Potentiation of excitatory synaptic transmission ameliorates aggression in mice with Stxbp1 haploinsufficiency

Abstract

Genetic studies point to a major role of de novo mutations in neurodevelopmental disorders of intellectual disability, autism spectrum disorders, and epileptic encephalopathy. The STXBP1 gene encodes the syntaxin-binding protein 1 (Munc18-1) that critically controls synaptic vesicle exocytosis and synaptic transmission. This gene harbors a high frequency of de novo mutations, which may play roles in these neurodevelopmental disorders. However, the system and behavioral-level pathophysiological changes caused by these genetic defects remain poorly understood. Constitutional (Stxbp1+/-), dorsal-telencephalic excitatory (Stxbp1fl/+/Emx), or global inhibitory neuron-specific (Stxbp1fl/+/Vgat) mice were subjected to a behavioral test battery examining locomotor activity, anxiety, fear learning, and social interactions including aggression. Furthermore, measurements of local field potentials in multiple regions of the brain were performed. Stxbp1+/- male mice exhibited enhanced aggressiveness and impaired fear learning associated with elevated gamma activity in several regions of the brain including the prefrontal cortex. Stxbp1fl/+/Emx mice showed fear-learning deficits, but neither Stxbp1fl/+/Emx nor Stxbp1fl/+/Vgat mice showed increased aggressiveness. Pharmacological potentiation of the excitatory transmission at active synapses via the systemic administration of ampakine CX516, which enhances the excitatory postsynaptic function, ameliorated the aggressive phenotype of Stxbp1+/- mice. These findings suggest that synaptic impairments of the dorsal telencephalic and subcortical excitatory neurons cause learning deficits and enhanced aggression in Stxbp1+/- mice, respectively. Additionally, normalizing the excitatory synaptic transmission is a potential therapeutic option for managing aggressiveness in patients with STXBP1 mutations.

Nav1.2 haplodeficiency in excitatory neurons causes absence-like seizures in mice

“…An antibiotic (ampicillin) was used in surgery. LFPs (filtered 0.7–70 Hz, 1 kHz sampling) were recorded using the MAP data acquisition system (Plexon, Dallas, TX, USA) and analyzed off-line using a software, NeuroExplorer 4 (Nex Technologies, Madison, AL, USA) 63 .…”

Stxbp1/Munc18-1 haploinsufficiency in mice recapitulates key features of STXBP1 encephalopathy and impairs cortical inhibition

“…Thus, despite the large phenotypic spectrum of STXBP1 377 encephalopathy in humans, our Stxbp1 haploinsufficient mice recapitulate all key features of this 378 neurodevelopmental disorder and are construct and face valid models of STXBP1 379 encephalopathy. About 20% of the STXBP1 encephalopathy patients showed autistic traits 380 (Stamberger et al, 2016), but we and others (Kovačević et al, 2018;Miyamoto et al, 2017) did 381 not observe an impairment of social interaction in mutant mice using the three-chamber and 382 partition tests. Perhaps the elevated aggression in Stxbp1 haploinsufficient mice confounds these 383 tests, or new mouse models that more precisely mimic the genetic alterations in that subset of 384 STXBP1 encephalopathy patients are required to recapitulate this phenotype.…”

“…However, a subtle but perhaps key difference is the Stxbp1 protein levels in different lines of 398 heterozygous mutant mice. Stxbp1 is reduced by 50% in both of our Stxbp1 tm1d/+ and Stxbp1 tm1a/+ 399 mice, but only by 25-40% in other heterozygous knockout mice (Miyamoto et al, 2017;Orock 400 et al, 2018), which may lead to fewer or less severe phenotypes in the previous models. 401 402 Dysfunction of cortical GABAergic inhibition has been widely considered as a primary defect in 403 animal models of autism spectrum disorder, schizophrenia, Down syndrome, and epilepsy among 404 other neurological disorders (Contestabile et al, 2017;Lee et al, 2017;Marín, 2012;Nelson and 405 Valakh, 2015;Paz and Huguenard, 2015;Ramamoorthi and Lin, 2011).…”

“…They also had 182 normal nociception as measured by the hot plate test (Figure 1-supplemtent 4C) Intellectual disability is a core feature of STXBP1 encephalopathy, as all patients are 187 intellectually disabled and the vast majority are severe to profound (Stamberger et al, 2016). 188 However, the learning and memory deficits described in the previous Stxbp1 heterozygous 189 knockout mice are mild and inconsistent (Kovačević et al, 2018;Miyamoto et al, 2017;Orock 190 et al, 2018). To assess cognitive functions, we tested Stxbp1 haploinsufficient mice in three 191 different paradigms, object recognition, associative learning and memory, and working memory.…”

“…Prior studies using the other three lines of Stxbp1 heterozygous knockout mouse models reported 387 only a subset of the neurological and neuropsychiatric deficits that we observed here (Hager et 388 al., 2014;Kovačević et al, 2018;Miyamoto et al, 2017;Orock et al, 2018). For example, the 389 reduced survival, hindlimb clasping, motor dysfunction, and increased repetitive behavior were 390 not documented in the previous models.…”