We report an early-onset autosomal-recessive neurological disease with cerebellar atrophy and lysosomal dysfunction. We identified bi-allelic loss-of-function (LoF) variants in Oxidative Resistance 1 ...(OXR1) in five individuals from three families; these individuals presented with a history of severe global developmental delay, current intellectual disability, language delay, cerebellar atrophy, and seizures. While OXR1 is known to play a role in oxidative stress resistance, its molecular functions are not well established. OXR1 contains three conserved domains: LysM, GRAM, and TLDc. The gene encodes at least six transcripts, including some that only consist of the C-terminal TLDc domain. We utilized Drosophila to assess the phenotypes associated with loss of mustard (mtd), the fly homolog of OXR1. Strong LoF mutants exhibit late pupal lethality or pupal eclosion defects. Interestingly, although mtd encodes 26 transcripts, severe LoF and null mutations can be rescued by a single short human OXR1 cDNA that only contains the TLDc domain. Similar rescue is observed with the TLDc domain of NCOA7, another human homolog of mtd. Loss of mtd in neurons leads to massive cell loss, early death, and an accumulation of aberrant lysosomal structures, similar to what we observe in fibroblasts of affected individuals. Our data indicate that mtd and OXR1 are required for proper lysosomal function; this is consistent with observations that NCOA7 is required for lysosomal acidification.
Biallelic variants in PUS3 have recently been recognized as a rare cause of neurodevelopmental disorders. Pseudouridine synthase‐3 encoded by PUS3 is an enzyme important for modification of various ...RNAs, including transfer RNA (tRNA). Here we present the clinical and genetic features of 21 individuals with biallelic PUS3 variants: seven new and 14 previously reported individuals, where clinical features of two were updated. The clinical and genetic information were collected through collaborations or by literature search. All individuals were characterized by the local clinicians and the gene variants were identified by next generation sequencing (NGS) based methodologies. The clinical picture was dominated by global developmental delay, epilepsy, hypotonia and microcephaly. Gray sclera, which has previously been suggested to be a characteristic feature of PUS3‐associated phenotypes, was reported in only seven individuals. The patients had some dysmorphic facial features, but a recognizable gestalt was not observed. In conclusion, homozygous and compound heterozygous PUS3 variants lead to a rare neurodevelopmental disorder. Further functional studies are necessary to understand involvement of PUS3 and tRNA biogenesis in normal and abnormal brain development.
OBJECTIVETo assess nonparoxysmal movement disorders in ATP1A3 mutation-positive patients with alternating hemiplegia of childhood (AHC).
METHODSTwenty-eight patients underwent neurologic examination ...with particular focus on movement phenomenology by a specialist in movement disorders. Video recordings were reviewed by another movement disorders specialist and data were correlated with patientsʼ characteristics.
RESULTSTen patients were diagnosed with chorea, 16 with dystonia (nonparoxysmal), 4 with myoclonus, and 2 with ataxia. Nine patients had more than one movement disorder and 8 patients had none. The degree of movement disorder was moderate to severe in 12/28 patients. At inclusion, dystonic patients (n = 16) were older (p = 0.007) than nondystonic patients. Moreover, patients (n = 18) with dystonia or chorea, or both, had earlier disease onset (p = 0.042) and more severe neurologic impairment (p = 0.012), but this did not correlate with genotype. All patients presented with hypotonia, which was characterized as moderate or severe in 16/28. Patients with dystonia or chorea (n = 18) had more pronounced hypotonia (p = 0.011). Bradykinesia (n = 16) was associated with an early age at assessment (p < 0.01). Significant dysarthria was diagnosed in 11/25 cases. A history of acute neurologic deterioration and further regression of motor function, typically after a stressful event, was reported in 7 patients.
CONCLUSIONSDespite the relatively limited number of patients and the cross-sectional nature of the study, this detailed categorization of movement disorders in patients with AHC offers valuable insight into their precise characterization. Further longitudinal studies on this topic are needed.
Cognitive impairment in children with CACNA1A mutations Humbertclaude, Veronique; Riant, Florence; Krams, Benjamin ...
Developmental medicine and child neurology,
March 2020, 2020-03-00, 20200301, Letnik:
62, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Aim
To describe the clinico‐radiological phenotype of children with a CACNA1A mutation and to precisely evaluate their learning ability and cognitive status.
Method
Children between the ages of 3 and ...18 years harboring a pathogenic CACNA1A mutation associated with episodic ataxia, hemiplegic migraine, benign paroxysmal torticollis, benign paroxysmal vertigo, or benign paroxysmal tonic upgaze, were enrolled in this cross‐sectional study. Data concerning psychomotor development, academic performance, educational management, clinical examination at inclusion, and brain imaging were collected. Cognitive assessment was performed using age‐standardized scales.
Results
Eighteen patients (nine males, nine females; mean age at inclusion: 11y 7mo SD 4y 5mo; range 3y–17y 11mo) from 14 families were enrolled. Eleven patients displayed the coexistence or consecutive occurrence of more than one type of episodic event. Nine patients exhibited abnormal neurological examination at inclusion. Brain magnetic resonance imaging (MRI) showed cerebellar atrophy in five patients. Psychomotor development was delayed in nine patients and academic difficulties were reported by the parents in 15 patients; nine patients were in special education. Impairment of intellectual function was assessed in six of the 12 patients with interpretable Full‐scale IQ scores and was more frequent when cerebellar atrophy was present on MRI.
Interpretation
Cognitive impairment is commonly associated with CACNA1A mutations. We suggest that CACNA1A‐associated phenotype should be considered a neurodevelopmental disorder.
What this paper adds
Cognitive disabilities and academic difficulties are common in children with CACNA1A mutations associated with episodic syndromes.
Cognitive function ranges from normal to moderate intellectual disorder in wheelchair‐dependent children.
Patients with vermian atrophy are at a higher risk of cognitive impairment.
What this paper adds
Cognitive disabilities and academic difficulties are common in children with CACNA1A mutations associated with episodic syndromes.
Cognitive function ranges from normal to moderate intellectual disorder in wheelchair‐dependent children.
Patients with vermian atrophy are at a higher risk of cognitive impairment.
Mutations in the gene ATP1A3 have recently been identified to be prevalent in patients with alternating hemiplegia of childhood (AHC2). Based on a large series of patients with AHC, we set out to ...identify the spectrum of different mutations within the ATP1A3 gene and further establish any correlation with phenotype.
Clinical data from an international cohort of 155 AHC patients (84 females, 71 males; between 3 months and 52 years) were gathered using a specifically formulated questionnaire and analysed relative to the mutational ATP1A3 gene data for each patient.
In total, 34 different ATP1A3 mutations were detected in 85 % (132/155) patients, seven of which were novel. In general, mutations were found to cluster into five different regions. The most frequent mutations included: p.Asp801Asn (43 %; 57/132), p.Glu815Lys (16 %; 22/132), and p.Gly947Arg (11 %; 15/132). Of these, p.Glu815Lys was associated with a severe phenotype, with more severe intellectual and motor disability. p.Asp801Asn appeared to confer a milder phenotypic expression, and p.Gly947Arg appeared to correlate with the most favourable prognosis, compared to the other two frequent mutations. Overall, the comparison of the clinical profiles suggested a gradient of severity between the three major mutations with differences in intellectual (p = 0.029) and motor (p = 0.039) disabilities being statistically significant. For patients with epilepsy, age at onset of seizures was earlier for patients with either p.Glu815Lys or p.Gly947Arg mutation, compared to those with p.Asp801Asn mutation (p < 0.001). With regards to the five mutation clusters, some clusters appeared to correlate with certain clinical phenotypes. No statistically significant clinical correlations were found between patients with and without ATP1A3 mutations.
Our results, demonstrate a highly variable clinical phenotype in patients with AHC2 that correlates with certain mutations and possibly clusters within the ATP1A3 gene. Our description of the clinical profile of patients with the most frequent mutations and the clinical picture of those with less common mutations confirms the results from previous studies, and further expands the spectrum of genotype-phenotype correlations. Our results may be useful to confirm diagnosis and may influence decisions to ensure appropriate early medical intervention in patients with AHC. They provide a stronger basis for the constitution of more homogeneous groups to be included in clinical trials.
Hypomyelinating leukodystrophies are genetically heterogeneous disorders with overlapping clinical and neuroimaging features reflecting variable abnormalities in myelin formation. We report on the ...identification of biallelic inactivating mutations in NKX6-2, a gene encoding a transcription factor regulating multiple developmental processes with a main role in oligodendrocyte differentiation and regulation of myelin-specific gene expression, as the cause underlying a previously unrecognized severe variant of hypomyelinating leukodystrophy. Five affected subjects (three unrelated families) were documented to share biallelic inactivating mutations affecting the NKX6-2 homeobox domain. A trio-based whole exome sequencing analysis in the first family detected a homozygous frameshift change c.606delinsTA; p.(Lys202Asnfs*?). In the second family, homozygosity mapping coupled to whole exome sequencing identified a homozygous nucleotide substitution (c.565G>T) introducing a premature stop codon (p.Glu189*). In the third family, whole exome sequencing established compound heterozygosity for a non-conservative missense change affecting a key residue participating in DNA binding (c.599G>A; p.Arg200Gln) and a nonsense substitution (c.589C>T; p.Gln197*), in both affected siblings. The clinical presentation was homogeneous, with four subjects having severe motor delays, nystagmus and absent head control, and one individual showing gross motor delay at the age of 6 months. All exhibited neuroimaging that was consistent with hypomyelination. These findings define a novel, severe form of leukodystrophy caused by impaired NKX6-2 function.
ABSTRACT
Mutations in the KCNQ2 and KCNQ3 genes encoding for Kv7.2 (KCNQ2; Q2) and Kv7.3 (KCNQ3; Q3) voltage‐dependent K+ channel subunits, respectively, cause neonatal epilepsies with wide ...phenotypic heterogeneity. In addition to benign familial neonatal epilepsy (BFNE), KCNQ2 mutations have been recently found in families with one or more family members with a severe outcome, including drug‐resistant seizures with psychomotor retardation, electroencephalogram (EEG) suppression‐burst pattern (Ohtahara syndrome), and distinct neuroradiological features, a condition that was named “KCNQ2 encephalopathy.” In the present article, we describe clinical, genetic, and functional data from 17 patients/families whose electroclinical presentation was consistent with the diagnosis of BFNE. Sixteen different heterozygous mutations were found in KCNQ2, including 10 substitutions, three insertions/deletions and three large deletions. One substitution was found in KCNQ3. Most of these mutations were novel, except for four KCNQ2 substitutions that were shown to be recurrent. Electrophysiological studies in mammalian cells revealed that homomeric or heteromeric KCNQ2 and/or KCNQ3 channels carrying mutant subunits with newly found substitutions displayed reduced current densities. In addition, we describe, for the first time, that some mutations impair channel regulation by syntaxin‐1A, highlighting a novel pathogenetic mechanism for KCNQ2‐related epilepsies.
Mutations in KCNQ2 and KCNQ3, encoding for Kv7.2 and KV7.3 voltage‐dependent K+ channel subunits, respectively, cause neonatal epilepsies with wide phenotypic heterogeneity.
We describe data from 17 patients/families with the diagnosis of benign familial neonatal epilepsy and with a mutation in KCNQ2 (n = 16) or KCNQ3 (n = 1). Electrophysiological studies in mammalian cells revealed that newly found substitutions displayed reduced current densities. In addition, some mutations impair channel regulation by syntaxin‐1‐A, highlighting a novel pathogenic mechanism for KCNQ2‐related epilepsies.
To explore the phenotypic spectrum of
-related disorders and specifically to determine whether patients fulfill criteria for alternating hemiplegia of childhood (AHC), we report the clinical features ...of 11 affected individuals.
Individuals with
-related disorders were identified through a movement disorder clinic at a specialist pediatric center, with additional cases identified through collaboration with other centers internationally. Clinical data were acquired through retrospective case-note review.
Eleven affected patients were identified. All had heterozygous missense variants involving exon 9 of
, confirmed as de novo in 9 cases. All had a complex motor phenotype, including at least 2 different kinds of movement disorder, e.g., ataxia and dystonia. Many patients demonstrated several features fulfilling the criteria for AHC: 10 patients had a movement disorder including paroxysmal elements, and 8 experienced hemiplegic episodes. In contrast to classic AHC, commonly caused by mutations in
, these events were reported later only in
mutation-positive patients from 20 months of age. Seven patients had epilepsy, but of these, 4 patients achieved seizure freedom. All patients had intellectual disability, usually moderate to severe. Other features include episodes of marked skin color change and gastrointestinal symptoms, each in 4 patients.
Although heterozygous
mutations were originally described in early infantile epileptic encephalopathy type 64, our study confirms that they account for a more expansive clinical phenotype, including a complex polymorphic movement disorder with paroxysmal elements resembling AHC.
testing should therefore be considered in patients with an AHC-like phenotype, particularly those negative for
mutations.
Developmental and epileptic encephalopathies (DEE) refer to a heterogeneous group of devastating neurodevelopmental disorders. Variants in KCNB1 have been recently reported in patients with ...early‐onset DEE. KCNB1 encodes the α subunit of the delayed rectifier voltage‐dependent potassium channel Kv2.1. We review the 37 previously reported patients carrying 29 distinct KCNB1 variants and significantly expand the mutational spectrum describing 18 novel variants from 27 unreported patients. Most variants occur de novo and mainly consist of missense variants located on the voltage sensor and the pore domain of Kv2.1. We also report the first inherited variant (p.Arg583*). KCNB1‐related encephalopathies encompass a wide spectrum of neurodevelopmental disorders with predominant language difficulties and behavioral impairment. Eighty‐five percent of patients developed epilepsies with variable syndromes and prognosis. Truncating variants in the C‐terminal domain are associated with a less‐severe epileptic phenotype. Overall, this report provides an up‐to‐date review of the mutational and clinical spectrum of KCNB1, strengthening its place as a causal gene in DEEs and emphasizing the need for further functional studies to unravel the underlying mechanisms.
KCNB1 encodes the α subunit of the delayed rectifier voltage‐dependent potassium channel Kv2.1. In this mutation update, we provide an up‐to‐date review of the mutational and clinical spectrum of the KCNB1 encephalopathy and report 18 novel variants.
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