Sickle cell disease is a genetic disorder that is caused by a single amino acid substitution in the β-globin subunit of haemoglobin in red blood cells (RBCs). This results in the formation of deoxygenated haemoglobin fibrils, which in turn affect RBC morphology and membrane elasticity. Thus, RBC morphology is used as a predictor of sickle cell disease in the clinic, but this mainly relies on data obtained in 2D. In this Tool and Techniques article (p. 3511) Carolyn Larabell, Wah Chiu and co-workers now develop a new approach to characterise RBC morphology in 3D throughout the sickling process by using cryogenic soft X-ray tomography (SXT). By imaging and volume-reconstructing several hundreds of RBCs, they were able to classify sickle RBCs based on the number of protrusions they form, with those in the severe category exhibiting between two and four protrusions. Using this classification system, the authors then investigate the effect of inhibition of sphingosine kinase 1 (Sphk1) by compound 5C, because Sphk1 signalling has been shown to contribute to the disease and its inhibition can reduce RBC sickling in mice. Indeed, treatment of RBCs with 5C results in a shift in protrusion numbers towards the less severe categories of sickling, which, as confirmed here, also resulted in an increase in erythrocyte survival time. Thus, this study not only presents SXT as a promising tool to categorise sickling disease progression, but also illustrates its usefulness in assessing the molecular basis of potential therapeutics.
- © 2016. Published by The Company of Biologists Ltd