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Fig. 2 rasl11b expression pattern during zebrafish embryogenesis.(A) RT-PCR analysis showing that rasl11b has a maternal and a zygotic component. RNA extractions have been done before (1 cell stage) and after (gastrula) the midblastula transition, the time of activation of the zygotic transcription. The maternally and zygotically expressed oep gene and the strictly zygotic sonic hedgehog (shh) gene have been used as controls. (B) During the cleavage period (dome stage), rasl11b is ubiquitously expressed. (C) At the onset of gastrulation (shield stage), rasl11b is still detected at the animal pole (Black arrowhead) but is also expressed in a dorso-ventral gradient at the dorsal margin (white arrowhead). This marginal expression overlaps with the mesendodermal territory in zebrafish embryos. (D) Sagittal section. rasl11b transcript accumulates in both hypoblastic and epiblastic dorsal blastomeres. (E, F) rasl11b expression is maintained at the margin throughout gastrulation (white arrowheads). Gastrulae also expressed n. rasl11b transcript accumulates in both hypoblastic and epiblastic dorsal blastomeres. (E, F) rasl11b exprerasl11b mRNA in ectodermal precursors located at the lateral borders of the blastoderm (black arrowheads). (G–K) During somitogenesis and organogenesis, rasl11b is expressed in the tail tip and the spinal cord (sc), and in several head structures such as the hindbrain (hb), the isthmic organizer (i), the otic vesicle (ov), the pineal gland (p), the ventral hypothalamus (h) and the posterior boundary of the telencephalon (t). (J) lateral close up and (K) frontal v