Progressive Myoclonus Epilepsy Caused by a Homozygous Splicing Variant of SLC7A6OS.

Exome sequencing was performed in 2 unrelated families with progressive myoclonus epilepsy. Affected individuals from both families shared a rare, homozygous c.191A > G variant affecting a splice site in SLC7A6OS. Analysis of cDNA from lymphoblastoid cells demonstrated partial splice site abolition and the creation of an abnormal isoform. Quantitative reverse transcriptase polymerase chain reaction and Western blot showed a marked reduction of protein expression. Haplotype analysis identified a ~0.85cM shared genomic region on chromosome 16q encompassing the c.191A > G variant, consistent with a distant ancestor common to both families. Our results suggest that biallelic loss-of-function variants in SLC7A6OS are a novel genetic cause of progressive myoclonus epilepsy. ANN NEUROL 2021;89:402-407.

The largest caucasian kindred with dentatorubral-pallidoluysian atrophy: A founder mutation in italy.

BACKGROUND: Dentatorubral-pallidoluysian atrophy is a hereditary neurodegenerative disease prevalently reported in Japan but rare in Caucasians. The objective of this study was to reconstruct the pedigree of Italian dentatorubral-pallidoluysian atrophy familial cases describing their clinical features. METHODS: We investigated 6 apparently unrelated dentatorubral-pallidoluysian atrophy families comprising a total of 51 affected individuals: 13 patients were clinically examined, and for 38 patients clinical data were collected from clinical sources. The dentatorubral-pallidoluysian atrophy diagnosis was genetically confirmed in 18 patients. Genealogical data from historical archives were analyzed. RESULTS: All 6 families were unified in a large pedigree deriving from a founder couple originating from Monte San Giuliano (Italy) in the late 1500s, with 51 affected subjects over the last 4 generations. Wide phenotypical variability in age at onset and clinical features was confirmed. Epilepsy was more frequent in juvenile cases than in late adults, with cognitive/psychiatric and motor disorders observed regardless of age at onset. CONCLUSIONS: We have described the largest Caucasian dentatorubral-pallidoluysian atrophy pedigree from a single founder couple. The introduction of the dentatorubral-pallidoluysian atrophy gene in Italy could have arisen as a result of trade relationships between the Spanish or Portuguese and the Japanese in the 1500s. © 2019 International Parkinson and Movement Disorder Society.

Teenage-onset progressive myoclonic epilepsy due to a familial C9orf72 repeat expansion.

BACKGROUND: The progressive myoclonic epilepsies (PME) are a heterogeneous group of disorders in which a specific diagnosis cannot be made in a subset of patients, despite exhaustive investigation. C9orf72 repeat expansions are emerging as an important causal factor in several adult-onset neurodegenerative disorders, in particular frontotemporal lobar degeneration and amyotrophic lateral sclerosis. An association with PME has not been reported previously. OBJECTIVE: To identify the causative mutation in a Belgian family where the proband had genetically unexplained PME. RESULTS: We report a 33-year old woman who had epilepsy since the age of 15 and then developed progressive cognitive deterioration and multifocal myoclonus at the age of 18. The family history suggested autosomal dominant inheritance of psychiatric disorders, epilepsy, and dementia. Thorough workup for PME including whole exome sequencing did not reveal an underlying cause, but a C9orf72 repeat expansion was found in our patient and affected relatives. Brain biopsy confirmed the presence of characteristic p62-positive neuronal cytoplasmic inclusions. CONCLUSION: C9orf72 mutation analysis should be considered in patients with PME and psychiatric disorders or dementia, even when the onset is in late childhood or adolescence.

The first identified Central-Eastern European patient with genetically confirmed dentatorubral-pallidoluysian atrophy.

AIMS: Dentatorubral-pallidoluysian atrophy (DRPLA) is an inherited neurodegenerative disorder characterized by a trinucleotide repeat expansion. The disease mainly occurs amongst the Japanese and is extremely rare in the European population. The characteristic clinical symptoms are cerebellar ataxia, dementia, choreoathetoid movements, epileptic seizures and myoclonus. The aim of this study is to present the first genetically confirmed Hungarian case of DRPLA. CASE REPORT: The middle-aged female patient developed the characteristic clinical symptoms except myoclonus over her late thirties with positive family history. The major finding in the skull magnetic resonance imaging was the atrophy of infratentorial brain structures with the consequential dilation of related cerebrospinal fluid spaces. A detailed neuropsychological examination was also performed and it revealed moderate cognitive dysfunctions, mild depression and anxiety. As underlying conditions, Huntington's disease and common spinocerebellar ataxia forms all came into consideration, but all the result of the respective genetic tests were negative. However, the test for mutation in the ATN1 gene revealed pathological heterozygous CAG repeat expansion. CONCLUSION: This case study serves as the first description of genetically confirmed DRPLA in the Central-Eastern region of Europe, the clinical features of which seems to be very similar to the previously reported cases.

Effects of SCA1, MJD, and DPRLA triplet repeat polymorphisms on cognitive phenotypes in a normal population of adolescent twins.

The expansion of unstable trinucleotide CAG repeat polymorphisms of a number of genes causes several neurodegenerative disorders with decreased cognitive function, the severity of the disorder being related to allele length at the triplet repeat locus. While the effects of repeat length have been well studied in clinical samples, there has been little investigation of the effects of triplet repeat variation in the normal range for these genes. We have, therefore, examined linkage and association for three CAG triplet repeat markers (Spinocerebellar Ataxia Type 1, SCA1; Machado-Joseph Disease, MJD; Dentatorubro-pallidoluysian Atrophy, DRPLA) to assess their contribution to variation in cognitive ability (IQ, reading ability, processing speed) in a normal, unselected sample of adolescent twins (248 dizygotic (DZ) sibling pairs, aged 16 years). Association tests, performed in Mx and QTDT, showed a consistent positive association of SCA1 with Arithmetic (P = 0.04). While association was supported between SCA1 and Cambridge reading scores and between DRPLA and inspection time, results were inconsistent across software packages. Given the number of statistical tests performed, it is unlikely that trinucleotide repeat variation in the normal range for these genes influences variation in normal cognition.

The development of behavioral abnormalities in the motor neuron degeneration (mnd) mouse.

The motor neuron degeneration (mnd) mouse, which has widespread abnormal accumulating lipoprotein and neuronal degeneration, has a mutation in CLN8, the gene for human progressive epilepsy with mental retardation (EPMR). EPMR is one of the neuronal ceroid lipofuscinoses (NCLs), a group of neurological disorders characterized by autofluorescent lipopigment accumulation, blindness, seizures, motor deterioration, and dementia. The human phenotype of EPMR suggests that, in addition to the motor symptoms previously categorized, various types of progressive behavioral abnormalities would be expected in mnd mice. We have therefore examined exploratory behavior, fear conditioning, and aggression in 2-3 month and 4-5 month old male mnd mice and age-matched C57BL/6 (B6) controls. The mnd mice displayed increased activity with decreased habituation in the activity monitor, poor contextual and cued memory, and heightened aggression relative to B6 controls. These behavioral deficits were most prominent at 4-5 months of age, which is prior to the onset of gross motor symptoms at 6 months. Our results provide a link from the mutation via pathology to a quantifiable multidimensional behavioral phenotype of this naturally occurring mouse model of NCL.

Dentatorubral-pallidoluysian atrophy (DRPLA).

Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder caused by expansion of CAG repeats coding for a polyglutamine stretch. The prominent anticipation and broad spectrum in the clinical presentations of DRPLA have been demonstrated to be tightly correlated with the instability of CAG repeats in the DRPLA gene. Discovery of the causative gene for DRPLA has made it possible to investigate molecular mechanisms of neurodegeneration caused by expanded polyglutamine stretches. Recent investigations suggest that nuclear transport of mutant proteins containing expanded polyglutamine stretches and intranuclear aggregate formation play important roles in neuronal degeneration. We have recently demonstrated that the aggregate formation and apoptosis are partially suppressed by transglutaminase inhibitors, raising the possibility that transglutaminase is involved in the aggregate body. The results may open new prospects for developing therapeutic measures for the polyglutamine diseases.

Progressive myoclonic epilepsies syndrome (Ramsay Hunt syndrome) with mental disorder: report of two cases.

Ramsay Hunt syndrome (RHS) is a rare condition within the progressive myoclonic epilepsies syndrome (PME), with a triad of action myoclonus, grand mal seizure and severe cerebellar ataxia. There are few reports about the psychiatric disturbances associated with PME or RHS. The present study examines the evidence that RHS may accompany an organic mental syndrome, ethanol's effective suppression of myoclonus, and the possible resultant problem of alcohol dependence in RHS patients. Two brothers with the previous long-standing diagnosis of RHS and their mental symptoms of persecutory delusion and depression are reported, as well as the additional problem of alcohol dependence in one of them. The cerebellar dysfunction found in RHS may be associated with an underlying organic condition. Determination of the relationship between cerebellar dysfunction and psychosis in RHS will require further study. Although the mechanism of the suppression of myoclonus by alcohol remains unclear, patients should be allowed to drink socially, and alcohol consumption should not be totally prohibited. However, effective treatment of the problems of alcohol tolerance, abuse, or dependence requires the cooperation of both neurologists and psychiatrists.