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Dorsal-ventral patterning of the Drosophila embryo

Published on September 29, 2008 Reviewed on May 31, 2018   36 min

A selection of talks on Reproduction & Development

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0:00
I'm Mike Levine at UC Berkeley and I'm going to discuss the dorsal-ventral patterning of the Drosophila embryo. This process is controlled by a sequence-specific transcription factor called 'dorsal' (dl), which is shown on the next slide.
0:15
This is a side view of a 2-hour Drosophila embryo, stained with an antibody against the dorsal protein. Initially the protein is distributed uniformly throughout the cytoplasm of the egg and early embryo, but shortly after fertilization the protein begins to enter nuclei. Here you can see that in ventral regions (bottom regions) the protein has entered nuclei, but in the top (or dorsal) regions of the embryo, the dorsal protein remains in the cytoplasm. So regulated nuclear transport produces a broad dorsal nuclear gradient with peak levels present in ventral regions, progressively lower levels in lateral and more dorsal regions. This dorsal nuclear gradient controls dorsal-ventral patterning by regulating something like 60 to 70 different target genes, in a concentration-dependent fashion. The next slide shows several examples of dorsal target genes, which reveal distinct threshold readouts of the dorsal gradient.
1:18
High levels of the dorsal gradient activate the genes stained in yellow, lower levels of the gradient activate the transcripts encoded by the genes visualized in blue, green and red. Altogether the dorsal gradient establishes several basic embryonic tissues, high levels of the gradient establish the mesoderm at the bottom of the embryo as visualized by the marker gene seen in yellow, low levels of the gradient establish the presumptive neurogenic ectoderm in lateral regions as seen in the expression of these genes in blue, green and red, and finally the absence of the dorsal gradient permits the expression of genes in the very top of the embryo, not shown here, which will form the dorsal ectoderm. The dorsal gradient does not produce these different thresholds of gene activity alone, instead it works in concert with two other sequence-specific transcription factors, shown on the next slide.

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Dorsal-ventral patterning of the Drosophila embryo

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