Role of Reelin protein in the cellular and behavioral response to drugs of abuse

PROJECT SUMMARY
Substance use disorder (SUD) is a national health crisis, with over 93,000 deaths due to overdose in 2020.
Currently, no FDA-approved therapeutics exist for SUD, with targeted therapeutics out of reach due to
incomplete understanding of the neurobiology of addiction. Our lab has identified expression of Reln mRNA as
necessary for cocaine-responsiveness in NAc Drd1+ medium spiny neurons (MSNs). Reelin is a secreted
glycoprotein that plays a critical role in cortical cell migration during brain development, with mutations leading
to lissencephaly, defined by a smooth-brain phenotype. In the adult brain, Reln expression remains high in the
cerebellum, hippocampus and striatum. Brain-wide Reelin signaling blockade attenuates response to
methamphetamines, indicating a critical role for Reelin in the striatum. Despite high striatal Reln expression
and evidence suggesting Reelin modulates behavioral output of the striatum, Reelin’s role in the striatum
remains under-studied. Using RNA single-molecule fluorescent in-situ hybridization (smFISH), I have validated
our single-cell data showing Reln marks cocaine-sensitive Drd1+ cells. I have also found Drd1+ cells are
enriched in Reln compared to Drd2+ cells in both rat and human brain tissue. My smFISH data show Reln
expression is restricted to the dorsal striatum and nucleus accumbens (NAc) core and absent in the NAc shell.
As these regions have distinct functions, this pattern may reflect the functional relevance of Reelin signaling. I
have assessed the role of Reelin signaling using a CRISPR-interference (CRISPRi) strategy to knockdown
Reln. NAc whole-cell patch clamp demonstrates that CRISPRi at Reln significantly impairs MSN excitability.
Critically, in vivo CRISPRi-knockdown of striatal Reln attenuates cocaine preference in a rat model.
Given these findings, I hypothesize that Reelin facilitates the dopamine-induced neuronal adaptations that
follow drug exposure and promote drug-seeking behavior. The proposed study will take a multidisciplinary
approach to rigorously investigate the following aims: (1) Reelin is required for cocaine-related behavioral
adaptations and (2) Reelin regulates membrane excitability to facilitate dopamine signaling. The proposed
studies will deepen our understanding of the molecular underpinnings of SUD, providing avenues for
therapeutic exploration for a disease completely lacking targeted treatments. Under this award, I will master
intravenous self-administration and locomotor sensitization assays to assess the relevant consequences of
genetic manipulations. I will hone patch clamp electrophysiology skills to assess mechanisms behind
behavioral adaptations. These techniques will aid my success as a physician-scientist studying mechanisms of
and engineering therapeutics for brain disorders.

Grant Number: 5F30DA057821-03
NIH Institute/Center: NIH
Principal Investigator: Kasey Brida