Figure 1.

Overview of the genotype discovered in this study

(A) Schematic of HNRNPU pre-mRNA and the three allelic haplotypes. Two closely spaced 1-bp deletions (c.1463del and c.1466del) occur on the paternal allele, with ambiguous positioning of c.1466del. Long-read phasing confirmed both variants on the paternal haplotype and mutual exclusivity at the molecular level.

(B) Pedigree of the family studied. Checkered boxes resemble mosaic occurrences of the variants c.1463del and c.1466del.

(C) Illustration of the three different allelic combinations identified in blood leukocytes. Observed allele fractions based on whole-genome sequencing differed between twins, consistent with early postzygotic segregation.