Biology subjects

Dwyer, B. E.

Publications and source records attributed to Dwyer, B. E..

3 recordsLinked to original sources

bioRxiv2020

Csmd2 interacts with Dab1 and is Required in Reelin-Mediated Neuronal Maturation

Reelin is a glycoprotein secreted by Cajal-Retzius cells to regulate development of the cerebral cortex. Reelin binding to its receptors on immature neurons initiates a signaling cascade through the downstream adaptor protein, Dab1. Defects in this signaling mechanism result in perturbed neuronal migration, reductions in dendrite complexity, and deficits in synapse development and function. How Reelin controls neuronal migration and brain lamination have been extensively investigated over the years, but the pathways that regulate dendrite and spine development downstream of Reelin and Dab1 have yet to be fully elucidated. Here, we have identified a novel interaction between Dab1 and Csmd2, a synaptic transmembrane protein required for dendrite and dendritic spine development in forebrain excitatory neurons. We demonstrate that Csmd2 contains an NPxY motif on its intracellular region, through which Dab1 interacts with Csmd2. Interestingly, we find that this NPxY consensus motif is not required for Csmd2 to localize at the postsynaptic densities of spiny neurons. Rather, the introduction of an NPxY mutant form of Csmd2 results in a significant overproduction of immature, filopodia-like dendritic spines in maturing neurons. Moreover, we show that knockdown of Csmd2 mRNA expression in immature developing neurons abolishes the ability of Reelin to promote dendrite elaboration and dendritic spine maturation. This suggests that the Csmd2-Dab1 interaction may be a requirement of Reelin/Dab1 signaling to mediate the structural maturation of neurons. Together, these results point toward a role of Csmd2 in the Reelin/Dab1 signaling axis that promotes the development of dendrites and dendritic spines in maturing neurons. Summary StatementHow Reelin controls neuronal maturation remains to be understood. We demonstrate that the synaptic protein Csmd2 interacts with the Reelin-associated adaptor protein Dab1. We also determine that Reelin requires Csmd2 to regulate structural development and maturation of forebrain neurons.

neuroscience↗

bioRxiv2018

Lmx1a drives Cux2 expression in the cortical hem through activation of a conserved intronic enhancer.

During neocortical development, neurons are produced by a diverse pool of neural progenitors. A subset of progenitors express the Cux2 gene and are fate-restricted to produce certain neuronal subtypes, but the upstream pathways that specify these progenitor fates remain unknown. To uncover the transcriptional networks that regulate Cux2 expression in the forebrain, we characterized a conserved Cux2 enhancer that we find recapitulates Cux2 expression specifically in the cortical hem. Using a bioinformatic approach, we found several potential transcription factor (TF) binding sites for cortical hem-patterning TFs. We found that the homeobox transcription factor, Lmx1a, can activate the Cux2 enhancer in vitro. Furthermore, we show that multiple Lmx1a binding sites required for enhancer activity in the cortical hem in vivo. Mis-expression of Lmx1a in neocortical progenitors caused an increase in Cux2+-lineage cells. Finally, we compared several conserved human enhancers with cortical hem-restricted activity and found that recurrent Lmx1a binding sites are a top shared feature. Uncovering the network of TFs involved in regulating Cux2 expression will increase our understanding of the mechanisms pivotal in establishing Cux2-lineage fates in the developing forebrain.\n\nSummary StatementAnalysis of a cortical hem-specific Cux2 enhancer reveals role for Lmx1a as a critical upstream regulator of Cux2 expression patterns in neural progenitors during early forebrain development.

neuroscience↗

bioRxiv2018

Csmd2 is a Synaptic Transmembrane Protein that Interacts with PSD-95

Mutations and copy number variants of the Cub and Sushi Multiple Domains 2 (CSMD2) gene are associated with schizophrenia and autism spectrum disorder. CSMD2 is a single-pass transmembrane protein with a large extracellular domain comprising repeats of Cub and Sushi domains. Although the biological functions of CSMD2 have not been studied, the association between CSMD2 variants and cognitive function suggest that it may have a role in brain development or function. In this study, we show that mouse Csmd2 is expressed in excitatory and inhibitory neurons in the brain. Csmd2 protein exhibits a somatodendritic localization in the neocortex and hippocampus, with smaller puncta localizing further out in the neuropil. We show that many of these Csmd2 puncta co-localize with the synaptic protein PSD-95. Using immunohistochemical and biochemical methods, we further demonstrate that Csmd2 localizes to dendritic spines and is enriched in the postsynaptic density. We also find Csmd2 at ribbon synapses of the inner plexiform layer of the retina, suggesting a broader synaptic function of Csmd2 in the central nervous system. Finally, we show that the cytoplasmic tail domain of Csmd2 interacts with synaptic scaffolding proteins of the membrane-associated guanylate kinase (MAGUK) family. The association between Csmd2 and MAGUK member PSD-95 is dependent on a PDZ-binding domain on the Csmd2 tail, which is also required for synaptic targeting of Csmd2. Together, these results point toward a function for Csmd2 in dendrites and synapses, which may account for its association with several psychiatric disorders.

cell biology↗