Lecture 12 - Stem Cell Signalling in Health & Disease

Question 1

Pluripotent Stem Cells can be used to Model Normal Development & Disease
TRUE OR FALSE

Answer 1

TRUE

Question 2

Signalling Pathways Control Stem Cell BLANK AND BLANK

Answer 2

Signalling Pathways Control Stem Cell Self-Renewal & Differentiation

Extracellular Signals -> Signalling Pathways -> Cell-Specific Gene Expression Programmes

Question 3

ERK5 MAP Kinase Signalling BLANKS Stem Cell Differentiation

Answer 3

ERK5 MAP Kinase Signalling Inhibits Stem Cell Differentiation

The ERK5 pathway drives expression of stem cell genes, i.e. goes ERK5 causes a primed stem cell to revert to a naive stem cell via expression of factors such as Klf2, Klf4, Nanog, Zfp42, and Esrrb

Question 4

ERK5 has the [SAME/OPPOSITE] Function [AS/TO] its Close Relative ERK1/2

Answer 4

ERK5 has the Opposite Function to its Close Relative ERK1/2

Question 5

ERK5 maintains the [naive/primed] state of pluripotency

Answer 5

ERK5 maintains the naive state of pluripotency

Question 6

Activation of ERK5 Kinase and Transcriptional Functions:

Answer 6

When the cell receives a signal (e.g. growth factor, hormone, cellular stress) dimerisation of kinases called MEKK2 and MEKK3 is enabled.

These dimerised kinases are able to catalyse their own phosphorylation and activation.

This leads to the phosphorylation and activation of a downstream kinase called MEK5. MEK5 is a highly specific upstream kinase for ERK5 and it phosphorylates the ERK5 activation loop on the kinase domain.

[ERK5 uniquely encodes both a kinase domain and a transcriptional activation domain (TAD).]

ERK5 kinase activation by MEK5 then enables it to autophosphorylate its own C-terminal TAD, which leads to nuclear translocation and activation of target genes.

In stem cells, this includes TFs that govern stem cell pluripotency and maintenance

In summary. ERK5 is able to regulate stem cell pluripotency via both its kinase activity and TAD function.

Question 7

SRSF Protein Kinase (SRPK) is Implicated in mRNA Splicing via Phosphorylation of BLANKS

Answer 7

SRSF Protein Kinase (SRPK) is Implicated in mRNA Splicing via Phosphorylation of Ser-Arg Rich Splicing Factors (SRSFs)

• SRPKs phosphorylate splicing factors at SR-motifs to promote spliceosome assembly
• Conserved from yeast to human

Question 8

RNF12/RLIM E3 Ubiquitin Ligase is a Key Developmental Regulator
TRUE OR FALSE

Answer 8

TRUE

Question 9

RNF12 controls X-chromosome inactivation (XCI) for gene dosage compensation & stem cell maintenance
TRUE OR FALSE

Answer 9

TRUE

Question 10

RNF12 localises to the nucleus where it….?

Answer 10

RNF12 localises to the nucleus where it ubiquitinates developmental transcription factors (e.g. CLIM, REX1, SMAD7)

Question 11

RNF12 is what type of protein?

Answer 11

An E3 ubiquitin ligase

Question 12

Example of a disease involving a mutation in RNF12:

Answer 12

• RNF12/RLIM E3 Ubiquitin Ligase is Mutated in Tonne-Kalscheuer Syndrome (TOKAS), an X-linked Intellectual Disability Disorder
• Characterised by low cognitive function (IQ >70) motor, adaptive & behavioural deficits
• Dysmorphic facial features & autism
• RNF12 TOKAS mutations cluster within the key basic region and RING domain

Question 13

RNF12 TOKAS Mutations Specifically Disrupt E3 Ubiquitin Ligase Activity:

Answer 13

TOKAS mutations impair RNF12 substrate ubiquitylation & E2 ubiquitin discharge
RNF12 stability, localization, dimerization & substrate binding largely unaffected

Question 14

RNF12 E3 Ligase Activity [Promotes/Represses] Stem Cell Maintenance

Answer 14

RNF12 E3 Ligase Activity Promotes Stem Cell Maintenance

Question 15

RNF12 TOKAS Mutations Disrupt E3 Ubiquitin Ligase Activity & Supress Aberrant Neuronal Differentiation

Answer 15

FALSE

RNF12 TOKAS Mutations Disrupt E3 Ubiquitin Ligase Activity & Drive Aberrant Neuronal Differentiation

Question 16

SRPK Directly Phosphorylates RNF12 at Characteristic BLANK Motifs

Answer 16

SRPK Directly Phosphorylates RNF12 at Characteristic SR Motifs

Question 17

What is the function of SRPK phosphorylation in RNF12 regulation?

Answer 17

SRPK Phosphorylates RNF12 SR Motifs to Promote 
Nuclear Anchoring (Localises RNF12 in the Nucleus) & Stimulate E3 Ubiquitin Ligase Activity