Impaired OTUD7A-dependent Ankyrin regulation mediates neuronal dysfunction in mouse and human models of the 15q13.3 microdeletion syndrome

Abstract

Copy number variations (CNVs) are associated with psychiatric and neurodevelopmental disorders (NDDs), and most, including the recurrent 15q13.3 microdeletion disorder, have unknown disease mechanisms. We used a heterozygous 15q13.3 microdeletion mouse model and patient iPSC-derived neurons to reveal developmental defects in neuronal maturation and network activity. To identify the underlying molecular dysfunction, we developed a neuron-specific proximity-labeling proteomics (BioID2) pipeline, combined with patient mutations, to target the 15q13.3 CNV genetic driver OTUD7A. OTUD7A is an emerging independent NDD risk gene with no known function in the brain, but has putative deubiquitinase function. The OTUD7A protein–protein interaction network included synaptic, axonal, and cytoskeletal proteins and was enriched for ASD and epilepsy risk genes (Ank3, Ank2, SPTAN1, SPTBN1). The interactions between OTUD7A and Ankyrin-G (Ank3) and Ankyrin-B (Ank2) were disrupted by an epilepsy-associated OTUD7A L233F variant. Further investigation of Ankyrin-G in mouse and human 15q13.3 microdeletion and OTUD7AL233F/L233F models revealed protein instability, increased polyubiquitination, and decreased levels in the axon initial segment, while structured illumination microscopy identified reduced Ankyrin-G nanodomains in dendritic spines. Functional analysis of human 15q13.3 microdeletion and OTUD7AL233F/L233F models revealed shared and distinct impairments to axonal growth and intrinsic excitability. Importantly, restoring OTUD7A or Ankyrin-G expression in 15q13.3 microdeletion neurons led to a reversal of abnormalities. These data reveal a critical OTUD7A-Ankyrin pathway in neuronal development, which is impaired in the 15q13.3 microdeletion syndrome, leading to neuronal dysfunction. Furthermore, our study highlights the utility of targeting CNV genes using cell type-specific proteomics to identify shared and unexplored disease mechanisms across NDDs.

JNK and PI3K signaling pathways mediate synapse formation and network spontaneous activities in primary neurons

“…The in vitro dynamics of NBs may be impact by diversified cellular mechanisms and phenomena, including synaptic scaling (28), AMPAR/NMDAR trafficking extra-synaptic receptors (29) and even ephaptic coupling (30) signaling restriction significantly affected voltage-gated ion channel activity, synaptic transmission and synaptic plasticity of neurons. Changes in the electrophysiological activity of neuronal networks after PI3K inhibition may be closely related to the alteration of these BPs (31).…”

“…Furthermore, PI3K signaling restriction significantly affected voltage-gated ion channel activity, synaptic transmission and synaptic plasticity of neurons. Changes in the electrophysiological activity of neuronal networks after PI3K inhibition may be closely related to the alteration of these BPs ( 31 ). PI3K pathway regulates GABAergic receptors related to NBD, resulting in phenotypic defect of the electrophysiology.…”

JNK and PI3K signaling pathways mediate synapse formation and network spontaneous activities in primary neurons

“…Furthermore, PI3K signaling restriction signi cantly affected voltage-gated ion channel activity, synaptic transmission and synaptic plasticity of neurons. Changes in the electrophysiological activity of neuronal networks after PI3K inhibition may be closely related to the alteration of these BPs (31). PI3K pathway regulates GABAergic receptors related to NBD, resulting in phenotypic defect of the electrophysiology.…”

The OTUD7A-Ankyrin pathway: a newly identified disease mechanism for the 15q13.3 microdeletion disorder

“…No specific treatments are available for many neurodevelopmental disorders (NDDs), including the 15q13.3 microdeletions disorder, mostly due to unknown disease mechanisms. A recent study by Unda et al [1] in Molecular Psychiatry reveals a new critical mechanism for neurodevelopment, which is impaired in the 15q13.3 microdeletion disorder.…”

“…The recent study by Unda et al [1] for the first time identified the interaction between OTUD7A and Ankyrins which regulate important aspects of dendritic spine and axon initial segment (AIS) formation. While impaired dendritic branching and spines formation in cortical neurons of Df(h15q13)/+ mice have been previously described, in this paper they provide cross-species evidence for a role of OTUD7A in this phenotype [4][5][6].…”