Automated Analysis of Embryonic Hair Follicle Phenotypes

Abstract

Planar Cell Polarity (PCP) regulates alignment and long-range coordination of cellular structures and collective cell behaviors in diverse processes during development and in disease conditions. One such process is the polarization and alignment of hair follicles on the mammalian skin; this system provides an excellent model to study PCP coordination as there are thousands of hair follicles distributed across the skin, providing an accessible and easily visualizable readout of PCP function. In many PCP mutants, hair follicle phenotypes change over the course of development and early postnatal stages, occasionally even correcting to a near-wildtype phenotype. Thus, following hair follicle phenotypes over the time course of development is essential to understanding the subtleties of disruptions to the PCP pathway. While some tools exist to automate analysis of postnatal hair follicle orientations, no such a tool currently exists for embryonic skins. In addition, no currently available tool is able to assign a 360° vector of polarization to hair follicles at any stage; rather, current analysis relies on a 180° axis of alignment or manual measurements. Here I present a new tool, ARTICHOC (Automated Recognition of Two Immunostains to Compute Hair follicle Orientation and Coordination), an automated tool that assigns a 360° angle to hair follicles in the embryonic skin. ARTICHOC analyzes stitched images covering the full skin of an embryo and generates intuitive plots to easily differentiate hair follicle phenotypes with full spatial resolution. Using ARTICHOC, I analyze the embryonic phenotype and genetic interactions of a novel mutation affecting global coordination of hair follicle alignment and provide support for the hypothesis that this mutation represents a hypomorphic allele of a core PCP pathway component.