The transition of unicellular to multicellular organisms is one of the major transitions in biology. However, very little is known about how multicellular organisms evolve, even though understanding why organisms are multicellular is fundamental to almost all aspects of biology including fields such as developmental biology and cancer biology.

The Olson lab works at the intersection of genomics and bioinformatics, cell biology, evolutionary biology, mathematics and machine learning to address this complex problem.

To study the evolution of multicellularity, my laboratory uses green algae as a model system. The volvocacean algae have been an important “textbook” model for multicellular evolution for many years. The volvocales are an order of closely related, recently diverged algal species that range from unicellular to multicellular (Fig. 1). Well known member species include the unicellular algae Chlamydomonas reinhardtii and Volvox carteri.

Morphology of key volvocales suggests stepwise evolution of multicellularity

The morphological and evolutionary progression of the volvocales suggests stepwise evolution of multicellularity, starting with colony formation between unicells (e.g. Gonium), then a stepwise progression of cell expansion, division of labor, specialization and tissue differentiation (e.g. Volvox). Despite their morphological differences, the genomes of Chlamydomonas and Volvox are remarkably similar, suggesting that multicellularity requires few genetic changes.

My laboratory is utilizing two key approaches for understanding the molecular basis of multicellular evolution. First, my laboratory is leading a consortium to sequence the genomes and determine the developmental transcriptional profiles of several key volvocales. Second, my laboratory is using a systems biology approach toward determining which genes are important for all steps of multicellularity. My laboratory is particularly interested in understanding how and why individual unicells formed groups of cooperative cells, termed colonialism. To do this we are focusing on Gonium as a model for colonial evolution.

Understanding how and why individual cells evolved into multicellular organisms is an important evolutionary question and is important for our understanding of how human bodies maintain organizational control over cells. For example, human cancer is a fundamental loss of control of the growth and division of cells within the tissues of the body. Many of the genes defective in human cancers have been identified, however little is known about how multicellular organisms evolved control over their individual constituent cells. Long-term, research in my laboratory is aimed at understanding how organisms evolved regulatory pathways controlling cell growth, division, and differentiation so that new approaches to cancer treatment could be developed.