CECILIA DOMINGUEZ CONDE, United Kingdom

Wellcome Sanger Institute Cellular Genetics

Presenter of 1 Presentation

Oral Communications DNA repair disorders

POLYMERASE DELTA DEFICIENCY CAUSES SYNDROMIC IMMUNODEFICIENCY WITH REPLICATIVE STRESS

Lecture Time
11:40 - 11:50
Room
Gold
Date
20.09.2019, Friday
Session Time
11:00 - 12:40
Presentation Topic
DNA repair disorders

Abstract

Background and Aims

Polymerase δ is essential for eukaryotic genome maintenance and synthesizes DNA at the leading and the lagging strand. The polymerase δ complex is a heterotetramer comprising the catalytic subunit POLD1 and the accessory subunits POLD2, POLD3 and POLD4. To date, no germline biallelic mutations affecting this complex have been reported in humans.

Methods

The reported patients were genetically diagnosed by exome sequencing or target panel sequencing. The cellular phenotype of primary patient cells was defined using a combination of flow cytometry, immunoblotting and immunofluorescence analysis to assess cell proliferation, cell cycle progression, the activation of DNA repair pathways and the dynamics of replication fork progression. Furthermore, we used overexpression systems to assess mutant stability and interactions as well as recombinant expression of polymerase δ for in vitro assessment of the polymerase enzymatic activity.

Results

Cells from polymerase d-deficient patients showed impaired cell cycle progression and replication-associated DNA lesions, reversible upon overexpression of polymerase δ. The mutations affected the stability and interactions within the polymerase δ complex or its intrinsic polymerase activity.

Conclusions

In patients from two independent pedigrees, we here identify a novel syndrome with reduced functionality of the polymerase d complex caused by germline biallelic mutations in POLD1 or POLD2, as the underlying etiology of a previously unknown, autosomal-recessive syndrome combining replicative stress, neurodevelopmental abnormalities and immunodeficiency. Our discovery of human polymerase δ deficiency identifies the central role of this complex in prevention of replication-related DNA lesions with particular relevance to adaptive immunity.

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