Alessandra Terracciano

Spectrum of phenotypes in female patients with epilepsy due to protocadherin 19 mutations.

Purpose:  To describe clinical and neuropsychological features of six consecutive sporadic girls with protocadherin 19 (PCDH19) mutations.

Motor Chip: A Comparative Genomic Hybridization Microarray for Copy-Number Mutations in 245 Neuromuscular Disorders

BACKGROUND Array-based comparative genomic hybridization (aCGH) is a reference high-throughput technology for detecting large pathogenic or polymorphic copy-number variations in the human genome; however, a number of quantitative monogenic mutations, such as smaller heterozygous deletions or duplications, are usually missed in most disease genes when proper multiplex ligation-dependent probe assays are not performed. METHODS We developed the Motor Chip, a customized CGH array with exonic coverage of 245 genes involved in neuromuscular disorders (NMDs), as well as 180 candidate disease genes. We analyzed DNA samples from 26 patients with known deletions or duplications in NMDs, 11 patients with partial molecular diagnoses, and 19 patients with a clinical diagnosis alone. RESULTS The Motor Chip efficiently confirmed and refined the copy-number mutations in all of the characterized patients, even when only a single exon was involved. In noncharacterized or partially characterized patients, we found deletions in the SETX (senataxin), SGCG [sarcoglycan, gamma (35kDa dystrophin-associated glycoprotein)], and LAMA2 (laminin, alpha 2) genes, as well as duplications involving LAMA2 and the DYSF [dysferlin, limb girdle muscular dystrophy 2B (autosomal recessive)] locus. CONCLUSIONS The combination of exon-specific gene coverage and optimized platform and probe selection makes the Motor Chip a complementary tool for molecular diagnosis and gene investigation in neuromuscular diseases.

Mutations in MFSD8/CLN7 are a frequent cause of variant-late infantile neuronal ceroid lipofuscinosis.

The neuronal ceroid lipofuscinoses (NCL) are a group of genetically heterogeneous neurodegenerative disorders. The recent identification of the MFSD8/CLN7 gene in a variant‐late infantile form of NCL (v‐LINCL) in affected children from Turkey prompted us to examine the relative frequency of variants in this gene in Italian patients with v‐LINCL. We identified nine children harboring 11 different mutations in MFSD8/CLN7. Ten mutations were novel and included three nonsense (p.Arg35Stop, p.Glu381Stop, p.Arg482Stop), four missense (p.Met1Thr, p.Gly52Arg, p.Thr294Lys, p.Pro447Leu), two splice site mutations (c.863+3_4insT, c.863+1G>C), and a 17‐bp deletion predicting a frameshift and premature protein truncation (c.627_643del17/p.Met209IlefsX3). The clinical phenotype, which was similar to that of the Turkish v‐LINCL cases, was not influenced by type and location of the mutation nor the length of the predicted residual gene product. As well as identifying novel variants in MFSD8/CLN7, this study contributes to a better molecular characterization of Italian NCL cases, and will facilitate medical genetic counseling in such families. The existence of a subset of v‐LINCL cases without mutations in any of the known NCL genes suggests further genetic heterogeneity.

Focal seizures with affective symptoms are a major feature of PCDH19 gene-related epilepsy

Purpose:  Mutations of the protocadherin19 gene (PCDH19) cause a female‐related epilepsy of variable severity, with or without mental retardation and autistic features. Despite the increasing number of patients and mutations reported, the epilepsy phenotype associated with PCDH19 mutations is still unclear. We analyzed seizure semiology through ictal video–electroencephalography (EEG) recordings in a large series of patients.

PCDH19-related epilepsy in two mosaic male patients

PCDH19 gene mutations have been recently associated with an epileptic syndrome characterized by focal and generalized seizures. The PCDH19 gene (Xq22.1) has an unusual X‐linked inheritance with a selective involvement for female subjects. A cellular interference mechanism has been hypothesized and male patients can manifest epilepsy only in the case of a mosaicism. So far about 100 female patients, and only one symptomatic male have been described. Using targeted next generation sequencing (NGS) approach we found a PCDH19 point mutation in two male patients with a clinical picture suggestive of PCDH19‐related epilepsy. The system allowed us to verify that the two c.1352 C>T; p.(Pro451Leu) and c.918C>G; p.(Tyr306*) variants occurred in mosaic status. Mutations were confirmed by Sanger sequencing and quantified by real‐time polymerase chain reaction (PCR). Up to now, the traditional molecular screening for PCDH19‐related epilepsy has been targeted to all females with early onset epilepsy with or without cognitive impairment. Male patients were generally excluded. We describe for the first time two mosaic PCDH19 point mutations in two male patients with a clinical picture suggestive of PCDH19‐related epilepsy. This finding opens new opportunities for the molecular diagnoses in patients with a peculiar type of epilepsy that remains undiagnosed in male patients.

The use of muscle biopsy in the diagnosis of undefined ataxia with cerebellar atrophy in children

Childhood cerebellar ataxias, and particularly congenital ataxias, are heterogeneous disorders and several remain undefined. We performed a muscle biopsy in patients with congenital ataxia and children with later onset undefined ataxia having neuroimaging evidence of cerebellar atrophy. Significant reduced levels of Coenzyme Q10 (COQ10) were found in the skeletal muscle of 9 out of 34 patients that were consecutively screened. A mutation in the ADCK3/Coq8 gene (R347X) was identified in a female patient with ataxia, seizures and markedly reduced COQ10 levels. In a 2.5-years-old male patient with non syndromic congenital ataxia and autophagic vacuoles in the muscle biopsy we identified a homozygous nonsense mutation R111X mutation in SIL1 gene, leading to early diagnosis of Marinesco-Sjogren syndrome. We think that muscle biopsy is a valuable procedure to improve diagnostic assesement in children with congenital ataxia or other undefined forms of later onset childhood ataxia associated to cerebellar atrophy at MRI.

PRRT2 is mutated in familial and non-familial benign infantile seizures

BACKGROUND Mutations of protein-rich transmembrane protein 2 (PRRT2) were recently associated to benign familial infantile seizures (BFIS) (MIM 605751) and paroxysmal kinesigenic dyskinesias (PKD) (MIM12800). AIMS To report mutations of PRRT2 in BFIS, infantile convulsions and choreoathetosis (ICCA), and in sporadic cases affected by benign infantile epilepsy (BIE). METHODS A mutational screening of PRRT2 was performed in 5 families, and in 7 sporadic cases affected by BIE. All clinical and neurophysiological details were reviewed. RESULTS Thirty-three members among 5 families were collected. Fifteen individuals had infantile seizures and one had infantile seizures followed by paroxysmal kinesigenic dyskinesia (PKD). We found the c.649_650InsC PRRT2 mutation in all tested patients (13 out of 15). Age at onset ranged from 3.5 to 10 months. Focal seizures, with or without secondary generalization, occurred mainly in cluster. One patient at the age of 11 years presented with PKD successfully treated with carbamazepine. All patients had a normal cognitive development. Two out of 7 non-familial cases (28.5%) carried a de novo PRRT2 mutation: the c.649_650InsC mutation in one with clustered seizures at the age of 5 months and an unreported c.718C-T p.R240X mutation in the other who, after cluster focal seizures at the age of 5 months, experienced absences at the age of 5 years. CONCLUSION Our findings emphasize that PRRT2 mutations might be responsible of both BFIS and ICCA, but might be causative also for sporadic cases of benign infantile seizures. The phenotypic spectrum comprises BFIS, ICCA, and PKD.

PRRT2 mutation causes paroxysmal kinesigenic dyskinesia and hemiplegic migraine in monozygotic twins

PRRT2 gene mutations have recently been identified as a causative gene of Paroxysmal kinesigenic dyskinesia (PKD), a rare movement disorder characterised by the occurrence of chorea, dystonia or athetosis triggered by sudden action. Some patients have additional intermittent neurologic disorders like infantile convulsions. The association with migraine has been rarely reported in this condition. Here we report the coexistence of PKD and hemiplegic migraine in twins harbouring a heterozygous mutation in PRRT2. Two monozygotic twins manifesting PKD together with repeated episodes of migraine with some severe attacks of hemiplegic migraine have been followed and treated for more than 10 years. Molecular genetic analysis disclosed the c.649_650insC, p.R217Pfs*8 heterozygous mutation in both twins. This mutation was segregating from the mother who likewise harboured the same mutation c.649dupC although she had never manifested PKD but complained of rare common migraine attacks in her past history. The association of PKD and hemiplegic migraine has been previously reported in one large family, associated to febrile convulsions and afebrile seizures in some individuals, but our report relates this association of symptoms to a mutation in PRRT2. The co-occurrence of both hemiplegic migraine and PKD in monozygotic twins expands the phenotypic spectrum of intermittent manifestations related to PRRT2 and perhaps suggests an additional causing gene for hemiplegic migraine.

Somatic mosaicism of PCDH19 mutation in a family with low-penetrance EFMR

The occurrence of epilepsy with mental retardation limited to females (EFMR; MIM 300088) has been recently associated to mutations in the PCDH19 gene, located on chromosome X and encoding for protocadherin 19. EFMR shows a rare X-linked inheritance wherein affected females may be segregating a mutation through unaffected transmitting males (Fabisiak and Erickson Clin Genet 38(5):353–358, 1990; Juberg and Hellman J Pediatr 79:726–732, 1971; Ryan et al. Nat Genet 17(1):92–95, 1997). The description of a pedigree segregating PCDH19 mutations from unaffected mothers to patients (Depienne et al. Hum Mutat 32:E1959–1975, 2011; Dibbens et al. Neurology 76:1514–1519, 2011) complicates disease inheritance and genetic counseling. In the present study, we describe a PCDH19 mutation segregating from an asymptomatic mother to an EFMR patient. In order to correlate the healthy phenotype with the genotype of the transmitting mother, we quantified in a few tissues the level of the mutant allele by real-time PCR, disclosing a somatic mosaicism. This finding has a great impact on genetic counseling.

Cognitive development in females with PCDH19 gene-related epilepsy

Mutations in the PCDH19 gene are now recognized to cause epilepsy in females and are claiming increasing interest in the scientific world. Clinical features and seizure semiology have been described as heterogeneous. Intellectual disability might be present, ranging from mild to severe; behavioral and psychiatric problems are a common feature of the disorder, including aggressiveness, depressed mood, and psychotic traits. The purpose of our study was to describe the cognitive development in 11 girls with a de novo mutation in PCDH19 and early-onset epilepsy. Six patients had average mental development or mild intellectual disability regardless of persistence of seizures in clusters. Five patients presented moderate or severe intellectual disability and autistic features. In younger patients, we found that despite an average developmental quotient, they all presented a delay of expressive language acquisition and lower scores at follow-up testing completed at older ages, underlining that subtle dysfunctions might be present. Larger cohort and long-term follow-up might be useful in defining cognitive features and in improving the care of patients with PCDH19.