A study conducted by Northwestern University biologists has found that sea lampreys, one of just two vertebrates without a jaw, are helping scientists understand the origins of two important stem cells that drove the evolution of vertebrates. These stem cells include pluripotent blastula cells, or embryonic stem cells, and neural crest cells, both of which have the ability to become all other cell types in the body. Through a comparison of lamprey genes to those of the Xenopus, a jawed aquatic frog, researchers discovered a similar pluripotency gene network across jawless and jawed vertebrates, while also identifying a key difference related to the expression of a stem cell regulator gene in lampreys’ neural crest cells.
The findings of the study are significant in revealing insights into the evolutionary origins of vertebrates, including humans. By comparing the biology of jawless and jawed vertebrates, researchers are able to understand how differences in gene expression contribute to key differences in the body plan. The study also sheds light on what the common ancestor of all vertebrates may have looked like. Northwestern’s Carole LaBonne, who led the study, emphasized the importance of looking back at primitive versions of animals, such as lampreys and hagfish, to understand the origins of features that define vertebrate animals.
The study conducted by LaBonne and her colleagues explored the evolutionary origins of the links between blastula stem cells and neural crest stem cells. They found that neural crest stem cells retain a molecular toolkit that controls pluripotency later into development, allowing them to give rise to a variety of cell types. The research revealed a completely intact pluripotency network within lamprey blastula cells, indicating that blastula and neural crest stem cell populations of jawless and jawed vertebrates co-evolved at the base of vertebrates. This insight helps in understanding the developmental relationships between different types of stem cells.
The study also pointed out the similarities between lampreys and Xenopus, with notable differences in the expression of a key gene, pou5, in lamprey neural crest cells. The researchers found that even though pou5 isn’t expressed in lamprey neural crest cells, it could promote neural crest formation when expressed in frogs, suggesting its role in an ancient pluripotency network present in early vertebrate ancestors. The results of the experiment led to the hypothesis that the loss of this gene in certain creatures was a specific evolutionary event, rather than a feature developed later in jawed vertebrates.
Funded by various organizations including the National Institutes of Health, the National Science Foundation, and the Simons Foundation, the study highlights the importance of understanding the molecular basis of evolutionary changes in vertebrate development. The researchers’ exploration of gene expression patterns in lampreys and frogs provides valuable insights into the evolutionary origins of key stem cells that played a critical role in vertebrate evolution. The study also raises questions about the constraints on gene expression levels needed to promote pluripotency and opens up new avenues for further research in developmental biology and evolutionary science.
