A novel photoactivatable tool for intermediate filament disruption indicates a role for keratin filaments in early embryogenesis

The significance of cytoplasmic intermediate filament proteins has previously been examined largely through various genetic approaches, including knockdown, knockout and transgenic overexpression. Few studies to date have attempted to examine the role of specifically the filamentous intermediate filament network in orchestrating various cell functions. To directly assess the role of the filamentous keratin intermediate filament network in regulation of cellular behavior, we created a P hoto A ctivatable d isruptor of keratin Intermediate F ilaments (PA-dIF). This genetically encoded construct consists of a peptide derived from the 2B2 region of Keratin 8 fused to the photosensitive LOV2 domain from Avena sativa phototropin-1. Upon 458 nm photoirradiation, PA-dIF disrupts keratin intermediate filaments in multiple species and cell types. Marked remodeling of the keratin intermediate filament network accompanies collective cellular morphogenetic movements that occur during gastrulation and neurulation in the Xenopus laevis frog embryo. Light-based activation of PA-dIF was able to disrupt keratin intermediate filaments in Xenopus cells and lead to tissue-specific disruption of morphogenetic processes. Altogether our data show a fundamental requirement for keratin intermediate filaments in orchestrating morphogenetic movements during early embryonic development that have yet to be revealed in other model systems. Moreover, our data validate the utility of a new genetically encoded photoactivatable tool for the disruption and examination of intermediate filaments.