The ingredients for pluripotent stem cells are more ancient than we thought

Despite the incredible diversity among the different specialized cells of the human body – muscle cells contracting a beating heart, eye cells converting light into vision, and skin cells acting as our barrier to the outside world – they all came from the same pluripotent stem cells. These stem cells have the unique ability to give rise to all other cells, and themselves, and are regulated by a set of “stemness” or Yamanaka factors. These stem cell proteins were thought to be unique to multicellular organisms, a distinction separating us and many other organisms from single-celled life, but recent research has revealed that we’re not so special.

An international team of scientists recently discovered that pluripotent stem cells can be generated and maintained using replacement stemness proteins borrowed from our closest living single-celled relatives, choanoflagellates. The Sox protein in choanoflagellates was found to be similar enough to mouse Sox2 that it could fully function as the stemness reprogrammer, regulating the development of induced pluripotent stem cells (iPSCs) which could then be used to generate a living mouse. This finding demonstrates that one of the most important proteins involved in pluripotency emerged before the origin of animals, predating what we define as stem cells today. The question now remains: what were these stemness genes doing in the first place, and how did they integrate the stem cell regulatory system evolved in animals today?

It’s difficult to imagine life on planet Earth only existing in single-cell form. Yet, for about 3.4 billion years, early life bopped along in our ancient oceans, surviving and slowly evolving through generations until that leap to multicellularity and diverse cell functions. The intricacies of this surprisingly common evolutionary event continue to keep scientists’ minds buzzing, but the answer to why cells found their way to multicellularity might be quite simple: community conquers all.

This study was led by Ya Gao, a postdoctoral researcher at the University of Hong Kong in the laboratory of Ralf Jauch.

Managing Correspondent: Morgan Glass

Press Article: The origin of stem cells, EurekaAlert-AAAS

Original Research Article: The emergence of Sox and POU transcription factors predates the origins of animal stem cells, Nature Communications

Image Credit: Leadbeater BSC. Historical perspectives. In: The Choanoflagellates: Evolution, Biology and Ecology. Cambridge University Press; 2015:1-17.