NEIL1 and NEIL2 DNA glycosylases protect neural crest development against mitochondrial oxidative stress.

Dandan Han,Medhavi Mallick,Christof Niehrs,Annika Von Seggern,Katrin M Schüle,Laura Krebs,Emil Karaulanov,Lars Schomacher,Michael U Musheev

doi:10.7554/elife.49044

Dandan Han, Medhavi Mallick + Show 7 more

Open Access

https://doi.org/10.7554/elife.49044

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Abstract

Base excision repair (BER) functions not only in the maintenance of genomic integrity but also in active DNA demethylation and epigenetic gene regulation. This dual role raises the question if phenotypic abnormalities resulting from deficiency of BER factors are due to DNA damage or impaired DNA demethylation. Here we investigate the bifunctional DNA glycosylases/lyases NEIL1 and NEIL2, which act in repair of oxidative lesions and in epigenetic demethylation. Neil-deficiency in Xenopus embryos and differentiating mouse embryonic stem cells (mESCs) leads to a surprisingly restricted defect in cranial neural crest cell (cNCC) development. Neil-deficiency elicits an oxidative stress-induced TP53-dependent DNA damage response, which impairs early cNCC specification. Epistasis experiments with Tdg-deficient mESCs show no involvement of epigenetic DNA demethylation. Instead, Neil-deficiency results in oxidative damage specific to mitochondrial DNA, which triggers a TP53-mediated intrinsic apoptosis. Thus, NEIL1 and NEIL2 DNA glycosylases protect mitochondrial DNA against oxidative damage during neural crest differentiation.

Highlights

DNA repair is crucial to maintain genomic integrity in the face of exogenous and endogenous challenges
We showed previously that in Xenopus embryos knockdown of Neil2 with an antisense morpholino oligonucleotide induces head and tail abnormalities at tailbud stage, which are caused by impaired cranial neural crest cell specification at neurula stage (Schomacher et al, 2016)
We investigated if the role of NEIL DNA glycosylases to protect against reactive oxygen species (ROS) damage and safeguard neural crest development is conserved in mammals, and used mouse embryonic stem cells as a model system

Summary

Introduction

DNA repair is crucial to maintain genomic integrity in the face of exogenous and endogenous challenges. Removing APEX1, which is involved in DNA damage repair, had similar effects to the removal of NEIL1 and NEIL2, while removing TDG, which only works in demethylation, did not This indicates that NEIL1 and NEIL2’s role in DNA damage repair is likely necessary for stem cells to become cranial neural crest cells. These results suggest that antioxidants, which are molecules that protect the cells from the damaging oxygen derivatives, may help prevent deformities in the face and skull This theory could be tested using mice that do not produce proteins involved in base excision repair, which could be derived from the cells lacking NEIL1 and NEIL2. Our study contributes to the understanding of aberrant cNCC development, the root cause of congenital craniofacial malformations (Wilkie and MorrissKay, 2001)

Results

Discussion

Materials and methods

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