Federico Zara

Genome-wide association analysis of genetic generalized epilepsies implicates susceptibility loci at 1q43, 2p16.1, 2q22.3 and 17q21.32

Genetic generalized epilepsies (GGEs) have a lifetime prevalence of 0.3% and account for 20-30% of all epilepsies. Despite their high heritability of 80%, the genetic factors predisposing to GGEs remain elusive. To identify susceptibility variants shared across common GGE syndromes, we carried out a two-stage genome-wide association study (GWAS) including 3020 patients with GGEs and 3954 controls of European ancestry. To dissect out syndrome-related variants, we also explored two distinct GGE subgroups comprising 1434 patients with genetic absence epilepsies (GAEs) and 1134 patients with juvenile myoclonic epilepsy (JME). Joint Stage-1 and 2 analyses revealed genome-wide significant associations for GGEs at 2p16.1 (rs13026414, P(meta) = 2.5 × 10(-9), OR[T] = 0.81) and 17q21.32 (rs72823592, P(meta) = 9.3 × 10(-9), OR[A] = 0.77). The search for syndrome-related susceptibility alleles identified significant associations for GAEs at 2q22.3 (rs10496964, P(meta) = 9.1 × 10(-9), OR[T] = 0.68) and at 1q43 for JME (rs12059546, P(meta) = 4.1 × 10(-8), OR[G] = 1.42). Suggestive evidence for an association with GGEs was found in the region 2q24.3 (rs11890028, P(meta) = 4.0 × 10(-6)) nearby the SCN1A gene, which is currently the gene with the largest number of known epilepsy-related mutations. The associated regions harbor high-ranking candidate genes: CHRM3 at 1q43, VRK2 at 2p16.1, ZEB2 at 2q22.3, SCN1A at 2q24.3 and PNPO at 17q21.32. Further replication efforts are necessary to elucidate whether these positional candidate genes contribute to the heritability of the common GGE syndromes.

Epilepsy, hippocampal sclerosis and febrile seizures linked by common genetic variation around SCN1A

Epilepsy comprises several syndromes, amongst the most common being mesial temporal lobe epilepsy with hippocampal sclerosis. Seizures in mesial temporal lobe epilepsy with hippocampal sclerosis are typically drug-resistant, and mesial temporal lobe epilepsy with hippocampal sclerosis is frequently associated with important co-morbidities, mandating the search for better understanding and treatment. The cause of mesial temporal lobe epilepsy with hippocampal sclerosis is unknown, but there is an association with childhood febrile seizures. Several rarer epilepsies featuring febrile seizures are caused by mutations in SCN1A, which encodes a brain-expressed sodium channel subunit targeted by many anti-epileptic drugs. We undertook a genome-wide association study in 1018 people with mesial temporal lobe epilepsy with hippocampal sclerosis and 7552 control subjects, with validation in an independent sample set comprising 959 people with mesial temporal lobe epilepsy with hippocampal sclerosis and 3591 control subjects. To dissect out variants related to a history of febrile seizures, we tested cases with mesial temporal lobe epilepsy with hippocampal sclerosis with (overall n = 757) and without (overall n = 803) a history of febrile seizures. Meta-analysis revealed a genome-wide significant association for mesial temporal lobe epilepsy with hippocampal sclerosis with febrile seizures at the sodium channel gene cluster on chromosome 2q24.3 [rs7587026, within an intron of the SCN1A gene, P = 3.36 × 10−9, odds ratio (A) = 1.42, 95% confidence interval: 1.26–1.59]. In a cohort of 172 individuals with febrile seizures, who did not develop epilepsy during prospective follow-up to age 13 years, and 6456 controls, no association was found for rs7587026 and febrile seizures. These findings suggest SCN1A involvement in a common epilepsy syndrome, give new direction to biological understanding of mesial temporal lobe epilepsy with hippocampal sclerosis with febrile seizures, and open avenues for investigation of prognostic factors and possible prevention of epilepsy in some children with febrile seizures.

A Novel SCN2A Mutation in Family with Benign Familial Infantile Seizures

Summary:u2002 Benign familial infantile seizures (BFIS) is a clinical entity characterized by focal seizures with or without secondary generalization, occurring mostly in clusters, and usually first seen between 4 and 8 months of life. Psychomotor development is normal, and seizures usually resolve within the first year of life. BFIS is a genetically heterogenous condition with loci mapped to chromosomes 19 and 16. Mutations in the voltage‐gated sodium channel α2 subunit (SCN2A) gene on chromosome 2 were recently identified in families affected by neonatal and infantile seizures (benign familial neonatal–infantile seizures, BFNIS) with typical onset before 4 months of life. The identification of SCN2A mutations in families with only infantile seizures indicated that BFNIS and BFIS show overlapping clinical features.

Novel Compound Heterozygous Mutations in TBC1D24 Cause Familial Malignant Migrating Partial Seizures of Infancy

Early‐onset epileptic encephalopathies (EOEEs) are a group of rare devastating epileptic syndromes of infancy characterized by severe drug‐resistant seizures and electroencephalographic abnormalities. The current study aims to determine the genetic etiology of a familial form of EOEE fulfilling the diagnosis criteria for malignant migrating partial seizures of infancy (MMPSI). We identified two inherited novel mutations in TBC1D24 in two affected siblings. Mutations severely impaired TBC1D24 expression and function, which is critical for maturation of neuronal circuits. The screening of TBC1D24 in an additional set of eight MMPSI patients was negative. TBC1D24 loss of function has been associated to idiopathic infantile myoclonic epilepsy, as well as to drug‐resistant early‐onset epilepsy with intellectual disability. Here, we describe a familial form of MMPSI due to mutation in TBC1D24, revealing a devastating epileptic phenotype associated with TBC1D24 dysfunction.

Therapeutic potential of proteasome inhibition in Duchenne and Becker muscular dystrophies.

Duchenne muscular dystrophy (DMD) and its milder allelic variant, Becker muscular dystrophy (BMD), result from mutations of the dystrophin gene and lead to progressive muscle deterioration. Enhanced activation of proteasomal degradation underlies critical steps in the pathogenesis of the DMD/BMD dystrophic process. Previously, we demonstrated that treatment with the proteasome inhibitor MG-132 rescues the cell membrane localization of dystrophin and the dystrophin glycoprotein complex in mdx mice, a natural genetic mouse model of DMD. The current work aims to thoroughly define the therapeutic potential in dystrophinopathies of Velcade, a drug that selectively blocks the ubiquitin-proteasome pathway. Velcade is particularly intriguing since it has been approved for the treatment of multiple myeloma. Therefore, its side effects in humans have been explored. Velcade effects were analyzed through two independent methodological approaches. First, we administered the drug systemically in mdx mice over a 2-week period. In this system, Velcade restores the membrane expression of dystrophin and dystrophin glycoprotein complex members and improves the dystrophic phenotype. In a second approach, we treated with the compound explants from muscle biopsies of DMD or BMD patients. We show that the inhibition of the proteasome pathway up-regulates dystrophin, alpha-sarcoglycan, and beta-dystroglycan protein levels in explants from BMD patients, whereas it increases the proteins of the dystrophin glycoprotein complex in DMD cases.

Autosomal dominant cortical tremor, myoclonus and epilepsy: many syndromes, one phenotype

The association of cortical tremor, myoclonus and epileptic seizures has been reported in many Japanese and European families with different acronyms. We reviewed the familial cases presenting the clinical picture of autosomal dominant cortical tremor, myoclonus and epilepsy and analysed the phenotypic differences between the pedigrees, according to the recent genetic acquisitions. We concluded that BAFME, FAME, FEME, FCTE and ADCME are the same clinical entity even if genetically heterogeneous, with Japanese families linked to 8q24 and Italian ones to 2p11.1‐q12. A third locus could also be involved. Further studies should better clarify the electrophysiological features of this condition and identify the underlying molecular defects.

Novel mutations in CLN8 in Italian variant late infantile neuronal ceroid lipofuscinosis: another genetic hit in the Mediterranean

Neuronal ceroid lipofuscinoses (NCLs) are autosomal recessive neurodegenerative disorders typically characterized by the accumulation of autofluorescent material in tissues. On the basis of clinical features, age at onset, and molecular genetic defects, it is possible to distinguish at least nine forms. The CLN8 form was first described in Finland, where all the patients are homozygous for a p.Arg24Gly mutation in CLN8. More recently, it has been found that a subset of a Turkish variant of late infantile NCL (v-LINCL) is also associated with CLN8 mutations. To identify the molecular defect in Italian patients with v-LINCL, the CLN8 gene was directly sequenced in 10 patients. Controls were screened by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. Five fluorescent-labeled microsatellite markers covering 1xa0cM around the gene were used for haplotype analysis. In three Italian v-LINCL patients, identified in a small area in southern Italy, we detected four new mutations in CLN8: c.66delG (p.Gly22fs), c.88G>C (p.Ala30Pro), c.473A>G (p.Tyr158Cys), and c.581A>G (p.Gln194Arg). The single-base deletion was found in two unrelated patients. The novel missense mutations were not identified in ethnically matched control chromosomes. Our findings expand the number of CLN8 variants and corroborate the notion that CLN8 patients are not confined to the Finnish population.

6q terminal deletion syndrome associated with a distinctive EEG and clinical pattern: A report of five cases

Summary:u2002 Purpose: Mental retardation, facial dysmorphisms, and neurologic and brain abnormalities are features of 6q terminal deletions. Epilepsy is frequently associated with this chromosome abnormality, but electroclinical findings are not well delineated. We report five unrelated patients with 6q terminal deletions and a peculiar clinical, EEG, and neuroradiologic picture of epilepsy, mental retardation, and colpocephaly.

Genome-wide linkage meta-analysis identifies susceptibility loci at 2q34 and 13q31.3 for genetic generalized epilepsies

Purpose:u2002 Genetic generalized epilepsies (GGEs) have a lifetime prevalence of 0.3% with heritability estimates of 80%. A considerable proportion of families with siblings affected by GGEs presumably display an oligogenic inheritance. The present genome‐wide linkage meta‐analysis aimed to map: (1) susceptibility loci shared by a broad spectrum of GGEs, and (2) seizure type–related genetic factors preferentially predisposing to either typical absence or myoclonic seizures, respectively.

Benign adult familial myoclonic epilepsy (BAFME): evidence of an extended founder haplotype on chromosome 2p11.1-q12.2 in five Italian families

Benign adult familial myoclonic epilepsy (BAFME or FAME) is an autosomal dominant condition, characterized by shivering-like tremors of cortical origin, myoclonus, and epilepsy. Linkage to chromosomes 2p11.1-q12.2 and 8q23.1-q24.11 has been reported in Japanese and Italian families, respectively. We aimed to determine whether a common founder haplotype was shared by five BAFME families from southern Italy and attempted preliminary genotype–phenotype correlation analyses. Five Italian BAFME families were identified. One family has not been previously reported. DNA from 53 affected individuals was genotyped with highly polymorphic microsatellite markers spanning chromosomes 2p11.1-q12.2 and 8q23.1-q24.11. Multipoint linkage analysis was performed using LINKMAP 5.1 software assuming an autosomal dominant trait with 0.99 penetrance and frequency of 0.001. Significant linkage was found on chromosome 2p11.1-q12.2 and a maximum cumulative lod score of 18.5 was found for markers D2S2161 and D2S388. The haplotype “5332” of adjacent markers D2S388, D2S2216, D2S113, and D2S2175 segregates with the disease in all families indicating that the same mutation inherited from a common ancestor segregates in these families. Preliminary genotype–phenotype showed that patients carrying the disease haplotype show minor clinical differences, suggesting that expressivity of the founder mutation is not markedly influenced by other factors. The identification of causative mutations in BAFME requires an extensive and collaborative screening effort.