Inducing your neighbors to become like you: cell recruitment in developmental patterning and growth

Abstract

Cell differentiation, proliferation, and morphogenesis are generally driven by instructive signals that are sent and interpreted by adjacent tissues, a process known as induction. Cell recruitment is a particular case of induction in which differentiated cells produce a signal that drives adjacent cells to differentiate into the same type as the inducers. Once recruited, these new cells may become inducers to continue the recruitment process, closing a feed-forward loop that propagates the growth of a specific cell-type population. So far, little attention has been given to cell recruitment as a developmental mechanism. Here, we review the components of cell recruitment and discuss its contribution to development in three different examples: the Drosophila wing, the vertebrate inner ear, and the mammalian thyroid gland. Finally, we posit some open questions about the role of cell recruitment in organ patterning and growth.

Functional evaluation of the insulin/insulin‐like growth factor signaling pathway in determination of wing polyphenism in pea aphid

“…In Drosophila, Hh acts as a morphogen which activates Dpp, another morphogen, to control the morphogenesis of the central part of the wing (Tanimoto et al, 2000;Vervoort, 2000). Vg, when bound to Sd (Scalloped), functions as a transcriptional activator, in response to Wingless (Wg) and Decapentaplegic (Dpp) signaling gradients for wing formation (Muñoz-Nava et al, 2021). Furthermore, Dpp and Vg are associated with wing development in brown planthopper (Li et al, 2019;Zhang et al, 2021).…”

Coupling cell proliferation rates to the duration of recruitment controls final size of the Drosophila wing

“…Cell recruitment operates as a patterning-driven growth mechanism in a plethora of systems [55], but whether there is a specific role in developmental growth control is unknown. What advantages would cell recruitment offer as a growth mechanism during development when growth can potentially reach any target size by modulating cell proliferation, cell growth or apoptosis?…”

“…Such an implementation may provide insights into the feasibility of this mechanism in other growth control contexts such as in stopping tumour growth [62]. Furthermore, given that cell recruitment is a widespread mechanism in developing organs [55], the mechanism described here provides a previously unidentified role for cell recruitment in the robust determination of size to variations in cell proliferation rates, a long-standing problem in developmental biology.…”

Interplay between cell proliferation and recruitment controls the duration of growth and final size of the Drosophila wing

“…Cell recruitment has been recently recognized as a patterning-driven growth mechanism in a plethora of systems [32], but whether there is a specific role in developmental growth is unknown. Why would a developing system use cell recruitment as a growth mechanism when it can potentially reach any target size by controlling cell proliferation, cell growth, or apoptosis?…”

“…In summary, our work suggests that a growth control strategy to compensate against fluctuations in cell proliferation rates may be at work in the Drosophila wing disc and provides guidance into how this can be tested experimentally using the genetic toolkit available in Drosophila. Given that cell recruitment is a widespread mechanism in developing organs [32], the mechanism described here provides a more general solution to the problem of how organs robustly attain a reproducible size despite variations in cell proliferation rates, a long-standing problem in developmental biology.…”