Synthetic self‐patterning and morphogenesis in mammalian cells: a proof‐of‐concept step towards synthetic tissue development

Abstract

This study reports a proof-of-concept study as a step toward synthetic-biological morphogenesis of tissues. Events in normal animal development usually follow the sequence: patterning → differential gene expression → morphogenesis. A synthetic biological approach to development might follow a similar sequence, with each stage under the control of synthetic biological modules. The authors have constructed and published a synthetic module that drives self-organised patterning of mammalian cell populations into patches of different cell types. Here, as a proof of concept, they extend the self-patterning module with a morphogenetic effector that drives elective cell death in just one cell type. The result is a self-constructing pattern of two cell types, one of which can be selectively eliminated to leave remaining cells as a monolayer with a net-like structure. This simple device demonstrates and validates the idea of coupling synthetic biological morphogenetic effectors to synthetic biological patterning devices. It opens the path to engineering more sophisticated structures and, perhaps eventually, tissues.

Using Synthetic Biology to Engineer Spatial Patterns

“…[40] Finally, the understanding of how physico-chemical laws determine patterning (for example during bacterial colony formation, or in adhesion-driven phase separation) has also benefitted from the building and examination of controllable synthetic systems. [48,51,52,[60][61][62] The ability to build, understand and modify synthetic patterns may enable their use as a tool to study, with a new perspective, not only patterning events but also other varied biological problems. For instance, stripe-forming networks have recently been employed to address questions of GRN evolution.…”

“…[48,50] Cachat and coauthors used cadherin-based sorting to achieve incomplete (constrained) separation that resulted in random reticular patterns in 2-and 3-dimensions ( Figure 3C). [51,52] Toda et al also engineered complex self-organizing 3D patterns using phase separation and lateral inhibition, as we discuss below. [50] In bacteria, a recent work employed surface-displayed nanobody-antigen pairs as adhesin analogues to separate cells in different phases depending on their binding capabilities.…”

Novel synthetic biology approaches for developmental systems

“…Finally, synthetic morphogenetic systems have been generated, where morphogenesis is driven by user-introduced genetic circuits in non-developmental cell lines. Overexpression and mixing of cells with different members of the cadherin family of adhesion proteins enabled creation of spatial patterns in 2D and 3D using the HEK293 cell line (Cachat et al, 2016(Cachat et al, , 2017. Combining changes in cadherin expression downstream of synNotch-based signaling circuits has been used to program self-organized multicellular structures such as spheroids composed of two-and three-layer structures in L929 fibroblast cell lines (Toda et al, 2018).…”

Engineering pattern formation and morphogenesis

“…More recently, however, there has been the beginning of a connection between patterning systems and the morphogenetic modules. In one example, patterning by phase separation generates patches of one phase amongst cells of the other phase, then a cell death programme is induced in the patches to leave a sieve-like sheet of cells with holes ( Figure 5 ) [ 29 ]. Work is now underway to couple patterning to more sophisticated morphogenetic responses than simple elimination.…”