Fig. 4

Quantitative expression analysis of hmgb genes. Real-Time RT-PCR was performed using cDNAs retrotranscribed from RNA samples of adult ovary and a series of developmental stages with TaqMan probes specific for zf hmgb genes, to analyze their expression levels during zebrafish development. Averaged data for each gene were normalized to an 18S rRNA endogenous control, thus obtaining ΔCt values; standard deviations are shown. The results are represented as relative expression levels (2^ΔCt × 10⁶ on the y axis) versus developmental stages or ovary on the x axis. The ovary RNA sample has been included to analyze maternal RNA content. RNA samples are as follows: ovary, 1-2 cell stage, 50% epiboly, tailbud, 6 somite stage, 15-20 somite stage, 24 hpf, 2 and 3 dpf. All transcripts are maternally expressed, at different levels. hmgb2a/2b are the most highly expressed hmgb genes until 1 dpf; their mRNA levels peak during somitogenesis. hmgb1a/1b display a moderate peak during somitogenesis but their expression reaches the highest level at 2 dpf, when hmgb1b level becomes comparable to hmgb2a/2b while hmgb1a even exceeds them. hmgb3b is the lowest expressed gene at every examined stage, while hmgb3a expression increases during development and it is the most highly expressed hmgb gene at 2-3 dpf.