BACKGROUND:Heterozygous gain-of-function variants in SAMD9L are associated with ataxia-pancytopenia syndrome (ATXPC) and monosomy 7 myelodysplasia and leukemia syndrome-1 (M7MLS1). Association with peripheral neuropathy has rarely been described.METHODS:Whole-exome sequencing (WES) from DNA extracted from peripheral blood was performed in a 10-year-old female presenting with demyelinating neuropathy, her similarly affected mother and the unaffected maternal grandparents. In addition to evaluation of single nucleotide variants, thorough work-up of copy number and exome-wide variant allele frequency data was performed.RESULTS:Combined analysis of the mother's and daughter's duo-exome data and analysis of the mother's and her parents' trio-exome data initially failed to detect a disease-associated variant. More detailed analysis revealed a copy number neutral loss of heterozygosity of 7q in the mother and led to reanalysis of the exome data for respective sequence variants. Here, a previously reported likely pathogenic variant in the SAMD9L gene on chromosome 7q (NM_152703.5:c.2956C>T; p.(Arg986Cys)) was identified that was not detected with standard filter settings because of a low percentage in blood cells (13%). The variant also showed up in the daughter at 32%, a proportion well below the expected 50%, which in each case can be explained by clonal selection processes in the blood due to this SAMD9L variant.CONCLUSION:The report highlights the specific pitfalls of molecular genetic analysis of SAMD9L and, furthermore, shows that gain-of-function variants in this gene can lead to a clinical picture associated with the leading symptom of peripheral neuropathy. Due to clonal hematopoietic selection, displacement of the mutant allele occurred, making diagnosis difficult.

As per recent reports, there is an association between glucocerebrosidase (Gcase) enzyme and Parkinson's disease (PD). In addition, certain mutations in the Gcase gene (GBA) and the progranulin (PGRN) gene are found to be linked with the imbalance in the levels of Gcase enzyme. This imbalance or decrease or impairment in Gcase activity can lead to Gaucher disease, frontotemporal lobar degeneration (FTLD), dementia, etc. Recent evidences suggest that the drugs used to treat these diseases can be used for PD. The present review has focused on the therapeutic approaches used for diseases linked with Gcase enzyme, which can be used for PD. The review also considered possible target specific novel strategies, which may help to meet the unmet needs in the treatment of PD.

Bei einer 25-jährigen Patientin mit klinischem Verdacht auf Muskeldystrophie fand sich in der Muskelbiopsie eine ausgeprägte chronische Myopathie mit zahlreichen trabekulären (lobulierten) Muskelfasern und erheblichen Anomalien der Myofibrillenstruktur. Im Rahmen einer NGS-Panel-Untersuchung wurde eine homozygote c.3070+1G>C Sequenzvariante gefunden, die wahrscheinlich zu einem fehlerhaften Spleißen und damit zu einem verkürzten oder anderweitig veränderten Protein führt.

We present clinical features and genetic results of 1206 index patients and 124 affected relatives who were referred for genetic testing of Charcot–Marie–Tooth ( CMT ) neuropathy at the laboratory in Aachen between 2001 and 2012. Genetic detection rates were 56% in demyelinating CMT (71% of autosomal dominant (AD) CMT1 / CMTX ), and 17% in axonal CMT (24% of AD CMT2 / CMTX ). Three genetic defects ( PMP22 duplication/deletion, GJB1 /Cx32 or MPZ / P0 mutation) were responsible for 89.3% of demyelinating CMT index patients in whom a genetic diagnosis was achieved, and the diagnostic yield of the three main genetic defects in axonal CMT ( GJB1 /Cx32 , MFN2 , MPZ / P0 mutations) was 84.2%. De novo mutations were detected in 1.3% of PMP22 duplication, 25% of MPZ / P0 , and none in GJB1 /Cx32 . Motor nerve conduction velocity was uniformly <38 m/s in median or ulnar nerves in PMP22 duplication, >40 m/s in MFN2 , and more variable in GJB1 /Cx32 , MPZ / P0 mutations. Patients with CMT2A showed a broad clinical severity regardless of the type or position of the MFN2 mutation. Out of 75 patients, 8 patients (11%) with PMP22 deletions were categorized as CMT1 or CMT2 . Diagnostic algorithms are still useful for cost‐efficient mutation detection and for the interpretation of large‐scale genetic data made available by next generation sequencing strategies.

Silver–Russell syndrome ( SRS ) is a growth retardation syndrome characterized by intrauterine and postnatal growth retardation, relative macrocephaly and protruding forehead, body asymmetry and feeding difficulties. Nearly 50% of cases show a hypomethylation in 11p15.5, in 10% maternal uniparental disomy of chromosome 7 is present. A significant number of patients with SRS features also exhibit chromosomal aberrations. We analyzed 43 individuals referred for SRS genetic testing by molecular karyotyping. Pathogenic variants could be detected in five of them, including a NSD1 duplication in 5q35 and a 14q32 microdeletion. NSD1 deletions are detectable in overgrowth disorders (Sotos syndrome and Beckwith–Wiedemann syndrome), whereas NSD1 duplications are associated with growth retardation. The 14q32 deletion is typically associated with Temple syndrome ( TS14 ), but the identification of a patient in our cohort reflects the clinical overlap between TS14 and SRS . As determination of molecular subtypes is the basis for a directed counseling and therapy, the identification of pathogenic variants in >10% of the total cohort of patients referred for SRS testing and in >16% of characteristic individuals with the characteristic SRS phenotype confirms the need to apply molecular karyotyping in this cohort.

Der Einsatz hochauflösender molekularer Karyotypisierungsverfahren auf der Basis von Mikroarrays hat zu einer wesentlichen Verbesserung der humangenetischen Diagnostik bei der Ursachenabklärung von Entwicklungsstörungen in der Pädiatrie beigetragen. Ihr hohes Auflösungsvermögen führt zu einer Verdopplung der Detektionsrate für ursächliche chromosomale Imbalancen (Deletionen oder Duplikationen) von etwa 10 % durch die herkömmliche zytogenetische Abklärung auf nun etwa 20 % bei Patienten mit mentaler Retardierung und weiteren klinischen Auffälligkeiten. Es zeichnet sich inzwischen ab, dass die molekulare Karyotypisierung zur diagnostischen Einordnung bei Verdacht auf eine Chromosomenstörung die klassische Chromosomenanalyse zunehmend ablöst, sofern nicht ein bekanntes chromosomales Syndrom, z. B. Down-Syndrom, Ullrich-Turner-Syndrom, anzunehmen ist. Während die Array-Diagnostik also zu einer erhöhten Erkennungsrate von chromosomalen Imbalancen führt, ist sie derzeit für den Nachweis von balancierten Chromosomenumbauten, die ein erhöhtes genetisches Risiko beinhalten (z. B. familiäre Translokationen), nicht geeignet. Hier bleibt die konventionelle zytogenetische Analytik die Methode der Wahl. An dieser Stelle sollte darauf hingewiesen werden, dass die allgemein verfügbaren Daten bisher noch nicht ausreichen, um für jede nachweisbare Veränderung eine eindeutige Aussage über die klinische Relevanz zu treffen. Weiterhin stehen Regelungen zum Umgang mit Zusatzbefunden (Zufallsbefunden) noch aus. Vor dem Hintergrund dieser Herausforderungen der Interpretation und Vermittlung von Array-Daten ist die enge, auch fallbezogene Zusammenarbeit zwischen Pädiatrie und Humangenetik umso wesentlicher, um – u. a. auch im Sinne des Gendiagnostik-Gesetzes – eine optimale Betreuung des Patienten und seiner Familie zu gewährleisten.

We reviewed the natural history and assessed the SMN2 copy number of 66 patients with infantile spinal muscular atrophy (SMA) type I born between 2000 and 2005 in Germany whose diagnosis was confirmed by a homozygous SMN1 deletion in the first 6 months of life. After excluding patients who had received valproic acid, the median/mean age at disease endpoint was 6.1/7.3 months (range 0.0–34.0). Four (6.1%) patients with one SMN2 copy had severe SMA type ‘0’ with joint contractures and respiratory distress from birth. Median/mean age at onset (months) in 57 (86.3%) patients with two SMN2 copies was 1.2/1.3, and 3.5/3.4 in 5 (7.6%) patients with three SMN2 copies. Median/mean age at disease endpoint was 6.5/7.8 months (range 0.5–30) in patients with two SMN2 copies. All patients with three SMN2 copies were still alive at 10–55 months, two of them under permanent ventilation. Our data are relevant for prognostication and genetic counselling. The observed clinical variability, especially in the group with two SMN2 copies, might be important for clinical trials in SMA I where a possible control group could be defined as follows: age at onset within 4–5 months, age at genetic diagnosis <6 months, two SMN2 copies present, head control in less than 10%, no respiratory distress from birth, disease endpoint either age at death or age at permanent ventilation.

Silver–Russell syndrome (SRS) describes a malformation syndrome with severe intrauterine and postnatal growth retardation. Currently, two major (epi)mutations have been described: while approximately 10% of patients carry a maternal uniparental disomy of chromosome 7 (UPD7), 35–60% show a hypomethylation at the H19 differentially methylated regions (DMRs) in 11p15. Until recently, a Southern‐blot based test was routinely used to identify epimutation carriers. Nevertheless, this test was time consuming and hampered by the huge amount of genomic DNA needed. With the methylation‐specific multiplex ligation‐dependent probe amplification assay (MLPA) for SRS, a PCR‐based test is now available, allowing the analysis also of small amounts of DNA. Probes in this assay hybridize to the H19 DMRs but do not cover the genomic target of the Southern‐blot probe. We now screened 72 patients with SRS by MLPA. Hypomethylation of the H19 DMRs was confirmed in all patients analyzed by Southern blot. In addition, we identified six individuals with hypomethylation of the H19 DMR who had previously normal blot results. This discrepancy can be explained by the observed generally lower degree of demethylation in this group, possibly not detectable by the less sensitive Southern‐blot method but also with a varying degree of methylation at different DMRs in the same individual. Apart from hypomethylation in the H19 DMR, we observed a slight demethylation for one of the IGF2 probes. The total detection rate of 11p15 hypomethylation is now increased to >38%. Considering maternal UPD7 and chromosomal aberrations, (epi)genetic alterations now account for more than 50% of SRS patients. In summary, MLPA represents an easy, low cost and reliable system in the molecular diagnostics of SRS.

OBJECTIVE:Homozygous deletions/mutations of the SMN1 gene cause infantile spinal muscular atrophy (SMA). The presence of at least one SMN2 gene copy is required for normal embryogenesis. Lack of SMN protein results in degeneration of motor neurons, while extraneuronal manifestations have been regarded as a chance association with SMA. We report on heart defects in the subgroup of congenital SMA type I patients.METHODS:Data were recruited from 65 unselected SMA I patients whose diagnosis had been confirmed genetically within the first 6 months of age. SMN2 copy numbers were analysed retrospectively and correlated with clinical findings including heart malformations.RESULTS:Four (6%) patients had one copy of SMN2, 56 (86%) had two and five (8%) had three SMN2 copies. Three out of four (75%) patients with a single SMN2 copy had congenital SMA with haemodynamically relevant atrial or ventricular septal defects.CONCLUSIONS:Previous case reports of SMA I patients with congenital heart defects did not clarify whether the cardiac malformations were coincidental. Given the respective incidences of congenitally lethal SMA with a single SMN2 copy and of cardiac septal defects in humans, a chance association of both conditions would occur in less than one out of 50 million individuals. Our findings suggest that the SMN protein is relevant for normal cardiogenesis.

Introduction: Silver-Russell syndrome (SRS; also know as Russell-Silver syndrome) is a heterogeneous syndrome which is characterised by severe intrauterine and postnatal growth retardation and typical dysmorphic features. Recently, the first SRS patients with (epi)genetic mutations in 11p15 affecting the telomeric imprinting domain have been identified. Interestingly, opposite mutations are associated with Beckwith-Wiedemann syndrome (BWS). However, the general significance of epigenetic mutations in 11p15 for the aetiology of SRS remained unclear.Methods: We screened a cohort of 51 SRS patients for epimutations in ICR1 and KCNQ1OT1 by methylation sensitive Southern blot analyses.Results: ICR1 demethylation could be observed in 16 of the 51 SRS patients, corresponding to a frequency of approximately 31%. Changes in methylation at the KCNQ1OT1 locus were not detected.Discussion: Combining these data with those on maternal duplications in 11p15, nearly 35% of SRS cases are associated with detectable ( epi) genetic disturbances in 11p15. We now have to also consider a general involvement of 11p15 alterations in growth retarded patients with only minor or without further dysmorphic features. SRS and BWS may now be regarded as two diseases caused by opposite ( epi) genetic disturbances of the same chromosomal region displaying opposite clinical pictures.

(Epi)mutations affecting chromosome 11p15 are meanwhile well known to be associated with growth disturbances. The finding of 11p15 mutations in the overgrowth disease Beckwith–Wiedemann syndrome (BWS) led to the identification of imprinted growth-promoting genes which are expressed paternally and of imprinted growth-suppressing genes in the same region that are expressed maternally. Recently, the opposite (epi)mutations of the same region have been reported to result in growth retardation: maternal duplications of 11p15 as well as hypomethylation of the telomeric 11p15 imprinting domain (ICR1) could be identified in patients with Silver–Russell syndrome (SRS), a disease which is in particular characterised by intrauterine and postnatal growth retardation. To elucidate whether 11p15 mutations are generally involved in growth retardation we screened 125 growth retarded patients, among them 47 patients with SRS-like features and 20 with isolated growth retardation. Additional 58 patients were presented with clinical signs not consistent with SRS. We excluded 11p15 duplications in all 123 families by short tandem repeat typing. ICR1 hypomethylation was investigated by Southern-blot analyses and was therefore restricted to samples with a large amount of DNA. We identified ICR1 hypomethylation in 20% of the patients with SRS-like features (n = 25). No further cases were detectable in the other two subgroups with isolated growth retardation (n = 20) and with clinical signs not consistent with SRS (n = 23), respectively. Our data show that 11p15 duplications are rare in growth retardation in general and that they seem to be restricted to patients with SRS features. Furthermore, testing for the ICR1 hypomethylation should also be focused on patients with SRS features. While the ICR1 epimutation is detectable with a significant frequency only in SRS patients, its role for isolated growth retardation remains to be elucidated.

Chromosomal rearrangements involving the (sub)telomeres are an important cause of human genetic diseases: with the development of advanced molecular cytogenetic methods they have been identified as a major cause of mental retardation and/or congenital malformation syndromes. We identified a cryptic unbalanced de novo translocation 10p/13q by subtelomere FISH in a boy with mental and growth retardation (karyotype: 46,XY,der(10)t(10;13)(p15.1;q34)(D10S2488–,D13S296+)). Craniofacial dysmorphisms included frontal bossing, epicanthal folds, long philtrum, thin upper lip, short nose, mild retrognathy and a flat midface. In addition the patient had ASDII, a pyloric stenosis, bilateral inguinal hernias and cryptorchidism. His psychomotor development was significantly delayed. Microsatellite typing revealed the paternal origin of the two chromosomes involved in the rearrangement. By comparing our case with previously published patients with similar aberrations we conclude that the congenital malformations in our case are associated with the partial 10p deletion. The craniofacial features might be attributed to the 13q duplication. The identification of a 10p/13q translocation in our case highlights the importance of searching for cryptic subtelomeric imbalances in mentally retarded patients and helps to further delineate genotype–phenotype correlations in rare chromosomal disturbances.