The methylation status of the embryonic limb skeletal progenitors determines their cell fate in chicken

Area of Science:

• Developmental Biology
• Epigenetics
• Molecular Biology

Background:

• Limb skeletal development involves programmed cell death to sculpt digits.
• Interdigital tissue undergoes apoptosis, while digit-forming precursors survive and differentiate.

Purpose of the Study:

• To investigate the role of DNA methylation and genome instability in interdigital programmed cell death during limb development.
• To elucidate the epigenetic mechanisms regulating cell death versus chondrogenesis in limb skeletal precursors.

Main Methods:

• Analysis of DNA breakage and genome instability in interdigital versus digit-forming precursors.
• Assessment of regional DNA methylation patterns and DNA-Methyl-Transferase (DNMT) expression.
• Functional experiments involving Dnmt3b to study its role in regulating cell death and chondrogenesis.

Main Results:

• DNA breakage at 5-methylcytosine foci precedes cell death in interdigital precursors.
• Interdigital cells exhibit higher genome instability than digit precursors upon irradiation or BMP treatment.
• Regional DNA methylation differences and specific DNMT expression patterns (DNMT1, DNMT3B, DNMT3A) were observed in degenerating regions.
• Dnmt3b regulates cell death and cartilage differentiation via transcriptional control of genes like Sox9, Scleraxis, p21, and Bak1 through CpG island methylation.

Conclusions:

• Epigenetic mechanisms, particularly DNA methylation regulated by DNMTs, play a crucial role in controlling the balance between cell death and chondrogenesis in limb skeletal development.
• These findings reveal a novel regulatory pathway involving DNA instability and epigenetic modifications in shaping limb morphology.