Seminars

During sperm development in the liverwort Marchantia polymorpha, DNA methylation undergoes extensive changes, including widespread methylation associated with global transcriptional shutdown. We also identified methylation targeting specific developmental genes earlier in sperm development, but these changes were not accompanied by changes in gene expression measured using bulk RNA-seq. To investigate this, we developed single-nucleus approaches to measure DNA methylation and gene expression in the same nucleus during male reproductive development. These analyses reveal that methylation of developmental genes is associated with reduced gene expression specifically in the male germline. We further show that the DNA methyltransferase DNMT3A is required for establishing these methylation patterns and normal male reproductive development. Finally, we examine how DNA methylation changes during the cell cycle in developing germ cells, revealing temporary losses during DNA replication followed by restoration of transposon methylation. Together, these findings reveal the dynamic nature of DNA methylation during sperm development and its role in regulating gene expression.