Fig. 4

unc45-derived transgenes phenocopy the response to misfolded myosin. a Scheme representing the 3.3-kb sequence of the unc45b gene that recapitulates muscle-specific expression (-1.8unc45b:tfp) and its derivatives -505/-310(unc45b)gata2:gfp (Figure S3c in Additional file 8, construct 16) and -505/-405(unc45b)gata2:gfp (Figure S3i in Additional file 8, construct 31). All positions are indicted relative to the A of the ATG start codon (+1) of unc45b. Red bars represent the untranslated region (UTR). The first exon is indicated in brown. Blue bars represent the gata2 minimal promoter. Green bars represent TFP or green fluorescent protein (GFP) reporter genes. The pink vertical bar indicates the heat shock element (HSE); the yellow vertical bar indicates the Mef2 binding motif. b–e Deficiency in myosin folding activates the -1.8unc45b:tfp construct. Tg(-1.8unc45b:tfp) embryos injected with either hsp90a-mo (c), unc45b-mo (d) or smyd1b-mo (e) show an increase of TFP compared with the uninjected control (b). f, g In comparison with transgenic wild-type sibling embryos (f), expression of Tg(-1.8unc45b:tfp) in unc45b mutant embryos (g) is elevated. This confirms the results from the morpholino knock-down experiments (b, d). h, iTg(-505/-310(unc45b)gata2:gfp) embryos injected with hsp90a-mo (i) show an increase of GFP expression compared with the uninjected control (h). j, k Embryos injected with the construct -505/-405(unc45b)gata2:gfp show no GFP expression (j). However, co-injection with unc45b-mo triggers GFP expression in skeletal muscle (k). Thus, this transgene containing only 100 bp of the unc45b upstream region from -505 to -405 lost the basal muscle expression but retained the response to misfolded myosin. All embryos are 72 h old; anterior left, dorsal up