Mitochondrial disease
Gene: FASTKD5
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
Phenotypes
Mitochondrial complex IV deficiency, nuclear type 24, MIM# 621431
3 unrelated individuals with Leigh syndrome (1 x severe/early-onset/fatal, 1 x milder/childhood-onset, 1 x adult-onset). WES identified compound heterozygous variants in FASTKD5 gene (3 x missense variants, 2 x frameshift variants leading to a premature stop codon). The FASTKD5 gene codes for a mitochondrial protein essential for processing mRNAs at non-canonical cleavage sites in the primary mitochondrial transcript.
Analysis of fibroblasts from two subjects showed reduced steady-state levels of FASTKD5 protein by immunoblot, reduced translation of the cytochrome c oxidase subunit 1, impaired assembly of complex IV, and a consequent decrease in cytochrome c oxidase enzymatic activity. The extent of these deficiencies appeared to correlate with the severity of the clinical phenotype. Expression of a wild-type FASTKD5 cDNA, but not cDNAs expressing the missense variants, rescued all the molecular defects in the subjects' fibroblasts, demonstrating that the alleles are pathogenic. 2/3 missense variants resulted in near complete loss of function, while one was hypomorphic, resulting from impaired protein stability.
Sources: LiteratureCreated: 16 Jul 2025, 7:24 a.m.
Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal
Phenotypes
Leigh syndrome MONDO:0009723
Publications
Phenotypes for gene: FASTKD5 were changed from Leigh syndrome MONDO:0009723, FASTKD5-related to Mitochondrial complex IV deficiency, nuclear type 24, MIM# 621431
Gene: fastkd5 has been classified as Green List (High Evidence).
Phenotypes for gene: FASTKD5 were changed from Leigh syndrome MONDO:0009723 to Leigh syndrome MONDO:0009723, FASTKD5-related
Gene: fastkd5 has been classified as Green List (High Evidence).
gene: FASTKD5 was added gene: FASTKD5 was added to Mitochondrial disease. Sources: Literature Mode of inheritance for gene: FASTKD5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: FASTKD5 were set to PMID: 40499538 Phenotypes for gene: FASTKD5 were set to Leigh syndrome MONDO:0009723 Review for gene: FASTKD5 was set to GREEN