Purpose: Neurodevelopmental disorders (NDD) caused by protein phosphatase 2A (PP2A) dysfunction have mainly been associated with de novo variants in PPP2R5D and PPP2CA, and more rarely in PPP2R1A. Here, we aimed to better understand the latter by characterizing 30 individuals with de novo and often recurrent variants in this PP2A scaffolding Aα subunit. Methods: Most cases were identified through routine clinical diagnostics. Variants were biochemically characterized for phosphatase activity and interaction with other PP2A subunits. Results: We describe 30 individuals with 16 different variants in PPP2R1A, 21 of whom had variants not previously reported. The severity of developmental delay ranged from mild learning problems to severe intellectual disability (ID) with or without epilepsy. Common features were language delay, hypotonia, and hypermobile joints. Macrocephaly was only seen in individuals without B55α subunit-binding deficit, and these patients had less severe ID and no seizures. Biochemically more disruptive variants with impaired B55α but increased striatin binding were associated with profound ID, epilepsy, corpus callosum hypoplasia, and sometimes microcephaly. Conclusion: We significantly expand the phenotypic spectrum of PPP2R1A-related NDD, revealing a broader clinical presentation of the patients and that the functional consequences of the variants are more diverse than previously reported.

Polyamines are endogenous molecules involved in cell damage following neurological insults, although it is unclear whether polyamines reduce or exacerbate this damage. We used a developmental seizure model in which we exposed Xenopus laevis tadpoles to pentylenetetrazole (PTZ), a known convulsant. We found that, after an initial PTZ exposure, seizure onset times were delayed in response to a second PTZ exposure 4 h later. This protective effect was a result of activity-dependent increases in synthesis of putrescine, the simplest polyamine. Unlike more complex polyamines that directly modulate ion channels, putrescine exerted its effect by altering the balance of excitation to inhibition. Tectal neuron recordings, 4 h after the initial seizure, revealed an elevated frequency of GABAergic spontaneous inhibitory postsynaptic currents. Our data suggest that this effect is mediated by an atypical pathway that converts putrescine into GABA, which then activates presynaptic GABA(B) receptors. Our data suggest that polyamines have a previously unknown neuroprotective role in the developing brain.

Objective Neck-Tongue syndrome (NTS) is characterized by brief attacks of neck or occipital pain, or both, brought out by abrupt head turning and accompanied by ipsilateral tongue symptoms. As the disorder is rare, we undertook a systematic review of the literature to identify all reported cases in order to phenotype clinically the disorder and subsequently inform clinical diagnostic criteria. Methods Two electronic databases were searched using the search term "neck tongue syndrome". All English language references were reviewed in full. Cases were abstracted using a standardized abstraction form and the references of the retrieved articles were reviewed by hand to identify additional references and cases. Conference proceedings from recent headache meetings were searched. We also report six new cases from our centers. Results There were 39 primary cases, 56% of which were female. Mean age (SD) at onset was 16 (12) years. Twenty (53%) experienced neck pain, seven (18%) occipital pain, and 11 (29%) both. Pain was most often sharp or stabbing and severe, lasting several seconds to several minutes. Eleven experienced numbness and/or tingling in the neck/occiput following the pain. Thirty-six had an accompanying tongue sensory disturbance and three a motor/posture disturbance; five had both. Thirteen had other headaches, and four a family history of Neck-Tongue syndrome. Conclusions Neck-Tongue syndrome typically has pediatric or adolescent onset, suggesting that ligamentous laxity during growth and development may facilitate transient subluxation of the lateral atlantoaxial joint with sudden head turning. Familial cases suggest a genetic predisposition in some individuals. Neck-Tongue syndrome should be re-instated in the International Classification of Headache Disorders.

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