Hox genes underlie metazoan development, but what controls them?

TL;DR

This paper proposes a novel model of metazoan development as a Turing machine, where telomere shortening acts as an external counter controlling Hox gene expression and developmental steps.

Contribution

It introduces a new analogy between gene regulatory networks and computer architecture, emphasizing telomere shortening as a counting mechanism for development.

Findings

Development resembles a Turing machine.

Telomere shortening controls sequential Hox gene expression.

A universal model for metazoan development is proposed.

Abstract

Although metazoan development is conceived as resulting from gene regulatory networks (GRNs) controlled by Hox genes, a better analogy is computer architecture: i.e., a task accomplished in sequential steps linked to an external referent that "counts" each step. A developmental "step" equals the expression of genes in specific cells at specific times and telomeres represent external "counters" wherein "counting" is a function of telomere shortening at each cell division that permits the sequential expression of Hox genes and, ultimately, complex form. Metazoan development thus best resembles a Turing machine, which could be used to model the development of any metazoan.