A. Di Fonzo

ATP13A2 missense mutations in juvenile parkinsonism and young onset Parkinson disease

Objective: To assess the prevalence, nature, and associated phenotypes of ATP13A2 gene mutations among patients with juvenile parkinsonism (onset <21 years) or young onset (between 21 and 40 years) Parkinson disease (YOPD). Methods: We studied 46 patients, mostly from Italy or Brazil, including 11 with juvenile parkinsonism and 35 with YOPD. Thirty-three cases were sporadic and 13 had positive family history compatible with autosomal recessive inheritance. Forty-two had only parkinsonian signs, while four (all juvenile-onset) had multisystemic involvement. The whole ATP13A2 coding region (29 exons) and exon-intron boundaries were sequenced from genomic DNA. Results: A novel homozygous missense mutation (Gly504Arg) was identified in one sporadic case from Brazil with juvenile parkinsonism. This patient had symptoms onset at age 12, levodopa-responsive severe akinetic-rigid parkinsonism, levodopa-induced motor fluctuations and dyskinesias, severe visual hallucinations, and supranuclear vertical gaze paresis, but no pyramidal deficit nor dementia. Brain CT scan showed moderate diffuse atrophy. Furthermore, two Italian cases with YOPD without atypical features carried a novel missense mutation (Thr12Met, Gly533Arg) in single heterozygous state. Conclusions: We confirm that ATP13A2 homozygous mutations are associated with human parkinsonism, and expand the associated genotypic and clinical spectrum, by describing a homozygous missense mutation in this gene in a patient with a phenotype milder than that initially associated with ATP13A2 mutations (Kufor-Rakeb syndrome). Our data also suggest that ATP13A2 single heterozygous mutations might be etiologically relevant for patients with YOPD and further studies of this gene in Parkinson disease are warranted.

FBXO7 mutations cause autosomal recessive, early-onset parkinsonian-pyramidal syndrome

Background: The combination of early-onset, progressive parkinsonism with pyramidal tract signs has been known as pallido-pyramidal or parkinsonian-pyramidal syndrome since the first description by Davison in 1954. Very recently, a locus was mapped in a single family with an overlapping phenotype, and an FBXO7 gene mutation was nominated as the likely disease cause. Methods: We performed clinical and genetic studies in two families with early-onset, progressive parkinsonism and pyramidal tract signs. Results: An FBXO7 homozygous truncating mutation (Arg498Stop) was found in an Italian family, while compound heterozygous mutations (a splice-site IVS7 + 1G/T mutation and a missense Thr22Met mutation) were present in a Dutch family. We also found evidence of expression of novel normal splice-variants of FBXO7. The phenotype associated with FBXO7 mutations consisted of early-onset, progressive parkinsonism and pyramidal tract signs, thereby matching clinically the pallido-pyramidal syndrome of Davison. The parkinsonism exhibits varying degrees of levodopa responsiveness in different patients. Conclusions: We conclusively show that recessive FBXO7 mutations cause progressive neurodegeneration with extrapyramidal and pyramidal system involvement, delineating a novel genetically defined entity that we propose to designate as PARK15. 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.

The G6055A (G2019S) mutation in LRRK2 is frequent in both early and late onset Parkinson’s disease and originates from a common ancestor

Background: Mutations in the gene Leucine-Rich Repeat Kinase 2 (LRRK2) were recently identified as the cause of PARK8 linked autosomal dominant Parkinson’s disease. Objective: To study recurrent LRRK2 mutations in a large sample of patients from Italy, including early (<50 years) and late onset familial and sporadic Parkinson’s disease. Results: Among 629 probands, 13 (2.1%) were heterozygous carriers of the G2019S mutation. The mutation frequency was higher among familial (5.1%, 9/177) than among sporadic probands (0.9%, 4/452) (p<0.002), and highest among probands with one affected parent (8.7%, 6/69) (p<0.001). There was no difference in the frequency of the G2019S mutation in probands with early v late onset disease. Among 600 probands, one heterozygous R1441C but no R1441G or Y1699C mutations were detected. None of the four mutations was found in Italian controls. Haplotype analysis in families from five countries suggested that the G2019S mutation originated from a single ancient founder. The G2019S mutation was associated with the classical Parkinson’s disease phenotype and a broad range of onset age (34 to 73 years). Conclusions: G2019S is the most common genetic determinant of Parkinson’s disease identified so far. It is especially frequent among cases with familial Parkinson’s disease of both early and late onset, but less common among sporadic cases. These findings have important implications for diagnosis and genetic counselling in Parkinson’s disease.

Remarkable infidelity of polymerase γA associated with mutations in POLG1 exonuclease domain

Objective: To better understand the still unknown pathologic mechanism involved in the accumulation of multiple mtDNA deletions in stable tissues. Methods: A large-scale screening of mtDNA molecules from skeletal muscle was performed in 14 patients with progressive external ophthalmoplegia (PEO) and 2 patients with mitochondrial neurogastrointestinal encephalomyopathy carrying mutations on ANT1, C10ORF2 or POLG1, and TP genes. Results: Patients with at least one mutation in the exonuclease domain of POLG1 showed the highest frequency of individually rare point mutations only in the mtDNA control region; in addition, high levels, in terms of frequency and heteroplasmy, of recurrent mutations (A189G, T408A, and T414G) and alterations affecting the (HT)D310 region were detectable in many of the patients. Two homozygous POLG1 mutations, within the exonuclease domain, were able to induce an increased mutational burden also in fibroblasts from patients with PEO. Conclusions: Specific POLG1 mutations directly affect the integrity of the mtDNA by reducing its proof-reading exonuclease activity, resulting in the accumulation of heteroplasmic levels of both randomly rare and recurrent point mutations in the skeletal muscle tissue and fibroblasts.

Adaptive deep brain stimulation in patients with Parkinson’s disease: phase II clinical trial preliminary results

CO RR EC TE D P RO OF compared with entacapone (ENT) and placebo, in levodopa-treated patients with Parkinson’s disease (PD) and motor-fluctuations. Methods: Multinational, multicentre, double-blind, 14-15-week, placeboand active-controlled study. The primary efficacy variable was the change from baseline in absolute OFF-time based on patient’s diaries. Superiority vs. placebo and non-inferiority vs. ENT were tested under a gatekeeping procedure. Key secondary efficacy endpoint was the proportion of OFFand ON-responders (≥1-h improvement). Other measures included the global assessment of change, symptoms and quality-of-life scales (IGAC, SGAC, UPDRS, PDQ-39, NMSS, PDSS). Results: 600 patients were randomized to placebo (n = 121), 5 mgOPC (n = 122), 25 mg-OPC (n = 119), 50 mg-OPC (n = 116) or ENT (n = 122). Both 50 mg-OPC and ENT significantly reducedmean daily OFF-time (-1.95-h [p = 0.0015] 50 mg-OPC and -1.61-h [p = 0.0141] ENT vs. -0.93-h placebo) and increased the ON-time without troublesome dyskinesia (1.82-h [p = 0.0016] 50 mg-OPC and 1.57-h [p = 0.0150] ENT vs. 0.78-h placebo). Non-inferiority was met for 50 mg-OPC (p = 0.00518). Significantly more patients receiving 25 mgor 50 mg-OPC achieved the OFF-time responder endpoint (60.3% [p = 0.0464] 25 mg-OPC and 69.6% [p = 0.0011] 50 mg-OPC vs. 47.5% placebo). Either 5 mg-OPC and ENT missed statistical significance. A significant proportion ofON-responderswas also found for 50 mg-OPC (65.2% [p= 0.0028]). Significant improvements in IGAC and SGAC scores were observed for 25 mgand 50 mg-OPC, but not for ENT. OPC and ENT were generally safe and well tolerated. Conclusion: OPC, particularly 50 mg-OPC, was effective in reducing OFF-time in PD patients with a favourable profile compared to ENT.