Dilated Cardiomyopathy due to the Novel MT-CYB Missense Mutation m.14757T>C.

Mitochondrial DNA (mtDNA) mutations frequently manifest with multisystem disease, including cardiomyopathy (CM). Various studies described mutations in protein-encoding mtDNA genes, such as cytochrome-b, manifesting with CM. A detailed clinical, biochemical, and molecular genetic analysis was performed in a 40-year-old male with dilated CM (DCM) to detect the underlying mtDNA defect. Muscle biopsy showed complex-III deficiency, and sequencing of the cytochrome-b gene revealed the pathogenic variant m.14757T>C in MT-CYB, resulting in the replacement of the hydrophobic methionine by the polar threonine (M4T). By application of the PolyPhen algorithm the variant was predicted as pathogenic. The mutation was not found in 100 healthy controls and never reported as a neutral polymorphism despite extensive sequencing of the cytochrome-b gene in 2,704 normal healthy controls from different ethnic backgrounds. In conclusion, the novel variant m.14757T>C in MT-CYB is associated with DCM suggesting a pathophysiologic role of the variant in the development of DCM.

Novel m.15434C>A (p.230L>I) Mitochondrial Cytb Gene Missense Mutation Associated with Dilated Cardiomyopathy.

Background. Previously it has been shown that various types of hypertrophic and dilative cardiomyopathy (hCMP, dCMP) can be attributed to disturbed mitochondrial oxidative energy metabolism. Several studies described mutations in mitochondrial DNA-located genes encoding for subunits of respiratory chain complexes, including the cytochrome b gene (MT-CYB), causing CMPs. Methods and Results. In the present study the MT-CYB gene was analysed in 30 patients with hCMP, 40 patients with dCMP, and 50 controls for alterations. Altogether, 27 MT-CYB variants were detected. Twenty-four of them were single nucleotide polymorphisms defining common haplogroups. The variant m.15434C>A was found in a single patient with severe dCMP and assessed as novel mutation, since it was not found in healthy controls or available data sets, and was nonhaplogroup associated with Phylotree. This variant altered an amino acid (L230I) with a high interspecific amino acid conservation index (CI = 97.7%) indicative of the functional importance of the residue. Conclusions. Though the L230I mutation seems to play a causative role for dCMP, prospective studies on yeast or transgenic mice models with defined mutation are warranted to study the pathogenetic impact of this mutation.

HLA class I polymorphisms in Tunisian patients with otosclerosis.

BACKGROUND: Otosclerosis is a common form of hearing impairment among Western-Eurasian adults. The cause of otosclerosis remains unknown. Autoimmune reaction against the otic capsule has been suggested as a possible aetiologic factor in otosclerosis. AIM: The present study is the first report to evaluate the relationship between class I major histocompatibility complex (MHC) genes (HLA-A, HLA-B and HLA-Cw) and genetic susceptibility to otosclerosis in Tunisian patients. SUBJECTS AND METHODS: Fifty unrelated Tunisian patients exhibiting clinical otosclerosis were typed for HLA-A, HLA-B and HLA-Cw antigens and compared with 100 ethnically-matched healthy controls. RESULTS: Increased frequencies of HLA-A*03 (OR = 4.16, Pc < 0.043), HLA-B*35 (OR = 2.76, Pc < 0.043) and HLA-Cw*03 (OR = 4.57, Pc < 0.043) antigens were found in the patients with otosclerosis compared with healthy controls. Individuals with HLA-A*30 (OR=0.25, Pc < 0.043), HLA-B*51 (OR = 0.11, Pc < 0.043), HLA-Cw*16 (OR = 0.08, Pc < 0.043) and Cw*06 (OR=0.32, Pc < 0.043) antigens have a protective effect against otosclerosis. CONCLUSIONS: In conclusion, the data suggest that a variation in class I HLA antigens could be a genetic factor involved in susceptibility to otosclerosis in the Tunisian population.

Angiotensinogen gene polymorphism in acute myocardial infarction patients.

INTRODUCTION: The objective of the study was to explore the role of a genetic variant of angiotensinogen (AGT), M235T, as an independent risk factor for acute myocardial infarction (AMI) and to investigate the possible association with the severity of coronary artery disease (CAD), estimated on the basis of the number of coronary stenoses and critical arterial occlusions. PATIENTS AND METHODS: 123 AMI patients were compared to 144 healthy controls. AGT genotypes were determined by PCR. RESULTS: A significant association was found between AGT M235T polymorphism and AMI (p = .021). By logistic regression, the TT genotype appeared to confer 1.9-fold increased risk for AMI in both the univariate and the multivariate model. The frequencies of the TT genotype and T allele increased with the number of stenoses in coronary vessels. Moreover, the TT genotype and the T allele were more frequent in the subgroup of patients with stenoses in at least four coronary vessels than in other patients, including subjects with one- to three-vessel disease. Furthermore, the TT genotype and the T allele were significantly more frequent in patients with critical arterial occlusions (> 90%) than in subjects without critical stenoses. CONCLUSIONS: The AGT M235T polymorphism associates with AMI risk and influences CAD severity.

Genotypic interactions of renin-angiotensin system genes with diabetes type 2 in a Tunisian population.

AIMS: To explore the role of genetic variants of angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE I/D), and angiotensin type 1 receptor (AT1R A1166C) as predictors of diabetes risk and to examine their combined effects on type 2 diabetes mellitus (T2DM) patients. MAIN METHODS: One hundred and fourteen T2DM patients were compared to 175 healthy controls with similar age and sex. KEY FINDINGS: The genotypic frequencies for all three genes alone were significantly associated with increased risk of developing diabetes. Logistic regression analysis of classic coronary risk factors and the genetic polymorphisms demonstrated that hypertension and ACE DD genotype were the most significant contributors to T2DM. For the renin-angiotensin system (RAS) genes, the risk of T2DM in individuals with one risk genotype was 1.9 (95%CI: 1.1-3.0, p=0.017) higher than those with zero risk genotype. Individuals who carried two risk genotypes had a 4.0 (95%CI 1.7-9.4, p=0.001) times higher risk of T2DM than those who did not carry any risk genotypes of the RAS genes. Most interestingly, the risk of T2DM for individuals with three risk genotypes was 26.2 (95%CI: 5.8-117.9, p<0.001) higher than those with zero risk genotype. SIGNIFICANCE: The results of the present study imply that genotyping of renin-angiotensin system genes could become an important part of the clinical process of risk identification for T2DM in Tunisian population.

Association of ACE I/D polymorphism in Tunisian patients with dilated cardiomyopathy.

Primary cardiomyopathies are multifactorial diseases. Genetic factors other than the causal mutations in the modified genes affect the phenotypic expression of dilated cardiomyopathy. The aim of this study was to determine the association of angiotensin-converting enzyme I/D polymorphism with the risk of dilated cardiomyopathy in a Tunisian population. A total of 76 patients with dilated cardiomyopathy was compared to 151 ethnically, age- and gender-matched controls. The frequencies of the DD genotype and D allele were significantly higher in patients as compared with controls, and were associated with increased risk of dilated cardiomyopathy (ACE DD versus ID and II: OR = 3.05 (95% CI, 1.58-5.87; p = 0.001)); D versus I: OR = 2 (95% CI: 1.35-2.97; p = 0.001)). No association was found between the combined genotypes (DD+ID) or D allele and left ventricular end diastolic diameter in dilated cardiomyopathy patients with severe and moderate clinical phenotypes. DD genotype and D allele of angiotensin-converting enzyme I/D gene polymorphism are associated with increased risk of dilated cardiomyopathy in a Tunisian population but do not influence the cardiac phenotype severity.

Angiotensin-converting enzyme insertion/deletion gene polymorphism in a Tunisian healthy and acute myocardial infarction population.

INTRODUCTION: The role of the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme gene (ACE) on acute myocardial infarction (AMI) is controversial. OBJECTIVES: To assess the effect of the ACE I/D polymorphism on AMI compared with the healthy controls and its relationship with serum ACE activity in a Tunisian population. DESIGN AND METHODS: A total of 119 patients with AMI were compared with 238 healthy controls from the same geographical area. ACE genotyping was determined by polymerase chain reaction, and serum ACE activity was measured with N-[3-(2-furylacryloyl]-L-phenylalanyl-L-glycyl-L-glycine as substrate. RESULTS: The ACE I/D polymorphism was significantly different between patients and controls (p < 0.0001). The frequencies of the DD genotype and the D allele were statistically higher in patients with AMI as compared with the controls and were associated with increased risk of AMI (DD vs. ID and II: odds ratio = 4.27, p < 0.0001, 95% confidence interval = 2.65-6.86; D vs. I: odds ratio = 3.15, p < 0.0001, 95% confidence interval = 2.26-4.40). This association was independent of other cardiovascular risk factors but dyslipidemia (p = 0.002) that was not represented in AMI patients with II genotype and in a lower extent with hypertension (p < 0.05). Serum ACE activity was significantly higher in AMI patients with ACE DD genotype compared with the subjects with ID or II genotype (p = 0.034) and was not correlated with other cardiovascular risk factors. CONCLUSIONS: ACE DD genotype associated with higher serum ACE activity is increased in the studied population and might be clinically useful as markers to assess risk for AMI.

Relationship between genetic polymorphisms of angiotensin-converting enzyme and methylenetetrahydrofolate reductase as risk factors for type 2 diabetes in Tunisian patients.

BACKGROUND/AIMS: The role of methylenetetrahydrofolate reductase (MTHFR) and angiotensin-converting enzyme (ACE) gene polymorphisms as being risk factors for diabetes is still controversial. The aim was to investigate the distribution of ACE and MTHFR genotypes as well as to evaluate the role of plasmatic total homocysteine levels (tHcy) and ACE activity in Tunisian patients with type 2 diabetes mellitus (T2DM). DESIGN AND METHODS: 115 T2DM patients compared to 116 healthy volunteers. RESULTS: The ACE I/D polymorphism was significantly associated with diabetes (p<0.0001). The DD genotype and D allele were more frequent in patients compared to control group [DD: OR=4.93; p<0.0001; 95 % CI: 2.71-8.97; D: OR=3.08, 95% CI: 2.09-4.51 p<0.0001]. MTHFR allele and genotype frequencies did not differ between patients and controls. The susceptibility to diabetes in individuals with genotypes DD+vTT was 13.39 and in the individuals with DD+CT was 6.57 times that of the controls. However, individuals with genotypes ID+CC or II+CT have a protective effect against diabetes. The DD and TT genotypes were associated with significantly higher ACE activity and tHcy levels in diabetics. CONCLUSION: Our data suggest that ACE ID polymorphism may act synergistically with MTHFR C677T polymorphism to assess diabetes risk.

Markers of subtypes in inflammatory breast cancer studied by immunohistochemistry: prominent expression of P-cadherin.

BACKGROUND: Inflammatory breast cancer (IBC) is a distinct and aggressive form of locally-advanced breast cancer with high metastatic potential. In Tunisia, IBC is associated with a high death rate. Among the major molecular subtypes, basal breast carcinomas are poorly differentiated, have metastatic potential and poor prognosis, but respond relatively well to chemotherapy. The aim of this study was to determine the distribution of molecular subtypes in IBC and identify factors that may explain the poor prognosis of IBC. METHODS: To determine breast cancer subtypes we studied by immunohistochemistry the expression of 12 proteins in a series of 91 Tunisian IBC and 541 non-IBC deposited in tissue microarrays. RESULTS: We considered infiltrating ductal cases only. We found 33.8% of basal cases in IBC vs 15.9% in non-IBC (p < 0.001), 33.3% of ERBB2-overexpressing cases in IBC vs 14.5% in non-IBC (p < 0.001), and 29.3% of luminal cases in IBC vs 59.9% in non-IBC (p < 0.001). The most differentially-expressed protein between IBCs and non-IBCs was P-cadherin. P-cadherin expression was found in 75.9% of all IBC vs 48.2% of all non-IBC (p < 0.001), 95% of IBC vs 69% of non-IBC (p = 0.02) in basal cases, and 82% of IBC vs 43% of non-IBC (p < 0.001) in luminal cases. Logistic regression determined that the most discriminating markers between IBCs and non-IBCs were P-cadherin (OR = 4.9, p = 0.0019) MIB1 (OR = 3.6, p = 0.001), CK14 (OR = 2.7, p = 0.02), and ERBB2 (OR = 2.3, p = 0.06). CONCLUSION: Tunisian IBCs are characterized by frequent basal and ERBB2 phenotypes. Surprisingly, luminal IBC also express the basal marker P-cadherin. This profile suggests a specificity that needs further investigation.

A new locus for otosclerosis, OTSC8, maps to the pericentromeric region of chromosome 9.

Otosclerosis is a common disorder of the otic capsule resulting in hearing impairment in 0.3-0.4% of the Caucasian population. The aetiology of the disease remains unclear. In most cases, otosclerosis can be considered as a complex disease. In some cases, the disease is inherited as an autosomal dominant trait, sometimes with reduced penetrance. To date, seven autosomal dominant loci have been reported, but none of the disease-causing genes has been identified. In this study, we present the results of a genome-wide linkage analysis in a large Tunisian family segregating autosomal dominant otosclerosis. Linkage analysis localised the responsible gene to chromosome 9p13.1-9q21.11 with a maximal LOD score of 4.13, and this locus was named OTSC8. Using newly generated short tandem repeat polymorphism markers, we mapped this new otosclerosis locus to a 34.16 Mb interval between the markers D9S970 and D9S1799. This region comprises the pericentromeric region on both arms of chromosome 9, a highly complex region containing many duplicated sequences.

Consanguinity and endogamy in Northern Tunisia and its impact on non-syndromic deafness.

Deafness is an important health problem in the Tunisian population, especially in isolates where the prevalence ranges from 2 to 8%. To evaluate the effect of inbred unions on deafness, a study was conducted on 5,020 individuals (160 are deaf) between 2000 and 2002 in the North of Tunisia. The coefficient of inbreeding for all individuals and the levels of inbreeding in ten districts were computed. The higher levels were obtained in the rural districts. Our study revealed that geographic isolation, social traditions, and parental involvement in mode selection all contribute to increase consanguinity in these regions. The mean inbreeding seems to be similar to those estimated in highly inbred isolates in the world. The relative risk of the 35delG mutation, the single most frequent allele for non-syndromic recessive deafness in Tunisia, was estimated from the observed inbreeding coefficient and found to be 10.76 (SD 7.74) for first-cousin marriages, which are the most common form of consanguineous marriage encountered. Our knowledge of the risk rate of deafness and our understanding of consanguinity is required for the prevention of genetic deafness in the Tunisian population.