Extended Data Figure 2. Invasion process across Dantu genotype groups studied by timelapse video microscopy.
(a) RBC detachment force from a merozoite was measured using optical tweezers across genotype groups. RBCs attached to merozoites were pulled using optical traps, and the adhesive forces at the merozoite-RBC interface were quantified by evaluating the elastic morphological response of the RBC as it resisted merozoite detachment. Mean and standard deviation (SD) in Supplementary Table 3. Six biologically independent samples per genotype group were tested obtaining 21 events for non-Dantu, 19 for Dantu heterozygote, and 24 for Dantu homozygote. Importantly, the experimentalist was blinded to the RBC genotype group. The median is indicated by the middle red line in the boxplots, with the 25th and 75th percentiles indicated by the tops and bottoms of each plot, while whiskers denote total data range. If the median is not centered in the box, it shows sample skewness. Pairwise comparisons between genotype groups were performed using the two-sided Mann-Whitney U test. (b) The degree to which merozoites deformed RBCs during invasion was given by a simplified four-point deformation scale (0, 1, 2, and 3), based on the most extreme degree of deformation achieved (Weiss et al., PLoS Pathog 2015). The degree of deformation was compared across genotype groups with no significant difference noticed, and between successful and failed invasions. The percentage of RBCs undergoing strong deformations (score 2/3) is significantly higher in case of successful invasions, while RBCs that were contacted but not invaded experience weak deformations (score 0/1). Data from 155 cells for non-Dantu, 191 for Dantu heterozygote, and 233 for Dantu homozygote. Number of successfully invaded cells: 53 for non-Dantu, 43 for Dantu heterozygote, and 41 for Dantu-homozygote. The visual assessment was done with blinded data by two different experimentalists. (c) Successful invasions are usually followed by a reversible echinocyte phase that lasts between 5 and 11 minutes (Gilson and Crabb, Int J Parasitol, 2009), until the recovery of newly infected RBC biconcave shape. The time of echinocytosis was in agreement with literature and not significantly different across genotype groups. Data from 53 cells non-Dantu, 43 Dantu heterozygote, and 41 Dantu-homozygote.