Nela Maksimovic

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.

Degree of genetic homozygosity and distribution of AB0 blood types among patients with spina bifida occulta and spina bifida aperta

Introduction Assuming that spina bifida (SB) is a genetically controlled disease, the aim of our study was to evaluate the degree of genetic homozygosity and the distribution of AB0 blood types among patients with SB occulta and SB aperta by the homozygously recessive characteristics (HRC) test. Material and methods Our study included an analysis of the presence, distribution and individual combination of 15 selected genetically controlled morpho-physiological traits in a sample of 100 patients with SB (SB occulta N = 50 and SB aperta N = 50) and a control group of individuals (N = 100). Results We found a statistically significant difference between the mean values for genetic homozygosity (SB 4.5 ±0.3; control 3.0 ±0.2, p < 0.001) and also differences in the presence of certain individual combinations of such traits. In 12 (80.0%) of the 15 observed characteristics, recessive homozygosity was expressed to a greater degree among the group of SB patients, while for 9 (60.0%) of the traits this level of difference was statistically significant (Σχ 2 = 266.3, p < 0.001). There was no difference in average homozygosity of such genetic markers between groups of SB occulta and SB aperta patients, but the type of individual variation in the two studied groups significantly differed. In the group of patients with SB the frequency of 0 blood group was significantly increased while B blood group was significantly decreased. Conclusions Our results clearly show that there is a populational genetic difference in the degree of genetic homozygosity and variability between the group of patients with SB and individuals without clinical manifestations, indicating a possible genetic component in the aetiopathogenesis of spina bifida.

Polymorphisms of the eNOS gene are associated with disease activity in rheumatoid arthritis

Nitric oxide (NO) is a mediator in autoimmune responses and thus involved in the pathogenesis of a variety of rheumatic diseases. Genetic factors that influence the expression of the enzyme endothelial nitric oxide synthase (eNOS) that catalyzes NO synthesis are important for the control of NO level and consequently its activity. We have analyzed three functionally relevant polymorphisms of eNOS gene: T-786C, G894T and VNTR (4a/b), to investigate whether they are predisposing factors in pathogenesis of RA in Serbian population and to evaluate their role in clinical manifestations of RA. We performed genotyping of 196 patients with RA and the control group of 132 healthy individuals from Serbian population, using PCR and polymerase chain reaction–restriction fragment length polymorphism methods. Disease activity was prospectively assessed using number of tender joints, number of swollen joints and 28-joints disease activity score (DAS28). There were no differences between the patients and control groups in the genotypes and alleles frequencies of the three analyzed SNPs. Our results showed statistically significant differences in all three analyzed parameters of disease severity between 786TT/786CT and 786CC genotypes and between 894GG/894GT and 894TT genotypes. In the case of 4a/b polymorphism, carriers of minor allele had significantly lower DAS28 values. In conclusion, our results do not support the implication of analyzed eNOS gene polymorphisms in susceptibility to RA but associate them with the disease activity and give assumption that minor alleles are indicators of better clinical course.

Pharmacogenetics and the Treatment of Thrombophilia

Inherited forms of thrombophilia such as factor V Leiden mutation (FVL), prothrombin gene mutation (PT 20210A), and deficiencies of natural anticoagulants protein C, protein S, and antithrombin are well known. DNA tests for factor V Leiden and PT 20210A mutation have been incorporated in clinical practice for several years [1,2,3]. A number of studies have analyzed how this and other molecular genetic testing alter the clinical management and treatment of patients with thromboembolic disease or pregnancy complications. Data regard‐ ing the influence of the genotype to the disease phenotype as well as pharmacogenetic data are still controversial and emerging.