Enhanced Prefrontal Neuronal Activity and Social Dominance Behavior in Postnatal Forebrain Excitatory Neuron-Specific Cyfip2 Knock-Out Mice

Abstract

The cytoplasmic fragile X mental retardation 1 (FMR1)-interacting protein 2 (CYFIP2) gene is associated with epilepsy, intellectual disability (ID), and developmental delay, suggesting its critical role in proper neuronal development and function. CYFIP2 is involved in regulating cellular actin dynamics and also interacts with RNA-binding proteins. However, the adult brain function of CYFIP2 remains unclear because investigations thus far are limited to Cyfip2 heterozygous (Cyfip2 +/−) mice owing to the perinatal lethality of Cyfip2-null mice. Therefore, we generated Cyfip2 conditional knockout (cKO) mice with reduced CYFIP2 expression in postnatal forebrain excitatory neurons (CaMKIIα-Cre). We found that in the medial prefrontal cortex (mPFC) of adult Cyfip2 cKO mice, CYFIP2 expression was decreased in both layer 2/3 (L2/3) and layer 5 (L5) neurons, unlike the L5-specific CYFIP2 reduction observed in adult Cyfip2 +/− mice. Nevertheless, filamentous actin (F-actin) levels were increased only in L5 of Cyfip2 cKO mPFC possibly because of a compensatory increase in CYFIP1, the other member of CYFIP family, in L2/3 neurons. Abnormal dendritic spines on basal, but not on apical, dendrites were consistently observed in L5 neurons of Cyfip2 cKO mPFC. Meanwhile, neuronal excitability and activity were enhanced in both L2/3 and L5 neurons of Cyfip2 cKO mPFC, suggesting that CYFIP2 functions of regulating F-actin and excitability/activity may be mediated through independent mechanisms. Unexpectedly, adult Cyfip2 cKO mice did not display locomotor hyperactivity or reduced anxiety observed in Cyfip2 +/− mice. Instead, both exhibited enhanced social dominance accessed by the tube test. Together, these results provide additional insights into the functions of CYFIP2 in the adult brain.

Gut microbiota shapes social dominance through modulating HDAC2 in the medial prefrontal cortex

“…The mPFC was previously regarded as the major brain region governing social dominance (Tan et al, 2018;Zhang et al, 2020;Zhou et al, 2018). In parallel, only cortical HDAC2 was able to influence agonistic outcomes, while its expression in the hippocampus did not have the same effect (Figure 4J).…”

“…Electrophysiological recordings mEPSC recordings were performed in whole-cell configuration under voltage-clamp mode at -70 mV holding potentials as described previously (Zhang et al, 2020), with minor modifications. Briefly, coronal slices of mPFC were prepared (300 mm thickness), and transferred to a storage chamber in an incubator filled with oxygenated artificial cerebrospinal fluid (ACSF), which contained 124 mM NaCl, 2.5 mM KCl, 1.23 mM NaH 2 PO 4 , 1.5 mM MgCl 2 , 2.5 mM CaCl 2 , 26 mM NaHCO 3 and 10-dextrose.…”

“…Still, it remains to be understood whether additional inherent attributes can predispose individuals to a particular rank, when subjects are matched for body size, anxiety, and prior experiences. The allelic variation or cortical expressional changes of genes that encode synapse-related proteins, like Cyfip2, syn2b, AMPAR and KCC2b, were associated with dominance switch (Anacker et al, 2019;Ma et al, 2020;Tada et al, 2016;Zhang et al, 2020). A couple of gene-regulatory elements such as Lhx2 enhancer and long non-coding RNA (lncRNA) AtLAS were implicated in shaping social hierarchy, indicating a potential epigenetic relevance (Ma et al, 2020;Wang et al, 2020).…”

Protein interactome and cell‐type expression analyses reveal that cytoplasmic FMR1‐interacting protein 1 (CYFIP1), but not CYFIP2, associates with astrocytic focal adhesion

“…Several lines of evidence suggest that CYFIP1 and CYFIP2 proteins have both shared and distinct functions in neurons. For example, we recently reported that in layer 2/3 neurons of the medial prefrontal cortex of Cyfip2 conditional knock‐out (cKO) mice, CYFIP1 proteins were upregulated as a compensation, to maintain normal F‐actin levels (Zhang et al, 2020). However, in the same neurons of cKO mice, hyperexcitability was still observed, suggesting that CYFIP1 cannot compensate for CYFIP2 functional regulation of neuronal excitability (Lee, Zhang, Kang, et al, 2020; Zhang et al, 2020).…”

“…Whole lysates of the mouse tissue were prepared as previously described (Zhang et al, 2018; Zhang et al, 2020). Briefly, frozen mouse brain tissue was homogenized in RIPA buffer (50 mM Tris–HCl pH 8.0, 150 mM NaCl, 0.1% SDS, 1% Triton X‐100, 0.5% sodium deoxycholate) with freshly added protease and phosphatase inhibitors (Sigma‐Aldrich, #05892970001 and #04906837001, respectively).…”