SF3B1 and X-linked retinoschisis: However, it is widely recognized that any phenotypically defined HSC population also contains a substantial fraction of non-HSCs, and since the lymphoid lineages have not been found to be involved in the SF3B1-mutated clones, definitive evidence for recurrent SF3B1 mutations targeting true lymphomyeloid HSCs in MDS-RS is lacking (69, 70).