Inherent randomness of cell division patterns

In 1665, Robert Hooke described the arrangement of plant cells to be “much like a Honey-comb, but [that] the pores of it were not regular; yet it was not unlike a Honey-comb in these particulars” (1). Since then, the semiregular patterns of cell arrangements have been extensively studied due to their fundamental role in plant morphogenesis and their visual beauty. Cell division is a key factor determining cellular patterns, which raises the question of what mechanisms control when and how a cell divides. Rules that aim at predicting the position of the division plane, given the shape or growth directions of the cell, have been proposed since the 19th century (2, 3). More recently, the quest for such rules has been aided by computational models that facilitate the comparison of different rules (4). However, all these rules and models have failed to reproduce patterns that match the observations exactly. One possible interpretation of this discrepancy may be that some essential ingredient of the deterministic patterning mechanism is yet to be discovered. In an elegant PNAS paper, Besson and Dumais (5) propose a fundamentally different perspective, according to which the discrepancies between the models and real patterns are due to the inherent randomness of the patterning process. This randomness also explains the variability of patterns produced in similar conditions. Seeking an exact prediction of a cell division pattern is thus as futile as attempting to predict the exact sequence of numbers produced by repetitively throwing a die. Only the statistical characteristics of these processes, as opposed to individual outcomes, can be meaningfully anticipated.