Implication of Genetic Deletion of Wdr13 in Mice: Mild Anxiety, Better Performance in Spatial Memory Task, with Upregulation of Multiple Synaptic Proteins

Abstract

WDR13 expresses from the X chromosome and has a highly conserved coding sequence. There have been multiple associations of WDR13 with memory. However, its detailed function in context of brain and behavior remains unknown. We characterized the behavioral phenotype of 2 month old male mice lacking the homolog of WDR13 gene (Wdr13−/0). Taking cue from analysis of its expression in the brain, we chose hippocampus for molecular studies to delineate its function. Wdr13−/0 mice spent less time in the central area of the open field test (OFT) and with the novel object in novel object recognition test (NOR) as compared to the wild-type. However, these mice didn't show any significant changes in total time spent in arms or in frequency of arm entries in elevated plus maze (EPM). In the absence of Wdr13, there was a significant upregulation of synaptic proteins, viz., SYN1, RAB3A, CAMK2A etc. accompanied with increased spine density of hippocampal CA1 neurons and better spatial memory in mice as measured by increased time spent in the target quadrant of Morris water maze (MWM) during probe test. Parallel study from our lab has established c-JUN, ER α/β, and HDAC 1,3,7 as interacting partners of WDR13. WDR13 represses transcription from AP1 (c-JUN responsive) and Estrogen Receptor Element (ERE) promoters. We hypothesized that absence of Wdr13 would result in de-regulated expression of a number of genes including multiple synaptic genes leading to the observed phenotype. Knocking down Wdr13 in Neuro2a cell lines led to increased transcripts of Camk2a and Nrxn2 consistent with in-vivo results. Summarily, our data provides functional evidence for the role of Wdr13 in brain.

Absence of Wdr13 Gene Predisposes Mice to Mild Social Isolation – Chronic Stress, Leading to Depression-Like Phenotype Associated With Differential Expression of Synaptic Proteins

“…Based on our previous experiments, we hypothesized that WDR13 might have an important role under stress conditions. In brain, Wdr13 expresses prominently in the hippocampus, amygdala, cortex, PFC and cerebellum ( Mitra et al, 2016 ). We had earlier studied the hippocampus for structural and molecular changes associated with the absence of Wdr13 .…”

“…Protein was extracted with 0.5% SDS and quantified using BCA protein estimation kit. 200 μg of protein was digested using trypsin as described previously ( Mitra et al, 2016 ). 80 μg of samples were split into two groups and each group was labeled with iTRAQ-8plex (Applied Biosystems, Foster City, CA, United States) for technical duplicates and as per manufacturers protocol.…”

“…Data acquisition was done using Xcalibur 2.1 (Thermo Fisher Scientific, Bremen, Germany). MS spectra, mass range, scan resolution for MS, MS/MS, Normalized collision energy (NCE), precursor ion selection, the dynamic exclusion parameters were kept the same as described in iTRAQ 4-plex experiments ( Mitra et al, 2016 ). The nano source spray was set at 2.2 KV and the capillary temperature at 250°C without sheath gas.…”

“…; wild-type ( Wdr13 +/0 ) and knockout ( Wdr13 -/0 ). The protocol followed was similar to the iTRAQ 8-plex and as previously described ( Mitra et al, 2016 ). Socially isolated wild-types were labeled with 114, 115 and socially isolated mutant mice were labeled with 116, 117 labels.…”

“…Since insults in terms of chemical toxins or high fat diet accentuated the phenotypes observed in the absence of Wdr13 , we hypothesized that WDR13 might have an important physiological function when the system/homeostasis was challenged. We had shown earlier that Wdr13 has a brain specific function with the mutant mice exhibiting mild anxiety, better memory retention and increased expression of synaptic genes ( Mitra et al, 2016 ). There were other reports that had predicted that Wdr13 might have a neuro-protective role ( Price et al, 2003 ).…”