Abstract Detail

Systematics

Cell types as species: Exploring a metaphor.

The cell is a basic unit of biology that in multicellular eukaryotes such as plants can show great morphological, biochemical, and physiological diversity. Since the discovery of cells, biologists have attempted to classify cells into “cell types” to understand how cell form is related to cell function. But defining “cell type” turns out to be historically controversial, and the new era of single cell transcriptomics has further complicated simple classification schemes by revealing subtle differences between otherwise similar cells, as well as continuous variation among clusters of transcriptomically similar cells that might represent “types”. Cell biologists, particularly those confronted with the bewildering diversity of mammalian neurons, have long compared their “cell type problem” with the problem of defining “species” in systematics and evolutionary biology, and the new generation of cell biologists has looked to systematics for solutions. There are, indeed, many parallels between the two problems. The fundamental question of whether “cell types” are merely human constructs artificially breaking up a natural continuum of cell states certainly echoes the nihilistic position about the (un)reality of species. But if these entities are, in fact, “real”, are they groups, individuals, or something in between (e.g., homeostatic property clusters)? There are, of course, major differences—cells are not organisms, and because all cells of an organism share the same genome, differences among them are epigenetic, not genetic. Consequently, the meaning of “lineage” in cells and species is quite different—a key point given the centrality of evolutionary lineage in species definitions. But even this difference has its similarities: The gene tree vs. species tree relationship is paralleled by incongruence between cell developmental lineage and transcriptomic class. The “cell types as species” metaphor is a rich one and ripe for exploration as both systematics and cell biology seek to accommodate vast amounts of new data to understand the fundamental units of their respective disciplines, with major implications for both theory and practice.

1 - Cornell University, School of Integrative Plant Science, Plant Biology Section, 404 Mann Library Building, Ithaca, NY, 14853, USA

Keywords:
cell type
species delimitation
lineage
philosophy
incongruence
epigenetics
Development.

Presentation Type: Oral Paper
Number: SYST I008
Abstract ID:164
Candidate for Awards:None