RAB31 expression in platelets from RUNX1-haplodeficient patients (P) and normal control subjects (N). Platelet RAB31 messenger RNA (mRNA) levels by quantitative PCR in the index patient (P1) (A) or in 2 siblings (P2 and P3) from an unrelated family (B) with a RUNX1 mutation compared with 5 normal subjects (N1-N5). mRNA levels normalized to glyceraldehyde-3-phosphate dehydrogenase expression. (C) Platelet RAB31 by immunoblotting in 3 patients (P1-P3) and 5 healthy subjects (N1-N5). Protein expressions are shown in the ratio of RAB31 to actin.