PRKDC mutations in a SCID patient with profound neurological abnormalities

Area of Science:

• Genetics and Molecular Biology
• Immunology
• Neuroscience

Background:

• DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is crucial for DNA double-strand break repair via non-homologous end-joining (NHEJ).
• NHEJ is essential for V(D)J recombination during lymphocyte development.

Observation:

• A patient with compound heterozygous PRKDC mutations exhibited low DNA-PKcs expression, reduced kinase activity, and impaired DNA repair.
• The patient presented with severe combined immunodeficiency (SCID), dysmorphic features, microcephaly, seizures, and profound neurological dysfunction.
• MRI revealed cortical and hippocampal dysplasia and progressive brain atrophy, more severe than in other NHEJ-deficient individuals.

Findings:

• One PRKDC mutation fully inactivated DNA-PKcs, while the other conferred significantly diminished residual function.
• Human neuronal development, unlike in animal models, showed a stringent requirement for DNA-PKcs.
• High DNA-PKcs expression appears necessary for efficient prenatal and postnatal neurogenesis.

Implications:

• This study identifies a critical role for DNA-PKcs in human neurodevelopment, diverging from findings in animal models.
• It suggests potential therapeutic targets for neurodevelopmental disorders linked to DNA repair pathways.
• The research underscores the importance of species-specific differences in understanding genetic disease mechanisms.