Mutations in several autosomal genes, including the F-box only protein 7 (FBXO7) gene, have been found in patients suffering from juvenile-onset parkinsonism with pyramidal signs.
We review the literature of genetic PD autopsies from cases with molecularly confirmed PD or parkinsonism and summarize main findings on SNCA (n = 25), Parkin (n = 20, 17 bi-allelic and 3 heterozygotes), PINK1 (n = 5, 1 bi-allelic and 4 heterozygotes), DJ-1 (n = 1), LRRK2 (n = 55), GBA (n = 10 Gaucher disease patients with parkinsonism), DNAJC13, GCH1, ATP13A2, PLA2G6 (n = 8 patients, 2 with PD), MPAN (n = 2), FBXO7, RAB39B, and ATXN2 (SCA2), as well as on 22q deletion syndrome (n = 3).
The F-box protein 7 (FBXO7) mutations have been identified in families with early-onset parkinsonism and pyramidal tract signs, and designated as PARK15.
Analysis of the non-synonymous SNVs that were not shared between the two family members revealed non-synonymous SNVs related to parkinsonism including a novel heterozygous mutation (p.T44N) in FBX07 (PARK15) only in the proband, and non-synonymous SNVs related to neurodegeneration with brain iron accumulation in the affected brother.
Mutations in FBXO7 (PARK15) have been associated with a syndrome characterized by early-onset progressive parkinsonism with and without pyramidal tract signs.
Mutations in the F-box protein 7 gene (FBXO7) have been identified to cause Parkinsonian-pyramidal syndrome, an autosomal recessive form of Parkinsonism.
Among them, PARK15 -associated parkinsonism, also referred to as parkinsonian-pyramidal disease (PPD), was found to be caused by mutations in the F-box only protein 7 gene (FBXO7).
Recessive mutations in the F-box only protein 7 gene (FBXO7) cause PARK15, a mendelian form of early-onset, levodopa-responsive parkinsonism with severe loss of nigrostriatal dopaminergic neurons.
Mutations in other genes, including ATP13A2 (PARK9), PLA2G6 (PARK14), and FBX07 (PARK15), cause more rare forms of recessive parkinsonism with very early-onset (<30 years) and usually additional, atypical features (pyramidal, dystonic, ocular movement, and cognitive disturbances).
Mutations in the ATP13A2 (PARK9) and FBXO7 (PARK15) genes are linked to different forms of autosomal recessive juvenile-onset neurodegenerative diseases with overlapping phenotypes, including levodopa-responsive parkinsonism, pyramidal disturbances, cognitive decline, and supranuclear gaze disturbance.
In order to investigate the characteristics of FBXO7 gene mutations in Chinese early-onset Parkinsonism patients, we performed polymerase chain reaction and DNA direct sequencing on 135 patients and 200 controls.
We cover dopa-responsive dystonia, Wilson's disease, Parkin-, PINK1-, and DJ-1-associated parkinsonism (PARK2, 6, and 7), x-linked dystonia-parkinsonism/Lubag (DYT3), rapid-onset dystonia-parkinsonism (DYT12) and DYT16 dystonia, the syndromes of Neurodegeneration with Brain Iron Accumulation (NBIA) including pantothenate kinase (PANK2)- and PLA2G6 (PARK14)-associated neurodegeneration, neuroferritinopathy, Kufor-Rakeb disease (PARK9) and the recently described SENDA syndrome; FBXO7-associated neurodegeneration (PARK15), autosomal-recessive spastic paraplegia with a thin corpus callosum (SPG11), and dystonia parkinsonism due to mutations in the SLC6A3 gene encoding the dopamine transporter.
Understanding how FBXO7 mutations cause disease will shed further light on the molecular mechanisms of neurodegeneration, with potential implications also for more common forms of parkinsonism, such as Parkinson disease and multiple system atrophy.