20 Million Years Apart, Genes Still Aligned

A new study has found that two soil-dwelling nematode species—Caenorhabditis elegans and Caenorhabditis briggsae—despite diverging from a common ancestor over 20 million years ago, still exhibit remarkably similar patterns of gene expression during embryonic development. The research, conducted jointly by scientists at Washington University School of Medicine and the Perelman School of Medicine at the University of Pennsylvania, was published in the journal Science.

Using single-cell RNA sequencing, the team analyzed gene expression in every embryonic cell of both species. They discovered that genes involved in core functions like muscle formation and digestion remain highly conserved, whereas genes tied to specialized functions such as environmental sensing tend to vary more. This suggests that genes active across many cell types are more resistant to change, while those expressed in only a few cells may evolve more readily.

Despite millions of years of evolution, the two worms still share nearly identical body plans and cell types. Interestingly, some differences in gene expression appear to have little or no effect on overall anatomy, offering new insights into the evolutionary stability of developmental programs. However, whether these variations are driven by natural selection or random genetic drift remains an open question.

This marks the first comparative single-cell analysis of developmental processes in two species, opening up new avenues for studying gene regulation and the mechanisms of evolution. Researchers hope the approach will help unlock further mysteries about the origins and evolution of life.