Subplate and the formation of the earliest cerebral cortical circuits

© Springer Science+Business Media, LLC 2010. All rights reserved. Development of the cortex involves transient, dynamic cortical circuits, which get substantially remodelled according to the interplay between the developmental programme and the environment. Subplate constitutes a largely transient cortical neuron population. They are among the earliest generated neurons of our brain and lay the foundation of our developing cerebral cortex. Since most initial cortical input and output are directed through subplate neurons, understanding how the connectivity and functional integration of subplate develops, how the transient subplate circuits co-exist with the more permanent cortical networks and how regional variation across the cortex is programmed are issues critical to a broader understanding of cortical function. After subserving these functions, the majority of these fascinating subplate neurons die and give way to the permanent cortical circuits. The developing brain is particularly vulnerable if these transient circuits are damaged or malfunction. Subplate has been implicated in several brain developmental disorders (childhood epilepsy, schizophrenia, autism and cerebral palsy). The inability to identify these cells by criteria other than location in the brain was the major hindrance of progress in the understanding of the role of this enigmatic cell population in cortical development and disease. In this chapter we review the emerging information on the integration of subplate neurons into the cortical and extracortical circuitry using reporter gene expressing mouse transgenic lines; give a flavour of our current research on novel subtype specific markers of selected groups of subplate neurons. These markers started to have an effect in the monitoring of subplate neuronal populations in pathological animal models.