Biochemical features of primary cells from a pediatric patient with a gain-of-function ODC1 genetic mutation

Area of Science:

• Genetics
• Biochemistry
• Developmental Biology

Background:

• A novel autosomal dominant disorder is caused by a de novo mutation in the ornithine decarboxylase 1 (ODC1) gene.
• This condition presents with global developmental delay, alopecia, overgrowth, and dysmorphic features.
• The mutation is hypothesized to create a C-terminally truncated ODC protein resistant to degradation, leading to putrescine accumulation.

Purpose of the Study:

• To investigate the molecular mechanism underlying the ODC1-related genetic disorder.
• To quantify ODC protein and putrescine levels in patient-derived cells.
• To assess the functional activity of the mutated ODC protein and the therapeutic potential of an ODC inhibitor.

Main Methods:

• Analysis of primary dermal fibroblasts from a patient with the ODC1 mutation and control subjects.
• Quantification of ODC protein and putrescine levels using biochemical assays.
• Measurement of ODC enzyme activity via a 14C radioactive assay.
• Treatment of patient fibroblasts with the ODC inhibitor α-difluoromethylornithine (DFMO).

Main Results:

• Patient fibroblasts exhibited significantly elevated ODC protein and putrescine levels compared to controls.
• The mutated ODC protein variant showed markedly increased enzymatic activity (12-17 fold in fibroblasts, 125-137 fold in RBCs).
• DFMO treatment normalized ODC activity and putrescine levels without causing adverse effects on cell viability or morphology.

Conclusions:

• The identified ODC1 mutation leads to a gain-of-function variant causing putrescine accumulation and disease phenotype.
• Elevated ODC activity and putrescine levels are key pathological features of this disorder.
• DFMO demonstrates therapeutic potential for patients with ODC1 gain-of-function mutations, warranting further clinical investigation.