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SYT1-associated neurodevelopmental disorder: a case series.

ABSTRACT: Synaptotagmin 1 (SYT1) is a critical mediator of fast, synchronous, calcium-dependent neurotransmitter release and also modulates synaptic vesicle endocytosis. This paper describes 11 patients with de novo heterozygous missense mutations in SYT1. All mutations alter highly conserved residues, and cluster in two regions of the SYT1 C2B domain at positions Met303 (M303K), Asp304 (D304G), Asp366 (D366E), Ile368 (I368T) and Asn371 (N371K). Phenotypic features include infantile hypotonia, congenital ophthalmic abnormalities, childhood-onset hyperkinetic movement disorders, motor stereotypies, and developmental delay varying in severity from moderate to profound. Behavioural characteristics include sleep disturbance and episodic agitation. Absence of epileptic seizures and normal orbitofrontal head circumference are important negative features. Structural MRI is unremarkable but EEG disturbance is universal, characterized by intermittent low frequency high amplitude oscillations. The functional impact of these five de novo SYT1 mutations has been assessed by expressing rat SYT1 protein containing the equivalent human variants in wild-type mouse primary hippocampal cultures. All mutant forms of SYT1 were expressed at levels approximately equal to endogenous wild-type protein, and correctly localized to nerve terminals at rest, except for SYT1M303K, which was expressed at a lower level and failed to localize at nerve terminals. Following stimulation, SYT1I368T and SYT1N371K relocalized to nerve terminals at least as efficiently as wild-type SYT1. However, SYT1D304G and SYT1D366E failed to relocalize to nerve terminals following stimulation, indicative of impairments in endocytic retrieval and trafficking of SYT1. In addition, the presence of SYT1 variants at nerve terminals induced a slowing of exocytic rate following sustained action potential stimulation. The extent of disturbance to synaptic vesicle kinetics is mirrored by the severity of the affected individuals' phenotypes, suggesting that the efficiency of SYT1-mediated neurotransmitter release is critical to cognitive development. In summary, de novo dominant SYT1 missense mutations are associated with a recognizable neurodevelopmental syndrome, and further cases can now be diagnosed based on clinical features, electrophysiological signature and mutation characteristics. Variation in phenotype severity may reflect mutation-specific impact on the diverse physiological functions of SYT1.

SUBMITTER: Baker K

PROVIDER: S-EPMC6113648 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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SYT1-associated neurodevelopmental disorder: a case series.

Baker Kate K Gordon Sarah L SL Melland Holly H Bumbak Fabian F Scott Daniel J DJ Jiang Tess J TJ Owen David D Turner Bradley J BJ Boyd Stewart G SG Rossi Mari M Al-Raqad Mohammed M Elpeleg Orly O Peck Dawn D Mancini Grazia M S GMS Wilke Martina M Zollino Marcella M Marangi Giuseppe G Weigand Heike H Borggraefe Ingo I Haack Tobias T Stark Zornitza Z Sadedin Simon S Tan Tiong Yang TY Jiang Yunyun Y Gibbs Richard A RA Ellingwood Sara S Amaral Michelle M Kelley Whitley W Kurian Manju A MA Cousin Michael A MA Raymond F Lucy FL

Brain : a journal of neurology 20180901 9

Synaptotagmin 1 (SYT1) is a critical mediator of fast, synchronous, calcium-dependent neurotransmitter release and also modulates synaptic vesicle endocytosis. This paper describes 11 patients with de novo heterozygous missense mutations in SYT1. All mutations alter highly conserved residues, and cluster in two regions of the SYT1 C2B domain at positions Met303 (M303K), Asp304 (D304G), Asp366 (D366E), Ile368 (I368T) and Asn371 (N371K). Phenotypic features include infantile hypotonia, congenital ...[more]

PMID: 30107533

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Project description:Introduction: Autistic catatonia is an under-recognized debilitating syndrome with long-lasting negative effects for families, healthcare workers, and high-cost to the healthcare system. In this report, we describe two cases of excited catatonia in young men diagnosed with autism. Both endured a delay to diagnosis and difficulty to obtain appropriate treatment. Main concern: Each patient had a change in behavior from their baseline but with differences in severity and onset. The diagnosis in the first patient was made after only 3 months as the change was dramatic and sudden. Yet, despite a confirmed diagnosis, it was difficult to treat as the importance of M-ECT was not recognized by the clinicians. The second patient had been suffering for more than 5 years with a slow progression of worsening aggressive symptoms. The aggression was so uncontrollable that the patient required sedation, intubation and daily ECT. Both suffered from agitation, unprovoked aggression, urinary incontinence, stereotypic, and OCD behaviors and compulsive masturbation. Primary Diagnosis, intervention/outcomes: Both patients were diagnosed with autism, one high-functioning, attending high school and working a part-time job, the second low-functioning, nearly non-verbal, isolated to home and ABA school. The first patient's diagnosis of catatonia was only suspected after five psychiatric admissions and more than 20 medication trials. Lorazepam challenge was effective, he was treated with a short series of ECT but each time the treatments were tapered, the aggression returned. Ultimately, stabilized on weekly ECT. The second patient's behavior was escalating over a 5 month period, to the point, the aggression was uncontrollable. He presented to the ED under involuntary hold and the behavior could not be stabilized to the point that emergent ECT was initiated. Conclusion: Two cases of autistic catatonia diagnosed and treated within a year time span at a small community hospital indicates that this diagnosis is more common than previously recognized. We propose screening all patients with neurodevelopmental disorders with the Bush-Francis and Kanner scales to diagnose and treat them appropriately.

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SYT1-associated neurodevelopmental disorder: a case series.

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SYT1-associated neurodevelopmental disorder: a case series.

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