Sox17f/f mutants exhibit a significant threefold increase in HE ratios indicating increased haematopoietic output, in addition to significantly increased labelled hemogenic cluster populations (CD31+CD41+Td+) and maturing HSPC populations (CD31+CD117+Sca1+CD45+Td+; Fig. 2c–f). The gene discussed is PECAM1; the disease is hereditary elliptocytosis.