OTX2 controls chromatin accessibility to direct somatic versus germline differentiation

Area of Science:

• Developmental Biology
• Epigenetics
• Cell Fate Determination

Background:

• The differentiation of embryonic epiblast cells into somatic or germline fates is crucial for species survival.
• The transcription factor OTX2 plays a regulatory role in this cell fate decision.
• Previous studies indicate Otx2-null epiblast-like cells (EpiLCs) exhibit enhanced efficiency in forming primordial germ cell-like cells (PGCLCs).

Purpose of the Study:

• To elucidate the mechanism by which OTX2 regulates the choice between somatic and germline cell fates.
• To investigate how OTX2 influences chromatin accessibility to direct cell differentiation pathways.

Main Methods:

• Utilized CUT&RUN and ATAC-seq assays in wild-type and Otx2-null embryonic stem cells and EpiLCs.
• Analyzed OTX2 binding sites and their impact on chromatin accessibility.
• Investigated the effect of enforced OTX2 expression on somatic-associated regulatory regions during differentiation.

Main Results:

• OTX2 binding was found to open specific chromatin loci, facilitating somatic differentiation.
• Enforced OTX2 expression maintained chromatin accessibility and induced opening of approximately 4000 somatic-associated regions.
• These OTX2-induced changes in chromatin accessibility were observed in cells with dual competence for somatic and germline fates and were not sustained once germline identity was established.

Conclusions:

• OTX2 functions to increase chromatin accessibility at somatic regulatory regions in cells with dual differentiation potential.
• This action of OTX2 promotes somatic cell fate determination at the expense of germline differentiation.
• OTX2's role in modulating chromatin accessibility is critical for directing early cell fate decisions in development.