Spatial transcriptomics identifies L6 corticothalamic and L6b subplate-like heterotopic neurons in an epileptogenic SLC35A2-associated brain malformation.

Abstract

Increased white matter (WM) heterotopic neurons are a pathological feature observed in various neurological and psychiatric disorders. Mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE) is a drug-resistant epilepsy-associated cortical malformation characterized by increased WM heterotopic neurons and OLIG2-positive cells and frequently associated with somatic SLC35A2 mutations. However, the precise cellular identity of these heterotopic neurons remains unclear. Using imaging-based spatial transcriptomics (iST) of SLC35A2-mutated MOGHE tissues, we found that most WM heterotopic neurons exhibited molecular signatures of excitatory neurons. Further analyses revealed that these heterotopic excitatory neurons included prominent populations with layer 6 corticothalamic (CT)-like and layer 6b subplate neuron (SpN)-like molecular features. These findings were further supported by human immunohistochemistry and a Slc35a2 conditional knockout (cKO) mouse model. Together, our results provide a cellular characterization of WM heterotopic neurons in MOGHE and suggest a new perspective on disease pathophysiology centered on deep-layer excitatory neuronal populations.