Novel REST Truncation Mutations Causing Hereditary Gingival Fibromatosis

Area of Science:

• Genetics
• Molecular Biology
• Oral Pathology

Background:

• Hereditary gingival fibromatosis (HGF) is a rare genetic disorder causing pathological gingival overgrowth, leading to significant functional and esthetic issues.
• Previous studies identified mutations in the REST gene as a cause of HGF, but its role in gingival homeostasis and disease pathogenesis was unclear.

Purpose of the Study:

• To investigate the function of REST in gingival tissue and elucidate the molecular mechanisms underlying REST-associated HGF.
• To characterize novel mutations in the REST gene in HGF patients and assess their impact on REST protein function.

Main Methods:

• Genetic analysis of HGF families to identify mutations in the REST gene.
• In vitro reporter gene assays to evaluate the repressor activity of truncated REST proteins.
• Co-expression studies to assess the dominant-negative effect of mutant REST proteins.
• Immunofluorescence and immunohistochemistry to examine REST protein localization and expression in gingival tissues.

Main Results:

• Two novel REST mutations (c.2449C>T and c.2771_2793dup) were identified in HGF families, both resulting in truncated REST proteins.
• Truncated REST proteins exhibited partial or complete loss of repressor activity and exerted a dominant-negative effect on wild-type REST.
• Mutant REST proteins retained nuclear localization, and REST expression was reduced in HGF gingival tissues compared to normal tissues.

Conclusions:

• The study confirms the pathogenicity of REST truncation mutations in the last exon causing HGF.
• The findings suggest that REST-associated HGF results from an antimorphic (dominant-negative) disease mechanism, where truncated proteins interfere with normal REST function.