Neuron-specific deletion of presenilin enhancer2 causes progressive astrogliosis and age-related neurodegeneration in the cortex independent of the Notch signaling

Abstract

Introduction: Presenilin enhancer2 (Pen-2) is an essential subunit of γ-secretase, which is a key protease responsible for the cleavage of amyloid precursor protein (APP) and Notch. Mutations on Pen-2 cause familial Alzheimer disease (AD). However, it remains unknown whether Pen-2 regulates neuronal survival and neuroinflammation in the adult brain.

Methods: Forebrain neuron-specific Pen-2 conditional knockout (Pen-2 cKO) mice were generated for this study. Pen-2 cKO mice expressing Notch1 intracellular domain (NICD) conditionally in cortical neurons were also generated.

Results: Loss of Pen-2 causes astrogliosis followed by age-dependent cortical atrophy and neuronal loss. Loss of Pen-2 results in microgliosis and enhanced inflammatory responses in the cortex. Expression of NICD in Pen-2 cKO cortices ameliorates neither neurodegeneration nor neuroinflammation.

Conclusions: Pen-2 is required for neuronal survival in the adult cerebral cortex. The Notch signaling may not be involved in neurodegeneration caused by loss of Pen-2.

Keywords: Alzheimer disease; astrogliosis; microgliosis; neurodegeneration; presenilin enhancer2.