Christina Baboonian

Identification of a deletion in plakoglobin in arrhythmogenic right ventricular cardiomyopathy with palmoplantar keratoderma and woolly hair (Naxos disease)

BACKGROUND Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an autosomal dominant heart muscle disorder that causes arrhythmia, heart failure, and sudden death. Previously we mapped the genetic locus for the triad of autosomal recessive ARVC, palmoplantar keratoderma, and woolly hair (Naxos disease) to chromosome 17q21, in which the gene for plakoglobin is encoded. This protein is a key component of desmosomes and adherens junctions, and is important for the tight adhesion of many cell types, including those in the heart and skin. METHODS We studied 19 individuals with Naxos disease, as well as unaffected family members and unrelated individuals from the neighbouring Greek islands of Naxos and Milos. Gene sequence was determined by reverse transcriptase PCR from RNA isolated from the skin of an affected individual and mutations in other cases were confirmed by restriction-enzyme analysis. FINDINGS A homozygous 2 base pair deletion in the plakoglobin gene was identified only in the 19 affected individuals. This deletion caused a frameshift and premature termination of the protein, which was shown by western blot analysis. 29 clinically unaffected family members were heterozygous for the mutation; 20 unrelated individuals from Naxos and 43 autosomal dominant ARVC probands were homozygous for the normal allele. INTERPRETATION The finding of a deletion in plakoglobin in ARVC suggests that the proteins involved in cell-cell adhesion play an important part in maintaining myocyte integrity, and when junctions are disrupted, cell death, and fibrofatty replacement occur. Therefore, the discovery of a mutation in a protein with functions in maintaining cell junction integrity has important implications for other dominant forms of ARVC, related cardiomyopathies, and other cutaneous diseases.

Heat-Shock Protein 60-Reactive CD4+CD28null T Cells in Patients With Acute Coronary Syndromes

Background—CD4+CD28null T cells are present in increased numbers in the peripheral blood of patients with acute coronary syndrome (ACS) compared with patients with chronic stable angina (CSA). The triggers of activation and expansion of these cells to date remain unclear. Methods and Results—Twenty-one patients with ACS and 12 CSA patients with angiographically confirmed coronary artery disease and 9 healthy volunteers were investigated. Peripheral blood leukocytes were stimulated with human cytomegalovirus (HCMV), Chlamydia pneumoniae, human heat-shock protein 60 (hHSP60), or oxidized LDL (ox-LDL). CD4+CD28null cells were separated by flow cytometry and assessed for antigen recognition using upregulation of interferon-&ggr; and perforin mRNA transcription as criteria for activation. CD4+CD28null cells from 12 of 21 patients with ACS reacted with hHSP60. No response was detected to HCMV, C pneumoniae, or ox-LDL. Incubation of the cells with anti-MHC class II and anti-CD4 antibodies but not anti-class I antibodies blocked antigen presentation, confirming recognition of the hHSP60 to be via the MHC class II pathway. Patients with CSA had low numbers of CD4+CD28null cells. These cells were nonreactive to any of the antigens used. Circulating CD4+CD28null cells were present in 5 of the 9 healthy controls. None reacted with hHSP60. Conclusions—We have shown that hHSP60 is an antigen recognized by CD4+CD28null T cells of ACS patients. Endothelial cells express hHSP60 either constitutively or under stress conditions. Circulating hHSP60-specific CD4+CD28null cells may, along other inflammatory mechanisms, contribute to vascular damage in these patients.

Coxsackie B Viruses and Human Heart Disease

A large number of viruses can cause infections of the heart. Among these are the enteroviruses, adenoviruses, retroviruses and even orthomyxoviruses (Clements 1993). Human viruses causing systemic infections have a viremic stage during which the heart may be exposed to infectious agents. Thus the presence of virus in the myocytes or the infiltrating immune cells is likely to be a more common event than suspected. However, clinically overt cases of heart disease following common viral infections are rare and may represent a small percentage of all viral heart infections. Of the numerous agents commonly infecting humans, enteroviruses and in particular coxsackie B viruses (CVB) have been the most closely scrutinised agents implicated in human heart disease. The aim of this review is to discuss the evidence for an etiologic link between enteroviruses and in particular CVB and human heart disease.

A new mutation of the cardiac troponin T gene causing familial hypertrophic cardiomyopathy without left ventricular hypertrophy

AIM To screen for a mutation of the cardiac troponin T gene in two families where there had been sudden deaths without an increase in left ventricular mass but with myocardial disarray suggesting hypertrophic cardiomyopathy. METHODS DNA from affected individuals from both families was used to screen the cardiac troponin T gene on an exon by exon basis. Mutation screening was achieved by polymerase chain reaction and direct sequencing. Where appropriate, a mutation was confirmed by restriction digest. RESULTS A novel missense mutation of exon 9 was found in the affected individuals of one of the families. This mutation at amino acid 94 resulted in the substitution of arginine for leucine and was not found in 100 normal control samples. A mutation of the cardiac troponin T gene was excluded in the second family. CONCLUSIONS A mutation of the gene for the sarcomeric protein cardiac troponin T can cause familial hypertrophic cardiomyopathy with marked myocyte disarray and frequent premature sudden death in the absence of myocardial hypertrophy at clinical or macroscopic level.

Matrix metalloproteinase-9 expression is associated with the presence of Chlamydia pneumoniae in human coronary atherosclerotic plaques

Objective: To investigate the association between Chlamydia pneumoniae and matrix metalloproteinase-9 (MMP-9) in atherosclerotic plaques. Design: 31 coronary atherosclerotic plaque specimens were studied by immunohistochemistry, polymerase chain reaction (PCR), and reverse transcription PCR for the presence of C pneumoniae antigen and genomic DNA, and of MMP-9 protein and transcripts. Results: Immunohistochemical analysis identified a strong association between the presence of C pneumoniae antigen and production of MMP-9 in coronary atherosclerotic plaques (p  =  0.001). Furthermore, analysis of the intralesional amount of C pneumoniae and MMP-9 indicated an increased number of cells positive for MMP-9 in arterial sections that had increased C pneumoniae positivity (p < 0.05). Conclusions: This study provides evidence of an association between expression of MMP-9 and the intravascular presence of C pneumoniae and may suggest a potential pathological mechanism whereby C pneumoniae may contribute to the progression of coronary atherosclerosis.

Eradication of viral myocarditis: Is there hope?*

Adenoviruses acquired celebrity status when viral constructs began to be used as gene transfer vectors in man. Within a short period of time a virus ignored by all except dedicated virologists became known worldwide. A review of the current literature, however, reflects an omission. Adenoviruses as

Absence of viral nucleic acids in early and late dilated cardiomyopathy

OBJECTIVE To investigate whether viral infection acts as a trigger factor for the development of dilated cardiomyopathy in genetically predisposed individuals with a family history of disease. SETTING Patients attending the cardiomyopathy unit in a cardiac tertiary referral centre. DESIGN Nested polymerase chain reaction (nPCR) was used to determine whether enteroviral, adenoviral, or cytomegaloviral nucleic acids were detectable in the myocardium of 19 asymptomatic relatives of patients with dilated cardiomyopathy; all these relatives had echocardiographic abnormalities thought to represent early disease. Explanted hearts from patients with end stage dilated cardiomyopathy were also studied and were compared with 25 controls (ischaemic heart disease (21), valvar heart disease (2), hypertrophic cardiomyopathy (1), restrictive cardiomyopathy (1)). Myocardial tissue from two fatal cases of culture positive coxsackie myocarditis was used as a positive control. RESULTS No viral nucleic acid was detected in any group other than in those with myocarditis. Spiking of random wells with purified recombinant viral nucleic acids confirmed the sensitivity and reproducibility of the assays. CONCLUSIONS Myocardial viral infection is not detectable in relatives of patients with dilated cardiomyopathy who are suspected of having early disease. There is no evidence that viruses act as a trigger factor for initiating the dilated cardiomyopathy in these patients.

Cytosine methylation confers instability on the cardiac troponin T gene in hypertrophic cardiomyopathy

Editor—Hypertrophic cardiomyopathy (HCM) is an inherited disease (MIM 192600, 115195) of the heart muscle, characterised by unexplained left ventricular hypertrophy. HCM is also one of the major causes of sudden cardiac death,1sometimes occurring in young asymptomatic people.2-4Although sporadic forms do rarely occur,5 generally HCM has an autosomal dominant pattern of inheritance caused by mutations of the genes coding for proteins of the cardiac sarcomere. Subjects with HCM caused by mutations in the cardiac troponin T ( cTNT ) gene have been clinically shown to be at increased risk of sudden death,6 which may occur even in the absence of marked morphological abnormalities.7Since incomplete penetrance of the clinical phenotype, measured by ECG and echocardiographic parameters, is one of the hallmarks of “troponin” disease, the identification of cTNT mutation in probands would facilitate identification of “at risk” relatives who may not fulfil clinical diagnostic criteria. In the course of a study undertaken to characterise the cTNT mutation profile in HCM patients, we identified a cluster of mutations in exons 8 and 9. Five out of the 11 mutations published to date in this gene have been found in exons 88 and 9.7-10 We report here a novel Arg94Cys de novo mutation in a female patient presenting with HCM bringing the total of cTNT mutations to 12. Four of the mutations found in exon 9, Arg92Trp, Arg92Gln, Arg94Cys, and Ala104Val, involve C→T transitions (or G→A transitions in the opposite strand) within CpG dinucleotides. Approximately 70% of the cytosines within CpG dinucleotides in the mammalian genome contain highly mutable 5-methyl-cytosine (5mC) residues. These residues are not randomly distributed and the majority of the genome is CpG depleted.11 Although some CpG dinucleotides are found within coding regions, most CpG residues are in CpG islands, …

Placental infection with Chlamydia pneumoniae and intrauterine growth restriction

BACKGROUND The concept that low birth weight infants are more predisposed to coronary artery disease (CAD) in adulthood has been studied extensively. Although many infectious agents have been associated with intrauterine growth restriction (IUGR), Chlamydia pneumoniae an organism implicated in CAD has not been investigated. It was our aim to assess whether C. pneumoniae DNA is present in placental tissue and whether its detection is associated with IUGR. METHODS Fifty-nine pregnant women were studied: 32 women had an uncomplicated pregnancy with no antenatal or post-natal evidence of IUGR. Twenty-seven women had pregnancies with ultrasonographically demonstrated IUGR, defined as foetal abdominal circumference measuring less than 2 S.D.s from the mean for gestational age. At the time of delivery, maternal blood and placental tissue samples were obtained. Placental samples were taken from four sites centrally and peripherally on the maternal and foetal side of the placentas and tested by nested polymerase chain reaction for C. pneumoniae DNA. IgG antibodies to C. pneumoniae were measured using microimmunfluorescence. RESULTS C. pneumoniae DNA was detected in 44% of the placental tissue but there was no difference in the prevalence of bacterial DNA between the control and the low birth weight group (P=0.58). Additionally C. pneumoniae seropositivity did not differ between the index and control groups (78 vs. 70%, P=0.44). CONCLUSIONS C. pneumoniae is present in placental tissue. Its presence however does not correlate with IUGR. Similarly, maternal C. pneumoniae seropositivity is not related to low birth weight. Thus C. pneumoniae infection is unlikely to play a role in the pathogenesis of IUGR.

Immunological analysis of the tegument phosphoprotein ppUL83 of human cytomegalovirus

Immunological properties of the tegument phosphoprotein, ppUL83, of human cytomegalovirus (HCMV), expressed using a replication deficient recombinant adenovirus vector (RAd83) are described. The initial characterisation of this protein was carried out by immunofluorescence (IF), immunoprecipitation (RIP) and immunoblotting using nine mouse monoclonal antibodies (Mabs) directed against five linear and four conformational epitopes of ppUL83. The reactivity of the recombinant protein with the Mabs was similar to that observed with native ppUL83, although, the kinetics of its expression was in agreement with expression derived from the HCMV major immediate early promoter (MIEP). The recombinant antigen was used successfully in an Enzyme Immunoassay (EIA) for the detection of IgG class antibodies in 171 sequential sera taken from 21 heart transplant recipients. Comparison of HCMV-infected and RAd83-infected cell extracts in this experiment showed that recombinant antigen could substitute whole virus extracts as a single well-characterised protein in EIA. Serum IgG avidity measurements, using the recombinant ppUL83, differentiated between primary and past HCMV infections in the population studied.