Extensive N4 cytosine methylation is essential for Marchantia sperm function

Area of Science:

• Epigenetics
• Molecular Biology
• Developmental Biology

Background:

• N4-methylcytosine (4mC) is a known DNA modification in prokaryotes, but its presence and function in eukaryotes remained largely unknown.
• DNA methylation plays critical roles in gene regulation and genome stability.

Purpose of the Study:

• To investigate the presence and role of N4-methylcytosine (4mC) during eukaryotic spermatogenesis.
• To identify the mechanisms and biological significance of 4mC in reproductive development.

Main Methods:

• Analysis of DNA methylation patterns during spermatogenesis in Marchantia polymorpha.
• Identification and characterization of the methyltransferase responsible for 4mC installation.
• Gene deletion studies to assess the functional impact of MpDN4MT1a.

Main Results:

• Two waves of DNA methylation reprogramming were observed during spermatogenesis, including the installation of 4mC in genic regions.
• A specific methyltransferase, MpDN4MT1a, was identified as responsible for installing 4mC.
• Deletion of MpDN4MT1a led to altered sperm transcriptome, impaired sperm function, and defects in fertility and development.

Conclusions:

• This study demonstrates extensive N4-methylcytosine (4mC) modification in a eukaryote, Marchantia polymorpha.
• A novel family of eukaryotic methyltransferases involved in 4mC installation was identified.
• 4mC plays a critical role in eukaryotic reproductive development, expanding the known repertoire of functional DNA modifications.