Based on the tissue-autonomous role of IdoA in CS/DS, we propose that DS-epi1 knockdown affects PGs that are synthesized in the CNC. The integrin α5β1 heterodimer (encoded by the Itga5 and Itgb1 genes), members of the syndecan (Sdc) family, Bgn, Vcan and CD44 have been presented as CS or CS/DS PGs, some of which have functions in cell adhesion (Thelin et al., 2013). In CNC explants of stage 18 embryos, qPCR indicated abundant mRNA levels of Itga5, Itgb1 and Sdc4, whereas Sdc1, Sdc3, Bgn, Vcan and CD44 were not expressed or were only expressed at very low levels (Fig. 7A). We did not identify changes in the Itga5, Itgb1 or Sdc4 mRNA levels in the Dse-morphant compared with the Dse-5MM-MO-injected control CNC cells (Fig. 7B). Moreover, western blot analysis demonstrated similar levels of integrin β1 protein in the DS-epi1+ and DS-epi1-deficient NC- and epidermis-enriched explants (Fig. 7C), which suggests that reduced IdoA levels do not alter the expression of integrins. In some mammalian cell types, it has been reported that the α5 and β1 integrin subunits (Veiga et al., 1997;
