Transcription factors

Question 1

Which 3 main TFs maintain ES cell pluripotency?

Answer 1

Oct4, Sox2 and Nanog

Question 2

What is the evidence supporting Oct4 as an important player in maintaining ES cell pluripotency?

Answer 2

Oct4 knockout turns inner mass cells into trophectoderm

Question 3

Two key properties of an ES cell?

Answer 3

Self-renewal

Pluripotency

Question 4

Which are the MASTER TRANSCRIPTION FACTORS (MTFs) for ES cells? (which in particular?)

Answer 4

Oct4 - MAIN
Sox2
Nanog

Question 5

What is meant by pluripotency?

Answer 5

The ability to differentiate into many cell types

Question 6

What are: OCT4, SOX2 and NANOG?

Answer 6

Transcription factors with essential roles in early development that are required for the propogation of undifferentiated embryonic stem (ES) cells in culture

Question 7

How do master transcription factors (MTFs) ensure ES cell pluripotency?

Answer 7

Pluripotency genes (eg STAT3) are ACTIVATED

Lineage specific genes (eg HOXB1) are REPRESSED

Question 8

What is the MTF for red blood cell and platelet development?

Answer 8

GATA-1 (a ZnF TF)

Question 9

What does GATA-1 regulate? How?

Answer 9

Erythrocyte cell fate:

• activates and represses genes equally
• collaborates with other TFs, eg KLF1

Question 10

What is GATA-1’s pre-cursor? Which proteins does it complex with to form:

1) Red blood cells
2) Platelets

Answer 10

GATA-2 (oligopotent precursor (CMP))

1) KLF1
2) Fli-1

Question 11

What is the most important epigenetic modification?

Answer 11

DNA methylation

Question 12

Studies on lineage-specific MTFs are fundamental to understanding mechanisms of cell fate determination and lineage plasticity. Why?

Answer 12

Because they are involved in lineage commitment from hematopoietic stem cells through:

1) Regulating the activation of specific gene programs, and
2) Suppressing multipotential and alternate lineage gene programs.

Question 13

What are the target transcription factor genes of GATA-1?

Answer 13

Itself, GATA-2, KLF-1, etc… There are many

Question 14

Which three types of genes does GATA-1 target?

Answer 14

1) Transcription Factors
2) Signalling Molecules
3) Cytoskeletal Proteins

Question 15

Give three features of KLF-1

Answer 15

1) erythroid specific
2) ZnF
3) transcriptional activator

Question 16

What determines cell fate?

Answer 16

Mutually antagonistic transcription factors

Question 17

What are the main transcription factors involved in determining whether a haemopoietic stem cell will develop into a platelet or a red blood cell? Which are antagonistic?

Answer 17

Gata2, Gata1, KLF1 and Fli-1
KLF1 promotes platelet formation and inhibits rbc
Fli-1 promotes rbc formation and inhibits platelets
Gata1 inhibits Gata2
Gata 2 PROMOTES Gata1

Question 18

Give an example of transdifferentiation and how it can be induced.

Answer 18

Can convert heart FIBROBLASTS directly into heart MUSCLE CELLS.

By forcing the expression of an appropriate combination of factors (not Oct4, Sox2, Klf4 and Myc) like Gata4, Mef2c and Tbx5.

Question 19

What is an iPS cell?

Answer 19

Induced Pluripotent Stem cell

Question 20

Which 4 main MTFs were identified by Yamanaka in 2006 as important for inducing pluripotent stem (iPS) cells from fibroblasts?

Answer 20

Oct4
Sox2
Klf4
Myc

Question 21

How efficient is the reprogramming of a fibroblast into an iPS?

Answer 21

VERY LOW… only works for 1/10,000 cells

Question 22

What is the main obstacle to reprogramming?

Answer 22

Epigenetic modification: DNA methylation cannot be reversed in mammalian cells

Question 23

What is the principle of Waddington’s epigenetic landscape?

Answer 23

A stem cell ‘rolls down’ a landscape and falls into different valleys. With each valley it falls into, it becomes more specialised, and cannot go back from there. e.g. first trough decides whether it will be neuron/skin cell, or fibroblast/muscle.. etc..

Question 24

What regulates the transcriptional programme which determines cell fate?

Answer 24

Master transcription factors (e.g. Oct4 for stem cells)