Neurodevelopmental and synaptic defects in DNAJC6 parkinsonism, amenable to gene therapy.

DNAJC6 encodes auxilin, a co-chaperone protein involved in clathrin-mediated endocytosis (CME) at the presynaptic terminal. Biallelic mutations in DNAJC6 cause a complex, early-onset neurodegenerative disorder characterized by rapidly progressive parkinsonism-dystonia in childhood. The disease is commonly associated with additional neurodevelopmental, neurological and neuropsychiatric features. Currently, there are no disease-modifying treatments for this condition, resulting in significant morbidity and risk of premature mortality. To investigate the underlying disease mechanisms in childhood-onset DNAJC6 parkinsonism, we generated induced pluripotent stem cells (iPSC) from three patients harbouring pathogenic loss-of-function DNAJC6 mutations and subsequently developed a midbrain dopaminergic neuronal model of disease. When compared to age-matched and CRISPR-corrected isogenic controls, the neuronal cell model revealed disease-specific auxilin deficiency as well as disturbance of synaptic vesicle recycling and homeostasis. We also observed neurodevelopmental dysregulation affecting ventral midbrain patterning and neuronal maturation. To explore the feasibility of a viral vector-mediated gene therapy approach, iPSC-derived neuronal cultures were treated with lentiviral DNAJC6 gene transfer, which restored auxilin expression and rescued CME. Our patient-derived neuronal model provides deeper insights into the molecular mechanisms of auxilin deficiency as well as a robust platform for the development of targeted precision therapy approaches.

Selective Serotonin Reuptake Inhibitor Treatment Post Gene Therapy for an Ultrarare Neurometabolic Disorder (AADC Deficiency).

A 7-year-old girl presented with persistent anxiety symptoms for several years following gene therapy for an ultrarare neurometabolic disorder (aromatic L-amino acid decarboxylase [AADC] deficiency). AADC is the final enzyme in the monoamine synthesis pathway (Figure 1).1 Its absence results in a severe combined deficiency in serotonin, dopamine, epinephrine, and norepinephrine, causing significant developmental delays, hypotonia, and dystonia. The incidence of AADC deficiency is estimated at ∼1 in 500,000,2 and ∼200 cases have been described.1 Recently available disease-modifying gene therapy for this condition dramatically improves motor symptoms, and received regulatory approval in some regions in 2022.2 There are no data to guide psychiatric care post gene therapy for AADC or other neurologic disorders to date.3.

Caregiver descriptions of dystonia in cerebral palsy.

OBJECTIVE: To determine how caregivers describe dystonia in people with cerebral palsy (CP). METHODS: In this prospective cohort study, paper surveys were administered to caregivers between September 7, 2021 and October 28, 2021 during CP Center visits at a large tertiary care center. Caregivers were asked to describe involuntary movements triggered by voluntary movement or triggered by tactile stimulation in the people with CP they cared for. Their CP Center medical provider separately assessed people with CP for dystonia. Movement features described exclusively by caregivers of people with CP and dystonia were determined using conventional content analysis. RESULTS: 113 caregivers responded on behalf of 56 people with and 57 people without dystonia. If caregivers noted that both voluntary movement and tactile stimulation triggered involuntary movements, that had a 92% positive predictive value for a dystonia diagnosis. Movement features exclusively described in people with CP and dystonia included: (1) stiffening, tensing, or tightening (15% of respondents); (2) involvement of the head (10%), torso (5%), or feet (5%); and (3) triggers of stretching (12.5%), excitement (5%), or transfers (5%). INTERPRETATION: In addition to a thorough exam, asking caregivers of people with CP to describe involuntary movements triggered by voluntary movement or tactile stimulation may inform clinical dystonia diagnosis.

Under-recognition of leg dystonia in people with cerebral palsy.

Objective: To determine the rates of clinical under-documentation of leg dystonia in people with cerebral palsy (CP). Methods: In this prospective cohort study, we identified independently ambulatory people age 10-20yo with CP-associated spasticity seen in a tertiary care CP center between 1/1/20 to 11/4/21. Three pediatric movement disorders specialists assessed gait videos from these visits for leg dystonia using the Global Dystonia Rating Scale. We compared the gold standard expert consensus assessment for each patient with the clinical documentation of dystonia during a contemporaneous CP Center clinic visit and also with dystonia documentation longitudinally in their medical record. Results: Of 116 people with CP-associated spasticity assessed in this study, 70 were found to have leg dystonia in their gait videos. Only 13% of these 70 individuals (n=9/70) had leg dystonia documented in their contemporaneous CP Center clinic visit, even though they were assessed during this visit by clinicians well-trained in CP and dystonia assessment. Even with repeated assessment, only 54% (n=38/70) of these individuals had leg dystonia documented in their medical record. Conclusions: Leg dystonia is clinically under-documented in people with CP-associated spasticity, even when these people are evaluated by well-trained clinicians. Longitudinal evaluation and vigilance for leg dystonia is critical to address this diagnostic gap.