Biology subjects

Crittenden, J. R.

Publications and source records attributed to Crittenden, J. R..

10 recordsLinked to original sources

bioRxiv2026

MECP2-mutant marmosets exhibit primate-specific phenotypes of Rett syndrome

We used genome editing to generate MECP2-knockout marmosets and establish a new primate model for Rett syndrome (RTT), a neurodevelopmental disorder. MRI analysis of this marmoset model revealed diminished cortico-cortical connections, particularly those originating in the prefrontal cortex. Detailed histological analysis revealed reduced dendritic arborization and synaptic density, particularly in the upper layers of the cerebral cortex. Cortical layer II/III excitatory neurons appeared to be immature based on single-nucleus RNA sequencing and spatial transcriptomics, while PVALB-positive interneurons exhibited upregulation of neuronal maturation-related transcripts. Moreover, the neurodevelopmental disease gene GABAB receptor 2 (GABBR2) emerged as a conserved downstream target of MECP2, illuminating a cellular cascade that could be targeted in preclinical and therapeutic drug development. Many of the gene expression changes observed in the marmoset model are common in RTT patients, thereby highlighting molecular links from cell type-specific phenotypes in the marmoset model to the RTT clinical presentation.

neuroscience↗

bioRxiv2025

Molecular unbalances between striosome and matrix compartments characterize the pathogenesis of Huntington's disease model mouse

The pathogenesis of Huntingtons disease is still incompletely understood, despite the remarkable advances in identifying the molecular effects of the Htt mutation in this disease. When we focus on movement disorders, clinical studies offer us some hints about this issue. Human studies employing positron emission tomography have identified a reduction in phosphodiesterase 10A (PDE10A) as the earliest event in the brain of patients with Huntingtons disease, which occurs about 25 years before symptom onset. A PDE10A mutation is also known to cause childhood-onset chorea. GNAL encodes the olfactory type G-protein subunit (Golf), strongly expressed in the striatum, and its mutation causes familial dystonia. PDE10A and Golf are both critical regulators of cyclic AMP and are abundant in striatal spiny projection neurons. These findings suggest that maintaining cyclic AMP levels in the striatum might be an essential target for the pathogenesis of movement disorders such as chorea and dystonia. Why and how these changes in the striatum cause movement disorder are still a mystery. Here we suggest that a key might be evaluating these messenger systems in light of the circuit-level compartmental organization of the striatum, in which there is particular vulnerability of the striosome compartment. We developed machine learning algorithms to define with high precision and reproducibility the borders of striosomes in the brains of q175 Huntingtons disease model mice from 3-12 months of age. We demonstrate that multiple molecules including Golf, PDE10A, dopamine D1 and D2 receptors, adenosine 2A receptors, and mu-opioid receptors differentially change their expression patterns in striosomes across ages by comparison with their expression patterns in the matrix compartment. An early and pronounced differential vulnerability of striosomes has been demonstrated in studies of post-mortem Huntingtons brains. Our findings here, mapping the molecular distributions across age in a widely studied mouse model of Huntingtons disease, may help to pinpoint the pathogenic mechanisms of Huntingtons disease by demonstrating the differential molecular changes in the striosome compartment.

neuroscience↗

bioRxiv2025

State-dependent modulation of spiny projection neurons controls levodopa-induced dyskinesia in a mouse model of Parkinson's disease

In the later stages of Parkinsons disease (PD), patients often manifest levodopa-induced dyskinesia (LID), compromising their quality of life. The pathophysiology underlying LID is poorly understood, and treatment options are limited. To move toward filling this treatment gap, the intrinsic and synaptic changes in striatal spiny projection neurons (SPNs) triggered by the sustained elevation of dopamine (DA) during dyskinesia were characterized using electrophysiological, pharmacological, molecular and behavioral approaches. Our studies revealed that the intrinsic excitability and functional corticostriatal connectivity of SPNs in dyskinetic mice oscillate between the on- and off-states of LID in a cell- and state-specific manner. Although triggered by levodopa, these rapid oscillations in SPN properties depended on both dopaminergic and cholinergic signaling. In a mouse PD model, disrupting M1 muscarinic receptor signaling specifically in iSPNs or deleting its downstream signaling partner CalDAG-GEFI blunted the levodopa-induced oscillation in functional connectivity, enhanced the beneficial effects of levodopa and attenuated LID severity.

neuroscience↗

bioRxiv2024

Striosomes Target Nigral Dopamine-Containing Neurons via Direct-D1 and Indirect-D2 Pathways Paralleling Classic Direct-Indirect Basal Ganglia Systems

Balanced activity of canonical direct D1 and indirect D2 basal ganglia pathways is considered a core requirement for normal movement, and their imbalance is an etiologic factor in movement and neuropsychiatric disorders. We present evidence for a conceptually equivalent pair of direct-D1 and indirect-D2 pathways that arise from striatal projection neurons (SPNs) of the striosome compartment rather than from SPNs of the matrix, as do the canonical pathways. These S-D1 and S-D2 striosomal pathways target substantia nigra dopamine-containing neurons instead of basal ganglia motor output nuclei. They modulate movement oppositely to the modulation by the canonical pathways: S-D1 is inhibitory and S-D2 is excitatory. The S-D1 and S-D2 circuits likely influence motivation for learning and action, complementing and reorienting canonical pathway modulation. A major conceptual reformulation of the classic direct-indirect pathway model of basal ganglia function is needed, as well as reconsideration of the effects of D2-targeting therapeutic drugs. HIGHLIGHTSO_LIDirect S-D1 and Indirect S-D2 striosomal pathways target SNpc dopamine cells C_LIO_LIThe S-D2 indirect pathway targets a distinct central external pallidal zone (cGPe) C_LIO_LIStimulation of S-D2 increases, of S-D1 decreases, striatal dopamine and movement C_LIO_LIS-D1 SPNs activity brackets task, inverse to a mid-task peak of dopamine release C_LI

neuroscience↗

bioRxiv2024

Developmental and adult striatal patterning of nociceptin ligand marks striosomal population with direct dopamine projections

Circuit influences on the midbrain dopamine system are crucial to adaptive behavior and cognition. Recent developments in the study of neuropeptide systems have enabled high-resolution investigations of the intersection of neuromodulatory signals with basal ganglia circuitry, identifying the nociceptin/orphanin FQ (N/OFQ) endogenous opioid peptide system as a prospective regulator of striatal dopamine signaling. Using a prepronociceptin-Cre reporter mouse line, we characterized highly selective striosomal patterning of Pnoc mRNA expression in mouse dorsal striatum, reflecting early developmental expression of Pnoc. In the ventral striatum, Pnoc expression was was clustered across the nucleus accumbens core and medial shell, including in adult striatum. We found that PnoctdTomato reporter cells largely comprise a population of dopamine receptor D1 (Drd1) expressing medium spiny projection neurons localized in dorsal striosomes, known to be unique among striatal projections neurons for their direct innervation of midbrain dopamine neurons. These findings provide new understanding of the intersection of the N/OFQ system among basal ganglia circuits with particular implications for developmental regulation or wiring of striatal-nigral circuits.

neuroscience↗

bioRxiv2022

Huntington's Disease Produces Multiplexed Transcriptional Vulnerabilities of StriatalD1-D2 and Striosome-Matrix Neurons

Striatal cell-type-specific vulnerability in Huntingtons disease (HD) preferentially affects dopamine D2R-expressing projection neurons (SPNs), compatible with manifest motor symptomatology in HD. Transcriptional studies of striatal striosome-matrix compartmentalization in HD are, however, limited, despite pathologic evidence for striosome vulnerability aligning with early mood symptomatology. We used single-nucleus RNA-sequencing on striatal samples from two murine models, and rare Grade 1 HD patient tissues, to examine striosome and matrix sub-clusters within parent D1 and D2 SPN clusters. In human HD, striosomal SPNs were the most depleted SPN population. Surprisingly, for both mouse models, transcriptomic distinctiveness was diminished more for striosome-matrix SPNs than for D1-D2 SPNs. Compartmental markers were dysregulated so as to cancel endogenous identities as striosomal or matrix SPNs, but markers for D1-D2 exhibited less identity obscuring. The canonical striosome-matrix as well as D1-D2 organizations of the striatum thus are both strongly, but differentially, compromised in HD and are targets for therapeutics.

neuroscience↗

bioRxiv2022

Cannabinoid receptor 1 is required for neurodevelopment of striosome-dendron bouquets

Cannabinoid receptor 1 (CB1R) has strong effects on neurogenesis and axon pathfinding in the prenatal brain. Endocannabinoids that activate CB1R are abundant in the early postnatal brain and in mothers milk, but few studies have investigated their function in newborns. We examined postnatal CB1R expression in the major striatonigral circuit from striosomes of the striatum to the dopamine-containing neurons of the substantia nigra. CB1R enrichment was first detectable between postnatal days 5 and 7, and this timing coincided with the formation of striosome-dendron bouquets, the elaborate anatomical structures by which striosomal neurons control dopaminergic cell activity through inhibitory synapses. In Cnr1-/- knockouts lacking CB1R expression, striosome-dendron bouquets were markedly disorganized by postnatal day 11 and at adulthood, suggesting a postnatal pathfinding connectivity function for CB1R in connecting striosomal axons and dopaminergic neurons analogous to CB1Rs prenatal function in other brain regions. Our finding that CB1R plays a major role in postnatal wiring of the striatonigral dopamine system, with lasting consequences at least in mice, points to a crucial need to determine whether lactating mothers use of CB1R agonists (e.g., in marijuana) or antagonists (e.g., type 2 diabetes therapies) can disrupt brain development in nursing offspring.

neuroscience↗

bioRxiv2021

Effects of acute and repeated administration of the selective M4 PAM VU0152099 on cocaine vs. food choice in male rats

AO_SCPLOWBSTRACTC_SCPLOWLigands that stimulate muscarinic acetylcholine receptors 1 and 4 (M1, M4) have shown promising effects as putative pharmacotherapy for cocaine use disorder in rodent assays. We have previously shown reductions in cocaine effects with acute M4 stimulation, as well as long-lasting, delayed, reductions in cocaine taking and cocaine seeking with combined M1/M4 receptor stimulation or with M1 stimulation alone. M4 stimulation opposes dopaminergic signaling acutely, but direct dopamine receptor antagonists have proved unhelpful in managing cocaine use disorder because they lose efficacy with long-term administration. It is therefore critical to determine whether M4 approaches themselves can remain effective with repeated or chronic dosing. We assessed the effects of repeated administration of the M4 positive allosteric modulator (PAM) VU0152099 in rats trained to choose between intravenous cocaine and a liquid food reinforcer, to obtain quantitative measurement of whether M4 stimulation could produce delayed and lasting reduction in cocaine taking. VU0152099 produced progressively augmenting suppression of cocaine choice and cocaine intake, but produced neither rebound nor lasting effects after treatment ended. To compare and contrast effects of M1 vs. M4 stimulation, we tested whether the M4 PAM VU0152100 suppressed cocaine self-administration in mice lacking CalDAG-GEFI signaling factor, required for M1-mediated suppression of cocaine self-administration. CalDAG-GEFI ablation had no effect on M4-mediated suppression of cocaine self-administration. These findings support the potential usefulness of M4 PAMs as pharmacotherapy to manage cocaine use disorder, alone or in combination with M1-selective ligands, and show that M1 and M4 stimulation modulate cocaine-taking behavior by distinct mechanisms.

neuroscience↗

bioRxiv2019

Mutations in CalDAG-GEFI Lead to Striatal Signaling Deficits and Psychomotor Symptoms in Multiple Species Including Human

Syndromes caused by mutations in Ras-MAP kinase signaling molecules are known as RASopathies and share features such as developmental delay, autistic traits, and cancer. Syndromic features of Rap-MAP kinase signaling defects remain undefined. CalDAG-GEFI is a calcium-responsive Rap-GTPase activator that is enriched in the matrix of the sensorimotor striatum and down-regulated in Huntingtons disease. We show here that CalDAG-GEFI mutations, including striatum-specific deletions and spontaneous mutations in the enzymatic domain, are associated with psychomotor phenotypes in humans, dogs and mice. The identification of these neural mutants was guided by the overt bleeding phenotype in CalDAG-GEFI knockout mice, and then in humans and other species with conserved platelet signaling deficits. Knockout mice exhibit loss of striatal long-term potentiation and deficits in dopamine, acetylcholine and glutamate signaling, along with delayed motor learning and drug-induced perseverative behaviors. Thus, loss of CalDAG-GEFI signaling produces an evolutionarily conserved syndrome characterized by bleeding and psychomotor dysfunction.

neuroscience↗

bioRxiv2018

Drosophila mef2 is essential for normal mushroom body and wing development.

MEF2 (myocyte enhancer factor 2) transcription factors are found in the brain and muscle of insects and vertebrates and are essential for the differentiation of multiple cell types. We show that in the fruitfly Drosophila, MEF2 is essential for normal development of wing veins, and for mushroom body formation in the brain. In embryos mutant for D-mef2, there was a striking reduction in the number of mushroom body neurons and their axon bundles were not detectable. D-MEF2 expression coincided with the formation of embryonic mushroom bodies and, in larvae, expression onset was confirmed to be in post-mitotic neurons. With a D-mef2 point mutation that disrupts nuclear localization, we find that D-MEF2 is restricted to a subset of Kenyon cells that project to the /{beta}, and {gamma} axonal lobes of the mushroom bodies, but not to those forming the /{beta} lobes. Our findings that ancestral mef2 is specifically important in dopamine-receptive neurons has broad implications for its function in mammalian neurocircuits.

developmental biology↗