Computational Tools for the Analysis of Meiotic Prophase I Images

Abstract

Prophase I is a remarkable stage of meiotic division during which homologous chromosomes pair together and exchange DNA by meiotic recombination. Fluorescence microscopy of meiotic chromosome spreads is a central tool in the study of this process, with chromosome axis proteins being visualised as extended filaments upon which recombination proteins localise in focal patterns. Chromosome pairing and recombination are dynamic processes, and hundreds of recombination foci can be present in some meiotic nuclei. As meiotic nuclei can exhibit significant variations in staining patterns within and between nuclei, particularly in mutants, manual analysis of images presents challenges for consistency, documentation, and reproducibility. Here we share a combination of complementary computational tools which can be used to partially automate the quantitative analysis of meiotic images. 1) The segmentation of axial and focal staining patterns, to automatically measure chromosome axis length and count axis-associated (and non-axis associated) recombination foci; 2) Quantification of focus position along chromosome axes to investigate spatial regulation; 3) Simulation of random distributions of foci within the nucleus or along the chromosome axes to statistically investigate observed foci-axis associations and foci-foci associations; 4) Quantification of chromosome axis proximity to investigate relationships with chromosome synapsis/asynapsis; 5) Quantification of and orientation of focus-axis distances. Together these tools provide a framework to perform routine documentation and analysis of meiotic images, as well as opening up routes to build on this initial output and perform more detailed analyses.