Investigating the Role of AAK1 in Satellite Cell Polarization and Muscle Regeneration

Abstract

Satellite cells (SCs), or muscle stem cells, divide in two modalities in response to injury. They can divide symmetrically to give rise to two identical daughter cells, or asymmetrically giving rise to a satellite cell and a committed progenitor cell whose role is to aid in muscle regeneration. It is a tightly controlled process that is dysregulated in Duchenne Muscular Dystrophy (DMD). An siRNA screening approach previously identified AAK1 as a gene potentially involved in regulating the asymmetric division of satellite cells. Here, we characterized the role of AAK1 using a full-knockout and conditional knockout mouse models. AAK1 has been shown to be part of the Notch pathway, and it regulates NUMB's localization in the cell. Knowing that NUMB is involved in asymmetric cell division and the activation of the Notch pathway keeps cells quiescence, we hypothesized that ablation of AAK1 has positive effects by promoting asymmetric division and further increasing muscle force. In this study, using PARD3 polarization assay, MYOG staining, proliferation analysis, and senescence evaluation, we observed that ablation of AAK1 in mdx mice led to a rescue of satellite cell polarization, a precursor to asymmetric divisions, and reduced cellular senescence, potentially rescuing the altered division kinetics of mdx SCs. In examining the physiological effects in animals, muscle force did not improve following ablation of AAK1. This outcome may be attributable to potential masking effects from tamoxifen, which is used in our conditional knockout mice, or to kinase-independent functions of AAK1 that require further investigation. Nonetheless, the data suggest that AAK1 is an important factor in satellite cell function, indicating a need for additional research to clarify its mechanisms of action.