There was an error published in Development139, 783-792.

The left and right designations were inadvertently switched in Fig. 7. In Fig. 7C, the y-axis should refer to the right, not left, coelomic pouch. The corrected Fig. 7 legend is shown below. In addition, on p. 789 (lines 46 and 50) and p. 790 (line 58), where a 3/5 left-right distribution is referred to, the correct designation should be 5/3 left-right.

The authors apologise to readers for this mistake.

Fig. 7. Inhibiting ABC transporter activity in the whole sea urchin embryos causes small micromeres to become more randomly segregated. (A,B) MIPs of embryos injected with mCherry-SpVasa mRNA to localize the small micromeres in red, and treated with 0.3% DMSO, 5 μM MK571 or 3 μM PSC833 in (A) representative embryos and (B) coelomic pouches. Images combined with DIC channel in 96- to 110-hour-old plutei. White arrowheads indicate the right coelomic pouch. Numbers in B indicate the number of Vasa-positive cells counted in each right coelomic pouch. (C) Number and percent of small micromeres in the right coelomic pouch of mCherry-Sp-Vasa overexpressing embryos treated with DMSO (n=45), MK571 (n=38) or PSC833 (n=44). (D) Average percent (±s.e.m., ≥4 embryos measured per batch) of embryos with right/left coelomic pouch distributions outside of either 3/5 or 4/4 (right pouch/left pouch) from eight batches for the DMSO treatment, six batches for MK571 and seven batches for PSC833. Asterisk indicates values significantly different from the DMSO control (ANOVA, P≤0.5 with square root transformed values). Scale bars: 25 ▯m in A; 10 μm in B.