Marialuisa Quadri

Mutation in the SYNJ1 gene associated with autosomal recessive, early-onset Parkinsonism.

Autosomal recessive, early‐onset Parkinsonism is clinically and genetically heterogeneous. Here, we report the identification, by homozygosity mapping and exome sequencing, of a SYNJ1 homozygous mutation (p.Arg258Gln) segregating with disease in an Italian consanguineous family with Parkinsonism, dystonia, and cognitive deterioration. Response to levodopa was poor, and limited by side effects. Neuroimaging revealed brain atrophy, nigrostriatal dopaminergic defects, and cerebral hypometabolism. SYNJ1 encodes synaptojanin 1, a phosphoinositide phosphatase protein with essential roles in the postendocytic recycling of synaptic vesicles. The mutation is absent in variation databases and in ethnically matched controls, is damaging according to all prediction programs, and replaces an amino acid that is extremely conserved in the synaptojanin 1 homologues and in SAC1‐like domains of other proteins. Sequencing the SYNJ1 ORF in unrelated patients revealed another heterozygous mutation (p.Ser1422Arg), predicted as damaging, in a patient who also carries a heterozygous PINK1 truncating mutation. The SYNJ1 gene is a compelling candidate for Parkinsonism; mutations in the functionally linked protein auxilin cause a similar early‐onset phenotype, and other findings implicate endosomal dysfunctions in the pathogenesis. Our data delineate a novel form of human Mendelian Parkinsonism, and provide further evidence for abnormal synaptic vesicle recycling as a central theme in the pathogenesis.

Mutations in SLC30A10 cause parkinsonism and dystonia with hypermanganesemia, polycythemia, and chronic liver disease.

Manganese is essential for several metabolic pathways but becomes toxic in excessive amounts. Manganese levels in the body are therefore tightly regulated, but the responsible protein(s) remain incompletely known. We studied two consanguineous families with neurologic disorders including juvenile-onset dystonia, adult-onset parkinsonism, severe hypermanganesemia, polycythemia, and chronic hepatic disease, including steatosis and cirrhosis. We localized the genetic defect by homozygosity mapping and then identified two different homozygous frameshift SLC30A10 mutations, segregating with disease. SLC30A10 is highly expressed in the liver and brain, including in the basal ganglia. Its encoded protein belongs to a large family of membrane transporters, mediating the efflux of divalent cations from the cytosol. We show the localization of SLC30A10 in normal human liver and nervous system, and its depletion in liver from one affected individual. Our in silico analyses suggest that SLC30A10 possesses substrate specificity different from its closest (zinc-transporting) homologs. We also show that the expression of SLC30A10 and the levels of the encoded protein are markedly induced by manganese in vitro. The phenotype associated with SLC30A10 mutations is broad, including neurologic, hepatic, and hematologic disturbances. Intrafamilial phenotypic variability is also present. Chelation therapy can normalize the manganesemia, leading to marked clinical improvements. In conclusion, we show that SLC30A10 mutations cause a treatable recessive disease with pleomorphic phenotype, and provide compelling evidence that SLC30A10 plays a pivotal role in manganese transport. This work has broad implications for understanding of the manganese biology and pathophysiology in multiple human organs.

PARK20 caused by SYNJ1 homozygous Arg258Gln mutation in a new Italian family

SYNJ1 has been recently identified by two independent groups as the gene defective in a novel form of autosomal recessive, early-onset atypical parkinsonism (PARK20). Two consanguineous families were initially reported (one of Sicilian and one of Iranian origins), with the same SYNJ1 homozygous mutation (c.773G > A, p.Arg258Gln) segregating with a similar phenotype of early-onset parkinsonism and additional atypical features. Here, we report the identification of the same SYNJ1 homozygous mutation in two affected siblings of a third pedigree. Both siblings had mild developmental psychomotor delay, followed, during the third decade of life, by progressive parkinsonism, dystonia, and mild cognitive impairment. One sibling suffered one episode of generalized seizures. Neuroimaging studies revealed severe nigrostriatal dopaminergic defects, mild striatal and very mild cortical hypometabolism. Treatment with dopamine agonists and anticholinergics resulted in partial improvements. Genetic analyses revealed in both siblings the SYNJ1 homozygous c.773G > A (p.Arg258Gln) mutation. Haplotype analysis suggests that the mutation has arisen independently in this family and the Sicilian PARK20 family previously described by us, in keeping with the hypothesis of a mutational hot spot. This is the third reported family with autosomal recessive, early-onset parkinsonism associated with the SYNJ1 p.Arg258Gln mutation. This work contributes to the definition of the genetic and clinical aspects of PARK20. This newly recognized form must be considered in the diagnostic work-up of patients with early-onset atypical parkinsonism. The presence of seizures might represent a red flag to suspect PARK20.

DNAJC6 Mutations Associated with Early-Onset Parkinson's Disease

DNAJC6 mutations were recently described in two families with autosomal recessive juvenile parkinsonism (onset age < 11), prominent atypical signs, poor or absent response to levodopa, and rapid progression (wheelchair‐bound within ∼10 years from onset). Here, for the first time, we report DNAJC6 mutations in early‐onset Parkinsons disease (PD).

Manganese Transport Disorder: Novel SLC30A10 Mutations and Early Phenotypes

SLC30A10 mutations cause an autosomal recessive disorder, characterized by hypermanganesaemia, polycythemia, early‐onset dystonia, paraparesis, or late‐onset parkinsonism, and chronic liver disease. This is the first identified inborn error of Mn metabolism in humans, reported in 10 families thus far.

Novel GCH1 variant in Dopa-responsive dystonia and Parkinson's disease

Background GTP cyclohydrolase I (GCH1) mutations are the commonest cause of Dopa-responsive dystonia (DRD). Clinical phenotypes can be broad, even within a single family. Methods We present clinical, genetic and functional imaging data on a British kindred in which affected subjects display phenotypes ranging from DRD to Parkinsons disease (PD). Twelve family members were studied. Clinical examination, dopamine transporter (DAT) imaging, and molecular genetic analysis of GCH1 and the commonest known familial PD-related genes were performed. Results We have identified a novel missense variant, c.5A > G, p.(Glu2Gly), within the GCH1 gene in affected family members displaying a range of phenotypes. Two affected subjects carrying this variant had abnormal DAT imaging. These two with abnormal DAT imaging had a PD phenotype, while the remaining three subjects with the novel GCH1 variant had normal DAT imaging and a DRD phenotype. Conclusions We propose that this GCH1 variant is pathogenic in this family and these findings suggest that similar mechanisms involving abnormal GTP cyclohydolase I may underlie both PD and DRD. GCH1 genetic testing should be considered in patients with PD and a family history of DRD.

Analysis of LRRK2, SNCA, Parkin, PINK1, and DJ-1 in Zambian patients with Parkinson's disease

Recent studies delineate substantial genetic components in Parkinsons disease (PD). However, very few studies were performed in Sub-Saharan African populations. Here, we explore the contribution of known PD-causing genes in patients of indigenous Zambian ancestry. We studied thirty-nine Zambian patients, thirty-eight with PD and one with parkinsonian-pyramidal syndrome (18% familial; average onset age 54.9 ± 12.2 years). In the whole group, all SNCA exons and LRRK2 exons 29 to 48 (encoding for important functional domains) were sequenced. In the familial patients and those with onset <55 years (n = 22) the whole LRRK2 coding region was sequenced (51 exons). In the patients with onset <50 years (n = 12), all parkin, PINK1, and DJ-1 exons were sequenced, and dosage analysis of parkin, PINK1, DJ-1, LRRK2, and SNCA was performed. Dosage analysis was also performed in the majority of the late-onset patients. The LRRK2 p.Gly2019Ser mutation was not detected. A novel LRRK2 missense variant (p.Ala1464Gly) of possible pathogenic role was found in one case. Two heterozygous, likely disease-causing deletions of parkin (exon 2 and exon 4) were detected in an early-onset case. Pathogenic mutations were not detected in SNCA, PINK1, or DJ-1. We also report variability at several single nucleotide polymorphisms in the above-mentioned genes. This is the first molecular genetic study in Zambian PD patients, and the first comprehensive analysis of the LRRK2 and SNCA genes in a Sub-Saharan population. Common disease-causing mutations were not detected, suggesting that further investigations in PD patients from these populations might unravel the role of additional, still unknown genes.

Genetics of movement disorders in the next-generation sequencing era

Several innovative and extremely powerful methods for sequencing nucleic acids (DNA and RNA), collectively known as next‐generation sequencing technologies, have become available in the past few years. The application of these technologies is rapidly changing the landscape of both medical genetic research and clinical practice: the pace of discovery of novel disease‐causing or disease‐predisposing genes is markedly accelerating; the phenotypic spectra associated with previously known genes is expanding; and novel tools for rapid, cheap, and comprehensive genetic testing are entering the clinical practice. As with every technological revolution, next‐generation sequencing also comes with new challenges concerning the storage, the analysis, and crucially, the interpretation of the large amounts of generated data. The current possibility to sequence entire human exomes (the coding part of the genome) or entire genomes at affordable costs has brought the era of personalized medicine closer than ever, also raising new legal and ethical issues. In this article, we summarize the essential technological aspects of next‐generation sequencing and discuss their applications in the field of movement disorders. We review the different strategies for gene finding enabled by these technologies (including project designs, filtering approaches, and bioinformatic tools) and we then discuss their applications in clinical practice.

Paroxysmal exercise-induced dystonia within the phenotypic spectrum of ECHS1 deficiency

ECHS1 encodes a mitochondrial enzyme involved in the degradation of essential amino acids and fatty acids. Recently, ECHS1 mutations were shown to cause a new severe metabolic disorder presenting as Leigh or Leigh‐like syndromes. The objective of this study was to describe a family with 2 siblings affected by different dystonic disorders as a resulting phenotype of ECHS1 mutations.

An exome study of Parkinson's disease in Sardinia, a Mediterranean genetic isolate

Parkinson’s disease (PD) is a common neurodegenerative disorder of complex aetiology. Rare, highly penetrant PD-causing mutations and common risk factors of small effect size have been identified in several genes/loci. However, these mutations and risk factors only explain a fraction of the disease burden, suggesting that additional, substantial genetic determinants remain to be found. Genetically isolated populations offer advantages for dissecting the genetic architecture of complex disorders, such as PD. We performed exome sequencing in 100 unrelated PD patients from Sardinia, a genetic isolate. SNPs absent from dbSNP129 and 1000 Genomes, shared by at least five patients, and of functional effects were genotyped in an independent Sardinian case-control sample (n = 500). Variants associated with PD with nominal p value <0.05 and those with odds ratio (OR) ≥3 were validated by Sanger sequencing and typed in a replication sample of 2965 patients and 2678 controls from Italy, Spain, and Portugal. We identified novel moderately rare variants in several genes, including SCAPER, HYDIN, UBE2H, EZR, MMRN2 and OGFOD1 that were specifically present in PD patients or enriched among them, nominating these as novel candidate risk genes for PD, although no variants achieved genome-wide significance after Bonferroni correction. Our results suggest that the genetic bases of PD are highly heterogeneous, with implications for the design of future large-scale exome or whole-genome analyses of this disease.