A germline HLTF mutation in familial MDS induces DNA damage accumulation through impaired PCNA polyubiquitination

Area of Science:

• Genetics
• Molecular Biology
• Hematology

Background:

• Familial myelodysplastic syndromes (MDS) have known causal genes, but the full genetic landscape and molecular pathogenesis remain unclear.
• Identifying novel driver genes is crucial for understanding MDS development.

Purpose of the Study:

• To identify novel driver genes in familial MDS.
• To elucidate the molecular mechanisms underlying MDS pathogenesis associated with identified variants.

Main Methods:

• Whole-exome sequencing was performed on four individuals from a familial MDS pedigree.
• Candidate variants underwent knockdown screening in murine bone marrow stem/progenitor cells.
• DNA damage assays (γH2AX staining) were conducted in human acute myeloid leukemia (AML) cell lines.
• Protein interaction assays assessed the effect of the HLTF E259K mutation on binding with ubiquitin-conjugating enzymes.

Main Results:

• Whole-exome sequencing identified 10 candidate single-nucleotide variants, including HLTF.
• Downregulation of HLTF enhanced colony-forming capacity in primary murine bone marrow stem/progenitor cells.
• The HLTF E259K mutation, a loss-of-function variant, led to increased DNA damage in AML cells.
• The E259K mutation impaired HLTF's binding to specific ubiquitin-conjugating enzymes, resulting in reduced proliferating cell nuclear antigen (PCNA) polyubiquitination.

Conclusions:

• A familial MDS-associated germline mutation, HLTF E259K, induces DNA double-strand breaks.
• Impaired PCNA polyubiquitination is a potential mechanism by which HLTF E259K causes DNA damage.
• This study identifies HLTF as a novel gene implicated in MDS pathogenesis.