Dušanka Savić-Pavićević

Loss-of-function mutations in HINT1 cause axonal neuropathy with neuromyotonia.

Inherited peripheral neuropathies are frequent neuromuscular disorders known for their clinical and genetic heterogeneity. In 33 families, we identified 8 mutations in HINT1 (encoding histidine triad nucleotide–binding protein 1) by combining linkage analyses with next-generation sequencing and subsequent cohort screening of affected individuals. Our study provides evidence that loss of functional HINT1 protein results in a distinct phenotype of autosomal recessive axonal neuropathy with neuromyotonia.

Endothelial nitric oxide synthase gene polymorphisms and prostate cancer risk in Serbian population

Genome‐wide association studies (GWAS) have identified over 46 SNPs associated with human prostate cancer (PCa). Some studies have shown correlation of the nitric oxide synthase (NOS) NOS3 gene polymorphisms with the risk and/or progression of PCa. This study aimed to evaluate the association of NOS3 gene polymorphisms (−786T>C, −764A>G, −714G>T, −690C>T, −649G>A and 894G>T) with PCa risk and progression. 150 patients with PCa, 150 patients with BPH and 100 age‐matched healthy controls were recruited in this study. Genotyping of promoter polymorphisms was performed by bi‐directional DNA sequencing, and for 894G>T by RFLP analysis. There was no significant association between the alleles and genotypes of these genetic variants and PCa risk. For −786T>C polymorphism, we found that C allele is associated with absence of metastases, assuming dominant genetic model (P = 0.049; OR, 0.50; 95% CI, 0.25–1.00). It was found that, compared with NOS3 −690C>T variant CC genotype, CT and TT genotypes confer decreased risk of developing metastases (dominant model, P = 0.015, OR, 0.24; 95% CI, 0.07–0.88) and show association with low clinical tumour stage, compared with stages T3 and T4 (dominant model, P = 0.046, OR, 0.20; 95% CI, 0.04–1.02). Genetic variants −764A>G, −714G>T, −649G>A were not detected in our study group. There is evidence of an inverse correlation of the NOS3 894G>T minor allele with high serum PSA (>20 ng/ml) (dominant model, P = 0.013, OR, 0.37; 95% CI, 0.17–0.82). Our results suggest that NOS3 gene polymorphisms are genetic susceptibility factors for the progression of PCa and patient outcome.

Frequency of the hemochromatosis gene mutations in the population of Serbia and Montenegro

To the Editor: The most common form of hereditary hemochromatosis (HH) is HH type 1, which affects between 1 in 200 and 1 in 400 individuals of northern European descent (1, 2). It is an autosomal recessive iron-overload disorder frequently associated with two mutations in the hemochromatosis gene (HFE) resulting in the substitution of cysteine with tyrosine at amino acid position 282 (C282Y) and the substitution of histidine with aspartate at amino acid position 63 (H63D) (3). In the original work by Feder et al., 83% of HH type 1 patients were found to be homozygous for the C282Y mutation and 4% were compound heterozygotes (C282Y/H63D) (3). Numerous other genotyping studies have confirmed this finding (4, 5). One more mutation, the substitution of serine with cysteine at amino acid position 65 (S65C), has been identified in the HFE gene. Some C282Y/S65C individuals have mild iron loading (6). The high frequency of the C282Y mutation has been shown in the northern European populations (7–9), whereas lower mutation frequencies were detected in different populations from southern Europe (10–12). However, no HFE mutations frequency data have been published on the population of Serbia and Montenegro. In addition, there is a limited knowledge of those frequencies in populations of the Balkan Peninsula. Therefore, the aim of this study was to determine the frequency of the C282Y, H63D and S65C mutations in the healthy population of Serbia and Montenegro and compare it with some other European populations. The study was performed on 318 unrelated healthy individuals (181 females and 137 males) from Serbia and Montenegro. Informed consent was obtained from all participants of the study. The analysis of HFE gene mutations was performed using modified method described by Milman et al. (13). Chi-square test or Fischer’s exact test was used to compare proportions of HFE genotypes between males and females and allelic frequencies among different populations. The distribution ofHFE genotypes in the population of Serbia and Montenegro are shown in Table 1. The C282Y and S65C allele frequencies in the analyzed population were the same, 1.6% (95% confidence interval (CI): 0.9–2.9), and the H63D allele frequency was 15.7% (95% CI: 13.1–18.7) (Table 1). The frequency of C282Y homozygotes was estimated on approximately 1:3900 indicating the prevalence of hereditary hemochromatosis type 1 in Serbia and Montenegro. The frequencies of the HFE mutations in the population of Serbia and Montenegro were compared to already published data for other Slavic populations (14–16), populations that are geographically close to Serbia and Montenegro (11, 12, 17–19) and the Danish population (13), as a representative of northwestern European population (Table 2). The frequency of the C282Y mutation in the analyzed population is significantly lower than the frequency found in Austria, Czech Republic, Denmark, Hungary, Northern Italy, Poland and Slovenia. A statistically significant difference was found also in the frequency of H63D mutation between the population of Serbia and Montenegro and the population of Austria and Bulgaria. The distribution of the C282Y mutation decreases going from northwest to southeast Europe (20), with maximal frequency in Ireland (9.7%) and minimal in Bulgaria (0%) (21). According to the geographical position in Europe, the frequency of the C282Y mutation in Serbia and Montenegro (1.6%) fits in the observed north/south gradient. The frequency of the C282Y mutation in the population of Serbia and Montenegro is similar to that in the Croatian population, but, at the same time, it differs from that found in other populations of Slavic origin. In addition, there is similarity between the studied population and

Clusters of cognitive impairment among different phenotypes of myotonic dystrophy type 1 and type 2

Neuropsychological examinations in myotonic dystrophy (DM) patients show a great variability of results from a condition of intellectual disability to the subtle cognitive impairments. It is unclear if different clusters of neuropsychological deficits appear in different phenotypes of DM, or if there are patients with no cognitive deficit at all. The aim of this study is to assess cognitive impairments among patients with different phenotypes of DM type 1 (DM1) and type 2 (DM2), and to potentially define cognitive clusters in these disorders. Study comprised 101 DM1 and 46 DM2 adult patients who were genetically confirmed. Patients underwent analysis of five cognitive domains (visuospatial, executive, attention, memory and language). Virtually all DM1 patients had cognitive defect with approximately 2–3 cognitive domains affected. On the other hand, one-third of DM2 patients had completely normal neuropsychological findings, and in other two-thirds approximately 1–2 domains were affected. Cluster analysis showed that in both diseases visuospatial and executive dysfunctions seemed to be the main cognitive defects, while memory and language impairments appeared in more severe phenotypes. Our results showed that a single form of DM1 or DM2 may consist of several cognitive clusters. Understanding of cognitive impairments in DM is very important to follow positive and side effects in ongoing and future clinical trials.

Mutational analysis of GJB1, MPZ, PMP22, EGR2, and LITAF/SIMPLE in Serbian Charcot-Marie-Tooth patients

We report the results of mutational analysis in the following genes: GJB1, MPZ, PMP22, EGR2, and LITAF/SIMPLE in 57 Charcot‐Marie‐Tooth (CMT) patients of Serbian origin without the PMP22 duplication. We found 10 different mutations in 14 CMT patients: 6 mutations in GJB1, 3 in MPZ, and 1 in PMP22. Five of six GJB1 mutations are reported for the first time, and the most frequent one appears to be a founder mutation in the Serbian population. No mutations were found in EGR2 or LITAF. Thus, GJB1 mutation analysis should be done in patients without the PMP22 duplication and male‐to‐male transmission of CMT.

Novel GNB1 mutations disrupt assembly and function of G protein heterotrimers and cause global developmental delay in humans.

Global developmental delay (GDD), often accompanied by intellectual disability, seizures and other features is a severe, clinically and genetically highly heterogeneous childhood-onset disorder. In cases where genetic causes have been identified, de novo mutations in neuronally expressed genes are a common scenario. These mutations can be best identified by exome sequencing of parent-offspring trios. De novo mutations in the guanine nucleotide-binding protein, beta 1 (GNB1) gene, encoding the Gβ1 subunit of heterotrimeric G proteins, have recently been identified as a novel genetic cause of GDD. Using exome sequencing, we identified 14 different novel variants (2 splice site, 2 frameshift and 10 missense changes) in GNB1 in 16 pediatric patients. One mutation (R96L) was recurrently found in three ethnically diverse families with an autosomal dominant mode of inheritance. Ten variants occurred de novo in the patients. Missense changes were functionally tested for their pathogenicity by assaying the impact on complex formation with Gγ and resultant mutant Gβγ with Gα. Signaling properties of G protein complexes carrying mutant Gβ1 subunits were further analyzed by their ability to couple to dopamine D1R receptors by real-time bioluminescence resonance energy transfer (BRET) assays. These studies revealed altered functionality of the missense mutations R52G, G64V, A92T, P94S, P96L, A106T and D118G but not for L30F, H91R and K337Q. In conclusion, we demonstrate a pathogenic role of de novo and autosomal dominant mutations in GNB1 as a cause of GDD and provide insights how perturbation in heterotrimeric G protein function contributes to the disease.

Brain sonography insight into the midbrain in myotonic dystrophy type 2

Introduction: The aim of this study was to analyze transcranial sonography (TCS) findings in genetically confirmed myotonic dystrophy type 2 (DM2) patients. Methods: Forty DM2 patients and 38 gender‐ and age‐matched healthy controls (HCs) underwent TCS through the pre‐auricular acoustic bone window. Results: Substantia nigra hyperechogenicity was found in 20% of DM2 patients compared with 3% of HCs. Brainstem raphe (BR) hypoechogenicity was more common in DM2 patients compared with HCs (56% vs. 10%, P < 0.01), and it was more common in patients with fatigue and excessive daytime sleepiness (P < 0.05). Diameter of the third ventricle was increased in DM2 patients compared with HCs (5.8 ± 1.7 vs. 5.1 ± 1.0 mm, P < 0.05). Conclusions: Finding BR hypoechogenicity might have clinical implication because of the potential response to serotonin‐reuptake inhibitors. TCS revealed alterations in brain structures previously not seen in MRI studies. Muscle Nerve 53: 700–704, 2016

Assessment of association between common variants at 17q12 and prostate cancer risk-evidence from Serbian population and meta--analysis.

This study aimed to evaluate possible association between genotypes and alleles of two 17q12 polymorphisms (rs3760511 and rs7501939) and prostate cancer (PCa) risk and progression. Two hundred seventy‐one patients with PCa, 261 patients with benign prostatic hyperplasia (BPH), and 171 controls were included in the study. Single nucleotide polymorphisms (SNPs) were genotyped by using PCR followed by restriction fragment length (PCR‐RFLP) analysis. We conducted meta‐analysis of published studies regarding association of these SNPs with PCa risk. Evidence of positive association between the AC genotype of the SNP rs3760511 and BPH risk for the best‐fitting overdominant model of association (BPH vs. controls comparison, p = 0.026; odds ratio [OR] = 1.58; 95% confidence interval [95%CI] 1.05–2.36) were obtained. The association between T allele of rs7501939 and PCa risk was determined in PCa versus controls comparison (p = 0.0032; OR = 0.66, 95%CI 0.50–0.87) with the best‐fitting model of inheritance being log‐additive. This variant was also found to be associated with the risk of BPH (p = 0.0023; OR = 0.65, 95%CI 0.49–0.86). We found no association between parameters of PCa progression and the analyzed SNPs. Meta‐analysis showed strong association between these variants and PCa risk. Our study shows association between SNPs at locus 17q12 and the risk of prostatic diseases in Serbian population. At the same time, results of meta‐analysis suggest the association of these SNPs with PCa risk.

Schizophrenia and Apolipoprotein E Gene Polymorphism in Serbian Population

ABSTRACT Apolipoprotein E (APOE) gene variants are associated with alterations in brain function and increased risk of Alzheimers disease (AD) and conflicting results have been reported in schizophrenia. Our results showed no significant differences in APOE allele or genotype frequencies between the Serbian schizophrenic patients and control individuals. However, we observed a possible association between particular subtypes of schizophrenia and APOE ε3/ε3 genotype (p = .01221) and ε4 allele showed a tendency toward positive association with responding to typical neuroleptics. APOE genotypes have no major influence on risk of schizophrenia, treatment and response to conventional antipsychotics, and age of onset in schizophrenia.

Genetic testing of individuals with pre‐senile cataract identifies patients with myotonic dystrophy type 2

V. Rako cevi c-Stojanovi c, S. Peri c, J. Pe sovi c, I. Sen cani c, M. Bo zi c, S. Svikovi c, M. Brku sanin and D. Savi c-Pavi cevi c Neurology Clinic, Clinical Center of Serbia, University of Belgrade School of Medicine, Belgrade, Center for Human Molecular Genetics, University of Belgrade Faculty of Biology, Belgrade, Ophthalmology Department, Clinical Centre Zvezdara, Belgrade, and Ophthalmology Clinic, Clinical Centre of Serbia, Belgrade, Serbia