Heterozygous Form Research Articles

Changing the Conversation Regarding Pediatric Cholesterol Screening

Changing the Conversation Regarding Pediatric Cholesterol Screening

Prevalence of methylenetetrahydrofolate reductase C677T and A1298C polymorphisms in Egyptian patients with type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a major public health problem around the world. The C677T and A1298C polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene have been reported to be associated with T2DM and its complications. This study is a case-control study which was performed to clarify the association between polymorphisms in these two genes and T2DM among Egyptians. Study population (n=120) consists of 60 Egyptian diabetic patients and 60 healthy controls. The MTHFR C677T and A1298C polymorphisms were genotyped by polymerase chain reaction, followed by enzymatic digestion with HinfI and MboII enzymes, respectively. C677T and A1298C genetic polymorphisms conveyed an increase in T2DM risk (OR=3.5, 95% CI=1.1–11.6, p=0.032 and OR=2.2, 95% CI=0.7–6.9, p=0.004 respectively). Additionally, no significant associations between lipid/glucose metabolic indexes with MTHFR genotypes among diabetic patients were observed. Combined MTHFR gene polymorphisms revealed higher T2DM risk in homozygous and heterozygous forms compared to single gene polymorphism with pronounced risk in C677T/CT-A1298C/CC combined form (OR=6.56, 95% CI=0.76–56.2, p 0.041). In conclusion, our data suggest that MTHFR C677T and A1298C polymorphisms are risk factor for T2DM in Egyptian patients. Also, the two gene polymorphisms may act synergistically to increase the risk of diabetes. Furthermore, it should be noted that the size of the studied population was relatively small and therefore, large-scale prospective studies are needed to confirm these findings.

Therapeutic Strategies for Optimizing Outcomes in the Severe Familial Hypercholesterolemia Patient

Familial hypercholesterolemia (FH), in both its homozygous and heterozygous inheritance forms, is both underrecognized and undertreated in the United States and elsewhere. This is an important gap in current evidence-based clinical practice, for new recommendations from the NLA underscore the importance of early detection and treatment if the morbidity and mortality associated with FH is to be reduced. As discussed in this Journal of Clinical Lipidology open-access eCME activity (accessed at http://multimedia.lipidjournal.com/2012/SevereFH/), efforts to understand and address this gap are especially important at this point because after decades of relying on an established armamentarium of drugs for treating the severe elevations in low-density lipoprotein cholesterol and early cardiovascular heart disease that are caused by FH, several new classes of drugs show additional therapeutic benefit as possible future agents for treating FH. Underberg JA. J Clin Lipidol. 2012;6(6). Accessible at http://lipidjournal.com.

Effects of endoplasmic reticulum stressors on maturation and signaling of hemizygous and heterozygous wild-type and mutant forms of KIT

Gain of function mutations of KIT are frequent in some human tumors, and are sensible to tyrosine kinase inhibitors. In most tumors, oncogenic mutations are heterozygous, however most in vitro data of KIT activation have been obtained with hemizygous mutation. This study aimed to investigate the maturation and activation of wild-type (WT) and mutant (M) forms of KIT in hemizygous and heterozygous conditions. WT and two types of exon 11 deletions M forms of human KIT were expressed in NIH3T3 cell lines. Membrane expression of KIT was quantified by flow cytometry. Quantification of glycosylated forms of KIT and phosphorylated forms of AKT and ERK were performed by western blot. Simultaneous activation of WT KIT and treatment with endoplasmic reticulum (ER) inhibitors, tunicamycin or brefeldin A induced a complete inhibition of membrane expression of the 145 kDa form of KIT. By contrast activation or ER inhibitors alone, only partly inhibited this form. ER inhibitors also inhibited KIT activation-dependent phosphorylation of AKT and ERK1/2. Brefeldin A induced a complete down regulation of the 145 kDa form in hemizygous M, and induced an intra-cellular accumulation of the 125 kDa form in WT but not in hemizygous M. Heterozygous cells had glycosylation and response to ER inhibitors patterns more similar to WT than to hemizygous M. Phosphorylated AKT was reduced in hemizygous cells in comparison to WT KIT cells and heterozygous cells, and in the presence of brefeldin A in all cell lines. Effects of ER inhibitors are significantly different in hemizygous and heterozygous mutants. Differences in intra-cellular trafficking of KIT forms result in differences in downstream signaling pathways, and activation of PI3K/AKT pathway appears to be tied to the presence of the mature 145 kDa form of KIT at the membrane surface.

Generalized glucocorticoid resistance caused by a novel two-nucleotide deletion in the hormone-binding domain of the glucocorticoid receptor gene NR3C1

Generalized glucocorticoid resistance is characterized by impaired cortisol signaling, resulting from mutations of the glucocorticoid receptor (GR) gene NR3C1. The objective of our study was to identify the causative mutation in a patient with clinical manifestations compatible with generalized glucocorticoid resistance and to determine the functional consequences of the mutation. The possible occurrence of NR3C1 mutations in a selected group of hypertensive subjects with low plasma renin and aldosterone levels was also explored. The proband, a male athlete, was diagnosed with hypertension associated with low plasma renin activity and low serum aldosterone concentration at the age of 27 years. Liddle's syndrome was suspected and the patient was treated with amiloride with initial success. Subsequent examinations revealed elevated serum cortisol and ACTH levels, with resistance to suppression with low doses of dexamethasone. After identification of an NR3C1 mutation in the proband, the available family members and 51 nonrelated hypertensive subjects with low plasma renin and aldosterone concentrations were also studied. A two-nucleotide deletion in exon 9α, predicted to cause a frameshift mutation (p.L773VfsX25) in the hormone-binding domain of the GR, was identified in the patient in a heterozygous form. Affected brother and father died of premature coronary heart disease. Functional studies in COS-1 cells showed that this mutation eliminates both ligand-binding and transactivation ability of the receptor. No pathogenic NR3C1 mutations were identified in 51 unrelated hypertensive patients with low plasma renin and aldosterone levels. We identified a novel frameshift mutation in NR3C1 as the cause of glucocorticoid resistance. The mutation eliminates the functional activity of the GR, as studied by in vitro experiments. Mutations in NR3C1 do not seem to be common causes for hypertension with low renin and aldosterone levels.

Inactivation and Inducible Oncogenic Mutation of p53 in Gene Targeted Pigs

Mutation of the tumor suppressor p53 plays a major role in human carcinogenesis. Here we describe gene-targeted porcine mesenchymal stem cells (MSCs) and live pigs carrying a latent TP53R167H mutant allele, orthologous to oncogenic human mutant TP53R175H and mouse Trp53R172H, that can be activated by Cre recombination. MSCs carrying the latent TP53R167H mutant allele were analyzed in vitro. Homozygous cells were p53 deficient, and on continued culture exhibited more rapid proliferation, anchorage independent growth, and resistance to the apoptosis-inducing chemotherapeutic drug doxorubicin, all characteristic of cellular transformation. Cre mediated recombination activated the latent TP53R167H allele as predicted, and in homozygous cells expressed mutant p53-R167H protein at a level ten-fold greater than wild-type MSCs, consistent with the elevated levels found in human cancer cells. Gene targeted MSCs were used for nuclear transfer and fifteen viable piglets were produced carrying the latent TP53R167H mutant allele in heterozygous form. These animals will allow study of p53 deficiency and expression of mutant p53-R167H to model human germline, or spontaneous somatic p53 mutation. This work represents the first inactivation and mutation of the gatekeeper tumor suppressor gene TP53 in a non-rodent mammal.

Strokes and hemoglobinopathies in Burkina Faso

S and C hemoglobinopathies are a group of inherited blood disorders including sickle cell disease, characterized by the presence of abnormal S and C hemoglobins. They are common in tropical Africa. Stroke is a common complication of sickle cell disease. Studies of the relation between these two diseases are virtually nonexistent in sub-saharan Africa. Our work aimed to study the influence of these hemoglobinopathies on the onset of strokes in adults. This cross-sectional study took place from 1st December 2009 to 31st May 2010 at University Hospital Yalgado Ouedraogo. Out of 142 patients admitted to our neurology department during this period, 74 patients had had strokes. Their mean age was 55.9 years and their sex ratio 1.53. Ischemic strokes accounted for 57% of the total, followed by cerebral hemorrhage (39%). Forty-six patients (62%) were AA genotype, 27 (36%) patients had sickle cell trait (16 AC and 11 AS) and three patients were homozygous CC. This study showed a higher prevalence of hemoglobinopathies in patients with stroke than in the general population. Unlike heterozygous SC and homozygous SS forms, the existence of sickle cell trait in this population does not appear to increase the risk of onset of ischemic stroke but may reduce the age at onset of cerebral hemorrhage.

Oral contraception in women with mild thrombophilia: What have we learned recently?

Mild thrombophilias include heterozygous forms of Factor V Leiden and prothrombin G20210A mutation and high levels of factor VIII. These defects are responsible for only a moderate increase of venous thromboembolism (VTE) risk compared with strong thrombophilias (antithrombin III, protein C and protein S deficiencies and homozygous forms of factor V Leiden and G20210A prothrombin mutation). Combined oral contraceptives increase the VTE risk in women in a fertile age, and in a far more important way in thrombophilia carrier women. Universal screening of thrombophilia test before the use of combined oral contraceptives is not recommended. However, selective VTE-history based screening is associated with a better cost-effectiveness, especially in asymptomatic relatives of carriers of strong thrombophilia. Currently, combined oral contraceptives are discouraged in women with any thrombophilic defects. The VTE risk is higher during pregnancy and postpartum period compared to hormonal contraceptive use period in women with mil thrombophilia. For this reason, a careful election of an alternative birth control method is necessary in these women.

Association of polymorphism of some candidate genes of lipid and carbohydrate metabolism with anthropometric indices and inflammatory markers in patients with type 2 diabetes mellitus in the population of Azerbaijan

The purpose of the study was to analyze the association of gene polymorphisms of leptin, adiponectin, tumor necrosis factor alpha (TNF-α), insulin-induced gene, and the parameters of carbohydrate and lipid metabolism, level of C-reactive protein (CRP) in patients with type 2 diabetes mellitus (T2DM) with anthropometric data. A total of 95 patients with T2DM of Azerbaijan population. The average age at the time of the survey was 50,4±0,51 years. Duration of the disease was 5,8±1,5 years. We found that patients with T2DM and obesity in the Azerbaijan population have most common polymorphism of insulin-induced gene in the homozygous form (GG), a mutant version of the gene in heterozygous form of leptin, adiponectin gene mutant variant in homozygous form and the normal version of the gene TNF-α in homozygous form. In 47.3% of cases there was a high level of CRP, a linear body mass index with normal homozygous GG allele of the TNF-a gene , insulin-induced gene, and a mutant version of the adiponectin and leptin genes.

Two novel mutations in the tmprss6 gene associated with iron‐refractory iron‐deficiency anaemia (irida) and partial expression in the heterozygous form

Two novel mutations in the <i>tmprss6</i> gene associated with iron‐refractory iron‐deficiency anaemia (irida) and partial expression in the heterozygous form

Utility of testing for factor V Leiden.

Utility of testing for factor V Leiden.

Hypogonadism in a Patient with Two Novel Mutations of the Luteinizing Hormone β-Subunit Gene Expressed in a Compound Heterozygous Form

LH gene mutations are rare; only four mutations have been described. The affected individuals are hypogonadal. We describe the clinical features of a 31-yr-old man who presented with delayed puberty and azoospermia and was found to have hypogonadism associated with an absence of circulating LH. The patient had a 12-bp deletion in exon 2 in the LH β-subunit gene and a mutation of the 5' splice site IVS2+1G→T in the same gene present in a compound heterozygous state. The first mutation predicts a deletion of four leucines of the hydrophobic core of the signal peptide. The second mutation disrupts the splicing of mRNA, generating a gross abnormality in the processing. The patient's heterozygous parents were clinically normal. The phenotype of a 16-yr-old sister of the proband, carrying the same mutations, was characterized by normal pubertal development and oligomenorrhea. This report unravels two novel mutations of the LH gene critical for synthesis and activity of the LH molecule. The insight gained from the study is that normal pubertal maturation in women can occur in a state of LH deficiency, whereas LH is essential for maturation of Leydig cells and thus steroidogenesis, puberty, and spermatogenesis in man. These mutations should be considered in girls and boys with selective deficiency of LH.

Extended mutation spectrum of Usher syndrome in Finland

The Finnish distribution of clinical Usher syndrome (USH) types is 40% USH3, 34% USH1 and 12% USH2. All patients with USH3 carry the founder mutation in clarin 1 (CLRN1), whereas we recently reported three novel myosin VIIA (MYO7A) mutations in two unrelated patients with USH1. This study was carried out to further investigate the USH mutation spectrum in Finnish patients. We analysed samples from nine unrelated USH patients/families without known mutations and two USH3 families with atypically severe phenotype. The Asper Ophthalmics USH mutation chip was used to screen for known mutations and to evaluate the chip in molecular diagnostics of Finnish patients. The chip revealed a heterozygous usherin (USH2A) mutation, p.N346H, in one patient. Sequencing of MYO7A and/or USH2A in three index patients revealed two novel heterozygous mutations, p.R873W in MYO7A and c.14343+2T>C in USH2A. We did not identify definite pathogenic second mutations in the patients, but identified several probably nonpathogenic variations that may modify the disease phenotype. Possible digenism could not be excluded in two families segregating genomic variations in both MYO7A and USH2A, and two families with CLRN1 and USH2A. We conclude that there is considerable genetic heterogeneity of USH1 and USH2 in Finland, making molecular diagnostics and genetic counselling of patients and families challenging.

A newly identified missense mutation of the HR gene is associated with a novel, unusual phenotype of Marie Unna Hereditary Hypotrichosis 1 including limb deformities

Marie Unna Hereditary Hypotrichosis 1 (MUHH1; OMIM 146550), a rare monogenic condition characterized by the development of sparse, twisted hair or complete hair loss, is the consequence of mutations located in the hairless (HR) gene. We have identified a 68-year-old Hungarian woman affected by alopecia universalis and limb deformities of all four extremities. Direct sequencing of the coding regions of the HR gene revealed a novel missense mutation in the third exon of the HR gene (c.974G/A, p.Gly325Asp). The affected family member carried the mutation in a heterozygous form, while the only available, clinically unaffected family member (the son of the patient) and the unrelated controls carried the wild type sequence. The association between the presence of HR gene mutations and the development of alopecia is well-established, however, further studies are needed to elucidate the putative role of this novel HR mutation in the development of limb deformities.

Le syndrome de Lady Windermere : données cliniques, bactériologiques et évolutives

Described by Reich and Johnson in 1992 [2], the Lady Windermere syndrome occurs exclusively in non-smoking women over the age of 60 years, without significant pre-existing pulmonary disease. It comprises bronchial dilatation, typically in the middle lobe and lingula, together with secondary infection by atypical mycobacteria (Mycobacterium avium in the first cases). Among the 17 cases of atypical mycobacterial infection that we have seen in the past 14 years, there were seven cases of this syndrome. It was associated with cough, sputum, sometimes haemoptysis, febrile episodes and deterioration of general health. The diagnostic criteria and treatment were defined by the American Thoracic Society. The pathophysiological hypothesis proposed by Reich and Johnson was that voluntary suppression of the cough led to congestion of the bronchi and secondary infection with atypical mycobacteria. Currently it is thought more likely that the following factors are involved: progressive increase in dilatation of small bronchi, delayed diagnosis, morphological abnormalities of the thorax, hormonal factors, immune deficiency, genetic neutrophil dysfunction, and even heterozygous forms of cystic fibrosis.

Evaluation of recurrent venous thromboembolism in patients with Factor V Leiden mutation in heterozygous form

IntroductionTo evaluate the risk for recurrence after first venous thromboembolism (VTE) among patients with or without Factor V Leiden (FVL) mutation. Materials and MethodsA prospective population based study of 1465 consecutive unselected VTE patients was performed at Skåne University Hospital 1998–2008. The VTE was objectively verified and the patients answered questionnaire and left blood samples for evaluation. ResultsOut of 1465 patients (721[49%] men and 744[51%] women) thrombophilia data were available for 1267, and FVL mutation was found in heterozygous form in 339 (27). The homozygous form and prothrombin mutation (PTM) were much less common. Patients were followed during 4.8±2.3years (total 6133 patient years) and recurrence after first VTE (evaluated in 1108 patients) occurred in 131 (12%, 95%CI 10–14%), where of 49(37%) had heterozygous FVL mutation and 57(44%) were without thrombophilia. The remaining 25(19%) patients had either PTM, FVL in homozygous form, compound PTM/FVL or unknown thrombophilia status. Having FVL mutation in heterozygous form significantly increased the risk for VTE recurrence (odds ratio 2.4 (95 %CI 1.6–3.6; p<0.01). In a Kaplan-Meier analysis the FVL group also differed significantly (p<0.01) from the other patients concerning time to recurrence (almost 25% vs. 10% after 8years). ConclusionsFVL mutation in heterozygous form is common among VTE patients and significantly increases the risk for VTE recurrence.

Hb Haaglanden: a new nonsickling β7Glu&gt;Val variant. Consequences for basic diagnostics, screening, and risk assessment when dealing with HbS‐like variants

To report a new hemoglobin variant undistinguishable from the common HbS on HPLC. To show the efficiency of the simplest confirmation method for HbS and to discuss the implications that may occur if HbS-like variants are wrongly reported as HbS. Basic hematology, separation and measurement of the Hb fractions, 'sickle test,' and molecular analysis. The abnormal Hb fractions were eluting in the HbS window on HPLC, sickle test was however negative, and DNA sequencing of the beta globin gene revealed an unclassified variant HBBc.23A>T, p.Glu8Val in heterozygous form. Although the amino acid substitution of this new variant is identical to that of HbS and shifted of a single amino acid position, no polymerization occurs in vitro. The sickle test is a valid method to confirm or exclude HbS trait in individual cases. Whenever the case is part of a possible couple at risk, then one has to use full DNA analysis in both partners not to miss hidden concomitant defects important for genetic risk predictions.

The effect of the CYP 2C19*2 polymorphism on stroke care

Clopidogrel is an inhibitor of platelet-aggregation used in the prevention of secondary stroke. The molecule is activated by the cytochrome P450 2C19 (CYP2C19) enzyme. The frequent CYP2C19*2 point mutation causes loss of enzyme function, a decreased (heterozygous form) or blocked (homozygous form) formation of the active molecule. Thus, for a patient harboring a mutated allele, clopidogrel does not provide effective protection against stroke. Multiple drugs inhibit the CYP2C19 enzyme and their simultaneous use with clopidogrel is especially hazardous for patients with genetically decreased enzyme activity. Frequency of the CYP2C19*2 is variable in different populations, highest rates were detected in some Asian groups. In our study the CYP2C19 genotype was determined in one Hungarian sample of 354 stroke patients and 221 healthy controls. Frequency of the minor allele was found to be 12.87% (12.85% in stroke patients, 12.89% in healthy controls). The proportion of the homozygous CYP2C19*2 variant causing total loss of gene function was 1.74%, rate of the heterozygous allele causing reduced enzyme activity was 22.26% in the total population. Our results for the allele frequencies of the CYP2C19*2 gene are similar to those found in other Caucasian populations. In conclusion, the homozygous mutation, causing ineffectiveness of clopidogrel is relatively rare. However, the heterozygous form in which interaction of CYP2C19 inhibitors causes further decrease in the genetically impaired enzyme activity is present in every fifth drug-taking patient. Based on our findings, we would like to emphasize that it is important to adjust individually antiplatelet treatment in ischemic stroke patients and to take into consideration genetic factors as well as drugs taken for comorbid conditions.

Polymorphic variants of the genes encoding intrleukin-6 and fibrinogen: Risk for ischemic stroke and fibrinogen levels

Carriage frequencies of alleles and genotypes of polymorphous locus of -174G>C IL6 (rs1800795) were analyzed in the patients with ischemic stroke (IS) of Russian ethnic descent (200 cases) and in the control group of the same ethnic descent with similar sex and age (140 controls). Significant differences were identified in frequencies of carriage (in homo- or heterozygous form) of allele IL6*-174G (p = 0.0029, OR = 2.9, 95% CI: 1.4-5.8), which can be considered as risk factor for IS and in frequencies of IL6*-174C/C genotype carriage, correspondingly (p = 0.0029, OR = 0.35, 95% CI: 0.17-0.69). After sex stratification of patients and controls similar significant differences were observed only between female patients and controls, after age stratification the difference was observed only for the age group older 60 years. Complex analysis of association of SNP -174G>C IL6 alleles and genotypes carriage in combination with SNP 4266A>G (Thr312Ala) FGA (rs6050) (see symbol) -249C>T FGB (rs1800788) with IS revealed protective combinations IL6*-174C/C + FGA* 4266A (see symbol) IL6*-174C/C + FGB*-249C, which were slightly more significant than single protective genotype IL6*-174C/C associated with IS and their ORs didn't differ substantially from the single genotypes's OR value. At the same time the combinations of alternative allele IL6*-174G with the same FGB*-249C or FGA* 4266A alleles were revealed and their association significance levels as well as OR values were lower than the values for the single risk allele IL6*-174G. In case of the mutual carriage of IL6*-174G allele with FGA*4266A/A, FGB*-249C/C genotypes or with combinations of these alleles/genotypes the "neutralized" effect became stronger. In other words, we observed association of IS with allele/genotype combinations of genes IL6, FGA and FGB, in which IL6 plays key role and FGA and FGB have modulating function. In analysis of association of fibrinogen plasma levels with three analyzed polymorphous loci significant differences were not revealed.

Is universal pediatric lipid screening justified?

Is universal pediatric lipid screening justified?