# UBE3A gain-of-function and parent-of-origin influence on neurodevelopmental phenotypes

> **NIH NIH R01** · UNIV OF NORTH CAROLINA CHAPEL HILL · 2021 · $671,160

## Abstract

PROJECT SUMMARY
UBE3A is an E3 ubiquitin ligase that targets itself and other substrates for proteasomal degradation. In the
developing brain, neuronal progenitors and immature neurons biallelically express Ube3a, but as neurons
mature, Ube3a expression becomes restricted to the maternally-inherited allele. Mutations that elevate
maternal or paternal Ube3a are linked to autism risk, but precisely how UBE3A excess impairs
neurodevelopment is unclear. Recently, we found that phosphorylation of threonine 485 (T485) inhibits
UBE3A ubiquitin ligase activity. UBE3A T485 phosphorylation initiates embryonically and peaks at birth,
suggesting that phosphorylation might protectively limit UBE3A activity during early cortical development.
Additionally, we found that an autism-linked de novo mutation in UBE3A (T485A) disrupts this phosphorylation
site, effectively locking UBE3A always-on. We engineered a mouse that precisely models this human UBE3A
T485A mutation, allowing us to evaluate how this novel gain-of-function mutation affects brain and behavioral
phenotypes when inherited maternally or paternally. In preliminary studies, we found that cortical thickness
and brain weight were significantly increased at birth in all three Ube3a T485A genotypes (paternal, maternal,
homozygous). Mutations in other autism-linked genes increase brain weight to a similar extent. These
findings suggest a novel and previously unrecognized prenatal function for UBE3A in brain development. All
three Ube3a T485A mutant genotypes also had behavioral phenotypes consistent with neurodevelopmental
disorders. Since little is known about how UBE3A impairs brain function at any age, we performed unbiased
proteomics to identify brain-relevant substrates. Our preliminary proteomics data link UBE3A directly to the
proteasome, a structure that can influence the cell cycle and signaling pathways important for brain
development. These and other data lead us to hypothesize that UBE3A T485A alters the balance of cell
proliferation and differentiation during brain development, in part by impairing proteasome function,
and contributes to autism-associated phenotypes later in life. The experiments in this proposal will
rigorously demonstrate that (1) UBE3A T485A alters the balance of progenitor proliferation and differentiation
in the cerebral cortex, (2) parent-of-origin inheritance of Ube3a T485A influences autism-related brain and
behavioral phenotypes, and (3) UBE3A T485A interacts with the proteasome and impairs proteasome function
in the brain. Unbiased proteomics experiments will identify brain-relevant substrates of UBE3A, and broaden
our understanding of which molecular pathways are affected by gain-of-function mutations that enhance
UBE3A activity.

## Key facts

- **NIH application ID:** 10196989
- **Project number:** 5R01MH120229-03
- **Recipient organization:** UNIV OF NORTH CAROLINA CHAPEL HILL
- **Principal Investigator:** BENJAMIN D PHILPOT
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $671,160
- **Award type:** 5
- **Project period:** 2019-09-01 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10196989

## Citation

> US National Institutes of Health, RePORTER application 10196989, UBE3A gain-of-function and parent-of-origin influence on neurodevelopmental phenotypes (5R01MH120229-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10196989. Licensed CC0.

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