# Molecular Mechanisms of Developmental Spine Remodeling

> **NIH NIH R56** · UNIV OF NORTH CAROLINA CHAPEL HILL · 2022 · $388,750

## Abstract

Mechanisms of spine and synaptic remodeling in the prefrontal cortex (PFC) underlie critical functions of
working memory, cognitive flexibility, and sociability yet are incompletely understood. Impaired spine elimina-
tion during brain development likely contributes to increased spine and synapse density in autism spectrum
disorders (ASD). We identified a novel mechanism of selective spine pruning in which Semaphorin-3 receptor
complexes, comprising L1 adhesion molecules, Neuropilins, and PlexinAs, promote activity-dependent spine
elimination in the juvenile brain through Rho family GTPases. All L1-CAMs bind Ankyrin B (AnkB), an actin-
spectrin adaptor encoded by the high confidence ASD gene Ank2. A role for AnkB in spine regulation has not
been explored, because mouse models with germline deletion of the Ank2 gene are lethal. We generated a
novel, inducible Ank2 mouse line (Nex1Cre-ERT2:Ank2flox:EGFPflox) in which Ank2 can be deleted in postmitot-
ic pyramidal neurons (PNs) during postnatal development, circumventing lethality. The AnkB conditional mu-
tant resembles multiple human de novo ASD variants lacking both principal AnkB isoforms (220 and 440 kDa).
Preliminary results reveal elevated spine density and altered excitatory neurotransmission in AnkB mutant
PFC. We will investigate the hypothesis that AnkB regulates spine pruning and synapse elimination in develop-
ing PFC networks, and that genetic deficiency of AnkB disrupts these mechanisms at sensitive postnatal stag-
es, impacting cortical excitability and behaviors relevant to ASD.
 In Aim 1 Nex1Cre-ERT2:Ank2flox:EGFPflox mice will be analyzed to delineate how AnkB gene dosage in de-
veloping and adult PNs of each sex alters dendritic spine regulation and levels of excitatory and inhibitory syn-
apses in the PFC. A new mouse model Nex1Cre-ERT2:Ank2 exon37flox:EGFPflox deleting only AnkB-440 will
be generated to distinquish isoform-specific roles. In Aim 2 a novel molecular rescue assay in Ank2-deficient
neuronal cultures will interrogate AnkB function in Semaphorin-3 induced spine remodeling, receptor clustering
and intracellular signaling. Selected human de novo Ank2 missense mutations will be analyzed for impaired
L1-CAM and β-spectrin binding and signaling leading to spine pruning. Super-resolution microscopy will be
employed to explore a potentially new role for AnkB in organizing synaptic nanodomains in spines. In Aim 3
the hypothesis that AnkB deficiency increases cortical excitability will be tested by electrophysiological record-
ing of layer 2/3 PNs in cortical slices from normal and AnkB-deficient mice of each sex. Excitatory and inhibito-
ry transmission will be compared, and synaptic inputs mapped by laser scanning photo-stimulation. Behavioral
testing of Ank2 mutant mice will address roles for AnkB in sociability, reversal learning, and working memory.
 This project is expected to have significant impact, because it will illuminate novel molecular mechanisms
for regulating...

## Key facts

- **NIH application ID:** 10660377
- **Project number:** 2R56MH113280-06A1
- **Recipient organization:** UNIV OF NORTH CAROLINA CHAPEL HILL
- **Principal Investigator:** Patricia F Maness
- **Activity code:** R56 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $388,750
- **Award type:** 2
- **Project period:** 2017-04-01 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10660377

## Citation

> US National Institutes of Health, RePORTER application 10660377, Molecular Mechanisms of Developmental Spine Remodeling (2R56MH113280-06A1). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/10660377. Licensed CC0.

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