CD34 and myelodysplastic syndrome: In this study, firstly we have screened a large cohort of MDS cases with del(5q) for mutations in CSNK1A1. Secondly, we have investigated the impact of CSNK1A1 haploinsufficiency and mutation on the expression of β‐catenin‐related genes in the CD34+ cells from MDS patients with del(5q) using GEP.