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AIFM1
apoptosis inducing factor mitochondria associated 1
AIFM1 is located on the long (q) arm of chromosome X, at band Xq26.1. Arm ratio per GRCh38 - banding schematic.
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Clinical tests that include this
Overview
The AIFM1 gene encodes apoptosis-inducing factor, a protein essential for mitochondrial function and cellular responses to severe stress. Under normal conditions, AIF resides in the inner mitochondrial membrane, where it participates in the electron transport chain that generates cellular energy. The protein contains specialised signals that direct it to mitochondria and, under specific circumstances, to the cell nucleus.
Pathogenic changes in AIFM1 disrupt mitochondrial energy production, leading to disorders that predominantly affect tissues with high energy demands such as the brain, peripheral nerves, and heart muscle. Because AIFM1 is located on the X chromosome, the inheritance pattern and clinical severity often differ between males and females. The gene is included on multiple NHS Genomic Medicine Service panels for mitochondrial disorders, intellectual disability, and hereditary neuropathy.
What the gene does
The AIFM1 protein functions as an FAD-dependent oxidoreductase within mitochondria, meaning it uses flavin adenine dinucleotide (FAD) as a cofactor to catalyse electron transfer reactions. This enzymatic activity contributes to the respiratory chain's efficient operation, helping cells convert nutrients into usable energy in the form of ATP. The protein's oxidoreductase domain spans a substantial portion of its structure, reflecting its importance in mitochondrial metabolism.
Beyond energy production, AIF plays a context-dependent role in programmed cell death. When mitochondria sustain severe damage, AIF can be released and migrate to the nucleus, where it participates in DNA fragmentation and chromatin condensation. This dual function - supporting life under normal conditions whilst mediating death when necessary - makes AIF a critical regulator of cellular fate. The protein's ability to shuttle between compartments is controlled by specific localisation signals that respond to cellular stress cues.
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Chromosome location
AIFM1 is located on the long arm of the X chromosome at position Xq26.1. This chromosomal position places it in the context of X-linked inheritance, where males (who have only one X chromosome) are typically more severely affected by pathogenic variants than females (who have two X chromosomes and may benefit from random X-inactivation). The gene's X-linked location influences both clinical presentation patterns and family inheritance dynamics.
Protein structure
The AIFM1 protein comprises 613 amino acids organised into several functional regions. Two mitochondrial localisation signals occupy amino acids 1-31 and 63-89, directing the newly synthesised protein to mitochondria where it performs its primary metabolic functions. The central FAD-dependent oxidoreductase region spans amino acids 134-483, forming the catalytic core responsible for electron transfer activity.
A nuclear localisation signal at positions 446-451 enables the protein to enter the nucleus when cellular conditions trigger apoptotic pathways. Disordered regions at amino acids 100-127 and 513-554 likely provide structural flexibility, allowing the protein to interact with different binding partners and adapt to various functional contexts within the cell.
Key variants
Pathogenic variants in AIFM1 encompass missense changes that alter single amino acids, as well as deletions and insertions that disrupt protein production or stability. Variants affecting the oxidoreductase domain tend to impair mitochondrial energy metabolism, whilst those influencing localisation signals may alter the protein's distribution between cellular compartments. The severity of clinical features often correlates with how extensively a variant compromises protein function.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
AIFM1-related disorders form a spectrum of mitochondrial conditions affecting multiple organ systems. Affected individuals may present with progressive neurodegeneration, peripheral neuropathy causing muscle weakness and sensory changes, sensorineural hearing loss, or cardiomyopathy. Some patients develop intellectual disability or white matter abnormalities visible on brain imaging. The clinical presentation varies considerably, with some individuals experiencing isolated symptoms whilst others have multisystem involvement. Because energy-demanding tissues are most vulnerable to mitochondrial dysfunction, neurological features predominate in many cases.
No disease links recorded for this gene in our reference set.
UK clinical status
AIFM1 holds green (high evidence) classification on multiple NHS Genomic Medicine Service panels, reflecting its established role in inherited disease. These include the Mitochondrial Disorders panel, Hereditary Neuropathy panel, Intellectual Disability panel, and Likely Inborn Error of Metabolism panel. The gene also appears on panels for monogenic hearing loss, paediatric cardiomyopathy, white matter disorders, and undiagnosed metabolic conditions. This broad panel representation indicates that AIFM1 testing is appropriate across diverse clinical presentations where mitochondrial dysfunction is suspected.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
Why does AIFM1 affect males and females differently?
AIFM1 is located on the X chromosome, so males have only one copy whilst females have two. Males with a pathogenic variant typically show more severe symptoms because they lack a second, functional copy. Females may have milder features or be unaffected depending on which X chromosome is active in different cells.
What types of symptoms suggest an AIFM1-related condition?
Common features include progressive muscle weakness, peripheral neuropathy affecting sensation and movement, hearing loss, and intellectual disability. Some individuals develop heart muscle problems or brain white matter changes. The combination and severity of symptoms vary considerably between affected individuals.
How is AIFM1 tested in the NHS?
AIFM1 is included on multiple NHS Genomic Medicine Service gene panels for mitochondrial disorders, neuropathy, intellectual disability, and related conditions. Testing is typically arranged through specialist clinics when clinical features suggest a mitochondrial or neurogenetic disorder. Genetic counsellors can discuss testing options and implications for families.