Estacion, M. | bioRxiv Science

bioRxiv2025

Human-specific features of the cerebellum and ZP2-regulated synapse development

Understanding the unique features of the human brain compared to non-human primates has long intrigued humankind. The cerebellum refines motor coordination and cognitive functions, contributing to the evolutionary development of human adaptability and dexterity. To identify shared and divergent features across primates, we conducted single-nucleus transcriptomic and chromatin accessibility profiling of the adult cerebellar cortex in humans, chimpanzees, macaques, and marmosets. We revealed human-specific transcriptomic and regulatory features, particularly those involved in synaptogenesis. Notably, we identified an enrichment of the sperm receptor zona pellucida glycoprotein 2 (ZP2) and its potential interactors, known for their roles in gamete interaction, in human granule cells. Experimental data show that ZP2 expression in human granule cells is induced by pontine mossy fibers, reducing synaptic proteins at pontocerebellar glomerular synapses, and decreasing cerebellar neuron electrophysiological activity. This unexpected co-option of ZP2 in human-specific synapse regulation provides insights into the evolutionary specialization of the human cerebellum.

neuroscience↗

bioRxiv2021

Inhibition of sodium conductance by cannabigerol contributes to a reduction of neuronal dorsal root ganglion excitability

Cannabigerol (CBG), a non-psychotropic phytocannabinoid, is a precursor for cannabis derivatives, {Delta}9-tetrahydrocannabinol and cannabidiol (CBD). Like CBD, CBG has been suggested as an analgesic. A previous study reported CBG (10 M) blocks voltage-gated sodium (Nav) currents in CNS neurons. However, the manner in which CBG inhibits Nav channels, and whether this effect contributes to CBGs potential analgesic behavior remain unknown. Genetic and functional studies have validated Nav1.7 as an opportune target for analgesic drug development. The efforts to develop therapeutic selective Nav1.7 blockers have been unsuccessful thus far, possibly due to issues in occupancy; drugs have been administered at concentrations many folds above IC50, resulting in loss of isoform-selectivity, and increasing off-target effects. We reasoned that an alternative approach could use compounds possessing 2 important properties: ultra-hydrophobicity and functional selectivity. Hydrophobicity could enhance absorption into neuronal cells especially with local administration. Functional selectivity could reduce likelihood of side-effects. As CBG is ultra-hydrophobic (cLogD=7.04), we sought to determine whether it also possesses functional selectivity against Nav channels that are expressed in dorsal root ganglion (DRG). We found that CBG is a ~10-fold state-dependent Nav inhibitor (KI-KR: ~2-20 M) with an average Hill-slope of ~2. We determined that at lower concentrations, CBG predominantly blocks sodium Gmax and slows recovery from inactivation; however, as concentration is increased, CBG also hyperpolarizes Nav inactivation curves. Our modeling and multielectrode array recordings suggest that CBG attenuates DRG excitability, which is likely linked with Nav inhibition. As most Nav1.7 channels are inactivated at DRG resting membrane potential, they are more likely to be inhibited by lower CBG concentrations, suggesting functional selectivity against Nav1.7 compared to other Navs (via Gmax block).

pharmacology and toxicology↗