Chromatin remodeler ISW-1 orchestrates chromosome axis assembly and meiotic progression in C. elegans.

During meiotic prophase, chromosomes undergo dynamic morphological changes that coordinate key events, including axis assembly, homolog pairing and synapsis, recombination, crossover formation, and large-scale chromosomal remodeling. Chromatin remodelers are conserved and abundant regulators of gene expression and chromatin dynamics, yet their roles in meiosis remain incompletely understood. Here, we investigate the function of the ISWI chromatin remodeler ISW-1 in Caenorhabditis elegans meiosis. We show that ISW-1 is essential for meiotic progression and physically interacts with components of the chromosome axis. Loss of ISW-1 disrupts axis integrity, impairs synapsis and crossover formation, and reduces physiological apoptosis during oogenesis, defects that are attributable to a non-transcriptional regulatory role. Additionally, ISW-1 deficiency causes chromosome deformation in late prophase oogenic cells and leads to more severe defects in axis formation during spermatogenesis. These findings uncover a critical role for the ISWI complex in orchestrating meiotic chromosome structure and function, in part through direct regulation of axis assembly and chromosome-wide remodeling.