Monica Traverso

Clinical Significance of Rare Copy Number Variations in Epilepsy A Case-Control Survey Using Microarray-Based Comparative Genomic Hybridization

OBJECTIVE To perform an extensive search for genomic rearrangements by microarray-based comparative genomic hybridization in patients with epilepsy. DESIGN Prospective cohort study. SETTING Epilepsy centers in Italy. PATIENTS Two hundred seventy-nine patients with unexplained epilepsy, 265 individuals with nonsyndromic mental retardation but no epilepsy, and 246 healthy control subjects were screened by microarray-based comparative genomic hybridization. MAIN OUTCOME MEASURES Identification of copy number variations (CNVs) and gene enrichment. RESULTS Rare CNVs occurred in 26 patients (9.3%) and 16 healthy control subjects (6.5%) (P = .26). The CNVs identified in patients were larger (P = .03) and showed higher gene content (P = .02) than those in control subjects. The CNVs larger than 1 megabase (P = .002) and including more than 10 genes (P = .005) occurred more frequently in patients than in control subjects. Nine patients (34.6%) among those harboring rare CNVs showed rearrangements associated with emerging microdeletion or microduplication syndromes. Mental retardation and neuropsychiatric features were associated with rare CNVs (P = .004), whereas epilepsy type was not. The CNV rate in patients with epilepsy and mental retardation or neuropsychiatric features is not different from that observed in patients with mental retardation only. Moreover, significant enrichment of genes involved in ion transport was observed within CNVs identified in patients with epilepsy. CONCLUSIONS Patients with epilepsy show a significantly increased burden of large, rare, gene-rich CNVs, particularly when associated with mental retardation and neuropsychiatric features. The limited overlap between CNVs observed in the epilepsy group and those observed in the group with mental retardation only as well as the involvement of specific (ion channel) genes indicate a specific association between the identified CNVs and epilepsy. Screening for CNVs should be performed for diagnostic purposes preferentially in patients with epilepsy and mental retardation or neuropsychiatric features.

Caveolin-3 T78M and T78K missense mutations lead to different phenotypes in vivo and in vitro.

Caveolins are the principal protein components of caveolae, invaginations of the plasma membrane involved in cell signaling and trafficking. Caveolin-3 (Cav-3) is the muscle-specific isoform of the caveolin family and mutations in the CAV3 gene lead to a large group of neuromuscular disorders. In unrelated patients, we identified two distinct CAV3 mutations involving the same codon 78. Patient 1, affected by dilated cardiomyopathy and limb girdle muscular dystrophy (LGMD)-1C, shows an autosomal recessive mutation converting threonine to methionine (T78M). Patient 2, affected by isolated familiar hyperCKemia, shows an autosomal dominant mutation converting threonine to lysine (T78K). Cav-3 wild type (WT) and Cav-3 mutations were transiently transfected into Cos-7 cells. Cav-3 WT and Cav-3 T78M mutant localized at the plasma membrane, whereas Cav-3 T78K was retained in a perinuclear compartment. Cav-3 T78K expression was decreased by 87% when compared with Cav-3 WT, whereas Cav-3 T78M protein levels were unchanged. To evaluate whether Cav-3 T78K and Cav-3 T78M mutants behaved with a dominant negative pattern, Cos-7 cells were cotransfected with green fluorescent protein (GFP)-Cav-3 WT in combination with either mutant or WT Cav-3. When cotransfected with Cav-3 WT or Cav-3 T78M, GFP-Cav-3 WT was localized at the plasma membrane, as expected. However, when cotransfected with Cav-3 T78K, GFP-Cav-3 WT was retained in a perinuclear compartment, and its protein levels were reduced by 60%, suggesting a dominant negative action. Accordingly, Cav-3 protein levels in muscles from a biopsy of patient 2 (T78K mutation) were reduced by 80%. In conclusion, CAV3 T78M and T78K mutations lead to distinct disorders showing different clinical features and inheritance, and displaying distinct phenotypes in vitro.

Progressive exercise intolerance associated with a new muscle-restricted nonsense mutation (G142X) in the mitochondrial cytochrome b gene

We report a novel nonsense mitochondrial cytochrome b mutation (G15170A) in a 40‐year‐old woman with progressive exercise intolerance and lactic acidosis. Muscle biopsy showed several cytochrome c oxidase–positive ragged‐red fibers, and reduced activities of respiratory chain complexes I and III. This mutation, resulting in the loss of 228 amino acids of the protein, was very abundant in the patients muscle, but undetectable in lymphocytes and fibroblasts. Clinical and laboratory data indicate that this defect is the primary cause of the disease, thus adding a new mutation in the cytochrome b gene among the growing number of patients with exercise intolerance and lactic acidosis. Muscle Nerve 28: 508–511, 2003

Impairment of ceramide synthesis causes a novel progressive myoclonus epilepsy

Alterations of sphingolipid metabolism are implicated in the pathogenesis of many neurodegenerative disorders.

Linkage Analysis and Disease Models in Benign Familial Infantile Seizures: A Study of 16 Families

Summary:  Purpose: Benign familial infantile seizures (BFIS) is a genetically heterogeneous condition characterized by partial seizures, onset age from 3 to 9 months, and favorable outcome. BFIS loci were identified on chromosomes 19q12‐13.1 and 16p12‐q12, allelic to infantile convulsions and choreathetosis. The identification of SCN2A mutations in families with only infantile seizures indicated that BFNIS and BFIS may show overlapping clinical features. Infantile seizures also were in a family with familial hemiplegic migraine and mutations in the ATP1A2 gene. We have examined the heterogeneous genetics of BFIS by means of linkage analysis.

Dramatic effect of levetiracetam in early-onset epileptic encephalopathy due to STXBP1 mutation

BACKGROUND Syntaxin Binding Protein 1 (STXBP1) mutations determine a central neurotransmission dysfunction through impairment of the synaptic vesicle release, thus causing a spectrum of phenotypes varying from syndromic and non-syndromic epilepsy to intellectual disability of variable degree. Among the antiepileptic drugs, levetiracetam has a unique mechanism of action binding SV2A, a glycoprotein of the synaptic vesicle release machinery. PATIENT DESCRIPTION We report a 1-month-old boy manifesting an epileptic encephalopathy with clonic seizures refractory to phenobarbital, pyridoxine and phenytoin that presented a dramatic response to levetiracetam with full epilepsy control and EEG normalization. Genetic analysis identified a novel de novo heterozygous mutation (c.[922A>T]p.[Lys308(∗)]) in the STXBP1 gene that severely affects the protein. CONCLUSIONS The observation of a dramatic efficacy of levetiracetam in a case of STXBP1 epileptic encephalopathy refractory to other antiepileptic drugs and considerations regarding the specific mechanism of action of levetiracetam modulating the same system affected by STXBP1 mutations support the hypothesis that this drug may be able to reverse specifically the disease epileptogenic abnormalities. Further clinical observations and laboratory studies are needed to confirm this hypothesis and eventually lead to consider levetiracetam as the first choice treatment of patients with suspected or confirmed STXBP1-related epilepsies.

Early‐onset absence epilepsy: SLC2A1 gene analysis and treatment evolution

To determine the prevalence of SLC2A1 mutations in children with early‐onset absence epilepsy (EOAE) and to investigate whether there were differences in demographic and electroclinical data between patients who became seizure‐free with anti‐epileptic drug (AED) monotherapy (group I) and those who needed add‐on treatment of a second AED (group II).

A clinical and genetic study of 33 new cases with early-onset absence epilepsy.

PURPOSE To investigate the electroclinical features and the outcome of patients with typical absences starting before the 3 years of life. METHODS We reviewed the clinical data of patients with absences started before 3 years observed over a 15-year period. Mutation analysis of SLC2A1 (GLUT-1) gene was performed when possible. Their clinical features were compared with those of subjects with a diagnosis of childhood absence epilepsy (CAE). RESULTS Among 33 children with absence epilepsy starting before 3 years of life, there were 20 boys and 13 girls. Mean seizure onset was at 28.0 ± 8.3 (range: 8-36) months of life. Two children displayed borderline intellectual functioning at long-term follow-up. Twenty-eight (85%) patients showed excellent response to therapy. Three subjects evolved into a different form of idiopathic generalized epilepsy (IGE). No SLC2A1 mutation was identified in 20 (60.6%) patients tested. The main clinical features of patients with early-onset absences did not differ from those of CAE except for increased prevalence of males (p=0.002) and longer treatment duration (p=0.001) in the former. CONCLUSIONS Strong similarities in the electroclinical features and outcome between children with early-onset absences and those with CAE support the view that these conditions are part of the wide spectrum of IGE.

Different electroclinical picture of generalized epilepsy in two families with 15q13.3 microdeletion.

15q.13.3 microdeletion has been described in a variety of neurodevelopmental disorders. Epilepsy appears to be a common feature and, specifically, the 15q13.3 microdeletion is found in about 1% of patients with idiopathic generalized epilepsy. Recently, absence seizures with intellectual disability (ID) have been reported in patients carrying this mutation. We describe two families in which several affected members carry a 15q13.3 microdeletion in a pattern suggestive of autosomal dominant inheritance. Their phenotype includes mainly absence epilepsy and mild ID, suggesting only similarities with genetic/idiopathic generalized epilepsies but not typical features. The importance of studying such families is crucial to broaden the phenotype and understand the long‐term outcome of patients with this condition.

Genetic and Early Clinical Manifestations of Females Heterozygous for Duchenne/Becker Muscular Dystrophy

BACKGROUND Female carriers of Duchenne muscular dystrophy (DMD), although usually asymptomatic, develop muscle weakness up to 17% of the time, and a third present cardiac abnormalities or cognitive impairment. Clinical features of DMD carriers during childhood are poorly known. PATIENTS We describe a cohort of pediatric DMD carriers, providing clinical, genetic, and histopathologic features, with a mean follow-up of 7 years. RESULTS Fifteen females with a DMD mutation (age range 5 to 18 years) were included. Seven patients (46%) presented with clinically evident symptoms and signs such as limb girdle weakness, abnormal gait, and exercise intolerance. The other eight patients (53%) were evaluated because of an incidental finding of elevated level of creatine kinase. Creatine kinase level was elevated in all, ranging from 392 to 13,000 U/L. Calf hypertrophy was observed in eight patients (53%). No patient developed respiratory or cardiac involvement. The most frequent complication was scoliosis (46%). Four patients (29%) also presented minor learning disabilities or behavioral problems. We performed electromyography in half of patients, showing myopathic pattern in four (53%). Muscle biopsy revealed a mosaic reduction of dystrophin in nine available cases. DMD gene mutations were mostly deletions (71%), resulting in loss of reading frame in five patients (36%). The three patients who experienced the most severe disease course were affected either by a nonsense or frameshift mutation. CONCLUSIONS Our analysis suggests that DMD gene mutations may be suspected in a female child with persistently elevated levels of creatine kinase. Evidence of scoliosis, calf hypertrophy, or myopathic pattern at electromyography may also be helpful, and muscle biopsy is always indicative. DMD carriers should be followed for subtle orthopedic and psychiatric complications during childhood.