Ectoderm fate (neural or epidermal)

Question 1

Spemann and Mangold

Answer 1

1. implanted donor cells from dorsal lip of blastopore into other side of host
2. secondary neural tube develops where cells were implanted
   - neuralization factor in dorsal lip
   -epidermalization=default fate, implant induces neural

Question 2

Need to ID neuralization factor

Answer 2

IDed noggin as neural inducer
-UV blast resulted in no nervous system
-treated with Li=hyperdorsalized embryo
-extracted polyA mRNA from hyperdorsalized and implanted in UV treated embryo
-isolated noggin cDNA->noggin protein+A->neural genes

Question 3

Spemanns organizer

Answer 3

dorsal lip of the blastopore

Question 4

neuralization via blocking dominant negative receptor (activin)

Answer 4

pre-gasturla=not determined
-mRNRA was injected for truncated activin receptor (not normal signaling)
->RESULTED IN NEURAL TISSUE
->if epidermal was default, then the tissue should have been epidermal
-dissociated animal cap prior to gastrulation
-secrete a factor that ins’t being received due to distance->results in neural cells
-intact animal cap, factor is recieved->epidermalization

Question 5

Conclusion

Answer 5

-neural=default
-signaling pathway is related to activin signaling
->induces epidermal fate
-mesoderm secretes an unknown factor that inhibits an activin related signaling pathway

Question 6

sog

Answer 6

neuralization

Question 7

sog interacting with dpp

Answer 7

antagonize each other

Question 8

dpp

Answer 8

epidermalization

Question 9

BMP-4

Answer 9

homolog to dpp
-epidermalization
-overexpression=no neural cells
-addition of BMP4 to dissociated animal cap cells results in epidermal cells

Question 10

Current mode of neural induction

Answer 10

-noggin binds to BMP4 and blocks it from binding to receptor
-results in neural cells
-BMP4 +receptor=epidermal cells

Question 11

what supports current mode of neural induction?

Answer 11

1. BMP4 administration to dissociated cells resulted in epidermalization
2. BMP4 suppression experiment led to neural differentiation of animal caps without any inducers

Question 12

BMP4 +activin

Answer 12

forms heterodimer
-truncated activin=non functional BMP4
->results in neural cells