Jacek Zaremba

Unaffected patients with a homozygous absence of the SMN1 gene

In this report, we present three families in which we identified asymptomatic carriers of a homozygous absence of the SMN1 gene. In the first family, the bialleleic deletion was found in three of four siblings: two affected brothers (SMA type 3a and 3b) and a 25-years-old asymptomatic sister. All of them have four SMN2 copies. In the second family, four of six siblings are affected (three suffer from SMA2 and one from SMA3a), each with three SMN2 copies. The clinically asymptomatic 47-year-old father has the biallelic deletion and four SMN2 copies. In the third family, the biallelic SMN1 absence was found in a girl affected with SMA1 and in her healthy 53-years-old father who had five SMN2 copies. Our findings as well as those of other authors show that an increased number of SMN2 copies in healthy carriers of the biallelic SMN1 deletion is an important SMA phenotype modifier, but probably not the only one.

Genetic investigations on chronic forms of infantile and juvenile spinal muscular atrophy

SummaryA material of 247 cases selected from 260 cases of spinal muscular atrophy in the Warsaw Department of Neurology in 1960–1974 was analyzed. The size of sibships was established and calculations were made of the mean distribution of the age at onset, also according to sex, for the different clinical forms, genetical proportions by the method of siblings and of probands, and coefficient of sib-sib correlation for the material as a whole and separately for males, femals and male-female pairs.The analysis shows the course of the disease to differ between the sexes and to be mild in males more often than in females, as is particularly noticeable in the higher age groups. Cases of Kugelberg-Welanders disease are predominantly male. The hypothesis is advanced that a proportion of male patients have a sex-linked modifying gene of a fairly high frequency (possibly of the range of 1 in 5 males, and 1 in 25, in the homozygous state, in females).Although it would not disprove conclusively the nosological distinctness of different forms of infantile and juvenile spinal muscular atrophy, the existence of the modifying gene, if proved, would tend rather to add to the likelihood of their constituting a single recessive autosomal disease.ZusammenfassungDie vorliegenden 247 Fälle wurden aus insgesamt 260 Beobachtungen spinaler Muskelatrophie an der Neurologischen Klinik in Warschau in den Jahren 1960–1974 herausgegriffen. Die Größe der betroffenen Sippen wurde bestimmt, und es wurde errechnet, wie häufig der Befall, bezogen auf die verschiedenen klinischen Formen, getrennt nach Geschlechtern und Altersbeginn war. Dies wurde nach der Methode der Verwandten- und Probandenanalyse durchgeführt, und es wurde der Koeffizient der Realation von Sippe zu Sippe sowohl getrennt für Knaben, für Mädchen und für Knaben- und Mädchen-Paare bestimmt.Die Analyse ergab, daß der Verlauf der Erkrankung bei den Geschlechtern verschieden war und bei den männlichen Probanden gutartiger erschien, wobei dies besonders bei den älteren Gruppen deutlich war. Unter den Fällen von Kugelberg-Welanderscher Erkrankung überwiegen die männlichen Probanden. Es wird die Möglichkeit erwogen, daß ein Anteil der männlichen Patienten Träger eines geschlechtsgebundenen modifizierenden Gens von einer recht hohen Häufigkeit (einer unter 5 Männern und einer unter 25 Frauen im homozygoten Zustand) sind.Obwohl dies nicht endgültig gegen das Vorliegen von nosologisch unterschiedlichen Formen von infantiler und juveniler spinaler Muskelatrophie sprechen würde, würde doch das Vorliegen eines modifizierenden Gens — sofern dies bestätigt würde — eher dafür sprechen, daß diese scheinbar unterschiedlichen Formen doch eine einzige recessiv autosomale Erkrankung darstellen.

Chronic from of childhood spinal muscular atrophy: Are the problems of its genetics really solved?☆

The authors discuss the differences between the two large series of chronic childhood spinal muscular atrophies (SMA)--their own comprising 273 cases, and that of Pearn et al. comprising 141 cases. The main difference concerns the predominance of males in the clinically milder later-onset group in the present series. The data of Pearn et al. (1978a, b) are quite different. The reason for the discrepancies is apparently a different selection of material. The present material is highly selective in favour of chronic cases, and Kugelberg-Welander cases are well-represented, whereas the percentage of Kugelberg-Welander cases in the material of Pearn et al. was very small. Differences in selection also appear to be responsible for discordance in observations regarding influence of sex on the course of the disease. The present data seem to support the view that most of the cases revealing chronic forms of SMA (both mild and severe) are not distinct genetically. However, the possible existence of a distinct subgroup in which sex influence is strongly expressed is not excluded.

The occurrence of spinocerebellar ataxias caused by dynamic mutations in Polish patients.

BACKGROUND AND PURPOSE Autosomal dominant spinocerebellar ataxias (SCAs) belong to a group of neurodegenerative disorders usually of adult age at onset. Predominant clinical features are progressive ataxia, dysarthria, as well as pyramidal signs and polyneuropathy. Molecular analysis allows particular types of SCA to be distinguished. Genetic tests are applied in 10 types of SCA resulting from dynamic mutations: SCA1, SCA2, SCA3, SCA6, SCA7, SCA8, SCA10, SCA12, SCA17 and DRPLA. MATERIAL AND METHODS DNA samples from 1598 patients with ataxia symptoms were analysed to establish the number of CAG/CTG repeats in respective genes excluding SCA10. RESULTS We diagnosed 224 cases of SCA1 (120 families) and 49 cases of SCA2 (23 families). Moreover, presymptomatic testing was done in 85 individuals from SCA1 families and for 21 cases from SCA2 families. An increased number of CTG repeats in the SCA8 gene was observed in 14 families and in 3 families a rare type of SCA, SCA17, was detected. CONCLUSIONS Our data suggest that frequencies of some types of SCA in Poland are different from those in other European countries, with irregular distribution within the country. The most frequent types are SCA1 and SCA2. A striking feature of the Polish population is the lack of SCA3 - the most frequent type in Western Europe.

The natural history of SCO2 deficiency in 36 Polish children confirmed the genotype-phenotype correlation.

The aim of this study was to assess the natural history of the SCO2 deficiency in relation to the genotype in a cohort of 62 patients with SCO2 mutations (36 this study, 26 previous reports). A novel, milder phenotype (disease onset delayed until one year after birth, nonspecific encephalomyopathy, and 2-4 year survival period) associated with compound heterozygosity of the common p.E140K and a novel p.M177T mutations extends the range of symptoms of the SCO2 deficiency. The prevalence of SCO2 deficiency in Poland is relatively high. A search for SCO2 mutations in patients with histology resembling SMA appears to efficiently improve the detection rate.

MLPA based detection of mutations in the dystrophin gene of 180 Polish families with Duchenne/Becker muscular dystrophy

Duchenne/Becker muscular dystrophy (DMD/BMD) is a recessive, X-linked disorder caused by a mutation in the dystrophin gene. Deletions account for approximately 60-65% of mutations, duplications for 5-10%. The remaining cases are mainly point mutations. According to Monaco theory clinical form of the disease depends on maintaining or disrupting the reading frame. The purpose of the study was to determine frequency and location of deletions and duplications in the dystrophin gene, to determine the compliance between maintaining/disrupting the reading frame and clinical form of the disease and to check the effectiveness of MLPA (multiplex ligation-dependent probe amplification) in the detection of these mutations in hemizygous patients and heterozygous female carriers. The material is composed of combined results of molecular diagnosis carried out in years 2009-2012 in 180 unrelated patients referred with the diagnosis of DMD/BMD tested by use of MLPA. We identified 110 deletions, 22 duplication (in one patient two different duplications were detected) and 2 point mutations. Deletions involved mainly exons 45-54 and 3-21, whereas most duplications involved exons 3-18. The compliance with Monaco theory was 95% for deletions and 76% for duplications. Most of mutations in the dystrophin gene were localized in the hot spots - different for deletions and duplications. MLPA enabled their quick identification, exact localization and determination whether or not they maintained or disrupted the reading frame. MLPA was also effective in detection of deletions and duplications in female carriers.

Subtelomeric rearrangements in Polish subjects with intellectual disability and dysmorphic features

Fluorescent in situ hybridization (FISH) was performed in 76 patients referred to our department because of intellectual disability and dysmorphic features that can be related to subtelomeric microaberrations. In all the patients, conventional cytogenetic methods revealed normal karyotype. Four (5.3%) subtelomeric rearrangements were detected by FISH: 2 subtelomeric 1p36 deletions, an unbalanced translocation involving chromosomes 1 and 12 with 1p36 deletion, and a de novo balanced translocation involving chromosomes 19 and 22. Thus, 3 cases of 1p36 subtelomeric deletion were found (3.95%). To confirm subtelomeric rearrangements in 2 patients, comparative genomic hybridization (CGH) was applied. Moreover, 3 cases of polymorphism without phenotypic effects were found: in 2 patients, the polymorphism involved the long arm of chromosome 2 (maternal derivative in both patients), while in the third patient, a polymorphism of the long arm of chromosome 7 was diagnosed. The latter polymorphism was also found in the patient’s mother and grandfather.

A molecular and cytogenetic investigation of FMR1 gene premutations in Polish patients with primary ovarian insufficiency

OBJECTIVE The aim of this study was to determine the prevalence of premutations in the FMR1 gene that cause primary ovarian insufficiency (POI) in a group of affected women. STUDY DESIGN Forty DNA samples were purified from peripheral blood collected from women with ovarian failure who were under 40 years of age. A routine cytogenetic test was performed to eliminate chromosomal aberrations as the cause of POI. The DNA was analysed by polymerase chain reaction (PCR) with primers specific to the FMR1 gene region. The PCR products were then separated in denaturing polyacrylamide gels using an ABI Prism 377 sequencer. RESULTS Cytogenetic analysis of the samples revealed two X/autosome translocations. DNA analysis identified FMR1 gene premutations in three patients. The frequency of X/autosome translocations in the studied group was 2/40 (5.0%), and the frequency of FMR1 gene premutations was 3/38 cases (7.9%). Thus, genetic tests allowed for the identification of POI in five (12.5%) out of 40 women. CONCLUSION FMR1 gene premutation is a common genetic cause of POI.

No Evidence for Association of SCO2 Heterozygosity with High-Grade Myopia or Other Diseases with Possible Mitochondrial Dysfunction

SCO2 mutations cause recessively inherited cytochrome c oxidase deficiency. Recently Tran-Viet et al. proposed that heterozygosity for pathogenic SCO2 variants, including the common E140K variant, causes high-grade myopia. To investigate the association of SCO2 mutations with myopia, ophthalmic examinations were performed on 35 E140K carriers, one homozygous infant, and on a mouse model of Sco2 deficiency. Additionally, a screen for other putative effects of SCO2 heterozygosity was carried out by comparing the prevalence of the common E140K variant in a population of patients with undiagnosed diseases compatible with SCO2-related pathogenesis to that in a general population sample. High-grade myopia was not identified in any of the studied individuals. Of the carriers, 17 were emmetropic, and 18 possessed refractive errors. Additionally, no significant axial elongation indicative of high-grade myopia was found in mice carrying E129K (corresponding to E140K in humans) knock-in mutations. The prevalence of E140K carriers in the symptomatic cohort was evaluated as 1:103 (CI: 0.44-2.09) and did not differ significantly from the population prevalence (1:147, CI: 0.45-1.04).Our study demonstrates that heterozygosity for pathogenic SCO2 variants is not associated with high-grade myopia in either human patients or in mice.

Rodzinne występowanie zespołu FXTAS powodowanego premutacją w genie FMR1

Streszczenie Premutacją w genie FMR1 j est związana z neurodegeneracyjnym zespolem charakteryzującym sie wystepowaniem drzenia zamiarowego, ataksji chodu oraz zaburzen funkcji poznawczych u osob powyzej 50. roku zycia. W pracy przedstawiono przypadek 74-letniego mezczyzny z bardzo nasilonym drzeniem zamiarowym, niewielkim drzeniem pozycyjnym i ataksją chodu. Analiza genu FMR1 wykazala u probanda 91 powtorzen CGG, co spelnia kryterium rozpoznania premutacji. 68-letnia siostra chorego z drzeniem glowy o niewielkim nasileniu jest nosicielką premutacji z liczbą powtorzen 81 CGG, a mlodszy brat, u ktorego wystepuje niewielkie drzenie glowy oraz drzenie pozycyjne, ma 98 powtorzen CGG. Bezobjawowa corka probanda ma liczbe powtorzen powyzej 120 CGG, ale jeszcze w zakresie premutacji. U jej corki, z upośledzeniem umyslowym w stopniu niewielkim, bez innych objawow neurologicznych, stwierdzono pelną mutacje. W tej rodzinie ze zroznicowanymi objawami klinicznymi zostaly zidentyfikowane cztery osoby z premutacją i jedna z pelną mutacją w genie FMR1.