ADAM22 ethnic-specific variant reducing binding of membrane-associated guanylate kinases causes focal epilepsy and behavioural disorder.

Pathogenic variants of ADAM22 affecting either its biosynthesis and/or its interactions with either LGI1 and/or PSD-95 have been recently identified in individuals with developmental and epileptic encephalopathy. Here, we describe a girl with seizures, delayed psychomotor development, and behavioural disorder, carrying a homozygous variant in ADAM22 (NM_021723.5:c.2714C > T). The variant has a surprisingly high frequency in the Roma population of the Czech and Slovak Republic, with 11 of 213 (∼5.2%) healthy Roma individuals identified as heterozygous carriers. Structural in silico characterization revealed that the genetic variant encodes the missense variant p.S905F, which localizes to the PDZ-binding motif of ADAM22. Studies in transiently transfected mammalian cells revealed that the variant has no effect on biosynthesis and stability of ADAM22. Rather, protein-protein interaction studies showed that the p.S905F variant specifically impairs ADAM22 binding to PSD-95 and other proteins from a family of membrane-associated guanylate kinases, while it has only minor effect on ADAM22-LGI1 interaction. Our study indicates that a significant proportion of epilepsy in patients of Roma ancestry may be caused by homozygous c.2714C > T variants in ADAM22. The study of this ADAM22 variant highlights a novel pathogenic mechanism of ADAM22 dysfunction and reconfirms an essential role of interaction of ADAM22 with membrane-associated guanylate kinases in seizure protection in humans.

Identification of a dysfunctional exon-skipping splice variant in GLUT9/SLC2A9 causal for renal hypouricemia type 2.

Renal hypouricemia (RHUC) is a pathological condition characterized by extremely low serum urate and overexcretion of urate in the kidney; this inheritable disorder is classified into type 1 and type 2 based on causative genes encoding physiologically-important urate transporters, URAT1 and GLUT9, respectively; however, research on RHUC type 2 is still behind type 1. We herein describe a typical familial case of RHUC type 2 found in a Slovak family with severe hypouricemia and hyperuricosuria. Via clinico-genetic analyses including whole exome sequencing and in vitro functional assays, we identified an intronic GLUT9 variant, c.1419+1G>A, as the causal mutation that could lead the expression of p.Gly431GlufsTer28, a functionally-null variant resulting from exon 11 skipping. The causal relationship was also confirmed in another unrelated Macedonian family with mild hypouricemia. Accordingly, non-coding regions should be also kept in mind during genetic diagnosis for hypouricemia. Our findings provide a better pathogenic understanding of RHUC and pathophysiological importance of GLUT9.

Genetic testing is necessary for correct diagnosis and treatment in patients with isolated methylmalonic aciduria: a case report.

BACKGROUND: Isolated methylmalonic aciduria can be caused by pathogenic mutations in the gene for methylmalonyl-CoA mutase or in the genes encoding enzymes involved in the intracellular metabolism of cobalamin. Some of these mutations may be cobalamin responsive. The type of methylmalonic aciduria cannot always be assumed from clinical manifestation and the responsiveness to cobalamin has to be assessed for appropriate cobalamin administration, or to avoid unnecessary treatment. The cases presented herein highlight the importance of genetic testing in methylmalonic aciduria cases and the need for standardisation of the in vivo cobalamin-responsiveness assessment. CASE PRESENTATION: We describe two patients who presented in the first week of life with rapid neurological deterioration caused by metabolic acidosis with severe hyperammonaemia requiring extracorporeal elimination in addition to protein restriction, energy support, carnitine, and vitamin B12 treatment. The severity of the clinical symptoms and high methylmalonic acid concentrations in the urine (>30,000 µmol/mmol of creatinine) without hyperhomocysteinaemia in both of our patients suggested isolated methylmalonic aciduria. Based on the neonatal manifestation and the high methylmalonic acid urine levels, we assumed the cobalamin non-responsive form. The in vivo test of responsiveness to cobalamin was performed in both patients. Patient 1 was evaluated as non-responsive; thus, intensive treatment with vitamin B12 was not used. Patient 2 was responsive to cobalamin, but the dose was decreased to 1 mg i.m. every two weeks with daily oral treatment due to non-compliance. Genetic tests revealed bi-allelic mutations in the genes MMAB and MMAA in Patient 1 and 2, respectively. Based on these results, we were able to start intensive treatment with hydroxocobalamin in both patients. After the treatment intensification, there was no acute crisis requiring hospitalisation in Patient 1, and the urine methylmalonic acid levels further decreased in Patient 2. CONCLUSIONS: Despite carrying out the in vivo test of responsiveness to cobalamin in both patients, only the results of molecular genetic tests led us to the correct diagnosis and enabled intensive treatment with hydroxocobalamin. The combination of the standardized in vivo test of cobalamin responsiveness and genetic testing is needed for accurate diagnosis and appropriate treatment of isolated methylmalonic aciduria.

Renal Hypouricemia 1: Rare Disorder as Common Disease in Eastern Slovakia Roma Population.

Renal hypouricemia (RHUC) is caused by an inherited defect in the main reabsorption system of uric acid, SLC22A12 (URAT1) and SLC2A9 (GLUT9). RHUC is characterized by a decreased serum uric acid concentration and an increase in its excreted fraction. Patients suffer from hypouricemia, hyperuricosuria, urolithiasis, and even acute kidney injury. We report clinical, biochemical, and genetic findings in a cohort recruited from the Kosice region of Slovakia consisting of 27 subjects with hypouricemia and relatives from 11 families, 10 of whom were of Roma ethnicity. We amplified, directly sequenced, and analyzed all coding regions and exon-intron boundaries of the SLC22A12 and SLC2A9 genes. Sequence analysis identified dysfunctional variants c.1245_1253del and c.1400C>T in the SLC22A12 gene, but no other causal allelic variants were found. One heterozygote and one homozygote for c.1245_1253del, nine heterozygotes and one homozygote for c.1400C>T, and two compound heterozygotes for c.1400C>T and c.1245_1253del were found in a total of 14 subjects. Our result confirms the prevalence of dysfunctional URAT1 variants in Roma subjects based on analyses in Slovak, Czech, and Spanish cohorts, and for the first time in a Macedonian Roma cohort. Although RHUC1 is a rare inherited disease, the frequency of URAT1-associated variants indicates that this disease is underdiagnosed. Our findings illustrate that there are common dysfunctional URAT1 allelic variants in the general Roma population that should be routinely considered in clinical practice as part of the diagnosis of Roma patients with hypouricemia and hyperuricosuria exhibiting clinical signs such as urolithiasis, nephrolithiasis, and acute kidney injury.

Rare copy number variation in extremely impulsively violent males.

The genetic correlates of extreme impulsive violence are poorly understood, and there have been no studies that have systematically characterized a large group of affected individuals both clinically and genetically. We performed a genome-wide rare copy number variant (CNV) analysis in 281 males from four Czech prisons who met strict clinical criteria for extreme impulsive violence. Inclusion criteria included age ≥ 18 years, an ICD-10 diagnosis of Dissocial Personality Disorder, and the absence of an organic brain disorder. Participants underwent a structured psychiatric assessment to diagnose extreme impulsive violence and then provided a blood sample for genetic analysis. DNA was genotyped and CNVs were identified using Illumina HumanOmni2.5 single-nucleotide polymorphism array platform. Comparing with 10851 external population controls, we identified 828 rare CNVs (frequency ≤ 0.1% among control samples) in 264 participants. The CNVs impacted 754 genes, with 124 genes impacted more than once (2-25 times). Many of these genes are associated with autosomal dominant or X-linked disorders affecting adult behavior, cognition, learning, intelligence, specifically expressed in the brain and relevant to synapses, neurodevelopment, neurodegeneration, obesity and neuropsychiatric phenotypes. Specifically, we identified 31 CNVs of clinical relevance in 31 individuals, 59 likely clinically relevant CNVs in 49 individuals, and 17 recurrent CNVs in 65 individuals. Thus, 123 of 281 (44%) individuals had one to several rare CNVs that were indirectly or directly relevant to impulsive violence. Extreme impulsive violence is genetically heterogeneous and genomic analysis is likely required to identify, further research and specifically treat the causes in affected individuals.

An unusually high frequency of SCAD deficiency caused by two pathogenic variants in the ACADS gene and its relationship to the ethnic structure in Slovakia.

BACKGROUND: Short-chain acyl-CoA dehydrogenase deficiency (SCADD) represents a rare autosomal recessive inborn metabolic disorder of mitochondrial ß-oxidation of monocarboxylic acids. Clinical symptoms can vary from a severe life-threatening condition to an asymptomatic state, reported in the majority of cases. Since the expansion of newborn screenings, more than three hundred probands were admitted for molecular-genetic analysis, most selected because of elevated values of C4-acylcarnitine detected in newborn screenings in Slovakia. Searching for the principal genomic changes led us to the selection of sixty-two patients in whom the presence of sequence variants in the ACADS gene was analysed and correlated with the available biochemical and clinical data. METHODS: Biochemical and molecular genetic tests were performed. Acylcarnitine profiles focused on an elevated level of C4-acylcarnitine, which was analysed via tandem mass spectrometry. Urinary organic acids, specifically a quantity of ethylmalonic acid, were determined by gas chromatography/mass spectrometry. The entire coding region of the ACADS gene was sequenced. A low-cost restriction fragment length polymorphism of PCR amplified fragments analysis (PCR-RFLP) of pathogenic variants was introduced and implemented for the molecular-genetic algorithm appropriate for the Slovak population. RESULTS: Our molecular genetic study was performed on sixty-two patients with a pathological biochemical pattern related to short-chain acyl-CoA dehydrogenase deficiency. In this cohort, we discovered a high occurrence of two rare pathogenic variants-the deletion c.310_312delGAG and the substitution c.1138C>T, with allelic frequencies of 64% and 31%, respectively. Up to 86% of investigated individuals belong to the Roma ethnic group. CONCLUSIONS: Analogous to other countries, SCADD is not included in the newborn screening programme. Based on the exceeded levels of the specific biomarker C4-acylcarnitine as well as ethylmalonic acid, we revealed a high prevalence of short-chain acyl-CoA dehydrogenase deficiency cases, confirmed by the findings of two rare pathogenic variants. A deletion c.310_312delGAG and c.1138C > T substitution in the ACADS gene appear with a high frequency in the Roma ethnic group of Slovakia. Due to the uncertainty of the pathogenicity and clinical consequences, it is important to follow up the morbidity and mortality in these patients over time and evaluate SCADD in relation to clinical outcomes and preventive healthcare recommendations.

Spectrum of GBA mutations in patients with Gaucher disease from Slovakia: identification of five novel mutations.

BACKGROUND: Gaucher disease is the most common lysosomal storage disorder and is caused by a deficiency of the enzyme glucocerebrosidase. Enzyme deficiency leads to the accumulation of undegraded substrates, mainly in cells of the monocyte/ macrophage lineage, which is responsible for the clinical manifestations of the disease. To date, no study has attempted to identify the mutation spectrum of the glucocerebrosidase gene (GBA) in Slovak patients OBJECTIVES: To identify mutations in 14 Slovak patients with confirmed glucocerebrosidase deficiency. METHODS: Using molecular genetics methods PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) and direct sequencing of coding region GBA we identified the spectrum of mutations in our patients. RESULTS: Five mutations (N370S, L444P, G377S, D409H and RecNciI) accounted for 75% of the mutant alleles. The remaining 25% were rare and probably individual mutations. CONCLUSIONS: The mutational spectrum in our patients is similar to that observed in other European countries and corresponds to a Caucasian population, with N370S, L444P, RecNciI being the most common. Interestingly, mutation G377S was more frequent in our patients as compared to other published data. The C4W, L96P, H311N, 745delG and 1127_1128delTT mutations are described here for the first time in Gaucher disease, contributing to the panel of published GBA mutations.