Supplementary Material for: Dynamics of RTEL1 helicase in meiotic cells: spatiotemporal distribution during prophase I in the rat Rattus norvegicus

Introduction. DNA helicases are vital for preserving genome integrity and ensuring the correct process of meiosis. Despite their recognized significance, the precise roles and spatial dynamics of these enzymes during meiotic prophase I remain largely unexplored. Methods. The key methodology of this study consisted of immunocytochemical staining and statistical evaluation. Results. Our results demonstrate that RTEL1 is present in regions that have just initiated synapsis, emphasizing that chromosome synapsis is not only essential for this helicase but potentially for other proteins involved in meiotic processes. Since RTEL1 and replication protein A (RPA) were previously shown to colocalize in somatic cells, we sought to assess this relationship in meiosis. During early pachytene, when RTEL1 and RPA levels are at their peak, several immunofoci of these proteins exhibited complete or partial overlap, suggesting colocalization in some chromosomal regions, though some remained distinct. The earlier appearance of RPA in meiotic nuclei supports the notion that it may facilitate RTEL1 recruitment for DNA repair. As meiosis progresses from early pachytene to diplotene, the significant decrease in RTEL1 and RPA signals underscores their predominant involvement in early prophase I. Conclusion. This study identifies RTEL1 as the third helicase, following BLM and FANCJ, to be detected in prophase I, suggesting that additional helicases may be added to this list in the future. Its unique synapsis-dependent behavior distinguishes it from the other two helicases, which do not exhibit such a pattern. Furthermore, our findings suggest that RTEL1 can demonstrates antirecombinase activity and functions as part of the meiotic helicase complex, which regulates critical aspects of meiotic processes.