Bi-allelic MCM10 variants associated with immune dysfunction and cardiomyopathy cause telomere shortening

Ryan M Baxley,Jeanette Gowen Cook,Grant S Stewart,Liangjun Wang,Debashree Basu,Eric A Hendrickson,Alistair T Pagnamenta,Megan Schmit ,Jenny C Taylor ,Jacob P Matson ,Hideki Aihara,Adam Harvey ,Marissa K Oram,John M Taylor ,Emily M Mace,Wendy Leung,Colette B Rogers,Edward Blair,Hugh Watkins,Lulu Yin,Elizabeth Ormondroyd,Hélène Dreau ,Judith Craft ,Jordan S Orange,Jack Hedberg,Anja‐Katrin Bielinsky

doi:10.1038/s41467-021-21878-x

Abstract

Minichromosome maintenance protein 10 (MCM10) is essential for eukaryotic DNA replication. Here, we describe compound heterozygous MCM10 variants in patients with distinctive, but overlapping, clinical phenotypes: natural killer (NK) cell deficiency (NKD) and restrictive cardiomyopathy (RCM) with hypoplasia of the spleen and thymus. To understand the mechanism of MCM10-associated disease, we modeled these variants in human cell lines. MCM10 deficiency causes chronic replication stress that reduces cell viability due to increased genomic instability and telomere erosion. Our data suggest that loss of MCM10 function constrains telomerase activity by accumulating abnormal replication fork structures enriched with single-stranded DNA. Terminally-arrested replication forks in MCM10-deficient cells require endonucleolytic processing by MUS81, as MCM10:MUS81 double mutants display decreased viability and accelerated telomere shortening. We propose that these bi-allelic variants in MCM10 predispose specific cardiac and immune cell lineages to prematurely arrest during differentiation, causing the clinical phenotypes observed in both NKD and RCM patients.

Highlights

Minichromosome maintenance protein 10 (MCM10) is essential for eukaryotic DNA replication
Compound heterozygous MCM10 variants were identified in unrelated patients that presented with NKD or fetal restrictive cardiomyopathy (RCM) with thymic and splenic hypoplasia (Table 1; all genetic notation is in reference to MCM10 transcript NM_018518.5)
We have demonstrated that MCM10 is haploinsufficient in HCT116 and hTERT-immortalized RPE-1 cell lines

Summary

Introduction

Minichromosome maintenance protein 10 (MCM10) is essential for eukaryotic DNA replication. Terminally-arrested replication forks in MCM10deficient cells require endonucleolytic processing by MUS81, as MCM10:MUS81 double mutants display decreased viability and accelerated telomere shortening We propose that these bi-allelic variants in MCM10 predispose specific cardiac and immune cell lineages to prematurely arrest during differentiation, causing the clinical phenotypes observed in both NKD and RCM patients. We identified human germline MCM10 variants in two unrelated families that were associated with distinct phenotypes: natural killer (NK) cell deficiency (NKD)[12] and restrictive cardiomyopathy (RCM) associated with thymic and splenic hypoplasia. We demonstrate that human MCM10 is haploinsufficient in transformed HCT116 and non-transformed telomerase immortalized hTERT RPE-1 cells (referred to subsequently as RPE-1) These phenotypes were more severe in HCT116 cells, disrupting normal cell cycle distribution and affecting global DNA synthesis due to decreased origin firing. Our results revealed that MCM10 is critical for human telomere replication and suggest that defective telomere maintenance caused both MCM10-associated NKD and RCM

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Results

Conclusion