What is it about?

The survival of Apennine brown bears, a small group of a few dozen animals isolated in the heart of the Apennines in Central Italy, not far from Rome, is at stake: cutting-edge techniques in molecular and cellular biology revealed the malfunctioning of a basic biological process in the cells of these bears. One of the enzymes essential for converting nutrients into energy in the mitochondria is defective due to a mutation present only in this population. This enzyme is less efficient and more polluting for cells, producing an excess of free radicals that accelerate cellular aging.

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Why is it important?

For several years, we have been studying what is happening in this very small bear population from a genetic point of view. We know that the offspring of close relatives have a higher risk of expressing deleterious mutations. In the case of Apennine bears, inbreeding has occurred so many times that these harmful mutations are present in all individuals. Previously, we used genomic analyses and bioinformatic predictions to identify fixed deleterious mutations in this small population. In the current study, we focused on mutations in mitochondrial genes coding for the cellular energetic plant (the respiratory complex I) and demonstrated that one of these mutations are actually impairing the cellular bioenergetics. We creatively applied 1) in vitro bio-engineering of model cultured cells, 2) ex vivo experiments from real bear cells, and 3) molecular dynamics simulations to address an open question in conservation biology. Beside gaining knowledge on the potential molecular and physiological causes of reduced population size in this isolated group of bears, the misfortune of the Apennine bears becomes a natural experiment to better understand the functioning (or malfunctioning) of a fundamental component of all cells, including ours!

Perspectives

In light of this study, the fate of our Marsican bears may seem worrying, but every piece of additional information we obtain can be used to study new strategies for their conservation. On one hand, there could be other mutations in different genes, which are currently under investigation, that can somehow compensate for the energy deficit or excess of free radicals produced by this malfunction. On the other, given the rapid progress of biotechnology, it is also possible that innovative methods of genetic editing, i.e., the “correction” of harmful mutations, will soon be available for wild species as well. The small number of individuals is certainly the first limiting factor for this bear population. The "Abruzzo, Lazio, and Molise" National Park (PNALM) is playing a key role in their survival, and constant monitoring will allow the effects of deleterious mutations to be studied directly in the field.

Emiliano Trucchi
Marche Polytechnic University

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This page is a summary of: A fixed mutation in the respiratory complex I impairs mitochondrial bioenergetics in the endangered Apennine brown bear, Proceedings of the National Academy of Sciences, September 2025, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2504409122.
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