Table 1. MO specificity for islet2a.

	Number of Mismatches with Target
Gene	T-MO	Ctl MO	Sp-MO
islet1	0/25	5/25	0/25
islet2a	14/25	15/25	12/25
islet2b	9/25	10/25	8/25
isl1l	18/25	17/25	19/25

For islet1 and islet2b, the regions corresponding to the islet2a sequences targeted by the MO were identified and compared. We include isl1l, identified as the duplicate of islet1 on the basis of syntenic relationships [28, 29]. However, zebrafish embryos express little to no isl1l mRNA (zfin.org). Further, the predicted Isl1l amino acid sequence shares only 47% identity with islet1. S1 Table presents the sequences for the regions of interest in the islet genes and the sequence of the intended MO targets, to show the distribution of the mismatches.