Klf2 is an essential factor that sustains ground state pluripotency

Area of Science:

• Stem cell biology
• Molecular mechanisms of pluripotency
• Epigenetics and cell fate determination

Background:

• Mouse embryonic stem cells (mESCs) require Leukemia Inhibitory Factor (LIF) and serum for maintenance.
• A pluripotent "ground state" resembling preimplantation epiblasts can be achieved using dual inhibition (2i) of Mek/Erk and Gsk3/Tcf3 pathways.
• The role of Mek inhibition in maintaining this ground state remains incompletely understood, despite Gsk3 inhibition's link to Esrrb derepression.

Purpose of the Study:

• To elucidate the molecular mechanism by which Mek inhibition sustains pluripotency in mESCs.
• To investigate the role of Krüppel-like factor 2 (Klf2) in ground state pluripotency.
• To define the signaling axis involving Mek/Erk and Klf2 in maintaining pluripotency.

Main Methods:

• Investigated the interaction between Erk2 and Klf2.
• Analyzed Klf2 phosphorylation and proteasomal degradation.
• Utilized Klf2-null mESCs to assess Klf2's necessity for pluripotency under different culture conditions.
• Examined the effect of ectopic Klf2 expression on mESC culture.

Main Results:

• Erk2 phosphorylates Klf2, targeting it for proteasomal degradation.
• Mek inhibition prevents Klf2 phosphodegradation, thereby sustaining pluripotency.
• Klf2-null mESCs are non-viable under 2i conditions, confirming Klf2's essential role in ground state pluripotency.
• Ectopic Klf2 expression can substitute for Mek inhibition, enabling Gsk3 inhibition alone to maintain Klf2-null mESCs.

Conclusions:

• The Mek/Erk pathway regulates ground state pluripotency through Klf2 degradation.
• Klf2 is a critical mediator of Mek inhibition's effect on pluripotency.
• A Mek/Erk/Klf2 axis cooperates with the Gsk3/Tcf3/Esrrb pathway to maintain the pluripotent ground state in mESCs.