Lecture 9 - Development of a Body Pattern V

Question 1

Wnt

Answer 1

protein secreted from the posterior end of the neural plate to regulate gene expression

Question 2

Wnt receptors

Answer 2

frizzled

Question 3

retinoic acid

Answer 3

a steroid hormone secreted from the posterior end of neural plate

Question 4

RAR

Answer 4

intracellular protein that binds to DNA, informs cells in developing NS where to go along AP axis

Question 5

promoter of RAR

Answer 5

contains retinoic acid response elements (RARE)

Question 6

teratogen

Answer 6

a substance that uses malformation in development

Question 7

hh

Answer 7

contains a signal peptide, directs protein to secretory pathway > binding of hh to patched receptor halts suppression so genes are expressed

Question 8

shh

Answer 8

vertebrate homologue of hh

Question 9

shh produced and secreted by..

Answer 9

the notochord

Question 10

notochord study (question)

Answer 10

what factor secreted by the notochord induce the ventral neural tube to form a floor plate with motor neurons on either side?

Question 11

notochord study (hypothesis)

Answer 11

if shh is the factor secreted by the notochord to induce formation of the spinal cord floor plate, then supplying Shh to another part of the neural tube should induce the formation of an additional, ectopic floor plate

Question 12

notochord study (test)

Answer 12

transfect cells of a tumor line that grows readily in vitro, in this case COS cells, so that they secrete Shh and place such cells next to the neural tube to see if a floor plate forms

Question 13

notochord study (results)

Answer 13

control COS cells not transfected to express Shh to not induce ectopic floor plate; COS cell expressing and secreting Shh induce a secondary ectopic floor plate > differentiation of secondary motor neurons on each side of the ectopic floor plate

Question 14

notochord study (conclusion)

Answer 14

Shh directs the ventral half of the neural tube to differentiate into the floor plate (initial step in the production of motor neurons dorsal to the floor plate on either side of ventral spinal cord)

Question 15

roof plate

Answer 15

the dorsal portion of the vertebrate neural tube

Question 16

functions of shh

Answer 16

1. guide differentiation of ventral neural tube at anterior end (ventral brainstem)
2. inhibits outward growth at rostro end of telencephalon

Question 17

brain development effects from Shh inhibition

Answer 17

1. inhibits rostral growth of the cortex at midline, forming notch in developing telencephalon
2. eye flied splits to form left and right optic cups

Question 18

failure to split the telencephalon

Answer 18

single telencephalon and eye cup forms; in extreme cases - holoprosencephaly or cyclopia