Dab2ip Regulates Neuronal Migration and Neurite Outgrowth in the Developing Neocortex

Gum Hwa Lee,Sun Hong Kim,Ramin Homayouni,Gabriella D'Arcangelo,Debra L Silver

doi:10.1371/journal.pone.0046592

Gum Hwa Lee, Sun Hong Kim + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0046592

Copy DOI

Abstract

Dab2ip (DOC-2/DAB2 interacting protein) is a member of the Ras GTPase-activating protein (GAP) family that has been previously shown to function as a tumor suppressor in several systems. Dab2ip is also highly expressed in the brain where it interacts with Dab1, a key mediator of the Reelin pathway that controls several aspects of brain development and function. We found that Dab2ip is highly expressed in the developing cerebral cortex, but that mutations in the Reelin signaling pathway do not affect its expression. To determine whether Dab2ip plays a role in brain development, we knocked down or over expressed it in neuronal progenitor cells of the embryonic mouse neocortex using in utero electroporation. Dab2ip down-regulation severely disrupts neuronal migration, affecting preferentially late-born principal cortical neurons. Dab2ip overexpression also leads to migration defects. Structure-function experiments in vivo further show that both PH and GRD domains of Dab2ip are important for neuronal migration. A detailed analysis of transfected neurons reveals that Dab2ip down- or up-regulation disrupts the transition from a multipolar to a bipolar neuronal morphology in the intermediate zone. Knock down of Dab2ip in neurons ex-vivo indicates that this protein is necessary for proper neurite development and for the expression of several major neuronal microtubule associated proteins (MAPs), which are important for neurite growth and stabilization. Thus, our study identifies, for the first time, a critical role for Dab2ip in mammalian cortical development and begins to reveal molecular mechanisms that underlie this function.

Highlights

During the early development of the mammalian cerebral cortex, principal neurons born in ventricular or subventricular zone migrate radially toward the pial surface and become positioned in defined cellular layers [1]
Confocal analysis of brain sections obtained from embryonic day (E) 16.5 mice revealed that Dab2ip protein is expressed throughout the developing neocortex, at higher levels in the cortical plate, where principal cortical neurons migrate and mature (Fig. 1A and B)
Since Dab2ip has been shown to interact with Dab1, a critical adaptor molecule in the Reelin signaling pathway that controls neuronal migration and maturation, we investigated Dab2ip expression in several mutant mice carrying mutations in this pathway

Summary

Introduction

During the early development of the mammalian cerebral cortex, principal neurons born in ventricular or subventricular zone migrate radially toward the pial surface and become positioned in defined cellular layers [1]. Many postmitotic neurons move up from the ventricular zone and acquire a multipolar morphology in the subventricular and intermediate zone [3,4] They pause until they acquire a bipolar morphology that enables them to migrate by glial-guided locomotion into the developing cortical plate. This mode of migration requires a leading process that wraps around a radial glia fiber, this latter serving a guidance scaffold [3,4]. When the leading process of migrating neurons approaches the marginal zone, late-born neurons can use somal translocation to become properly positioned in the superficial aspect of the developing cortex [2]

Methods

Results

Conclusion