The Microscopic Imaging of Epigenetic Landscape- NeuroDevelopment (MIEL-ND) assay: a high throughput platform to screen compounds for neurodevelopmental effects - Neurodevelopmental diseases (NDDs – Autism Spectrum Disorder (ASD), Intellectual Disabilities,
Bipolar disorders, and Schizophrenia, etc.) are prevalent and due to errors in neurodifferentiation and
neurocircuitry. While NDDs, in many cases, are due to inherited mutations, evidence is mounting that
prenatal exposure to environmental toxicants also cause NDDs via disruption of epigenetics (e.g.,
modifications of histones [histone tags] or methylation of DNA). Our project will develop the
Microscopic Imaging of Epigenetic Landscape- NeuroDevelopment (MIEL-ND) assay, which will
enable testing of chemicals for epigenetic effects related to NDDs. In preliminary research by Alexey
Terskikh (Sanford Burnham Prebys Medical Discovery Institute) MIEL methods were developed in
which human Neural Precursor Cells (NPCs, from fetal brain) were treated with test compounds and
analyzed for changes in the pattern of histone tags within the nuclei (altered “epigenetic signature” –
which utilizes multiplexed immunolabeling, automated high throughput imaging, and cell-by-cell
analysis using machine learning). A subset of chemicals from the US EPA ToxCast program was
analyzed, and “epigenetic hits” were identified. In a separate approach, Vala Sciences Inc, which
commercializes cell-based assays relevant to toxicology/drug discovery, tested EPA compounds on
synapses/neurite formation in neurons developed from induced pluripotent stem cells (iPSC-neurons),
which represent human neurons in early stages of maturation. When results from the assays were
compared, several epigenetic hits also altered synapse and neurite formation in the iPSC-neurons
consistent with the hypothesis that epigenetic alterations may alter fate decisions of NPCs and
neurodevelopment. To further develop the MIEL-ND, we propose to screen additional ToxCast
compounds for effects on epigenetic and cell fate NPCs and test the compounds for effects on
synapse/neurites in iPSC-neurons to develop a library of epigenetic hits with known effects on the two
cell types. We will use these data and emerging data from the ToxCast program, to develop and
optimize the MIEL-ND to predict NDD-inducing effects of possible environmental toxicants. The MIEL-
ND will identify compounds that affect neurodevelopment that are not cytotoxic (which are missed by
current assays) and represents a less expensive, higher throughput, more predictive alternative to
current tests which use animals, thus reducing the use of animals in toxicity testing. Phase II goals
include developing a version of the MIEL-ND featuring iPSC-NPCs (enabling use of cells derived from
patients with NDDs), and adaptation of the assay to identify potential therapeutics for NDDs.
