UBE3A isoform-selective and non-selective contributions to Angelman syndrome phenotypes

Area of Science:

• Neuroscience
• Genetics
• Developmental Biology

Background:

• Angelman syndrome (AS) is a neurodevelopmental disorder resulting from UBE3A gene loss.
• The UBE3A gene produces three human isoforms: one nuclear and two cytoplasmic.
• The nuclear-enriched isoform is crucial for AS phenotypes, but the role of the predominant cytoplasmic isoform is unclear.

Purpose of the Study:

• To investigate whether the cytoplasmic UBE3A isoform can rescue AS phenotypes.
• To determine if AS-related epilepsy is linked to the loss of nuclear UBE3A function specifically.

Main Methods:

• Developed a mouse model overexpressing the cytoplasmic UBE3A isoform (mIso2-OE).
• Crossed mIso2-OE mice with AS mice to create WT, mIso2-OE, AS, and AS/mIso2-OE genotypes.
• Assessed behavioral deficits, kindling-induced epileptogenesis, and perineuronal net (PNN) accumulation.

Main Results:

• Overexpression of the cytoplasmic UBE3A isoform rescued most AS-related behavioral deficits.
• Epilepsy and PNN accumulation in AS mice were not rescued by cytoplasmic UBE3A isoform overexpression.
• AS-associated epilepsies appear linked to the loss of the nuclear-enriched UBE3A isoform.

Conclusions:

• Many AS phenotypes may result from a general reduction in UBE3A levels.
• AS-associated epilepsy is likely caused by the loss of the nuclear-specific UBE3A isoform.
• Findings may guide future gene therapy strategies for Angelman syndrome.