iiinova — where your digital self keeps evolving

jameswalker303.bsky.social

@jameswalker303.bsky.social

208 followers 363 following 23 posts

jameswalker303.bsky.social @jameswalker303.bsky.social · 09/04/2025

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

111

jameswalker303.bsky.social @jameswalker303.bsky.social · 09/04/2025

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

110

jameswalker303.bsky.social @jameswalker303.bsky.social · 09/04/2025

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

110

jameswalker303.bsky.social @jameswalker303.bsky.social · 09/04/2025

The MpDN4MT1 gene appears to have originated via horizontal gene transfer from prokaryotes and has been retained for at least 200 million years— we detect it even in Lunularia cruciata, a liverwort from a distinct lineage to Marchantia. 4/13

210

jameswalker303.bsky.social @jameswalker303.bsky.social · 09/04/2025

We show that MpDN4MT1a, a eukaryotic homolog of bacterial 4mC methyltransferases, is the enzyme required for this modification. Loss of MpDN4MT1a abolishes 4mC, and reintroduction of wild-type—but not the catalytic mutant—restores it. 3/13

111

jameswalker303.bsky.social @jameswalker303.bsky.social · 09/04/2025

In our new paper, we use six methods to unambiguously validate the presence of extensive 4mC at CG sites across genic regions in mature sperm: 🧪 immunodot blot 🧪 LC-MS 🧬 Bisulfite-seq 🧬 SMRT-seq 🧬 4mC-TAB-seq 🧬 4mC-AMD-seq 2/13

111