What is it about?

Moderate expression levels of the neural cell adhesion molecule Fasciclin 2 during organ growth promote Epidermal Growth Factor Receptor function. In turn, Epidermal Growth Factor Receptor activity promotes Fasciclin 2 expression in an auto-stimulatory loop. In contrast, high expression levels of Fasciclin 2 correlate with the termination of cell proliferation and the onset of cell differentiation in epithelial organs. Indeed, Fasciclin 2 has been previously shown to act as an Epidermal Growth Factor Receptor repressor during retinal differentiation.

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Why is it important?

How organs grow and then stop growing when reaching their species-specific size is a major unsolved problem in developmental genetics. Local control of growth is necessary to achieve a correct organ size and shape. We suggest that the auto-stimulatory loop between Fasciclin 2 and the Epidermal Growth Factor Receptor may correspond with an expression level switch mechanism. Fasciclin 2 first promotes local growth at moderate expression levels by activating the Epidermal Growth Factor Receptor, which in turn promotes Fasciclin 2 expression. Then, at high expression levels, Fasciclin 2 would terminate growth by repressing the Epidermal Growth Factor Receptor.


This work is based on a genetic analysis of loss of function conditions of Fasciclin2. The analysis of gain of function conditions for Fasciclin 2 during epithelial organ growth can validate the idea that expression of Fasciclin 2 acts as a level switch to determine organ size.

Luis Garcia-Alonso
Instituto de Neurociencias CSIC

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This page is a summary of: Fasciclin 2 engages EGFR in an auto-stimulatory loop to promote imaginal disc cell proliferation in Drosophila, PLoS Genetics, June 2022, PLOS, DOI: 10.1371/journal.pgen.1010224.
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