Lecture 11

Question 1

define terms differentiation, dedifferentiation, transdifferentiation, and reprogramming

Answer 1

differentiation: expression of the phenotypic characteristic of the functionally mature cell in vivo, can be irreversible or reversible depending on cell
Dedifferentiation: loss of differentiation. reverse developmental process to undifferentiated progenitor. adaptive vs selective (?)
Transdifferentiation: irreversible conversion from one differentiated cell type to another
Reprogramming: reversal, differentiated cell back to undifferentiated cell state embryo. ALL the way back

Question 2

explain the concept of potency and list examples for cell types with different developmental potential

Answer 2

totipotent: makes everything. only zygotes
pluripotent: makes any cell except placental. embryonic cells, iPS cells
multipotent: lineage is committed, but can still form multiple types. Adult stem cells
unipotent: can divide but only makes one cell type. differentiated cells

Question 3

list the Yamanaka factors and describe their importance

Answer 3

Oct4, Sox2, Klf4, c-Myc, NanoG

can induce dedifferentiation and create iPS cells from adult differentiated cells

Question 4

describe two common natural dedifferentiation pathways

Answer 4

1: naturally renewing tissues: stem cells - progenitor cells - terminally differentiated cells
ex: skin, intestine, blood
2: naturally resting tissues have trauma: mature cells reenter cell cycle - progenitor cells - terminally differentiated cells
ex: liver

Question 5

describe examples for in vivo and in vitro nuclear reprogramming

Answer 5

most in vivo are either differentiated or proliferation. reprogramming only happens in fertilization.
in vitro reprogramming can happen by somatic cell nuclear transfer and induced pluripotency (Yamanaka factors)

Question 6

list factors and conditions that induce differentiation in vitro

Answer 6

cell-cell interaction: can be homotypic or heterotypic. in vitro, high density makes cells signal differentiation
systemic factors: hormones, vitamins, etc. in vitro medium additives
matrix interaction: collagen, laminin, etc signaling. in vitro use specific products in matrix
stress: stretch, compression for certain types. in vitro simulate with force transducers
shape and polarity: in vitro use filter well inserts, scaffolds, etc
oxygen tension: in vitro distance from medium surface alters oxygen concentration

Question 7

define constitutive differentiation, adaptive differentiation, commitment/lineage, and terminal differentiation

Answer 7

constitutive: stably expressed, no need for further induction
adaptive: regulation of mature phenotype is possible
commitment/lineage: transition from stem cell to define lineage
terminal: phenotype is fully expressed (can be irreversible or reversible). cell is not dividing anymore

Question 8

bottom line for induction of differentiation

Answer 8

provide correct microenvironment and optimal cell-cell interaction for cell type of interest. use appropriate selective medium, high cell density, differentiating inducing medium, and elevate in a filter well