Nature 428, 717–723 (2004)

In this Article, we showed that Pitx1 maps to the major locus controlling pelvic reduction in sticklebacks and shows altered expression, but not altered amino-acid sequence, in a pelvic-reduced population. Owing to a technical error, Figs 3 and 4 of the Article incorrectly show results from a Pitx1 sense probe, rather than from an antisense probe. Similar staining is not observed for sense probes from other genes, raising the possibility that sticklebacks may express some endogenous antisense transcripts from the Pitx1 region.

 A new antisense probe (see Fig. 1, below) shows strong expression in the mouth, lower jaw and developing pelvis of marine larvae. Pitx1 expression appears normal in the mouth and lower jaw of the Paxton benthic population, but is completely missing in the pelvic region. No expression was detected in neuromasts, thymus, olfactory pits or tail in either population, unlike the pattern seen with the original probe. Despite these differences, our major conclusion, that pelvic reduction results from cis-acting regulatory changes in the Pitx1 locus, remains unchanged. This is because the endogenous sense transcript loses its expression along with the presumptive antisense transcript in the pelvic region of the larval progeny of fish missing the pelvis.

Figure 1: Pitx1 is expressed in the prospective pelvic region of marine but not Paxton Lake benthic sticklebacks.
figure 1

a, Whole-mount in situ hybridization shows Pitx1 expression in the mouth, jaw and pelvic buds of stage-29 marine larvae. (Details are available from the corresponding author, D.M.K.) c, d, Enlarged views of the lateral head (c) and ventral pelvis (d) of stage-29 marine larvae; arrowheads indicate sites of expression. b, e, f, In Paxton benthic larvae, Pitx1 expression is absent from the prospective pelvic region (f), but is present in the mouth and jaw (e, arrowheads). Scale bars, 1 mm; pect, pectoral fin.