Methylcellulose challenge does not increase transcriptional upregulation of CASA in kyyo1/kyyo1 embryos. (A) qPCR of bag3, flnca and flncb shows significantly increased transcription in 5 dpf kyyo1/kyyo1 embryos compared with WT controls when grown in normal (E3) media (one-way ANOVA/Dunnett's; *P<0.05, **P<0.01, n=3). Swimming in media enriched with 1% methylcellulose (Me) from 3 dpf to 5 dpf induces significant increases in bag3 and flnca transcription and reveals a trend towards increased flncb transcription in WT embryos (one-way ANOVA/Dunnett's; *P<0.05, **P<0.01, n=3). No significant changes in transcription are observed between challenged and unchallenged kyyo1/kyyo1 embryos. Error bars indicate s.e.m. (B) Fibre-typing of embryonic zebrafish muscle shows no changes to slow (green) or fast (red) muscle distribution. Images are representative of five WT and four kyyo1/kyyo1 embryos per treatment group (see Fig. S4 for full panel). (C) Representative images of birefringence analysis of whole zebrafish embryos, showing no gross muscle damage or deformation in any treatment group. These observations indicate that transcriptional changes are not secondary to gross muscle damage.