Stem Cells

Question 1

Discuss The concept of stem cell potency and how this property is important for determining the biological roles of stem cells in developing embryos and adult tissues

Answer 1

totipotent = stem cells that can generate all cell types of an organism including the embryonic lineages 
pluripotent = can differentiate into any cell of the embryo 
multipotent = can differentiate into any cell of a specific system

Question 2

define self renewal and differentiation and discuss how these critical stem cell characteristics are maintained and regulated at the level of gene expression

Answer 2

Self renewal = the ability to replicate itself without differentiation
differentiation = the process that creates cell diversity, the ability for a cell to turn into a specific cell type
self renewal is maintained through interaction with the stem cell niche and regulated by things like transcription, epigenetic, cell communication, mechanical forces etc.

Question 3

discuss the role of stem cell niche in regulating stem cell function and maintenance

Answer 3

• niche houses and protect stem cells from damage

- provides molecules needed for stem cell function and survival

Question 4

describe several techniques for the identification and analysis of stem cells in vivo

Answer 4

1. serial transplantation
   - remove stem cells from one mouse, label them with LacZ(blue) then inject back in and observe the recovery of an organ with the new implanted cells
2. colony forming assay
   
   • studies proliferation and differentiation of stem cells based on their ability to grow on semi-solid growth medium. number and morphology tell you how well the progeny cell can differentiate
3. asymmetric expression and analysis of differentiation markers
   
   • specific markers track the proliferation of stem cells

Question 5

what are the roles of stem cells in regenerative medicine

Answer 5

1. to replace lost/damaged/diseased tissues

2. used to generate differentiated tissue for in vitro studies: disease modeling and drug screening/development

Question 6

what is the use of stem cell in therapeutics

Answer 6

1. beta cell transplants for diabetics
2. muscle, hair, bone, tooth, hearing and vision loss
3. skin renewal
4. cardiovascular, joint and organ repair
5. neural, immune, metabolic dysfunction

Question 7

two main properties of a stem cell

Answer 7

the ability to self renew and differentiate

Question 8

what is serial transplantation

Answer 8

removal of cells from one mouse, that are grown in culture and tagged with LacZ then microinjected into a mouse and will be able to visual where those cell regenerated organs etc.

Question 9

what is the colony forming assay

Answer 9

used to study proliferation and differentiation

based on the ability stem cells to grow on a semi-solid growth medium

Question 10

how to determine self renewal vs differentiation experimentally

Answer 10

asymmetric expression of differentiation markers, colony forming assay, serial transplantation

Question 11

what is stem cell potency

Answer 11

the number of possible fates that a cell can adopt

-becomes restricted over time

Question 12

what is totipotent

Answer 12

the ability for a stem cell to generate any cell type including embryonic lineages
ex: zygote

Question 13

what is pluripotent

Answer 13

the ability of a stem cell to become any cell type of the embryo
ex: Embryonic stem cell

Question 14

what is multipotent

Answer 14

the ability of a stem cell to become any cell or a particular system
ex: hematopoietic stem cell

Question 15

what transcription factors are necessary to keep cells in a pluripotent state

Answer 15

Oct4, Nanog, and Sox2

Question 16

how do you experimentally determine stem cell potency (i.e. pluripotent, multipoint etc.)

Answer 16

Lineage tracing

• the process of identifying all progeny of a single cell
• label cells, trace their progeny over time, determine whether all cells of a tissue are “marker” (GFP or LacZ)
• allows for study of dynamics of proliferation, differentiation, and migration of these cells in vivo during many stages, including ideas

Question 17

Summarize drosophila gremlin niches

Answer 17

Testes:
-stem cells are at the apical domain, Hub cells adhere to germ line stem cells and jai-stat pathway regulates the uncommitted portion
Ovarian
-stem cells are housed at the apical end in germanium, cap cells at most apical end provide signal for differentiation
differentiation is regulated by Mad/Med signaling

Question 18

Describe the mammalian intestinal stem cell niche

Answer 18

-stem cells are housed at the base of the crypt
–then amplifying cells
-the top is differentiation cells
-Wnt2B decreases with proliferation
Bmp4 increases with proliferation
-when cells reach the top of the villa, they undergo apoptosis

Question 19

name the cells in intestinal niche

Answer 19

1. Lgr5+ cells
   - crypt base columnar cells
   - divide every 9-12 hours
2. +4 cells (Bmi1+)
   - quiescent intestinal stem cells

Question 20

describe label retention

Answer 20

-pulse cells with BrdU then measure it after certain time points, those with less BrdU are cycling more

Question 21

what is reprogramming

Answer 21

taking a cell of one type and turning it into another

Question 22

what is dedifferentiation

Answer 22

an example of reprogramming where cells regress back to a simpler, more potent state

Question 23

what is transdifferentation

Answer 23

conversion of one differentiated cell type into another

Question 24

what are the application of iPS cells

Answer 24

can take cells from a patient and introduce reprogramming factors (OSKM) and turn them into pluripotent cells then correct genes, allow them to differentiate and translate corrected cells back into a patient