Predicting novel histopathological microlesions in human epileptic brain through transcriptional clustering

Abstract

Although epilepsy is associated with a variety of abnormalities, exactly why some brain regions produce seizures and others do not is not known. We developed a method to identify cellular changes in human epileptic neocortex using transcriptional clustering. A paired analysis of high and low spiking tissues recorded in vivo from 15 patients predicted 11 cell-specific changes together with their 'cellular interactome'. These predictions were validated histologically revealing millimetre-sized 'microlesions' together with a global increase in vascularity and microglia. Microlesions were easily identified in deeper cortical layers using the neuronal marker NeuN, showed a marked reduction in neuronal processes, and were associated with nearby activation of MAPK/CREB signalling, a marker of epileptic activity, in superficial layers. Microlesions constitute a common, undiscovered layer-specific abnormality of neuronal connectivity in human neocortex that may be responsible for many 'non-lesional' forms of epilepsy. The transcriptional clustering approach used here could be applied more broadly to predict cellular differences in other brain and complex tissue disorders.

Mechanistic target of rapamycin complex 1 and 2 in human temporal lobe epilepsy

“…Another important finding of our study is the robust activation of ERK signaling in both hippocampus and temporal cortex of patients suffering from therapy-resistant TLE, consistent with previous studies showing upregulated ERK signaling in several neocortical epilepsy syndromes, including TSC and FCD (90–92). ERK is upstream of mTORC1 and both kinases are simultaneously induced at activated synapses to regulate local protein synthesis (20).…”

“…87,89 Another important finding of our study is the robust activation of ERK signaling in both hippocampus and temporal cortex of patients suffering from therapyresistant TLE, consistent with previous studies showing upregulated ERK signaling in several neocortical epilepsy syndromes, including TSC and FCD. [90][91][92] ERK is upstream of mTORC1 and both kinases are simultaneously induced at activated synapses to regulate local protein synthesis. 20 In addition to activating mTOR, ERK also regulates the activity of cAMP response element binding protein and therefore may be critically involved in seizure-induced dysregulated gene expression.…”

A distinct clinicopathological variant of focal cortical dysplasia IIId characterized by loss of layer 4 in the occipital lobe in 12 children with remote hypoxic–ischemic injury

“…However, FCD associated with SWS was not reported to specifically affect layer 4, thus presenting another distinguishing feature of our presented case series. Microlesions defined by transcriptional clustering and spike activity of preserved neurons not immunoreactive for NeuN were recently described in human epileptic neocortex, 25 and may represent yet another FCD variant. Laminar loss of NeuN staining was different in our cases, however.…”

Coalescence of deep and superficial epileptic foci into larger discharge units in adult rat neocortex

“…The observation of broader fields in superficial layers of this acute preparation is novel and may provide an electrophysiological correlate to molecular observations indicating MAP-kinase/CREB pathway expression in superficial layers of chronic human epileptic cortex and animal models of neocortical epilepsy (Rakhade et al, 2005, 2007; Barkmeier and Loeb, 2009; Barkmeier et al, 2012; Beaumont et al, 2012; Dachet et al, 2015). MAP-kinase CREB is a candidate to play a role in the development of interictal spikes measured from surface potential and may be due so through the strengthening of synaptic connections (Thomas and Huganir, 2004).…”