Deterministic or stochastic choices in retinal neuron specification

Abstract

There are two views on vertebrate retinogenesis: a deterministic model dependent on fixed lineages and a stochastic model in which choices of division modes and cell fates cannot be predicted. In this issue of Neuron, He et al. (2012) address this question in zebrafish using live imaging and mathematical modeling.

Figure 1

Comparison between a Drosophila neuroblast lineage (A) and a conceptual zebra fish retinal progenitor cell lineage (B). (A) The Drosophila embryonic ventral nerve cord NB 7-1 lineage (after Pearson and Doe, Annu Rev Cell Dev Biol 20, 619–647, 2004). As the NB undergoes several rounds of asymmetrical divisions, it sequentially expresses five transcription factors: Hb, Kr, Pdm, Cas and Grh. The lineage of this specific NB is predetermined. (B) In vertebrate retinogenesis, there is no predefined order of modes of cell division. In the zebra fish lineages analyzed by (He et al., 2012), RPCs stochastically choose one of three modes of division (PP, PD and DD). As retinogenesis progresses, RPCs shift from mostly PP divisions to PD and DD divisions. The neural cell type decisions appear to also be largely stochastic.