Identification of Dysregulated Long Noncoding RNAs in the Midbrain of Human Cocaine Abusers

Maintenance of the drug-addicted state involves changes in gene expression in different neuronal cell types and neural circuits. Midbrain dopamine neurons in particular mediate numerous responses to drugs of abuse. Long noncoding RNAs (lncRNAs) regulate CNS gene expression through a variety of mechanisms, but very little is known about their role in drug abuse. The proportion of lncRNAs that are primate-specific provides a strong rationale for their study in human drug abusers. We examined the profile of lncRNA expression in postmortem human midbrain specimens from chronic cocaine abusers and well-matched control subjects (n=11 subject pairs) using a custom lncRNA microarray. Differential expression was validated by quantitative PCR, and cellular localization investigated by in situ hybridization histochemistry.A profile of lncRNAs significantly dysregulated in chronic cocaine abusers was determined. LncRNAs with dopamine cell-specific expression, differential subcellular distribution, covariance with protein-coding genes, and tissue-specific drug-responsiveness were identified. Dysregulation of midbrain lncRNA expression may reflect pathophysiological processes associated with chronic cocaine abuse. LncRNAs may be central mediators of cellular responses to drug abuse. cRNAs were generated from postmortem human midbrain specimens from chronic cocaine abusers and well-matched control subjects and hybridized to a custom Agilent 4 x 44,000-feature high-density oligonucleotide microarray platform using 60-mer probes. Cocaine control pairs were run together in a dye-flip two-color design, meaning each sample was run in quadruplicate, twice with each dye (Alexa-647 and Alexa-555; Invitrogen, Carlsbad, CA). Microarray slides were scanned with the default Agilent protocol and the intensity of fluorescence between dyes was normalized using a Loess correction. There are 7 probes per gene. Data across all cases and quadruplicates were quantile-normalized.