Lecture 11

Question 1

One of the distinctive characteristics of myocytes is they are multi-______ (located toward the periphery of the cell.)

Answer 1

multi-Nucleate

Question 2

_____, basically balls of cells on the sides of the neural tube during development, form the trunk musculature. The head and neck muscles are derived from the head _____.

Answer 2

Somites

Mesoderm

Question 3

The more _____ the somites are located, the more quickly they develop.

Answer 3

Rostral

Question 4

As the somites develop, they form the _____ which gives rise to the skin, then the _____ which gives rise to the muscle, and finally the ______ which gives rise to bone (like ribs.)

Answer 4

Dermatome

Myotome

Scleratome

Question 5

_____20 is a marker for myosin heavy chain, used to identify formation of the early musculature from the somites.

Answer 5

MF20

Question 6

The ______, which regresses during development, secretes important factors like sonic hedgehog which direct the development of somites into particular tissue types.

Answer 6

Notochord

Question 7

Somitic stem cells are ____3+ and ____7+ and MRF-. They give rise to embryonic and fetal ______ which are ___3+, ____7+, ___5+ and ____D+.

Answer 7

Pax3+

Pax7+

Myoblasts

Pax3+

Pax7+

Myf5+

MyoD+

Question 8

Keep in mind there are 4 MRFs, 2 of which are ____5 and ___D.

Answer 8

Myf5

MyoD

Question 9

Satellite cells which are Pax3+, Pax7+ and ____5+, produce post-natal muscle.

Answer 9

Myf5+

Question 10

At about mid-gestation, a ____ bud forms and is populated with cells that delaminate from the Ventrolateral ______. These cells form the dorsal and ventral muscle mass in the bud.

Answer 10

Limb

Ventrolateral Dermomyotome

Question 11

Satellite cells are located between the muscle fiber and the ____ lamina, so they’re considered sublaminarly located.

Answer 11

Basal lamina

Question 12

When satellite cells form new myofibers, the nuclei are ______ located. This is a good way to distinguish regenerated myofibers from previously existing ones. When they are quiescent, satellite cells express ____44. Once activated, they express ____7. As they proliferate and differentiate, they’ll express ____5 and ___D.

Answer 12

Centrally

CD44

Pax7

Myf5

MyoD

Question 13

There are 3 key factors that determine the robustness of satellite cell response/muscle repair:

1. _____ factors
2. Local _____ factors
3. Systemic _____ factors

Answer 13

Intrinsic

Local extrinsic

Systemic extrinsic

Question 14

Satellite cells have 2 distinct ways of dividing. In the first, for example in response to ____7A, they divide ______, producing two ______ cells. In the second, they divide _____, producing one ______ cell, and one progenitor.

Answer 14

WNT7A

Symmetrically

Quiescent

Asymmetrically

Quiescent

Question 15

Dystrophin, located just below the sarcolemma, forms a _________ complex which anchors the actin cytoskeleton to the ECM. This is what helps prevent muscular damage during contraction.

Answer 15

Dystrophinglycoprotein complex

Question 16

Pseudo-_______ can be observed in infants with Muscular Dystrophy –> the calves look large, but it’s because they are filled with fibrosis and adiposis.

Answer 16

pseudo-hypertrophy

Question 17

Along with satellite cells, though to a lesser degree, ___45- Pericytes and ___45+ HSCs can differentiate into skeletal muscle. Aslo, ______ can transdifferentiate into myocytes with exposure to factors like Pax3, Pax7 and MyoD.

Answer 17

CD45-

CD45+

Fibroblasts

Question 18

Fortunately, satellite cells do not lose their regenerative capacity when expanded _____.

Answer 18

Exvivo

Question 19

One experiment showed that Human embryonic stem and iPSCs could be induced to express ___7 via genetic modification such that administration of Dox would activate the promoter of the ___7 gene. These cells were found to produce _____, and engrafted in with mouse cells when transplanted into dystrophic models.

Answer 19

Pax7

Pax7

Dystrophin

Question 20

In another experiment, a double KO mouse for utrophin and dystrophin (more extreme dystrophic phenotype), researchers de-differentiated ______ into iPSCs. They then used a vector to restore the _____ gene, and induced expression of _____3. They found they were able to differentiate the iPSCs into myoblasts via induced expression of ____3, and these myoblasts now produced _____, which partially restored the dystrophinglycoprotein complex and neuromuscular junctions.

Answer 20

Fibroblasts

Utrophin

Pax3

Pax3

Utrophin

Question 21

One last experiment showed that injection of WT _____ stem cells into a dystrophic blastocyst rescued the WT phenotype. What’s interesting is that only about ____-____% replacement of dystrophic cells with WT cells rescued the WT phenotype. This suggests there’s ____-talk (paracrine mechanism) between the injected cells and the original cells.

Answer 21

Embryonic stem cells

10-30%

Cross-talk

Question 22

Keep in mind when dystrophin is expressed, _____ is not expressed much. Also, when dystrophin is not expressed, ______ can compensate.

Answer 22

Utrophin

Dystrobrevin