Dissecting the genetic basis of Parkinson disease, dystonia and chorea

In this thesis I used of a range of genetic methodologies and strategies to unravel the genetic bases of Parkinson disease (PD), myoclonus-dystonia (M-D), and chorea. First, I detail the work I performed in PD, including (1) the screening of GBA in a cohort of early-onset PD cases, which led to the identification of the allele E326K (p.Glu365Lys) as the single most frequent, clinically relevant, risk variant for PD; (2) a detailed genetic analysis in a large cohort of PD cases who underwent deep-brain stimulation treatment and a longitudinal comparison of the phenotypic features of carriers of mutations in different genes; (3) the observation that rare GCH1 coding variants, known to be responsible for the childhood-onset disorder DOPA-responsive dystonia, are a novel risk factor for PD. Then, I describe the work I performed to identify novel causes of M-D, including (1) the discovery of the missense p.Arg145His mutation in KCTD17 as a novel cause of autosomal dominant M-D; (2) the identification of tyrosine hydroxylase deficiency as a novel treatable cause of recessive M-D; and (3) the conclusive disproof of the pathogenic role of the p.Arg1389His variant in CACNA1B as a cause of M-D. Finally, I detail my work in the field of choreic syndromes, including (1) the genetic screening of NKX2-1 in the Queen Square cohort of benign hereditary chorea (BHC) cases; (2) the identification of ADCY5 mutations, the gene thought to be responsible for the condition familial dyskinesias with facial myokymia, as an important cause of BHC; and (3) the identification of de novo mutations in PDE10A as a novel genetic cause of chorea. These findings are discussed in light of the recent literature. Following my analysis, I suggest future directions for the identification of novel genetic causes of movement disorders, in light of my recent findings and ongoing research.