetics.
  • Thumbnail Image
    Item
    Identification of a melanoma susceptibility locus and somatic mutation in TET2
    (Oxford University Press, 2014-09) Song, Fengju; Amos, Christopher I.; Lee, Jeffrey E.; Lian, Christine G.; Fang, Shenying; Liu, Hongliang; MacGregor, Stuart; Iles, Mark M.; Law, Matthew H.; Lindeman, Neil I.; Montgomery, Grant W.; Duffy, David L.; Cust, Anne E.; Jenkins, Mark A.; Whiteman, David C.; Kefford, Richard F.; Giles, Graham G.; Armstrong, Bruce K.; Aitken, Joanne F.; Hopper, John L.; Brown, Kevin M.; Martin, Nicholas G.; Mann, Graham J.; Bishop, D. Timothy; Bishop, Julia A. Newton; Kraft, Peter; Qureshi, Abrar A.; Kanetsky, Peter A.; Hayward, Nicholas K.; Hunter, David J.; Wei, Qingyi; Han, Jiali; Department of Epidemiology, Richard M. Fairbanks School of Public Health
    Although genetic studies have reported a number of loci associated with melanoma risk, the complex genetic architecture of the disease is not yet fully understood. We sought to identify common genetic variants associated with melanoma risk in a genome-wide association study (GWAS) of 2298 cases and 6654 controls. Thirteen of 15 known loci were replicated with nominal significance. A total of 69 single-nucleotide polymorphisms (SNPs) were selected for in silico replication in two independent melanoma GWAS datasets (a total of 5149 cases and 12 795 controls). Seven novel loci were nominally significantly associated with melanoma risk. These seven SNPs were further genotyped in 234 melanoma cases and 238 controls. The SNP rs4698934 was nominally significantly associated with melanoma risk. The combined odds ratio per T allele = 1.18; 95% confidence interval (1.10-1.25); combined P = 7.70 × 10(-) (7). This SNP is located in the intron of the TET2 gene on chromosome 4q24. In addition, a novel somatic mutation of TET2 was identified by next-generation sequencing in 1 of 22 sporadic melanoma cases. TET2 encodes a member of TET family enzymes that oxidizes 5-methylcytosine to 5-hydroxymethylcytosine (5hmC). It is a putative epigenetic biomarker of melanoma as we previously reported, with observation of reduced TET2 transcriptional expression. This study is the first to implicate TET2 genetic variation and mutation in melanoma.
  • Thumbnail Image
    Item
    Importance of genetic evaluation and testing in pediatric cardiomyopathy
    (Baishideng, 2014-11-26) Tariq, Muhammad; Ware, Stephanie M.; Pediatrics, School of Medicine
    Pediatric cardiomyopathies are clinically heterogeneous heart muscle disorders that are responsible for significant morbidity and mortality. Phenotypes include hypertrophic cardiomyopathy, dilated cardiomyopathy, restrictive cardiomyopathy, left ventricular noncompaction and arrhythmogenic right ventricular cardiomyopathy. There is substantial evidence for a genetic contribution to pediatric cardiomyopathy. To date, more than 100 genes have been implicated in cardiomyopathy, but comprehensive genetic diagnosis has been problematic because of the large number of genes, the private nature of mutations, and difficulties in interpreting novel rare variants. This review will focus on current knowledge on the genetic etiologies of pediatric cardiomyopathy and their diagnostic relevance in clinical settings. Recent developments in sequencing technologies are greatly impacting the pace of gene discovery and clinical diagnosis. Understanding the genetic basis for pediatric cardiomyopathy and establishing genotype-phenotype correlations may help delineate the molecular and cellular events necessary to identify potential novel therapeutic targets for heart muscle dysfunction in children.
  • Thumbnail Image
    Item
    Inhibition of the Gab2/PI3K/mTOR signaling ameliorates myeloid malignancy caused by Ptpn11 (Shp2) gain-of-function mutations
    (Springer Nature, 2017-06) Liu, Wei; Yu, Wen-Mei; Zhang, Jing; Chan, Rebecca J.; Loh, Mignon L.; Zhang, Zheng; Bunting, Kevin D.; Qu, Cheng-Kui; Pediatrics, School of Medicine
    Activating mutations, such as E76K and D61Y, in PTPN11 (SHP2), a protein tyrosine phosphatase implicated in multiple cell signaling processes, are associated with 35% of patients with juvenile myelomonocytic leukemia (JMML), an aggressive childhood myeloproliferative neoplasm (MPN). Here we show that the interaction between leukemia-associated mutant Shp2 and Gab2, a scaffolding protein important for cytokine-induced PI3K/Akt signaling, was enhanced, and that the mTOR pathway was elevated in Ptpn11E76K/+ leukemic cells. Importantly, MPN induced by the Ptpn11E76K/+ mutation was markedly attenuated in Ptpn11E76K/+/Gab2-/- double mutant mice-overproduction of myeloid cells was alleviated, splenomegaly was diminished and myeloid cell infiltration in nonhematopoietic organs was decreased in these double mutants. Excessive myeloid differentiation of stem cells was also normalized by depletion of Gab2. Acute leukemia progression of MPN was reduced in the double mutant mice and, as such, their survival was much prolonged. Furthermore, treatment of Ptpn11E76K/+ mice with Rapamycin, a specific and potent mTOR inhibitor, mitigated MPN phenotypes. Collectively, this study reveals an important role of the Gab2/PI3K/mTOR pathway in mediating the pathogenic signaling of the PTPN11 gain-of-function mutations and a therapeutic potential of Rapamycin for PTPN11 mutation-associated JMML.
  • Thumbnail Image
    Item
    Insights into the Activity Change of Spore Photoproduct Lyase Induced by Mutations at a Peripheral Glycine Residue
    (Frontiers, 2017-03-28) Yang, Linlin; Li, Lei; Chemistry and Chemical Biology, School of Science
    UV radiation triggers the formation of 5-thyminyl-5,6-dihydrothymine, i.e., the spore photoproduct (SP), in the genomic DNA of bacterial endospores. These SPs, if not repaired in time, may lead to genome instability and cell death. SP is mainly repaired by spore photoproduct lyase (SPL) during spore outgrowth via an unprecedented protein-harbored radical transfer pathway that is composed of at least a cysteine and two tyrosine residues. This mechanism is consistent with the recently solved SPL structure that shows all three residues are located in proximity and thus able to participate in the radical transfer process during the enzyme catalysis. In contrast, an earlier in vivo mutational study identified a glycine to arginine mutation at the position 168 on the B. subtilis SPL that is >15 Å away from the enzyme active site. This mutation appears to abolish the enzyme activity because endospores carrying this mutant were sensitive to UV light. To understand the molecular basis for this rendered enzyme activity, we constructed two SPL mutations G168A and G168R, examined their repair of dinucleotide SP TpT, and found that both mutants exhibit reduced enzyme activity. Comparing with the wildtype (WT) SPL enzyme, the G168A mutant slows down the SP TpT repair by 3~4-fold while the G168R mutant by ~ 80-fold. Both mutants exhibit a smaller apparent (DV) kinetic isotope effect (KIE) but a bigger competitive (DV/K) KIE than that by the WT SPL. Moreover, the G168R mutant also produces a large portion of the abortive repair product TpT-[Formula: see text]; the formation of which indicates that cysteine 141 is no longer well positioned as the H-donor to the thymine allylic radical intermediate. All these data imply that the mutation at the remote glycine 168 residue alters the enzyme 3D structure, subsequently reducing the SPL activity by changing the positions of the essential amino acids involved in the radical transfer process.
  • Thumbnail Image
    Item
    Internal tandem duplication mutations in FLT3 gene augment chemotaxis to Cxcl12 protein by blocking the down-regulation of the Rho-associated kinase via the Cxcl12/Cxcr4 signaling axis
    (American Society for Biochemistry and Molecular Biology, 2014-11-07) Onish, Chie; Mori-Kimachi, Satomi; Hirade, Tomohiro; Abe, Mariko; Taketani, Takeshi; Suzumiya, Junji; Sugimoto, Toshitsugu; Yamaguchi, Seiji; Kapur, Reuben; Fukuda, Seiji; Department of Pediatrics, IU School of Medicine
    Internal tandem duplication mutations in the Flt3 gene (ITD-FLT3) enhance cell migration toward the chemokine Cxcl12, which is highly expressed in the therapy-protective bone marrow niche, providing a potential mechanism underlying the poor prognosis of ITD-FLT3(+) acute myeloid leukemia. We aimed to investigate the mechanisms linking ITD-FLT3 to increased cell migration toward Cxcl12. Classification of the expression of Cxcl12-regulated genes in ITD-FLT3(+) cells demonstrated that the enhanced migration of ITD-FLT3(+) cells toward Cxcl12 was associated with the differential expression of genes downstream of Cxcl12/Cxcr4, which are functionally distinct from those expressed in ITD-FLT3(-) cells but are independent of the Cxcr4 expression levels. Among these differentially regulated genes, the expression of Rock1 in the ITD-FLT3(+) cells that migrated toward Cxcl12 was significantly higher than in ITD-FLT3(-) cells that migrated toward Cxcl12. In ITD-FLT3(-) cells, Rock1 expression and Mypt1 phosphorylation were transiently up-regulated but were subsequently down-regulated by Cxcl12. In contrast, the presence of ITD-FLT3 blocked the Cxcl12-induced down-regulation of Rock1 and early Mypt1 dephosphorylation. Likewise, the FLT3 ligand counteracted the Cxcl12-induced down-regulation of Rock1 in ITD-FLT3(-) cells, which coincided with enhanced cell migration toward Cxcl12. Rock1 antagonists or Rock1 shRNA abolished the enhanced migration of ITD-FLT3(+) cells toward Cxcl12. Our findings demonstrate that ITD-FLT3 increases cell migration toward Cxcl12 by antagonizing the down-regulation of Rock1 expression. These findings suggest that the aberrant modulation of Rock1 expression and activity induced by ITD-FLT3 may enhance acute myeloid leukemia cell chemotaxis to the therapy-protective bone marrow niche, where Cxcl12 is abundantly expressed.