Regulatory logic and pattern formation in the early sea urchin embryo

Abstract

We model the endomesoderm tissue specification process in the vegetal half of the early sea urchin embryo using Boolean models with continuous-time updating to represent the regulatory network that controls gene expression. Our models assume that the network interaction rules remain constant over time and the dynamics plays out on a predetermined program of cell divisions. An exhaustive search of two-node models, in which each node may represent a module of several genes in the real regulatory network, yields a unique network architecture that can accomplish the pattern formation task at hand--the formation of three latitudinal tissue bands from an initial state with only two distinct cell types. Analysis of an eight-gene model constructed from available experimental data reveals that it has a modular structure equivalent to the successful two-node case. Our results support the hypothesis that the gene regulatory network provides sufficient instructions for producing the correct pattern of tissue specification at this stage of development (between the fourth and tenth cleavages in the urchin embryo).

Pattern formation on a growing oblate spheroid. an application to adult sea urchin development

“…Regarding the action of ets1 on pmar1, current understanding is far from complete and we have not been able to find in the literature mention of a direct effect. However, ets1 is repressed by hesC [46], and it is plausible that this effect is controlled, with higher concentrations of ets1 determining higher concentrations of its controller hesC. However, hesC also inhibits pmar1, therefore higher concentrations of ets1 would translate into higher concentrations or activity of hesC and into lower concentrations or activity of pmar1.…”