The Evolution of Neurons: Insights from Placozoans

Researchers from the Centre for Genomic Regulation in Barcelona have made a significant discovery regarding the evolution of neurons. They focused their study on placozoans, millimetre-sized marine creatures, and found that the specialized secretory cells in these ancient animals may have given rise to neurons in more complex organisms.

Placozoans are simple creatures that first appeared on Earth approximately 800 million years ago. These tiny animals have no body parts or organs and survive by grazing on algae and microbes. The researchers discovered that peptidergic cells in placozoans show signals of neurogenesis and possess gene modules similar to pre-synaptic neuronal structures. These cells also use a communication system similar to neuropeptide-driven processes found in neurons.

The study involved mapping the different cell types in placozoans and analyzing their characteristics and gene modules. The research revealed that placozoan cells differentiate from progenitor epithelial cells through signals resembling neurogenesis. They also have gene modules necessary for the pre-synaptic scaffold of a neuron. However, they lack the components for the receiving end of a neuronal message and are unable to conduct electrical signals.

The similarities between peptidergic cells in placozoans and neurons are remarkable. These cells have many common characteristics with primitive neuronal cells, suggesting that they may be an evolutionary stepping stone towards the development of neurons.

This discovery challenges previous notions about the evolution of neurons and suggests that the foundations of neurons began forming 800 million years ago. From an evolutionary standpoint, early neurons may have started as peptidergic secretory cells similar to those found in placozoans. Over time, these cells gained new gene modules and evolved into the intricate neural systems observed in more advanced animals.

While there is still more to learn about the evolutionary story of nerve systems, this research provides valuable insights into the origins of neurons. The presence of molecular similarities between placozoan cells and neurons raises questions about the trajectory of neuron evolution and the unique characteristics of different animal lineages.

Source: Center for Genomic Regulation