Alternative splicing expands the clinical spectrum of NDUFS6-related mitochondrial disorders.

PURPOSE: We describe 3 families with Charcot-Marie-Tooth neuropathy (CMT), harboring a homozygous NDUFS6 NM_004553.6:c.309+5G>A variant previously linked to fatal Leigh syndrome. We aimed to characterize clinically and molecularly the newly identified patients and understand the mechanism underlying their milder phenotype. METHODS: The patients underwent extensive clinical examinations. Exome sequencing was done in 4 affected individuals. The functional effect of the c.309+5G>A variant was investigated in patient-derived EBV-transformed lymphoblasts at the complementary DNA, protein, and mitochondrial level. Alternative splicing was evaluated using complementary DNA long-read sequencing. RESULTS: All patients presented with early-onset, slowly progressive axonal CMT, and nystagmus; some exhibited additional central nervous system symptoms. The c.309+5G>A substitution caused the expression of aberrantly spliced transcripts and negligible levels of the canonical transcript. Immunoblotting showed reduced levels of mutant isoforms. No detectable defects in mitochondrial complex stability or bioenergetics were found. CONCLUSION: We expand the clinical spectrum of NDUFS6-related mitochondrial disorders to include axonal CMT, emphasizing the clinical and pathophysiologic overlap between these 2 clinical entities. This work demonstrates the critical role that alternative splicing may play in modulating the severity of a genetic disorder, emphasizing the need for careful consideration when interpreting splice variants and their implications on disease prognosis.

Mutational screening of Greek patients with axonal Charcot-Marie-Tooth disease using targeted next-generation sequencing: Clinical and molecular spectrum delineation.

BACKGROUND AND AIMS: Axonal forms of Charcot-Marie-Tooth disease (CMT) are classified as CMT2, distal hereditary motor neuropathy (dHMN) or hereditary sensory neuropathy (HSN) and can be caused by mutations in over 100 genes. We presently aimed to investigate for the first time the genetic landscape of axonal CMT in the Greek population. METHODS: Sixty index patients with CMT2, dHMN or HSN were screened by a combination of Sanger sequencing (GJB1) and next-generation sequencing custom-made gene panel covering 24 commonly mutated genes in axonal CMT. RESULTS: Overall, 20 variants classified as pathogenic or likely pathogenic were identified in heterozygous state in 20 index cases, representing 33.3% of the cohort. Of these, 14 were known pathogenic/likely pathogenic and six were designated as such according to ACMG classification, after in silico evaluation, testing for familial segregation and further literature review. The most frequently involved genes were GJB1 (11.7%), MPZ (5%) and MFN2 (5%), followed by DNM2 (3.3%) and LRSAM1 (3.3%). Single cases were identified with mutations in BSCL2, HSPB1 and GDAP1. INTERPRETATION: A wide phenotypic variability in terms of severity and age of onset was noted. Given the limited number of genes tested, the diagnostic yield of the present panel compares favourably with studies in other European populations. Our study delineates the genetic and phenotypic variability of inherited axonal neuropathies in the Greek population and contributes to the pathogenicity characterization of further variants linked to axonal neuropathies.

Moderately and Late Preterm Infants: Short- and Long-Term Outcomes From a Registry-Based Cohort.

Background: While most studies on the association of preterm birth and cerebral palsy (CP) have focused on very preterm infants, lately, attention has been paid to moderately preterm [32 to <34 weeks gestational age (GA)] and late preterm infants (34 to <37 weeks GA). Methods: In order to report on the outcomes of a cohort of moderately and late preterm infants, derived from a population-based CP Registry, a comparative analysis of data on 95 moderately preterm infants and 96 late preterm infants out of 1,016 with CP, was performed. Results: Moderately preterm neonates with CP were more likely to have a history of N-ICU admission (p = 0.001) and require respiratory support (p < 0.001) than late preterm neonates. Birth weight was significantly related to early neonatal outcome with children with lower birth weight being more likely to have a history of N-ICU admission [moderately preterm infants (p = 0.006)/late preterm infants (p < 0.001)], to require ventilator support [moderately preterm infants (p = 0.025)/late preterm infants (p = 0.014)] and not to have neonatal seizures [moderately preterm infants (p = 0.044)/late preterm infants (p = 0.263)]. In both subgroups, the majority of children had bilateral spastic CP with moderately preterm infants being more likely to have bilateral spastic CP and less likely to have ataxic CP as compared to late preterm infants (p = 0.006). The prevailing imaging findings were white matter lesions in both subgroups, with statistically significant difference between moderately preterm infants who required ventilator support and mainly presented with this type of lesion vs. those who did not and presented with gray matter lesions, maldevelopments or miscellaneous findings. Gross motor function was also assessed in both subgroups without significant difference. Among late preterm infants, those who needed N-ICU admission and ventilator support as neonates achieved worse fine motor outcomes than those who did not. Conclusions: Low birth weight is associated with early neonatal problems in both moderately and late preterm infants with CP. The majority of children had bilateral spastic CP and white matter lesions in neuroimaging. GMFCS levels were comparable in both subgroups while BFMF was worse in late preterm infants with a history of N-ICU admission and ventilator support.

ADCY5-related movement disorders: Frequency, disease course and phenotypic variability in a cohort of paediatric patients.

INTRODUCTION: ADCY5 mutations have been recently identified as an important cause of early-onset hyperkinetic movement disorders. The phenotypic spectrum associated with mutations in this gene is expanding. However, the ADCY5 mutational frequency in cohorts of paediatric patients with hyperkinetic movement disorders has not been evaluated. METHODS: We performed a screening of the entire ADCY5 coding sequence in 44 unrelated subjects with genetically undiagnosed childhood-onset hyperkinetic movement disorders, featuring chorea alone or in combination with myoclonus and dystonia. All patients had normal CSF analysis and brain imaging and were regularly followed-up in tertiary centers for paediatric movement disorders. RESULTS: We identified five unrelated subjects with ADCY5 mutations (11% of the cohort). Three carried the p. R418W mutation, one the p. R418Q and one the p. R418G mutation. Mutations arose de novo in four cases, while one patient inherited the mutation from his similarly affected father. All patients had delayed motor and/or language milestones with or without axial hypotonia and showed generalized chorea and dystonia, with prominent myoclonic jerks in one case. Episodic exacerbations of the baseline movement disorder were observed in most cases, being the first disease manifestation in two patients. The disease course was variable, from stability to spontaneous improvement during adolescence. CONCLUSION: Mutations in ADCY5 are responsible for a hyperkinetic movement disorder that can be preceded by episodic attacks before the movement disorder becomes persistent and is frequently misdiagnosed as dyskinetic cerebral palsy. A residual degree of neck hypotonia and a myopathy-like facial appearance are frequently observed in patients with ADCY5 mutations.

Screening of UBE3A gene in patients referred for Angelman Syndrome.

Angelman Syndrome (AS) is a neurodevelopmental disorder characterized by severe developmental delay, speech impairment and unique behaviors including inappropriate laughter and happy disposition. AS is related to deficient maternal UBE3A gene expression caused either by chromosomal deletions, uniparental disomy, molecular defects of the imprinted 15q11-q13 critical region or by loss of function mutations in the maternally inherited UBE3A. In the present study, screening UBE3A was performed in 43 patients who were referred for AS but whom previous molecular diagnostic tests failed to provide a diagnosis. Two causative mutations--one of them novel--and four polymorphic variants one of which is also novel were revealed. Further investigation of 7 patients disclosed defects in other genes involved in clinical phenotypes mimicking AS. A typical EEG pattern and microcephaly in patients with developmental delay prompt for AS investigation while wide genetic screening should be applied to help resolution of the complex phenotypes characterized by developmental delay.

Neuropsychological sequelae and quality of life following treatment of posterior fossa ependymomas in children.

INTRODUCTION: Modern treatment of posterior fossa ependymomas in children has improved the overall survival, but as more children live longer, the neuropsychological problems that they endure as result of the disease and its treatment become more the focus of attention. MATERIAL: Early problems such as cerebellar mutism appear to be related to surgery and do not seem to be influenced in their incidence or outcome by the otherwise beneficial effect of oncological treatment. Indeed, the cause of cerebellar mutism is still elusive. While it was originally believed to be totally reversible, it is increasingly realized that it may be related to more complex delayed neuropsychological problems. Late problems such as the cerebellar cognitive affective syndrome are increasingly being recognized. The deleterious effect of both surgery and radiotherapy that is commonly administered afterwards is now well appreciated. CONCLUSION: Careful neuropsychological assessment of these children and early intervention will maximize chances for recovery and improvement of academic functions and quality of life issues.