Expression of Low Level of VPS35-mCherry Fusion Protein Diminishes Vps35 Depletion Induced Neuron Terminal Differentiation Deficits and Neurodegenerative Pathology, and Prevents Neonatal Death

• Main Authors: Yang Zhao, Fulei Tang, Daehoon Lee, Wen-Cheng Xiong
• Format: Article
• Language: English
• Published: MDPI AG 2021-08-01
• Series: International Journal of Molecular Sciences
• Subjects: Vps35; retromer complex; neurodegeneration; gliosis
• Online Access: https://www.mdpi.com/1422-0067/22/16/8394

Vps35 (vacuolar protein sorting 35) is a key component of retromer that consists of Vps35, Vps26, and Vps29 trimers, and sortin nexin dimers. Dysfunctional Vps35/retromer is believed to be a risk factor for development of various neurodegenerative diseases. <i>Vps35^Neurod6</i> mice, which selectively knock out Vps35 in Neurod6-Cre+ pyramidal neurons, exhibit age-dependent impairments in terminal differentiation of dendrites and axons of cortical and hippocampal neurons, neuro-degenerative pathology (i.e., increases in P62 and Tdp43 (TAR DNA-binding protein 43) proteins, cell death, and reactive gliosis), and neonatal death. The relationships among these phenotypes and the underlying mechanisms remain largely unclear. Here, we provide evidence that expression of low level of VPS35-mCherry fusion protein in <i>Vps35^Neurod6</i> mice could diminish the phenotypes in an age-dependent manner. Specifically, we have generated a conditional transgenic mouse line, <i>LSL-Vps35-mCherry</i>, which expresses VPS35-mCherry fusion protein in a Cre-dependent manner. Crossing <i>LSL-Vps35-mCherry</i> with <i>Vps35^Neurod6</i> to obtain <i>TgVPS35-mCherry</i>, <i>Vps35^Neurod6</i> mice prevent the neonatal death and diminish the dendritic morphogenesis deficit and gliosis at the neonatal, but not the adult age. Further studies revealed that the <i>Vps35-mCherry</i> transgene expression was low, and the level of <i>Vps35</i> mRNA comprised only ~5–7% of the <i>Vps35</i> mRNA of control mice. Such low level of VPS35-mCherry could restore the amount of other retromer components (Vps26a and Vps29) at the neonatal age (P14). Importantly, the neurodegenerative pathology presented in the survived adult <i>TgVps35-mCherry</i>; <i>Vps35^Neurod6</i> mice. These results demonstrate the sufficiency of low level of VPS35-mCherry fusion protein to diminish the phenotypes in <i>Vps35^Neurod6</i> mice at the neonatal age, verifying a key role of neuronal Vps35 in stabilizing retromer complex proteins, and supporting the view for Vps35 as a potential therapeutic target for neurodegenerative diseases.