Fig. 2

miR-1 and miR-206 silence different target genes and play opposing roles in zebrafish angiogenesis. Both miR-1 and miR-206 are muscle-specific microRNAs and share identical seed sequences. However, they silence different target genes to affect the secreted VegfAa level through different pathways [62]. The miR-1/SARS/VegfAa pathway plays a positive role in angiogenesis since SARS, a negative factor for VegfAa promoter transcription, is silenced by miR-1, resulting in the increase of VegfAa. However, the miR-206/VegfAa pathway plays a negative role since VegfAa is silenced directly by miR-206. Dynamic changes of miR-1 and miR-206 levels are also observed [62]. The miR-1 level gradually increases between 12 and 20 hpf and significantly increases further between 20 and 32 hpf, while the miR-206 level is only slightly changed during this same period. Consequently, VegfAa increases greatly from 24 to 30 hpf, which might be responsible for the continuous increase of miR-1/SARS/VegfAa pathway, but not miR-206/VegfAa pathway. Therefore, temporal regulation of the expression of miR-1 and miR-206 with different target genes occur during embryonic angiogenesis in somitic cells of zebrafish