Generation of a Mouse Model Lacking the Non-Homologous End-Joining Factor Mri/Cyren.

Sergio Castañeda-Zegarra,Valentyn Oksenych,Antonio Sarno,Wei Wang,Mengtan Xing,Qindong Zhang,Julia Werner,Nina-Beate Liabakk,Amin Alirezaylavasani,Ping Ji,Magnar Bjørås,Øystein Røsand,Raquel Gago-Fuentes,Camilla Huse

doi:10.3390/biom9120798

Abstract

Classical non-homologous end joining (NHEJ) is a molecular pathway that detects, processes, and ligates DNA double-strand breaks (DSBs) throughout the cell cycle. Mutations in several NHEJ genes result in neurological abnormalities and immunodeficiency both in humans and mice. The NHEJ pathway is required for V(D)J recombination in developing B and T lymphocytes, and for class switch recombination in mature B cells. The Ku heterodimer formed by Ku70 and Ku80 recognizes DSBs and facilitates the recruitment of accessory factors (e.g., DNA-PKcs, Artemis, Paxx and Mri/Cyren) and downstream core factor subunits X-ray repair cross-complementing group 4 (XRCC4), XRCC4-like factor (XLF), and DNA ligase 4 (Lig4). Accessory factors might be dispensable for the process, depending on the genetic background and DNA lesion type. To determine the physiological role of Mri in DNA repair and development, we introduced a frame-shift mutation in the Mri gene in mice. We then analyzed the development of Mri-deficient mice as well as wild type and immunodeficient controls. Mice lacking Mri possessed reduced levels of class switch recombination in B lymphocytes and slow proliferation of neuronal progenitors when compared to wild type littermates. Human cell lines lacking Mri were as sensitive to DSBs as the wild type controls. Overall, we concluded that Mri/Cyren is largely dispensable for DNA repair and mouse development.

Highlights

Non-homologous end-joining (NHEJ) is a molecular pathway that recognizes, processes, and repairs DNA double-strand breaks (DSBs) throughout the cell cycle [1]
Mice lacking either X-ray repair cross-complementing group 4 (XRCC4) or ligase 4 (Lig4) demonstrate p53- and Ku70 andKu80 form heterodimer (Ku)-dependent embryonic lethality, which correlates with massive neuronal apoptosis in the central nervous system [1,13,14,15,16,17]
MRI-deficient (M−/− ) mice were generated through a CRISPR/Cas9 gene-editing approach in 2017 by Horizon Discovery (Saint Louis, MO, USA) upon request from the Oksenych group (IKOM, Faculty of Medicine and Health Science, NTNU, Trondheim, Norway)

Summary

Introduction

Non-homologous end-joining (NHEJ) is a molecular pathway that recognizes, processes, and repairs DNA double-strand breaks (DSBs) throughout the cell cycle [1]. Mice lacking Ku70, Ku80, DNA-PKcs, or Artemis possess severe combined immunodeficient phenotype (SCID), while inactivation of both alleles of the Xlf gene results in 2–3-fold reduced B and T cell counts [1,4,5,6,7]. XLF is functionally redundant in mouse development with Mri [20], recombination activating gene 2, RAG2 [21], and a number of DNA damage response (DDR) factors including Ataxia telangiectasia mutated (ATM) [6], histone H2AX [6,22], mediator of DNA damage checkpoint protein 1 (MDC1) [10], and p53-binding factor (53BP1) [7,23]

Methods

Results

Discussion

Conclusion