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FIG. 6. (A) The expression of BMP4 behind the Pax-6 promoter inhibits most neural markers at early neurula stages of development. Left-hand column: embryos transgenic with Pax-6GFP (controls); right-hand column: embryos transgenic with Pax-6BMP4. All the embryos shown are also transgenic for CSGFP3 (as observed at stage 15 by fluorescence microscopy). Embryos were fixed between stages 15 and 19 and stained by whole-mount in situ hybridization to the neural plate markers listed on the left. A reduction in Xotx2, Xrx1, XSox3, and XBF-1 expression and, to some extent, a reduction in XBF-2 and Pax-6 expression was seen in Pax-6BMP4 transgenic embryos. In contrast, the expression of the pan-neural marker nrp1 was not significantly affected by the Pax-6BMP4 transgene, whereas X-dll3 was significantly expanded into the anterior neural plate by the Pax-6BMP4 transgene. Bottom panels show cross sections of the anterior neural region of Pax-6GFP control (left) and Pax-6BMP4 (right) transgenic embryos stained for X-dll3. (B) Bar graph comparing transgenic embryos containing Pax-6GFP with those containing Pax-6BMP4. Percentage of embryos showing no change (blue), decrease in expression (red), or increase in expression (yellow) of the markers listed underneath. Total numbers of embryos (n ﰆ x) are noted beneath each set of columns. (C) Image of microcephalic phenotype obtained by stage 40 in transgenic embryos containing Pax-6BMP4 (lower embryo) compared with transgenic embryos containing Pax-6GFP (upper embryo). |
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FIG. 1. The expression of genes in the neural plate are reduced by BMP4 mRNA injection into one dorsal cell of 4- to 8-cell- stage embryos. Embryos were coinjected with 200 pg of BMP4 and lacZ mRNA (light blue; right) or were uninjected (left) and were analyzed by whole-mount in situ hybridization (magenta) to the neural markers indicated. Embryos shown are at stages 19 0. |