Mcl-1 is a critical survival factor in neural precursor cells of the adult mammalian brain

Abstract

Although the aetiology of many neurodegenerative diseases differ, they all share a common feature in that they result in neural cell death. Neural precursor cells (NPCs) of the adult brain are thought to be capable of regenerating the injured brain by replacing cells that are injured or have died. NPCs of the adult brain are maintained in a balance of proliferation and death; however, little is known about the molecular mechanisms that regulate these processes. As Mcl-1 is a critical survival factor for NPCs in the embryonic brain, I questioned whether Mcl-1 regulates the survival of adult NPCs. To determine whether Mcl-1 is expressed in adult NPCs, I used BrdU to identify different subpopulations of NPCs based on their proliferation kinetics. In doing so, I demonstrated that Mcl-1 is expressed in both the neural stem and neural progenitor populations of the adult subventricular zone (SVZ). To determine the role of Mcl-1 in adult NPCs, I used the Cre/lox conditional knockout system to conditionally knock out Mcl-1 in adult NPCs. To assess Mcl-1 loss-of-function in NPCs in vitro, I first drove Cre recombinase off the chicken P-actin promoter and stained the cultures with Nestin. Secondly, I drove Cre recombinase off the Nestin promoter (NesCre), which resulted in Cre expression specifically in NPCs. In both experiments, Mcl-1 loss-of-function resulted in a 2-fold increase in apoptosis in Cre transfected Mcl-1 f/f NPCs. When Mcl-1 loss-of-function was characterized in vivo, there was a 2-fold increase in apoptosis in Cre transfected Mcl-1 f/f NPCs. Finally, Mcl-1 gain-of-function was assessed, in vitro, which resulted in a 2-fold reduction of apoptosis in Nestin+ NPCs. Collectively, these data demonstrate that Mcl-1 is a prosurvival factor in adult NPCs. Therefore, Mcl-1 gain-of-function may lead to an expansion of the adult NPCs, which could offer a putative therapy for neurodegenerative conditions and ultimately facilitate neural regeneration.