Neuroanatomical characterization of the cellular and axonal architecture of subcortical band heterotopia in the BXD29-Tlr4lps-2J/J mouse cortex

- Subcortical band heterotopia in BXD29-Tlr4lps-2J/J mice contains diverse subtypes of GABAergic neurons.
- Subcortical band heterotopia in BXD29-Tlr4lps-2J/J mice contains astrocytes, microglia, and oligodendrocytes.
- Subcortical and cortical projections are present in subcortical band heterotopia in BXD29-Tlr4lps-2J/J mice.
- Neocortical molecular layer heterotopia and hippocampal malformations are also present in BXD29-Tlr4lps-2J/J mice.

Subcortical band heterotopia (SBH) are malformations of the human cerebral cortex typically associated with epilepsy and cognitive delay/disability. Rodent models of SBH have demonstrated strong face validity as they are accompanied by both cognitive deficits and spontaneous seizures or reduced seizure threshold. BXD29-Tlr4lps-2J/J recombinant inbred mice display striking bilateral SBH, partial callosal agenesis, morphological changes in subcortical structures of the auditory pathway, and display sensory deficits in behavioral tests (Rosen et al., 2013; Truong et al., 2013, 2015). Surprisingly, these mice show no cognitive deficits and have a higher seizure threshold to chemi-convulsive treatment (Gabel et al., 2013) making them different than other rodent SBH models described previously. In the present report, we perform a detailed characterization of the cellular and axonal constituents of SBH in BXD29-Tlr4lps-2J/J mice and demonstrate that various types of interneurons and glia as well as cortical and subcortical projections are found in SBH. In addition, the length of neuronal cilia was reduced in SBH compared to neurons in the overlying and adjacent normotopic cortex. Finally, we describe additional and novel malformations of the hippocampus and neocortex present in BXD29-Tlr4lps-2J/J mice. Together, our findings in BXD29-Tlr4lps-2J/J mice are discussed in the context of the known neuroanatomy and phenotype of other SBH rodent models.