DNA Polymerase Epsilon Deficiency Causes IMAGe Syndrome with Variable Immunodeficiency

Area of Science:

• Genetics
• Molecular Biology
• Developmental Biology

Background:

• Polymerase epsilon (Pol ε) is crucial for DNA replication as the primary leading-strand polymerase.
• IMAGe syndrome, previously linked to CDKN1C mutations, presents with intrauterine growth restriction, metaphyseal dysplasia, adrenal hypoplasia, and genitourinary anomalies.

Purpose of the Study:

• To identify the genetic basis of a syndrome presenting with features similar to IMAGe syndrome.
• To investigate the role of DNA replication genes in developmental disorders.

Main Methods:

• Genetic analysis of 15 individuals from 12 families with IMAGe-like features.
• Sanger sequencing and haplotype analysis to identify causative variants in the POLE gene.
• Assessment of cellular Pol ε levels and cell cycle progression.

Main Results:

• Biallelic mutations in POLE, specifically in the POLE1 gene, were identified in all affected individuals.
• A shared intronic variant (c.1686+32C>G) combined with loss-of-function variants in trans led to Pol ε deficiency and delayed S-phase progression.
• Affected individuals displayed IMAGe syndrome features, distinctive facial characteristics, and immune dysfunction.

Conclusions:

• Mutations in POLE are a second identified cause of IMAGe syndrome, expanding the genetic spectrum of this disorder.
• This finding highlights DNA replication genes as a class associated with growth restriction, adrenal dysfunction, and immunodeficiency (replisome phenotypes).
• Further research is needed to elucidate the tissue-specific developmental roles of proteins involved in DNA replication.