How giant Burmese pythons regenerate their organs

Scientists have discovered how the organs of the massive Burmese python manage to dramatically increase after it feeds. They identified a few sets of genes that were influencing changes in the snake's internal organ structure.

Burmese pythons are among the largest snakes alive, in some cases reaching 4 metres in length. They are mostly found in forested regions, mostly in India and Indonesia, but have also been introduced in the wild in Florida via the pet trade, where they are now considered an invasive species.

Burmese pythons can feed on birds and other reptiles, but have a preference for large mammals. In Florida, the species has even been known to eat cattle, alligators and adult deer.

The large snakes can nevertheless go through long periods of fasting, using ingenuous mechanisms to save energy. Their metabolic and physiological functions come to a halt, and their organs shrink.

However, within 48 hours of feeding, the size and function of the snake's organs, along with their ability to generate energy, dramatically increase again to help digestion. On these occasions, the mass of their major organs - including the heart, liver, kidney, and small intestines - can increase by 40 to 100 percent.

Genes and gene pathways

Previous studies looking at post-feeding organ regeneration in the Burmese python had already identified thousands of genes linked to this process. But researchers still struggled to understand the mechanisms behind these genes' involvement in post-feeding regeneration.

In a study now published in the journal BMC Genomics, scientists have compared gene expression in the Burmese python's heart, liver, kidney, and small intestine across pre- and post-feeding time, to try and understand which genes were important and how they exerted their effects.

Specifically, they studied gene expression in pythons that were fasting and pythons that were one day post-feeding and then again four days post-feeding.

They sequenced the animals' genomes in these three states, and identified 1,700 genes that appeared to be expressed differently pre- and post-feeding.

The scientists then performed statistical analyses to identify which sets of genes among these were most important to trigger the changes in the pythons' internal organ structure.

They identified a few sets of genes (genes known as mTOR, PPAR/LXR/RXR and NRF2) which coded for proteins that activated a cascade of tissue-specific signals. These signals led to regenerative organ growth in the heart, liver, kidney, and small intestines.

Beyond improving our understanding of snake biology, these results may also provide clues on how best to treat diseases that affect the organs of humans in the future. "We're interested in understanding the molecular basis of this phenomenon to see what genes are regulated related to the feeding response," says Daren Card, one of the study's authors. "Our hope is that we can leverage our understanding of how snakes accomplish organ regeneration to one day help treat human diseases."