Fig. 5

hmgb genes are broadly expressed at early developmental stages in largely overlapping patterns. Some representative ISH pictures (40× magnification) are shown to summarize the expression of zebrafish hmgb genes. Embryos subject to short staining were chosen when expression details could not be clearly visualized upon prolonged staining (panels F, G and I); staining levels are therefore not directly comparable, unless specified. (A–D) At the earliest developmental stages, all hmgb genes are ubiquitously expressed although their expression levels are different: the hmgb2a/2b signals are much higher (B and D) while all the other genes are less expressed (exemplified in A and C) epi, epiboly. (E and F) At tailbud stage, only hmgb2a transcripts are under-represented at the midline (compare white arrowheads in F and E). (G and H) At 6–8 somites all hmgb genes are ubiquitously expressed in the whole embryo, excluding the notochord (G); only hmgb1a probe preferentially mark somites subdomains (H, white arrow). (I and L) During late somitogenesis, hmgb genes are ubiquitously expressed, with the exception of notochord and somites (grey arrows), but hmgb3a is not expressed in the eyes (compare white asterisk in inset L with the one in I).