Pten loss results in inappropriate excitatory connectivity

Abstract

Pten mutations are associated with Autism Spectrum Disorder. Pten loss of function in neurons increases excitatory synaptic connectivity, contributing to an imbalance between excitation and inhibition. We aimed to determine whether Pten loss results in aberrant connectivity in neural circuits. We compared postnatally generated wild-type and Pten knockout granule neurons integrating into the dentate gyrus using a variety of methods to examine their connectivity. We found that postsynaptic Pten loss provides an advantage to dendritic spines in competition over a limited pool of presynaptic boutons. Retrograde monosynaptic tracing with rabies virus reveals that this results in synaptic contact with more presynaptic partners. Using independently excitable opsins to interrogate multiple inputs onto a single neuron, we found that excess connectivity is established indiscriminately from among glutamatergic afferents. Therefore, Pten loss results in inappropriate connectivity whereby neurons are coupled to a greater number of synaptic partners.

PTEN in Autism and Neurodevelopmental Disorders

“…Pten cKO animals have been analyzed for synaptic connectivity and plasticity, showing that there is an imbalance between synaptic excitation and inhibition (E/I balance), which is now well accepted as a key pathological mechanism linked to developing ASD-related behavior (Lee et al 2017). Systematic approaches involve studies in which Cre-expressing virus or shRNA against Pten has been injected into the dentate gyrus (Luikart et al 2011;Williams et al 2015;Skelton et al 2019), amygdala (Haws et al 2014), or auditory cortex (Xiong et al 2012) of neonatal mice. Although differences in spine density upon Pten deletion have been observed, which may be because of different time points of virus injection and tissue specificity (P7 dentate gyrus vs. P49 basolateral amygdala vs. Pten f/f ;Nse-cre), the number of mature mushroom-like spines is increased compared to controls (Haws et al 2014;Williams et al 2015).…”

“…Although differences in spine density upon Pten deletion have been observed, which may be because of different time points of virus injection and tissue specificity (P7 dentate gyrus vs. P49 basolateral amygdala vs. Pten f/f ;Nse-cre), the number of mature mushroom-like spines is increased compared to controls (Haws et al 2014;Williams et al 2015). Additionally, Pten KO neurons receive accelerated afferent input from multiple neurons (Skelton et al 2019). As a consequence, neurons require a higher firing threshold to evoke an action potential but, at the same time, are more sensitive to afferent stimulation and fire more readily as shown by higher excitatory postsynaptic current (EPSC) frequency and amplitude ( Fig.…”

“…As a consequence, neurons require a higher firing threshold to evoke an action potential but, at the same time, are more sensitive to afferent stimulation and fire more readily as shown by higher excitatory postsynaptic current (EPSC) frequency and amplitude ( Fig. 5B; Luikart et al 2011;Haws et al 2014;Williams et al 2015;Skelton et al 2019). Inhibitory input on these neurons is unchanged (Williams et al 2015), indicating that Pten deletion in excitatory neurons makes them hyperexcitable.…”

Germline Nuclear-predominant Pten Murine Model Exhibits Impaired Social and Perseverative Behavior, Microglial Activation, and Increased Oxytocinergic Activity

“…Murine models of increasing speci city have established that Pten and related downstream signaling participates in the regulation of social behavior, CNS morphology, and neuronal and glial function [23,25,[44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61]. Consistent behavioral phenotypes of altered social behavior persist when loss of Pten expression is restricted to mature neurons or neuronal precursors, and these models often have impaired learning/memory, increased anxiety, or altered activity/motor ability [16,44,46,48].…”

Multi-model functionalization of disease-associated PTEN missense mutations identifies multiple molecular mechanisms underlying protein dysfunction

“…Aberrant neuronal morphology and excitatory/inhibitory synapse balance are hallmarks of ASD 46 , and ASD rodent models 20 . Reducing PTEN expression results in increased neuronal growth, with larger soma size, increased dendritic and axonal branch length, and increased excitatory, but not inhibitory synapse density 22,[47][48][49][50][51] . To assay variant function in these ASD-associated neuronal growth processes, we overexpressed WT and 19 PTEN variants, or GFP alone, in rat primary hippocampal and dorsal root ganglion (DRG) neuronal cultures.…”