Summary: A new mouse study demonstrates that disrupting the endocannabinoid system during prenatal brain development produces persistent changes in cortical structure, gene expression, and behavior. Reducing activity of a key endocannabinoid receptor in the developing prefrontal cortex impaired normal neuronal migration, altered expression of genes linked to brain formation and signaling, and produced social and motor deficits after birth.
These findings indicate that interfering with endocannabinoid signaling in the womb — whether experimentally or through prenatal exposure to substances that target the same receptor — can increase vulnerability to neuropsychiatric conditions that involve social impairments and altered motor function.
Key Facts
- Neuronal disruption: Prenatal reduction of CB1 receptor expression caused cortical neurons to migrate to incorrect layers.
- Gene expression changes: Affected neurons showed altered expression of genes associated with cortical development, cytoskeletal organization, and neurotransmission.
- Behavioral consequences: Adult offspring exhibited reduced social interaction and impaired motor behavior consistent with the observed cellular and molecular changes.
Source: SfN
Endocannabinoids are naturally occurring signaling molecules that act through cannabinoid receptors, including the CB1 receptor. These same receptors are the primary targets of many cannabis compounds. Endocannabinoid signaling plays an important regulatory role during neurodevelopment, but the long-term consequences of altering this pathway during prenatal stages have not been fully understood.
In a study published in the Journal of Neuroscience, researchers led by Ismael Galve-Roperh at the Complutense University of Madrid used a mouse model to investigate how transient prenatal downregulation of CB1 cannabinoid receptors (CB1Rs) in the prefrontal cortex affects subsequent brain organization, gene expression patterns, neuronal electrical properties, and adult behavior.
To model prenatal interference with endocannabinoid signaling, the investigators used in utero electroporation of small-interference RNA (siRNA) at embryonic day 14.5 (E14.5), a time when upper-layer cortical neurons are being generated. This transient knockdown specifically reduced CB1R expression in the developing prefrontal cortex.
The manipulation arrested normal neuronal migration: many neurons failed to reach their intended superficial cortical layers and instead remained ectopically positioned in deeper layers. Electrophysiological recordings revealed that these ectopic neurons were less excitable than native deep-layer pyramidal neurons, showing larger afterhyperpolarizations, reduced sag, and lower firing frequencies.
At the molecular level, fluorescence-activated cell sorting (FACS) and microarray analysis of electroporated neurons identified differentially expressed genes (DEGs) enriched in pathways important for cortical development, cell migration, neurotransmitter secretion, and cytoskeletal organization. Gene set enrichment also highlighted links to synaptic function and pathways previously associated with neurodegenerative disorders.
Notably, several DEGs that emerged from this manipulation have prior associations with intellectual disability, schizophrenia, and autism spectrum conditions. Comparative analyses identified the transcription factor ZBTB20 as a shared differentially expressed gene of interest across neuropsychiatric risk databases and the CB1R manipulation examined here.
Behaviorally, adult mice that experienced prenatal CB1R downregulation—both males and females—showed persistent deficits in social interaction and motor performance. These behavioral changes align with the disrupted cortical lamination, altered neuronal excitability, and the transcriptional signature detected in affected neurons.
Taken together, the results support a critical developmental role for CB1 cannabinoid receptors in shaping pyramidal neuron positioning and maturation within the prefrontal cortex. The study reinforces the idea that perturbations of endocannabinoid signaling during fetal brain development can produce long-lasting structural, molecular, and behavioral consequences that may contribute to neuropsychiatric vulnerability, particularly for conditions involving social impairments.
About this neurodevelopment and behavioral neuroscience research news
Author: SfN Media
Source: SfN
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Original Research: Closed access. “Prenatal Downregulation of CB1 Cannabinoid Receptors in the Mouse Prefrontal Cortex Disrupts Cortical Lamination and Induces a Transcriptional Signature Associated with Social Interaction Deficits” by Ismael Galve-Roperh et al., Journal of Neuroscience.
Abstract
Prenatal Downregulation of CB1 Cannabinoid Receptors in the Mouse Prefrontal Cortex Disrupts Cortical Lamination and Induces a Transcriptional Signature Associated with Social Interaction Deficits
Endocannabinoid signaling regulates key neurodevelopmental processes through CB1 cannabinoid receptors (CB1Rs), which guide pyramidal neuron differentiation, migration, and axonal guidance. This study examined the enduring impact of transient prenatal CB1R downregulation in the mouse prefrontal cortex by evaluating gene expression, neuronal electrophysiology, and behavioral outcomes.
Transient CB1R loss induced by in utero siRNA electroporation at E14.5, a stage when upper-layer neurons are generated, arrested migration and produced ectopic neurons occupying deeper cortical layers. Whole-cell current-clamp recordings demonstrated that ectopic neurons exhibited reduced excitability compared with native deep-layer pyramidal neurons. Differentially expressed genes identified in FACS-sorted electroporated neurons were significantly enriched in pathways governing cortical formation, migration regulation, neurotransmitter secretion, and cytoskeletal architecture. Gene set enrichment also implicated synaptic function and pathways linked to neurodegenerative disorders.
The transcriptional profile of siCB1R-derived neurons included genes previously associated with intellectual disability, schizophrenia, and autism spectrum disorders, with ZBTB20 emerging as a common DEG relevant to neuropsychiatric risk. Prenatal CB1R knockdown produced long-lasting behavioral changes in adult offspring of both sexes, notably impairments in social interaction and motor behavior. Collectively, the findings emphasize the role of CB1Rs in prefrontal pyramidal neuron development and support the contribution of altered endocannabinoid signaling to neuropsychiatric vulnerability.