Figure 4

Expression of other vertebrate MHB-specific genes in the early Drosophila brain. Head flat preparations. (a-d) mRNA expression of FGF8-related genes branchless (bnl; (a); stage 11), pyramus (pyr; (b); stage 10), or thisbe (ths; (c), stage 10) in relation to Engrailed (En)-lacZ. (a) In the pNE, bnl transcripts are confined to most dorsal sites of the ocular pNE (arrowheads). (b) pyr expression is detected in the labral ectoderm (black arrowheads) and in one protocerebral NB in each hemibrain (white arrowheads). (c,d) Expression of ths, similar to pyr, is found in the labral ectoderm (black arrowheads) and in one protocerebral NB (white arrowheads). ths is faintly detected in a further pNE domain (red arrowheads), slightly anterior to the en head spot (hs) and the Ppd5 (in (d)). (d) Higher magnification of framed area in (c). Protocerebral NBs (asterisks) emanating from that area express ths very faintly. (e,g,h) Expression of Wingless protein (Wg) (e) or buttonhead mRNA (btd) (g,h) in combination with En-lacZ, or (f) only Wg. (e,f) Wg is expressed in the ocular (blue arrowheads) and deutocerebral pNE (brown arrowheads) and (f) in the corresponding protocerebral and deutocerebral NBs (Dd1,7,8), respectively. (g,h) btd is weakly expressed in a deutocerebral pNE domain ((g), purple arrowheads) and in the deutocerebral Dd8 (h) of the IZ. (i) Scheme summarizing the expression of Wg, btd, ths,pyr, and En in brain NBs at stage 11. Red dashed lines indicate neuromeric boundaries, the blue line the posterior border of the otd domain, which corresponds (at least partially) to the otd/unpg interface. Coloured hatched areas indicate neuroectodermal regions in which yet unidentified NBs express btd (purple), or ths or pyr (brown). (j-n) Expression of Muscle segment homeobox (Msh-lacZ) (j,k) or Ventral nervous system defective (Vnd) (l,m) and En (Inv in (j,k); En-lacZ in (l,m)). (j,k) The anteriomost limit of Msh expression abuts the anterior border of the deutocerebrum (DC; red line), which roughly coincides with the anterior border of the IZ. (k) Msh is expressed in dorsal NBs of the IZ (Dd4,5,7,8,10).(l,m) Vnd expression is specifically lacking in the ventral pNE (indicated by red brackets in (l)) and in all ventral NBs of the deutocerebrum (m), including Dv7 (of the IZ) at the otd/unpg interface (blue line in (n)). (n) Scheme summarizing the expression of Msh and Vnd in brain NBs at stage 11.