Non-Homologous End Joining Factors XLF, PAXX and DNA-PKcs Maintain the Neural Stem and Progenitor Cell Population

Raquel Gago-Fuentes,Valentyn Oksenych

doi:10.3390/biom11010020

Raquel Gago-Fuentes, Valentyn Oksenych

Open Access

https://doi.org/10.3390/biom11010020

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Abstract

Non-homologous end-joining (NHEJ) is a major DNA repair pathway in mammalian cells that recognizes, processes and fixes DNA damage throughout the cell cycle and is specifically important for homeostasis of post-mitotic neurons and developing lymphocytes. Neuronal apoptosis increases in the mice lacking NHEJ factors Ku70 and Ku80. Inactivation of other NHEJ genes, either Xrcc4 or Lig4, leads to massive neuronal apoptosis in the central nervous system (CNS) that correlates with embryonic lethality in mice. Inactivation of either Paxx, Mri or Dna-pkcs NHEJ gene results in normal CNS development due to compensatory effects of Xlf. Combined inactivation of Xlf/Paxx, Xlf/Mri and Xlf/Dna-pkcs, however, results in late embryonic lethality and high levels of apoptosis in CNS. To determine the impact of NHEJ factors on the early stages of neurodevelopment, we isolated neural stem and progenitor cells from mouse embryos and investigated proliferation, self-renewal and differentiation capacity of these cells lacking either Xlf, Paxx, Dna-pkcs, Xlf/Paxx or Xlf/Dna-pkcs. We found that XRCC4-like factor (XLF), DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and paralogue of XRCC4 and XLF (PAXX) maintain the neural stem and progenitor cell populations and neurodevelopment in mammals, which is particularly evident in the double knockout models.

Highlights

Double-strand DNA breaks (DSBs) are common DNA damage events that threaten the stability of our genome
DSBs can be repaired by homologous recombination (HR), classical non-homologous end-joining (C-Non-homologous end-joining (NHEJ), or NHEJ) and alternative end-joining (A-EJ, known as backup end joining, or microhomology-mediated end joining) [1,2,3,4]
Our data further highlighted this observation, and our findings suggest that the DNA-PKcs is required for neural stem and progenitor cells (NSPCs) proliferation and self-renewal capacities, its role is partially compensated by X-ray repair cross-complementing factor 4 (XRCC4)-like factor (XLF) (Figure 2B,C)

Summary

Introduction

Double-strand DNA breaks (DSBs) are common DNA damage events that threaten the stability of our genome. DSBs can be repaired by homologous recombination (HR), classical non-homologous end-joining (C-NHEJ, or NHEJ) and alternative end-joining (A-EJ, known as backup end joining, or microhomology-mediated end joining) [1,2,3,4]. C-NHEJ acts throughout the entire cell cycle, sealing directly the broken ends and is the predominant repair pathway in mammalian cells [3,5]. A-EJ is often microhomology-mediated and more obvious in the absence of classical NHEJ [6]. C-NHEJ involves recognition of the DSBs by Ku70/Ku80 heterodimer (Ku), which in turn recruits DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to form a DNA-PK holoenzyme complex that protects free DNA ends. Ligation of the Biomolecules 2021, 11, 20.

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