Species-specific pace of development is associated with differences in protein stability

Area of Science:

• Developmental Biology
• Comparative Genomics
• Cell Biology

Background:

• Molecular mechanisms for embryonic development are often conserved across species.
• However, the rate of embryonic development can vary significantly between species.
• The genetic program for motor neuron differentiation is conserved between mice and humans.

Purpose of the Study:

• To investigate the reasons behind the differing tempos of embryonic development between species.
• To determine the factors contributing to the slower motor neuron differentiation in humans compared to mice.

Main Methods:

• Utilized in vitro directed differentiation of embryonic stem cells into motor neurons.
• Compared the rate of differentiation between mouse and human cells.
• Analyzed potential differences in signaling pathways, genomic sequences, and regulatory elements.
• Assessed protein stability and cell cycle duration.

Main Results:

• The motor neuron differentiation program runs more than twice as fast in mouse embryonic stem cells compared to human cells.
• Differences in signaling pathways, gene sequences, or regulatory elements do not account for this tempo variation.
• Human cells exhibit approximately a two-fold increase in protein stability and cell cycle duration compared to mouse cells.

Conclusions:

• Increased protein stability and cell cycle duration in human cells explain the slower pace of embryonic development.
• Protein turnover rates are a significant factor in interspecies variations of developmental tempo.
• This finding provides insights into the evolutionary regulation of developmental timing.