Fig. 1

ATAC-seq sample preparation and sequence analysis. a S. purpuratus embryos were cultured for 24 h at 15 °C in triplicate. PMCs and other cells were isolated and ATAC-seq libraries were generated and sequenced. Sequence reads were analyzed by the bioinformatics pipeline shown in Additional file 1: Fig. S1A. b Examples of ATAC-seq differential peaks. These differential peaks (yellow rectangles) are located near the Sp-kirrelL gene, which encodes a transmembrane protein required for PMC fusion [27]. The aligned reads for each replicate are visualized, and the difference in peak magnitudes can be seen when comparing differential peaks in the isolated PMC replicates (light green peak trace) to the other cell replicates (dark green trace). Nominal p-values for differential peaks are indicated. c The distribution of ATAC-seq peaks in the RPS with respect to the closest gene. See Methods for definitions of peak locations. d Distribution of ATAC-seq differential peaks with respect to the closest gene