DNMT1 mutations found in HSANIE patients affect interaction with UHRF1 and neuronal differentiation

Area of Science:

• Molecular Biology
• Genetics
• Epigenetics

Background:

• DNA methylation is crucial for maintaining genomic stability and gene regulation, primarily mediated by DNMT1.
• DNMT1 recruitment to replication sites involves PCNA and UHRF1, with its N-terminal regulatory domain playing a key role.
• Mutations in the DNMT1 targeting sequence (TS) domain are linked to neurological disorders like HSANIE.

Purpose of the Study:

• To investigate the molecular mechanisms by which DNMT1 mutations in HSANIE patients affect DNA methylation and cellular function.
• To elucidate the role of the DNMT1 TS domain in heterochromatin association, UHRF1 interaction, and protein stability.
• To understand the impact of these mutations on neuronal differentiation and cell survival.

Main Methods:

• Functional complementation assays in mouse embryonic stem cells.
• Cell-based assays to assess DNMT1 heterochromatin association and catalytic complex formation.
• DNMT1 rescue assays to evaluate neuronal differentiation and apoptosis.

Main Results:

• HSANIE-associated DNMT1 mutations (P496Y, Y500C) impair heterochromatin association and UHRF1 interaction, causing DNA hypomethylation.
• Deletion of DNMT1 interacting domains in UHRF1 also led to DNA methylation defects.
• Mutated DNMT1 exhibited decreased protein stability in late S and G2 phases and impaired neuronal differentiation, increasing apoptosis.

Conclusions:

• The DNMT1 TS domain is critical for proper DNA methylation regulation in pluripotent and differentiating cells.
• DNMT1 dysfunction due to HSANIE mutations underlies the observed neurological and cellular phenotypes.
• Understanding these mechanisms provides insight into HSANIE pathogenesis and potential therapeutic targets.