CHD9 upregulates RUNX2 and has a potential role in skeletal evolution

Area of Science:

• Evolutionary biology
• Molecular genetics
• Developmental biology

Background:

• Gene regulation changes drive adaptive evolution, but mechanisms are unclear.
• Chromatin remodellers, like CHD9, influence gene accessibility and expression.
• Convergent evolution in skull morphology between thylacines and wolves suggests shared genetic underpinnings.

Purpose of the Study:

• Investigate CHD9's role in osteogenesis.
• Determine if CHD9 regulates osteogenic genes RUNX2, Osteocalcin (OC), and ALP.
• Analyze the functional impact of an evolutionary substitution in CHD9's DNA binding domain.

Main Methods:

• Overexpression of CHD9 in HEK293T cells.
• Assessed upregulation of RUNX2, OC, and ALP gene expression.
• Examined CHD9's effect on an episomal RUNX2 promoter-reporter construct.

Main Results:

• CHD9 overexpression upregulated RUNX2, the master regulator of osteoblast differentiation.
• CHD9 did not affect OC or ALP expression, suggesting a role in osteogenic progenitors.
• The evolutionary substitution in CHD9's DNA binding domain showed no significant impact on RUNX2 activation in this context.
• CHD9 requires a complete chromatin environment for its function.

Conclusions:

• CHD9 plays a role in osteogenic differentiation by upregulating RUNX2.
• The study advances the functional investigation of protein homoplasy in developmental processes.
• Validating coding gene mutations is crucial for understanding adaptive evolutionary changes.