Functional characterization of a biallelic MIPEP variant associated with global developmental delay, infantile...

Area of Science:

• Biochemistry
• Genetics
• Cell Biology

Background:

• Mitochondrial intermediate peptidase (MIP) processes mitochondrial proteins.
• Biallelic MIPEP variants are associated with severe mitochondrial disease, including cardiomyopathy and neurological defects.
• The precise role of MIP in mitochondrial function and disease pathogenesis requires further elucidation.

Purpose of the Study:

• To identify and functionally characterize a novel homozygous MIPEP variant.
• To investigate the impact of this variant on MIP function and substrate processing.
• To expand the understanding of the genetic and phenotypic spectrum of MIPEP-linked mitochondrial disorders.

Main Methods:

• Genetic analysis of a patient with developmental delay and epilepsy.
• Functional characterization of the identified MIPEP variant using patient-derived fibroblasts.
• Assessment of MIP abundance and processing of known MIP substrates (MRPL12, NDUFV2, ATP5F1).

Main Results:

• A novel homozygous MIPEP variant was identified in a patient with a milder phenotype including global developmental delay, infantile epileptic spasms syndrome, and hypotonia.
• Patient fibroblasts showed reduced MIP protein levels and impaired processing of MIP substrates.
• Complementation with wild-type MIPEP restored normal MIP function and substrate processing.

Conclusions:

• The identified MIPEP variant is pathogenic and expands the known clinical spectrum of MIPEP-linked mitochondrial disease.
• This finding highlights the role of MIP in neurodevelopment and suggests a genotype-phenotype correlation.
• Further research into MIP function is crucial for understanding mitochondrial disorders.