Biology subjects

Bennett, V.

Publications and source records attributed to Bennett, V..

3 recordsLinked to original sources

bioRxiv2023

Live imaging of excitable axonal microdomains in ankyrin-G-GFP mice

The axon initial segment (AIS) constitutes not only the site of action potential initiation, but also a hub for activity-dependent modulation of output generation. Recent studies shedding light on AIS function used predominantly post-hoc approaches since no robust murine in vivo live reporters exist. Here, we introduce a reporter line in which the AIS is intrinsically labeled by an ankyrin-G-GFP fusion protein activated by Cre recombinase, tagging the native Ank3 gene. Using confocal, superresolution, and two-photon microscopy as well as whole-cell patch-clamp recordings in vitro, ex vivo, and in vivo, we confirm that the subcellular scaffold of the AIS and electrophysiological parameters of labeled cells remain unchanged. We further uncover rapid AIS remodeling following increased network activity in this model system, as well as highly reproducible in vivo labeling of AIS over weeks. This novel reporter line allows longitudinal studies of AIS modulation and plasticity in vivo in real-time and thus provides a unique approach to study subcellular plasticity in a broad range of applications.

neuroscience↗

bioRxiv2018

A giant ankyrin-B mechanism for neuro-diversity/divergence through stochastic ectopic axon projections

ANK2 is a high-confidence autism spectrum disorder (ASD) gene where affected individuals exhibit diverse symptoms with a wide range of IQ. We report a cellular mechanism resulting in stochastic brain connectivity that provides a rationale for both gain and loss of function due to ANK2 mutation. Deficiency of giant ankyrin-B (ankB), the neurospecific ANK2 mutation target, results in ectopic CNS axon tracts associated with increased axonal branching. We elucidate a mechanism limiting axon branching, whereby giant ankB is recruited by L1CAM to periodic axonal plasma membrane domains where it coordinates cortical microtubules and prevents microtubule stabilization of nascent axon branches. Heterozygous giant ankB mutant mice exhibit innate social deficits combined with normal/enhanced cognitive function. Thus, giant ankB-deficiency results in gain of aberrant structural connectivity with penetrant behavioral consequences that may contribute to both high and low-function ASD and other forms of neurodiversity/divergence.

neuroscience↗

bioRxiv2018

Ankyrin-G Regulates Forebrain Connectivity and Network Synchronization via Interaction with GABARAP

GABAergic circuits are critical for the synchronization and higher order function of brain networks, and defects in this circuitry are linked to neuropsychiatric diseases, including bipolar disorder, schizophrenia, and autism. Work in cultured neurons has shown that ankyrin-G plays a key role in the regulation of GABAergic synapses on the axon initial segment and somatodendritic domain of pyramidal neurons where it interacts directly with the GABAO_SCPCAPAC_SCPCAP receptor associated protein (GABARAP) to stabilize cell surface GABAO_SCPCAPAC_SCPCAP receptors. Here, we generated a knock-in mouse model expressing a mutation that abolishes the ankyrin-G/GABARAP interaction (Ank3 W1989R) to understand how ankyrin-G and GABARAP regulate GABAergic circuitry in vivo. We found that Ank3 W1989R mice exhibit a striking reduction in forebrain GABAergic synapses resulting in pyramidal cell hyperexcitability and disruptions in network synchronization. In addition, we identified changes in pyramidal cell dendritic spines and axon initial segments consistent with compensation for hyperexcitability. Finally, we identified the ANK3 W1989R variant in a family with bipolar disorder, suggesting a potential role of this variant in disease. Our results highlight the importance of ankyrin-G in regulating forebrain circuitry and provide novel insights into how ANK3 loss-of-function variants may contribute to human disease.

neuroscience↗