A heat shock-driven pulse of Msgn1 inhibits expression of progenitor-specific genes and drives progression through the PSM differentiation program. Batches of zebrafish embryos comprising heat shocked hsp70:HA-msgn1 transgenics along with wt sibling controls were analysed; ~50% of each batch showed a clear phenotype and were presumed to be the transgenics. (A-D′) Expression of ntl, wnt8, wnt3a and fgf8 after 1 hour of recovery post-heat shock (hpHS) in hsp70:HA-msgn1 embryos (A′-D′) and their wt siblings (A-D) heat shocked for 1 hour at the 13-somite stage. In the transgenics (32/59 embryos), tailbud expression of ntl was severely reduced (29/59 embryos) or totally eliminated (3/59 embryos). Tailbud expression of wnt8 in the transgenics (35/65 embryos) was also strongly reduced, but reduction in expression levels of wnt3a and fgf8 at this early time after heat shock was milder, making transgenics often hard to distinguish from sibling controls. (E,E′) tbx24 expression at 2 hpHS. In the hsp70:HA-msgn1 transgenics (29/76 embryos), tbx24 expression is intensified in the PSM and abnormally extended into the region of formed somites, but is still absent from the tailbud. (F,F′) fgf8 expression at 2 hpHS. In the hsp70:HA-msgn1 transgenics (10/23 embryos), fgf8 is downregulated but still detectable. (G-M′) Expression of ntl, wnt8, wnt3a, fgf8, tbx24 and tbx6l at 7 hpHS. In the hsp70:HA-msgn1 transgenics (G′, n=25/53; H′, n=46/92; I′, n=13/29; J2, n=32/66; K′, n=15/34; M′, n=10/22), the tailbud has now lost all expression of ntl, wnt3, wnt8 and fgf8 and instead expresses tbx24 and tbx6I. Asterisks, arrowhead and hash sign indicate ectopic expression of tbx24 in somites, tailbud and midline, respectively.
|
