KLF4 Nuclear Export Requires ERK Activation and Initiates Exit from Naive Pluripotency

Area of Science:

• Cell Biology
• Developmental Biology
• Molecular Biology

Background:

• The naive pluripotent state in embryonic stem cells (ESCs) is maintained by a transcription factor complex including OCT4, SOX2, NANOG, and KLF4.
• Mechanisms initiating exit from pluripotency by disrupting this complex are not well understood.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying the exit from pluripotency in ESCs.
• To identify the role of KLF4 in initiating differentiation.

Main Methods:

• Investigated KLF4 protein localization and transcription levels during ESC differentiation.
• Utilized ERK activation pathways and nuclear export factors (XPO1).
• Employed site-directed mutagenesis of KLF4 phosphorylation sites (S132).

Main Results:

• KLF4 protein is exported from the nucleus as ESCs exit pluripotency, preceding declines in Nanog and Klf4 transcription.
• ERK activation phosphorylates KLF4, promoting its interaction with XPO1 for nuclear export.
• Mutation of the KLF4 S132 phosphorylation site prevents nuclear export, maintains pluripotency gene expression, and inhibits differentiation.

Conclusions:

• KLF4 nuclear export is a critical early event in the initiation of ESC differentiation.
• The phosphorylation of KLF4 by ERK and subsequent export via XPO1 are key regulatory steps in exiting pluripotency.