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Relapsing encephalopathy with cerebellar ataxia, neopterin, ATP1A3, RECA, rapid-onset dystonia parkinsonism, alternating hemiplegia of childhood, CAPOS, anti-GAD Keywords: ATP1A3; relapsing encephalopathy with cerebellar ataxia; RECA; rapid-onset dystonia parkinsonism; alternating hemiplegia of childhood; CAPOS; neopterin; anti-GAD EN ATP1A3 relapsing encephalopathy with cerebellar ataxia RECA rapid-onset dystonia parkinsonism alternating hemiplegia of childhood CAPOS neopterin anti-GAD 1120 1123 4 11/07/22 20221101 NES 221101 We report a 23-year-old man with relapsing encephalopathy with cerebellar ataxia (RECA) secondary to a mutation in I ATP1A3 i , characterized by fever related exacerbations associated with elevated CSF neopterin, and possible response to immunotherapy. Dystonia and tremor of the hands, bilateral upper limb dysmetria and intention tremor, and action myoclonus of the upper limbs. [Extracted from the article]

The Na+/K+ ATPases are Sodium-Potassium exchanging pumps, with a heteromeric α-β-γ protein complex. The α3 isoform is required as a rescue pump, after repeated action potentials, with a distribution predominantly in neurons of the central nervous system. This isoform is encoded by the ATP1A3 gene. Pathogenic variants in this gene have been implicated in several phenotypes in the last decades. Carriers of pathogenic variants in this gene manifest neurological and non-neurological features in many combinations, usually with an acute onset and paroxysmal episodes triggered by fever or other factors. The first three syndromes described were: (1) rapid-onset dystonia parkinsonism; (2) alternating hemiplegia of childhood; and, (3) cerebellar ataxia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS syndrome). Since their original description, an expanding number of cases presenting with atypical and overlapping features have been reported. Because of this, ATP1A3-disorders are now beginning to be viewed as a phenotypic continuum representing discrete expressions along a broadly heterogeneous clinical spectrum.

The Na+/K+ ATPases are Sodium-Potassium exchanging pumps, with a heteromeric α-β-γ protein complex. The α3 isoform is required as a rescue pump, after repeated action potentials, with a distribution predominantly in neurons of the central nervous system. This isoform is encoded by the ATP1A3 gene. Pathogenic variants in this gene have been implicated in several phenotypes in the last decades. Carriers of pathogenic variants in this gene manifest neurological and non-neurological features in many combinations, usually with an acute onset and paroxysmal episodes triggered by fever or other factors. The first three syndromes described were: (1) rapid-onset dystonia parkinsonism; (2) alternating hemiplegia of childhood; and, (3) cerebellar ataxia, pes cavus, optic atrophy, and sensorineural hearing loss (CAPOS syndrome). Since their original description, an expanding number of cases presenting with atypical and overlapping features have been reported. Because of this, ATP1A3-disorders are now beginning to be viewed as a phenotypic continuum representing discrete expressions along a broadly heterogeneous clinical spectrum. [ABSTRACT FROM AUTHOR]

Introduction: Rapid-onset dystonia parkinsonism (RDP), also referred to as Dystonia 12, is a rare autosomal dominant genetic disease characterized by abrupt onset of a rostrocaudal gradient of dystonia with prominent bulbar symptoms, and parkinsonian features, primarily bradykinesia and postural instability without tremor. The purpose of this study was to identify the genetic defect in a Chinese pedigree with familial RDP and to explore genotype-phenotype correlation. Methods: A 3-generation Chinese Han pedigree consisting of 9 members and 3 patients with RDP, and 200 unrelated ethnically matched normal subjects were recruited in this study. Exome sequencing was performed in the proband, and Sanger sequencing was then conducted in other family members and 200 normal controls. Results: In addition to the typical clinical manifestations of RDP, the proband and her sister presented tongue tremor which developed at the onset, and intriguingly the proband showed a "re-emergent" tongue tremor. Both the proband and her sister had a medical history of hyperthyroidism, and at the psychiatric interview they both received diagnoses of depression and anxiety. Excessive grammar errors existed in most sentences written by the proband, and this written-expression disorder occurred years before the onset of RDP. The mother of the proband presented tongue enlargement, oromandibular dystonia, and limb dystonia, which were not observed in her 2 daughters at the time of study. A missense variant, c.1838C>T (p.T613M), in the ATP1A3 gene, was identified in the 3 patients in the family and in 2 young children but was absent in family members without RDP and in the 200 normal controls. Conclusion: These findings may broaden the phenotypic spectrums of RDP with mutations in the ATP1A3 gene, provide new insights into the diagnosis of RDP, and have implications for genetic counseling. [ABSTRACT FROM AUTHOR]

Keywords: ATP1A3; rapid-onset dystonia parkinsonism; alternating hemiplegia of childhood; CAPOS syndrome EN ATP1A3 rapid-onset dystonia parkinsonism alternating hemiplegia of childhood CAPOS syndrome 1263 1265 3 11/05/21 20211101 NES 211101 The I ATP1A3 i -related disorder is a recently described term for the different phenotypes resulting from I ATP1A3 i gene mutation. Parkinsonism Relat Disord 2020; 76: 46 - 48. 7 de Gusmao CM, Dy M, Sharma N. Beyond dystonia-parkinsonism: chorea and ataxia with ATP1A3 mutations. ATP1A3, rapid-onset dystonia parkinsonism, alternating hemiplegia of childhood, CAPOS syndrome. [Extracted from the article]

We describe the molecular basis of a distinctive syndrome characterized by infantile stress-induced episodic weakness, ataxia, and sensorineural hearing loss, with permanent areflexia and optic nerve pallor. Whole exome sequencing identified a deleterious heterozygous c.2452 G>A, p.(E818K) variant in the ATP1A3 gene and structural analysis predicted its protein-destabilizing effect. This variant has not been reported in context with rapid-onset dystonia parkinsonism and alternating hemiplegia of childhood, the 2 main diseases associated with ATP1A3. The clinical presentation in the family described here differs categorically from these diseases in age of onset, clinical course, cerebellar over extrapyramidal movement disorder predominance, and peripheral nervous system involvement. While this paper was in review, a highly resembling phenotype was reported in additional patients carrying the same c.2452 G>A variant. Our findings substantiate this variant as the cause of a unique inherited autosomal dominant neurologic syndrome that constitutes a third allelic disease of the ATP1A3 gene. [ABSTRACT FROM AUTHOR]

Background Alternating hemiplegia of childhood and rapid-onset dystonia parkinsonism are two separate movement disorders with different dominant mutations in the same sodium-potassium transporter ATPase subunit gene, ATP1A3. Patient We present a child with topiramate-responsive alternating hemiplegia of childhood who was tested for an ATP1A3 gene mutation. Results Gene sequencing revealed an identical ATP1A3 mutation as in three typical adult-onset rapid-onset dystonia parkinsonism cases but never previously described in an alternating hemiplegia of childhood case. Conclusion The discordance of these phenotypes suggests that there are other undiscovered environmental, genetic, or epigenetic factors influencing the development of alternating hemiplegia of childhood or rapid-onset dystonia parkinsonism. [ABSTRACT FROM AUTHOR]

The article presents a case study of a young male who was admitted due to genetically proven heterozygote mutation of the ATP1A3 gene. Neuropsychological testing and psychiatric evaluation were done and results were all normal. The pallidal deep brain stimulation (DBS) has been proven to be an effective therapy for primary dystonia and idiopathic Parkinson's disease.

Mutations in ATP1A3 have been found to cause rapid-onset dystonia Parkinsonism, alternating hemiplegia of childhood, epileptic encephalopathy and other syndromes. We report a four-year, nine-month-old boy with episodes of frequent and recurrent status epilepticus, who first began having generalized tonic-clonic seizures at four months of age. Development was normal until the age of four months, and markedly slowed down after the onset of seizures. Between the age of seven months and two and a half years, the patient had recurrent attacks of unilateral and bilateral hemiplegia. At the age of 21 months, after a febrile illness with status epilepticus, he regressed and developed continuous severe dystonia and bradykinesia with superimposed intermittent painful dystonic spasms. Extensive neurological and genetic workup revealed a de novo p.V589F ATP1A3 mutation (NM_152296.5:c.1765G>T, NC_000019.9:g.42482344C>A). This is a novel mutation associated with a novel phenotype that shares features with epileptic encephalopathy, alternating hemiplegia of childhood, and rapid-onset dystonia Parkinsonism.

The Na(+),K(+)-ATPase binds Na(+) at three transport sites denoted I, II, and III, of which site III is Na(+)-specific and suggested to be the first occupied in the cooperative binding process activating phosphorylation from ATP. Here we demonstrate that the asparagine substitution of the aspartate associated with site III found in patients with rapid-onset dystonia parkinsonism or alternating hemiplegia of childhood causes a dramatic reduction of Na(+) affinity in the α1-, α2-, and α3-isoforms of Na(+),K(+)-ATPase, whereas other substitutions of this aspartate are much less disruptive. This is likely due to interference by the amide function of the asparagine side chain with Na(+)-coordinating residues in site III. Remarkably, the Na(+) affinity of site III aspartate to asparagine and alanine mutants is rescued by second-site mutation of a glutamate in the extracellular part of the fourth transmembrane helix, distant to site III. This gain-of-function mutation works without recovery of the lost cooperativity and selectivity of Na(+) binding and does not affect the E1-E2 conformational equilibrium or the maximum phosphorylation rate. Hence, the rescue of Na(+) affinity is likely intrinsic to the Na(+) binding pocket, and the underlying mechanism could be a tightening of Na(+) binding at Na(+) site II, possibly via movement of transmembrane helix four. The second-site mutation also improves Na(+),K(+) pump function in intact cells. Rescue of Na(+) affinity and Na(+) and K(+) transport by second-site mutation is unique in the history of Na(+),K(+)-ATPase and points to new possibilities for treatment of neurological patients carrying Na(+),K(+)-ATPase mutations., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

The neurological disorders familial hemiplegic migraine type 2 (FHM2), alternating hemiplegia of childhood (AHC), and rapid-onset dystonia parkinsonism (RDP) are caused by mutations of Na(+),K(+)-ATPase α2 and α3 isoforms, expressed in glial and neuronal cells, respectively. Although these disorders are distinct, they overlap in phenotypical presentation. Two Na(+),K(+)-ATPase mutations, extending the C terminus by either 28 residues ("+28" mutation) or an extra tyrosine ("+Y"), are associated with FHM2 and RDP, respectively. We describe here functional consequences of these and other neurological disease mutations as well as an extension of the C terminus only by a single alanine. The dependence of the mutational effects on the specific α isoform in which the mutation is introduced was furthermore studied. At the cellular level we have characterized the C-terminal extension mutants and other mutants, addressing the question to what extent they cause a change of the intracellular Na(+) and K(+) concentrations ([Na(+)]i and [K(+)]i) in COS cells. C-terminal extension mutants generally showed dramatically reduced Na(+) affinity without disturbance of K(+) binding, as did other RDP mutants. No phosphorylation from ATP was observed for the +28 mutation of α2 despite a high expression level. A significant rise of [Na(+)]i and reduction of [K(+)]i was detected in cells expressing mutants with reduced Na(+) affinity and did not require a concomitant reduction of the maximal catalytic turnover rate or expression level. Moreover, two mutations that increase Na(+) affinity were found to reduce [Na(+)]i. It is concluded that the Na(+) affinity of the Na(+),K(+)-ATPase is an important determinant of [Na(+)]i.