None Dpp Epidermal Genes Neuronal Genes Dorsal Genes

None Dpp Epidermal Genes Neuronal Genes Dorsal Genes Brk, Sog AS-C Neural Genes Low High Rho Ventral Epidermal Genes Snail Twist Neural Genes Mesodermal Genes [Dorsal] = Mesoderm = Neuroectoderm = Non-Neural Ectoderm

Epi Neuro Dorsal Neuro Meso dpp “sog” sog snail

dpp versus sog Expression dpp sog

Dpp versus Sog Function Sog Dpp Receptor Outside Inside Dpp Protein Inside Signal Relay No Dorsal Repressor From Mother Epidermal genes (e. g. dpp) dpp m. RNA Off On Regulatory Region Codin g Region Nucleus Dorsal Region Cell Off DNA On Neural genes (e. g. AS-C) Off On Nucleus Dorsal or Lateral Region Cell

dpp- versus sog- Mutants X Dpp Epidermal Genes Neuronal Genes Sog Neuronal Genes Mesodermal Genes = Mesoderm = Neuroectoderm = Non-Neural Ectoderm

dpp- Mutant Sog Neuronal Genes Mesodermal Genes = Mesoderm = Neuroectoderm = Non-Neural Ectoderm

dpp- Mutant

sog- Mutant Dpp Epidermal Genes Neuronal Genes X Sog Neuronal Genes Mesodermal Genes = Mesoderm = Neuroectoderm = Non-Neural Ectoderm

sog- Mutant Dpp Epidermal Genes Neuronal Genes Mesodermal Genes = Mesoderm = Neuroectoderm = Non-Neural Ectoderm

sog- Mutant

The Default State of Ectoderm is Neural

Sog diffuses and patterns the dorsal region The Players Dpp: A signal that promotes epidermal fates Sog: A secreted inhibitor of Dpp Tolloid = Tld: A protease produced in dorsal cells that cleaves and destroys Sog

Sog diffuses and patterns the dorsal region Dorsal Embryonic Covering Hi Dpp Tld Sog Ventral Low Dpp Epidermis

Subdivision of the Neuroectoderm Dorsal None Non-neural genes Dpp Neural genes Msh Low Ind Neuronal genes Vnd High [Dorsal] = Mesoderm = Neuroectoderm = Non-Neural Ectoderm

Patterning the Neuroectoderm in Flies and Mice Drosophila Neuroectoderm Dpp dpp msh ind vnd Dorsal Msx Gsh Nkx 2. 2 BMPs Mouse Neural Tube Sonic Hh

Ventral Dominant Repression D msh ind vnd V

Dpp signaling represses ind more effectively than msh Dpp Dl Dl msh X ind msh ind vnd row 3 row 2 ind, msh row 1

Neuroectodermal patterning in a vnd- mutant Dpp Dl Dl msh X ind msh ind vnd X row 3 row 2 ind, msh row 1

Neuroectodermal patterning in a vnd- mutant Dpp Dl Dl msh X ind msh row 3 row 2

Dpp signaling represses ind more effectively than msh Dpp Dl Dl row 3 msh X ind row 2 msh ind X ind, msh row 1 vnd

Dpp signaling represses ind more effectively than msh Dpp Dl Dl msh vnd msh row 3 row 1

Reciprocal Patterning of the Ectoderm by Sog and Dpp Neuroectoderm vnd ind msh Sog Epidermal Ectoderm Dpp A. S. race Relative BMPActivity [Sog] [Dpp] V D 1) A Sog gradient creates an inverse BMP activation gradient dorsally -> Epidermal Ectoderm vs. Amnioserosa. 2) A BMP repression gradient forms within the neuroectoderm -> Three rows of neuroblasts.