Ivana Novakovic

Mutations in the gene encoding PDGF-B cause brain calcifications in humans and mice

Calcifications in the basal ganglia are a common incidental finding and are sometimes inherited as an autosomal dominant trait (idiopathic basal ganglia calcification (IBGC)). Recently, mutations in the PDGFRB gene coding for the platelet-derived growth factor receptor β (PDGF-Rβ) were linked to IBGC. Here we identify six families of different ancestry with nonsense and missense mutations in the gene encoding PDGF-B, the main ligand for PDGF-Rβ. We also show that mice carrying hypomorphic Pdgfb alleles develop brain calcifications that show age-related expansion. The occurrence of these calcium depositions depends on the loss of endothelial PDGF-B and correlates with the degree of pericyte and blood-brain barrier deficiency. Thus, our data present a clear link between Pdgfb mutations and brain calcifications in mice, as well as between PDGFB mutations and IBGC in humans.

Genotypic and phenotypic spectrum of PANK2 mutations in patients with neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) is a group of disorders characterized by magnetic resonance imaging (MRI) changes in basal ganglia. Both missense and nonsense mutations have been found in such patients in a gene encoding the mitochondrial pantothenate kinase (PANK2).

Cancer genes alterations and HPV infection in oral squamous cell carcinoma

The aim of this study was to gain a better understanding of cancer genes contributing to oral squamous cell (OSCC) development and progression and correlate genetic changes to clinical parameters. Human papilloma virus (HPV) 16 detection is also included in the study. 60 samples of OSCC were analysed for c-erbB2 and c-myc amplification by dPCR, H-ras and p53 point mutations by PCR/SSCP. HPV was detected via amplification of its E1 and E6 genes. c-erbB2 was altered in 45%, c-myc in 35%, H-ras in 22% and p53 in 60% of samples. HPV was detected in 10% of cases. The frequency of p53 gene mutations showed a statistically significant association with tumour stage. Patients with c-erbB2 and H-ras alterations had lower survival than patients without these alterations. The number of detected genetic changes was remarkable but statistical association with tumour natural history was poor, indicating high clonal heterogeneity and multiple pathways of carcinogenesis.

Association between the methylenetetrahydrofolate reductase polymorphisms and risk of acute lymphoblastic leukemia in Serbian children.

Methylenetetrahydrofolate reductase (MTHFR) regulates the metabolism of folate and methionine, essential components of DNA synthesis and methylation. Polymorphisms in the MTHFR gene have been associated with susceptibility to some types of cancer. We investigated a possible association of MTHFR polymorphisms (677C>T and 1298A>C) and increased risk for acute lymphoblastic leukemia in 78 affected children. The frequencies of both MTHFR 677 genotypes and alleles were significantly different between patients and controls. A significant association between CT/TT individuals and reduced risk of acute lymphoblastic leukemia was found. The odds ratios were 0.53 (95% confidence interval, 032-0.89) and 0.30 (95% confidence interval, 0.12-0.81). Polymorphism 1298 did not show statistical difference between patients and controls.

Bcl-2 Expression in Oral Squamous Cell Carcinoma

Abstract:  Apoptosis is a genetically regulated process involved in tissue size regulation, morphogenesis, and elimination of genetically damaged cells. A pallet of genes is involved in the control of apoptosis, such as bcl‐2 family whose oncogenic potential has been demonstrated in oral tumorigenesis. Different members of bcl‐2 family may promote or inhibit apoptosis by synthesizing anti‐ and proapoptotic proteins. One of antiapoptotic proteins, bcl‐2, with a crucial role in apoptosis regulation was the object of our study. By means of immunohistochemistry we estimated the level of overexpression of bcl‐2 proteins in a series of the 26 formalin fixed, paraffin‐embedded samples of oral squamous cell carcinoma (OSCC). Analyzed tumors originated from different sites of oral cavity; 7/26 belonged to stage II, 14/26 to stage III, and 5/26 to stage IV. Immunoreactivity was scored according to the percentage and intensity of positive cytoplasmic bcl‐2 staining. All tumors had low percentage of positively stained bcl‐2 cells, with mean values for lower/higher intensity of 8.3 ± 2.5/34.4 ± 7, 7.5 ± 1.1/31.9 ± 4.3, and 8.4 ± 5.8/31.5 ± 5.8 within stages II, III, and IV, respectively. Low level of bcl‐2 expression in our sample seems to be associated with higher survival rate: 77% for the 5‐year follow‐up period. Comparing clinicopathologic and risk factors data within each and between three groups of analyzed tumors (lip–tongue P= 0.58, tongue–floor of the mouth, P= 0.21, lip–floor of the mouth, P= 0.50) there was no significant difference. However, our results suggest that the level of bcl‐2 expression could be a valuable predictor of tumor behavior and disease outcome.

Gene polymorphisms as markers of disease susceptibility.

Gene Polymorphisms as Markers of Disease Susceptibility The most widespread diseases of modern man have a polygenic basis, including genetic predisposition and factors in the external environment. Such is the case with cardiovascular disease, malignancy, diabetes and so on. It should be borne in mind that risk factors usually include disorders that are themselves multifactorial, which further indicates the complexity of pathophysiological mechanisms. In the investigation of genetic factors in polygenic diseases studies are underway to determine the association with specific gene polymorphisms. Genetic or DNA polymorphisms are differences in the hereditary basis which are normally found in human populations. The human genome consists of 3×109 nucleotide (base) pairs, and it is considered that, on average, every 1000th nucleotide is polymorphic, i.e. varies between two loci or two individuals. The most common type of gene polymorphisms is the single nucleotide polymorphism (SNP). Although gene polymorphisms are an expression of normal variations in the hereditary basis, their effect on the phenotype is interesting, especially the association with proneness to certain diseases. Association studies examine the incidence of certain genetic variants, i.e. genetic polymorphisms in a group of patients, and compare it with the data of a healthy population. The results are often contradictory, so the number of polymorphisms whose role as markers of genetic predisposition has been clearly confirmed is still small. In this paper we review literature data and present experiences from our laboratory in studying genetic polymorphisms as susceptibility factors for the occurrence of thrombophilia and atherosclerosis and its clinical manifestations. Genski Polimorfizmi kao Markeri Predispozicije za Oboljenja Najrasprostranjenije bolesti savremenog čoveka imaju poligensku tj. multifaktorsku osnovu, koja uključuje genetičke faktore predispozicije i činioce iz spoljne sredine. Takav je slučaj sa kardiovaskularnim bolestima, malignitetom, dijabetesom itd. Treba imati na umu da faktori rizika obično obuhvataju poremećaje koji su sami po sebi takođe multifaktorski, što dodatno ukazuje na kompleksnost patofizioloških mehanizama. U okviru istraživanja genetičkih činilaca kod poligenskih bolesti pristupa se studijama asocijacije sa određenim genskim polimorfizmima. Pod genskim, odnosno DNK polimorfizmom podrazumevaju se razlike u naslednoj osnovi koje se normalno sreću u humanim populacijama. Genom čoveka se sastoji od 3×109 nukleotidnih (baznih) parova a smatra se da je u proseku svaki 1000. nukleotid polimorfan, tj. da se razlikuje između dva lokusa ili dve osobe. Najčešći tip genskih polimorfizama su polimorfizmi pojedinačnih nukleotida (engl. single nucleotide polymorphism - SNP). Iako genski polimorfizmi predstavljaju izraz normalnih varijacija u naslednoj osnovi, zanimljiv je njihov uticaj na fenotip, a naročito je aktuelno povezivanje sa sklonošću ka određenim bolestima. U studijama asocijacije ispituje se učestalost pojedinih genskih varijanti, tj. genskih polimorfizama u grupi obolelih i upoređuje sa podacima u zdravoj populaciji. Rezultati su često protivrečni, pa je još uvek mali broj polimorfizama sa jasno potvrđenom ulogom genetičkog markera predispozicije. U radu iznosimo iskustva naše laboratorije u ispitivanju genskih polimorfizama kao faktora predispozicije za pojavu trombofilije i ateroskleroze i njenih kliničkih manifestacija.

Increased total homocysteine level is associated with clinical status and severity of white matter changes in symptomatic patients with subcortical small vessel disease

OBJECTIVE Elevated plasma total homocysteine (tHcy) is an independent risk factor for ischemic stroke and has been linked to cerebral small vessel disease (SVD), in particular. Controversy persists as to whether increased tHcy is associated with functional status and cognitive decline in these patients. METHODS Plasma tHcy, MTHFR polymorphism, vascular risk factors, functional and cognitive status and severity of lesions on MRI, assessed with the Age-Related White Matter Changes (ARWMC) visual grading scale, were analyzed in 95 patients with SVD and 41 healthy control subjects. RESULTS Plasma tHcy levels were higher in patients with SVD (14.4±5.0 μmol/L) compared to healthy SVD-free controls (8.9±3.9 μmol/L). In SVD patients, tHcy levels strongly correlated with cognitive status (age-adjusted risk 5.8, 95% CI 1.3-25.3, p=0.015), functional status (age-adjusted risk 3.2, 95% CI 1.2-8.8, p=0.022) and severity of MRI lesions (age-adjusted risk 1.2, 95% CI 1.1-1.4; p=0.004). Only total ARWMC score was independently associated with increased tHcy levels (OR 1.2, 95%CI 1.1-1.4, p=0.004). Independent predictors of WMC occurrence were tHcy levels (OR 1.2, 95%CI 1.1-1.3, p=0.003) and mRS score (OR 2.2, 95%CI 1.2-4.1, p=0.017). CONCLUSIONS In patients with cerebral SVD there is a positive association of increased plasma tHcy levels with clinical status and severity of WMC.

Genetic Variation in Circadian Rhythm Genes CLOCK and ARNTL as Risk Factor for Male Infertility

Background The circadian system has a major role in maintaining homeostasis and proper body functions including reproductive capacity. The aim of this study was to examine whether there is an association between genetic variability in the primary clock genes CLOCK and ARNTL and male infertility in humans. Methodology/Principal Findings We performed a case-control study, where we searched for an association between polymorphisms of CLOCK and ARNTL genes and male infertility in 961 Slovenian and Serbian Caucasian men. The study group consisted of 517 patients with idiopathic infertility and a control group of 444 fertile men. A statistically significant difference was found in genotype distribution between the two groups in the CLOCK gene: rs11932595 (p = 6·10−5, q = 4·10−4, OR equaled 1.9 with 95% CI 1.4–2.7), rs6811520 (p = 2·10−3, q = 8·10−3, OR = 1.7 with 95% CI 1.2–2.2) and rs6850524 (p = 0.01, q = 0.02, OR = 1.4 with 95% CI 1.1–1.9). Further analyses of haplotypes were consistent with genotyping results. Conclusions/Significance We provide evidence that genetic variability in the CLOCK gene might be associated with male infertility warranting further confirmation and mechanistic investigations.

Phenotype of non-c.907_909delGAG mutations in TOR1A: DYT1 dystonia revisited.

BACKGROUND In addition to the most frequent TOR1A/DYT1 mutation (c.907_909delGAG), a growing number of TOR1A sequence variants are found in dystonia patients. For most, functional characterization has demonstrated pathogenicity at different levels, implying that TOR1A genetic testing should not be limited to screening for c.907_909delGAG. METHODS We tested 461 Serbian patients with isolated or combined dystonia for changes in the TOR1A gene and performed a systematic literature review of the clinical characteristics of patients carrying TOR1A mutations other than c.907_909delGAG. RESULTS One likely pathogenic TOR1A mutation (c.385G>A, p.Val129Ile) was detected in an adult-onset cervical dystonia patient. This change is in proximity to the previously reported p.Glu121Lys mutation and predicted to decrease the stability of TOR1A-encoded protein TorsinA. CONCLUSIONS Our patient and three other reported carriers of non-c.907_909delGAG-mutations within the first three exons of TOR1A showed similar phenotypes of adult-onset focal or segmental cervical dystonia. This observation raises the possibility of genotype-phenotype correlations in DYT1 and indicates that the clinical spectrum of this type of dystonia might be broader then previous classic descriptions.

No Association between Brain-Derived Neurotrophic Factor G196A Polymorphism and Clinical Features of Parkinson's Disease

Aims: To investigate association of the Val66Met polymorphism in the brain-derived neurotrophic factor (BDNF) gene with clinical features in Serbian patients with Parkinsons disease (PD). Methods: The study comprised 177 consecutive PD patients. A comprehensive set of clinical scales was applied in all patients. The controls (n = 366) were recruited among students. Single nucleotide polymorphisms (SNPs; rs6265) were analyzed using TaqMan assays. Results: PD patients (118 males) were aged 58.9 ± 10.9 years, with a mean age at onset of 49.0 ± 11.2 years. PD patients and controls had a similar distribution of genotypes and allele frequencies. The presence of the Met allele did not influence the clinical characteristics of PD patients (age at onset, family history, gender, disease duration, form of the disease, initial symptoms, cognitive abilities, depression, anxiety, disease severity, severity of motor and prevalence of nonmotor symptoms, and development of motor complications). Conclusion: Overall, the Val66Met polymorphism did not modify the clinical features in PD patients.