Neurogenesis and Migration III

Question 1

beginning migration

Answer 1

neural crest cells downregulate the expression of a CAM (neural cadherin) and genes for proteins forming tight junctions

Question 2

to commence migration…

Answer 2

neural crest cells must dissolve the basal lamina with metalloproteases

Question 3

ECM examples

Answer 3

collagen, laminin, fibronectin

Question 4

CAMs help….

Answer 4

form the basal lamina which anchors and attaches cells together

Question 5

how neural crest breaks free from basal membrane and neural tube

Answer 5

secretes a class of proteases called metalloproteases

Question 6

metalloproteases

Answer 6

enzymes that break down proteins and require a metal such as zinc to help break down the protein

Question 7

MMPs

Answer 7

matrix metalloproteases

Question 8

orientation of cells after breaking free from neural tube

Answer 8

form discrete streams, each from a different spinal segment; they avoid passing through the caudal/posterior half of each of the somites, which are laying alongside the neural tube

Question 9

ephrin

Answer 9

family of membrane-bound signaling molecules that bind to ephrin receptors, which are part of the receptor tyrosine kinase

Question 10

purkinje cells

Answer 10

class of GABAergic cells located in the cerebellum; one of the largest neurons in the human brain

Question 11

migration of purkinje cells

Answer 11

dorsally from 4th ventricle along radial glia, settle in a single layer and begin growing massive dendrites toward cerebellar pial surface

Question 12

population of small cells migrate…

Answer 12

leave edge of pons, rhombic lip, and move along the outer surface of the cerebellar cortex until they aggregate on dorsal side

Question 13

purkinje cells secrete…

Answer 13

Shh which promotes mitosis in granule cells

Question 14

bergmann glia

Answer 14

long, slender glial cells in cerebellar cortex that guide neurons migrating from external granule cell layer to the internal granule layer

Question 15

post mitotic granule cells begin migrating…

Answer 15

ventrally into the cortex, climbing down bergmann glia

Question 16

granule cell grow process

Answer 16

differentiate into axons, extending into a straight line perpendicular to purkinje cell dendrites

Question 17

parallel fibers

Answer 17

axonal processes of granule cells grow parallel to one another (of cerebellum, innervate purkinje neuron dendrites)

Question 18

mossy fibers

Answer 18

give excitatory input to granule cells from pontine neurons and make excitatory synapses with purkinje cell dendrites via parallel fiber they send out behind them during migration

Question 19

riding glial monorail

Answer 19

glia formed long processes and granule cells and granule cells would clasp on and migrate along them; once they end they reverse and migrate back in the other direction

Question 20

isolating only glia…

Answer 20

will not form long processes unless cocultures with neurons

Question 21

weaver mice experiment test

Answer 21

place granule cells and glia together in vitro to observe migration; wildtype granule cells with glia from weaver mice in some ad weaver granule cells with wildtype glia in other culture

Question 22

weaver mice result

Answer 22

granule cells from wildtype mice migrated equally well along either wildtype or weaver; granule cells from weaver mutant never attached to glia

Question 23

weaver mice conclusion

Answer 23

defect cause by gene mutation does not affect glia to support migrating neurons, failure of cerebellar migration due to inability of granule cells to grip glial fibers in order to climb along them (deficient n ability to direct glial partner)

Question 24

astrotactin

Answer 24

encodes a protein expressed in granule cells to help them grip glial fibers for migration

Question 25

reelin

Answer 25

gene that encodes the protein that is secreted into ECM

Question 26

secretion of reelin

Answer 26

secreted by granule cells in developing cerebellum when present at external granule cell layer on the plial surface of cerebellum

Question 27

reelin gradient

Answer 27

uniform along outer surface

Question 28

purkinje cell migration and reelin

Answer 28

purkinje cells stop migrating once they reach a particular concentration of reelin; migrate much more when reelin not present; lack of orderly purkinje cell layer seems affect granule cell migration down from external to internal granule layer

Question 29

olfactory placode

Answer 29

plate-shaped collection of ectodermal cells that migrate through the olfactory bulb and to the rest of the brain

Question 30

incoming cells from olfactory placode

Answer 30

migrate toward young olfactory bulb and take on several different fates

Question 31

GnRH expressing cells

Answer 31

settle into hypothalamus, where they differentiate into neurons that send axons to the hypothalamic-pituitary blood portal system

Question 32

release of GnRH

Answer 32

into portal system, reach pituitary gland and stimulate cells there to release FSH and LH

Question 33

FSH and LH

Answer 33

gonadotropins > stimulate development of gonads

Question 34

kallmann syndrome

Answer 34

the failure of the pituitary gland to release gonadotropins to stimulate the gonads at puberty, plus the lack of a sense of smell (hypogonadotropic hypogonadism); may be deaf

Question 35

cause of kallmann syndrome

Answer 35

mutations in several genes

Question 36

commonality in kallmann syndrome

Answer 36

failure to produce the olfactory ensheathing glia and primary olfactory sensory neurons with axons leading from olfactory epithelium into olfactory bulb