Thanks Max!! 😁😁

A putative 4mC methyltransferase is found in rotifers (N4CMT) that's also thought to have arisen through horizontal gene transfer from bacteria which we talk about briefly in the paper. Wouldn't be surprised if there are others examples out there to be found!

Thanks Jake!! 😄

Thanks Sean!! 😁😁😁

Thanks Li! 😎

Thanks Tatsuya!! :)

#DNA #methylation #4mC #epigenetics #germline #Marchantia #sperm #fertility #chromatin #reproduction #plantbiology #evolution

This work completes a story that started with strange bisulfite-seq anomalies during my PhD and ends with the discovery of a new epigenetic layer in eukaryotic reproduction.
Huge thanks to all co-authors, collaborators, and especially Xiaoqi Feng for guidance throughout.
13/13

In summary, our study establishes:
4mC is a functional DNA modification in eukaryotes
MpDN4MT1a is a eukaryotic 4mC writer
5mC and 4mC mark distinct chromatin domains in sperm
4mC coordinates transcriptional shutdown, chromatin compaction, sperm motility, and fertility
12/13

We also propose that 4mC could act as a paternal imprint—for example, guiding PRC2 targeting after fertilization. This may explain why loss of paternal 4mC reduces embryo viability and disrupts development.
11/13

Why deposit 4mC in Marchantia sperm?
We see no evidence of dual-modified 4,5mC, suggesting that 5mC blocks 4mC. This creates a clear division: 4mC marks genes, 5mC marks repeats.
This allows global methylation for compaction while preserving the TE-specific 5mC signature.
10/13

The motility defect is rescued by reintroducing wild-type MpDN4MT1a.
By contrast, sperm from global 5mC mutants show none of these distinctive phenotypes.
9/13

We now know that 4mC is essential for multiple aspects of sperm function.
Sperm lacking 4mC are motility-defective, outcompeted by wild-type sperm, and produce developmentally compromised embryos.
8/13

By contrast, transcripts for key sperm function genes—like CENTRIN1 and DYNEIN LIGHT CHAIN 7—are reduced, likely due to a dilution effect, helping explain the sperm motility defect in 4mC mutants.

7/13