Identification of biallelic POLA2 variants in two families with an autosomal recessive telomere biology disorder.

POLA2 encodes the accessory subunit of DNA polymerase α (polα)/primase, which is crucial for telomere C-strand fill-in. Incomplete fill-in of the C-rich telomeric strand after DNA replication has been proposed as a mechanism for Coats plus syndrome, a phenotype within the broader spectrum of telomere biology disorders (TBD). Coats plus syndrome has so far been associated with pathogenic variants in POT1, CTC1, and STN1. Here we report the findings of biallelic deleterious rare variants in POLA2 gene detected by whole genome sequencing and segregation analysis in five young adults from two unrelated families. All five individuals displayed abnormally short telomeres and a clinical phenotype suggesting a TBD disorder with Coats plus features including retinal and gastrointestinal telangiectasias. Our results suggest POLA2 as a novel autosomal recessive gene for a TBD with Coats plus features.