Human OPRM1 and murine Oprm1 promoter driven viral constructs for genetic access to μ-opioidergic cell types

Abstract

With concurrent global epidemics of chronic pain and opioid use disorders, there is a critical need to identify, target and manipulate specific cell populations expressing the mu-opioid receptor (MOR). However, available tools and transgenic models for gaining long-term genetic access to MOR+ neural cell types and circuits involved in modulating pain, analgesia and addiction across species are limited. To address this, we developed a catalog of MOR promoter (MORp) based constructs packaged into adeno-associated viral vectors that drive transgene expression in MOR+ cells. MORp constructs designed from promoter regions upstream of the mouse Oprm1 gene (mMORp) were validated for transduction efficiency and selectivity in endogenous MOR+ neurons in the brain, spinal cord, and periphery of mice, with additional studies revealing robust expression in rats, shrews, and human induced pluripotent stem cell (iPSC)-derived nociceptors. The use of mMORp for in vivo fiber photometry, behavioral chemogenetics, and intersectional genetic strategies is also demonstrated. Lastly, a human designed MORp (hMORp) efficiently transduced macaque cortical OPRM1+ cells. Together, our MORp toolkit provides researchers cell type specific genetic access to target and functionally manipulate mu-opioidergic neurons across a range of vertebrate species and translational models for pain, addiction, and neuropsychiatric disorders.

Single nuclei transcriptomics in human and non-human primate striatum in opioid use disorder

“…Opioids, including endogenous opioids, enkephalin, dynorphin, and β-endorphin, differentially activate several classes of opioid receptors, including mu, delta, and kappa, encoded by OPRM1, OPRD1 , and OPRK1 , respectively. Previous efforts have mapped striatal expression of opioid receptors in non-human primates and rodents, characterizing species-specific and cell type-specific patterns of expression 41 , 42 . We investigated the expression of opioid receptors and cognate ligands within the dorsal striatum.…”

Mimicking opioid analgesia in cortical pain circuits

“…Importantly, MORp -driven chemogenetics preserves sensory discriminative processes necessary for detecting and localizing noxious stimuli but diminished the unpleasant affective component of pain. Moreover, we did not find evidence of reinforcement in uninjured animals, suggesting reduced addiction liabilities with our ACC opioidergic circuit-targeted therapy (39) .…”

“…As morphine analgesia is driven by MOR signaling in the ACC, we hypothesized that chemogenetic mimicry of morphine anti-nociception via selective inhibition of ACC MOR-expressing neurons would alleviate pain aversion in a circuit-specific manner. Using our recently published (39) synthetic mouse mu-opioid receptor promoter ( mMORp ) to gain genetic access to cortical MOR+ cell-types, we cloned the DREADD-hM4 sequence into the mMORp vector for AAV-mediated hM4 delivery directly to ACC MOR neurons (AAV- mMORP -hM4-mCherry; Fig. 4K and Fig.…”

“…In total, these studies point to the same neural circuits in the ACC that drive adaptive behavior to acute noxious stimuli might also be maladaptive during chronic pain (34, 35) . Thus, leveraging personalized deep-brain stimulation (36) or cell-type-specific gene therapies (37, 38) to modulate neural activity in MOR-expressing neurons (39) may mimic the prefrontal cortical actions of opioid analgesia without the associated risks of off-target pharmacotherapies (1) .…”

Projection-TAGs enable multiplex projection tracing and multi-modal profiling of projection neurons

“…Among different types of GREs, enhancers initiate the recruitment of transcription complexes and drive the transcription of regulated genes while the silencers prevent the expression of regulated genes 70,71 . Identification of cell-type-specific GREs, specifically enhancers, has gained increased attention in the neuroscience field as they can be used as a valuable tool to mediate transgene (e.g eYFP, ChR2, DREADDS, etc) expression in the target cell populations for basic science research and potentially the development of novel therapeutics [72][73][74][75][76][77] . Though recent progress has been made in characterizing the landscape of GREs for the projection neurons, the current experimental workflow is tedious and painstaking as individual projection neurons are labeled via injection of retro Cre in floxed nuclear reporter mice, and regions of interest are pooled for analysis of potential GREs 23,45 .…”