Sox transcription factors require selective interactions with Oct4 and specific transactivation functions to mediate...

Area of Science:

• Stem Cell Biology
• Molecular Biology
• Genetics

Background:

• Sox2 and Oct4 are crucial for reprogramming somatic cells into induced pluripotent stem cells (iPSCs).
• Previous work showed Sox17 can become a reprogramming factor (Sox17EK) via a single amino acid mutation.

Purpose of the Study:

• To investigate if analogous mutations in other Sox proteins can confer reprogramming ability.
• To explore the role of N- and C-termini in Sox protein reprogramming efficiency.

Main Methods:

• Point mutations were introduced into 10 different Sox proteins.
• Fibroblast reprogramming assays were performed.
• ChIP-sequencing and expression data analysis were used to understand mechanisms.

Main Results:

• Sox7 and Sox17 with specific mutations (Sox7EK, Sox17EK) successfully reprogrammed human and mouse fibroblasts into iPSCs.
• Other mutated Sox proteins (Sox4, Sox5, Sox6, Sox8, Sox9, Sox11, Sox12, Sox13, Sox18) did not show reprogramming potential.
• The C-terminal transactivation domain of Sox17 and Sox7 enhanced Sox2 potency and conferred weak reprogramming to Sox4EK and Sox18EK.
• The β-catenin interaction region in Sox17's C-terminus contributed to enhanced reprogramming.
• A subset of genes specifically regulated by Sox17EK, not Sox2, was identified.

Conclusions:

• A single HMG domain mutation (E to K) is necessary but not sufficient for swapping Sox factor function.
• The C-terminus, particularly the β-catenin interaction region, plays a significant role in enhancing reprogramming efficiency.
• Sox17EK and Sox7EK represent novel reprogramming factors with potential applications in regenerative medicine.