The evolutionary secrets of the nervous system
The nervous system is one of the most vital and complex structures in living organisms, as it is responsible for transmitting signals between different parts of the body. It controls essential functions like movement, sensation, and cognition, making it critical for survival. Despite its importance, the evolutionary origins of the nervous system remain one of the great mysteries in biology. Understanding how this intricate system has developed across different species can provide key insights into both the workings of the human brain and the broader evolution of life on Earth.
Studying gene regulatory networks across species
Undertaken with the support of the Marie Skłodowska-Curie Actions (MSCA) programme, the RipGEESE project led by Carlos Rivera was designed to unravel the evolution of the nervous system. While traditional evolutionary studies often trace relationships by comparing genetic sequences, RipGEESE explored how gene regulatory networks have changed over time. “By investigating gene networks, we wanted to shed light on how the nervous system evolved its complexity across different animal species,” he explains. Experiments focused on three well-studied vertebrate neuronal cell types: serotonergic and adrenergic neurons, as well as glial cells. These cells were selected for their distinct functions in regulating neurotransmission and supporting neuronal function.
Specific nervous system genes across evolution
Single-cell RNA sequencing data from eight animal species led to the identification of 39 gene families expressed in the nervous system of all animals. Interestingly, the team discovered that many gene families crucial to the nervous system were present in choanoflagellates, single-celled ancestors of animals. This finding suggests that most of the core genetic machinery for the nervous system existed long before animals developed complex nervous systems. Moreover, the discovery of a single gene family directly linked to the presence of nervous systems is a key finding that could have far-reaching implications for our understanding of both evolutionary biology and the development of neurological diseases.
Simulating evolution
Since it remains unclear how the sequences of genes with a shared function evolve, RipGEESE created a predictive model that simulates how genes, that interact with one another, evolve. This tool provides an innovative way of modelling how gene networks evolve by analysing how the sequences of the involved genes change over time. The CastNet simulator allowed the team to model how selective pressures on organisms, particularly in their phenotypes, could lead to coevolutionary patterns in gene sequences and regulatory interactions. “This tool opens up new possibilities for exploring gene network evolution, providing a deeper understanding of how regulatory interactions influence the development of complex biological systems like the nervous system,” emphasises Rivera. Going forward, the RipGEESE team aims to continue investigating the evolution of gene regulatory networks across more species. The plan is to further refine the predictive models and expand research into other types of regulatory interactions. Overall, RipGEESE has made significant contributions to our understanding of nervous system evolution by focusing on the role of gene regulatory networks. It has also laid the groundwork for a new era in evolutionary biology, where gene regulation takes centre stage in explaining the diversity and complexity of life.
Keywords
RipGEESE, nervous system, evolution, gene, regulatory network
