A transgenic toolkit for visualizing and perturbing microtubules reveals unexpected functions in the epidermis

Differentiation induces reorganization of microtubules (MTs) into non-centrosomal arrays in a variety of tissues. The physiological functions of these microtubule arrays are just beginning to be understood as few tools currently exist to genetically perturb microtubule organization in vivo, particularly in mammals. We developed a genetic toolkit that can be broadly applied to the study of microtubule dynamics and function in many cell types. Using a TRE-EB1-GFP mouse we demonstrate that distinct differentiation transitions in the epidermis cause a decrease in microtubule growth rates and microtubule growth lifetimes, resulting in strong suppression of dynamics. To understand the physiological functions of these stable, non-centrosomal microtubules, we generated a TRE-spastin mouse, which can be used to perturb microtubule organization in a wide-variety of tissues in vivo. Unexpectedly, microtubule perturbation exclusively in post-mitotic keratinocytes had profound consequences on epidermal morphogenesis. We uncoupled novel cell-autonomous roles for MTs in differentiation-driven cell flattening from non-cell autonomous functions in regulating proliferation, differentiation, and tissue architecture. Taken together, we have created tools that will be broadly useful for the study of microtubule dynamics and function in mammalian tissue physiology and have used them to uncover previously unknown functions for non-centrosomal microtubules during mammalian epidermal development.