Ancient fish genes that shaped buttholes may have given us fingers: Study
Researchers from Switzerland and the United States found that DNA elements active in the cloaca of fish were later recycled during evolution to control digit growth in four-limbed animals
A genetic switch that once helped ancient fish form their rear openings may also explain why humans have fingers and toes today, scientists say.
Researchers from Switzerland and the United States found that DNA elements active in the cloaca of fish — the multi-purpose exit for waste and reproduction — were later recycled during evolution to control digit growth in four-limbed animals, according to research published in Nature.
"The fact that these genes are involved is a striking example of how evolution innovates, recycling the old to make the new," said Denis Duboule, a developmental geneticist at the University of Geneva. "Rather than building a new regulatory system for the digits, nature has repurposed an existing mechanism, initially active in the cloaca."
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The team compared zebrafish and mouse embryos, tagging the relevant DNA switches with fluorescent markers. In mice, the genes lit up in growing digits, while in fish they activated in the cloaca. When the switches were deleted with CRISPR-Cas9, mice failed to form proper digits and zebrafish developed cloaca defects.
"The common feature between the cloaca and the digits is that they represent terminal parts," said Aurélie Hintermann, a geneticist who worked on the study. "Sometimes they are the end of tubes in the digestive system, sometimes the end of feet and hands."
The study, published in Nature, suggests the same ancient genetic toolkit that once shaped fish anatomy may have been repurposed millions of years later to give humans wiggling fingers.
