Motile and non-motile cilia in human pathology: from function to phenotypes

Ciliopathies are inherited human disorders caused by both motile and non-motile cilia dysfunction that form an important and rapidly expanding disease category. Ciliopathies are complex conditions to diagnose, being multisystem disorders characterized by extensive genetic heterogeneity and clinical variability with high levels of lethality. There is marked phenotypic overlap among distinct ciliopathy syndromes that presents a major challenge for their recognition, diagnosis, and clinical management, in addition to posing an on-going task to develop the most appropriate family counselling. The impact of next-generation sequencing and high-throughput technologies in the last decade has significantly improved our understanding of the biological basis of ciliopathy disorders, enhancing our ability to determine the possible reasons for the extensive overlap in their symptoms and genetic aetiologies. Here, we review the diverse functions of cilia in human health and disease and discuss a growing shift away from the classical clinical definitions of ciliopathy syndromes to a more functional categorization. This approach arises from our improved understanding of this unique organelle, revealed through new genetic and cell biological insights into the discrete functioning of subcompartments of the cilium (basal body, transition zone, intraflagellar transport, motility). Mutations affecting these distinct ciliary protein modules can confer different genetic diseases and new clinical classifications are possible to define, according to the nature and extent of organ involvement. Copyright (C) 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd

X-Linked Parkinsonism: phenotypic and genetic heterogeneity

X-linked parkinsonism encompasses rare heterogeneous disorders mainly inherited as a recessive trait, therefore being more prevalent in males. Recent developments have revealed a complex underlying panorama, including a spectrum of disorders in which parkinsonism is variably associated with additional neurological and non-neurological signs. In particular, a childhood-onset encephalopathy with epilepsy and/or cognitive disability is the most common feature. Their genetic basis is also heterogeneous, with many causative genes and different mutation types ranging from "classical" coding variants to intronic repeat expansions. In this review, we provide an updated overview of the phenotypic and genetic spectrum of the most relevant X-linked parkinsonian syndromes, namely X-linked dystonia-parkinsonism (XDP, Lubag disease), fragile X-associated tremor/ataxia syndrome (FXTAS), beta-propeller protein-associated neurodegeneration (BPAN, NBIA/PARK-WDR45), Fabry disease, Waisman syndrome, methyl CpG-binding protein 2 (MeCP2) spectrum disorder, phosphoglycerate kinase-1 deficiency syndrome (PGK1) and X-linked parkinsonism and spasticity (XPDS). All clinical and radiological features reported in the literature have been reviewed. Epilepsy occasionally represents the symptom of onset, predating parkinsonism even by a few years; action tremor is another common feature along with akinetic-rigid parkinsonism. A focus on the genetic background and its pathophysiological implications is provided. The pathogenesis of these disorders ranges from well-defined metabolic alterations (PGK1) to non-specific lysosomal dysfunctions (XPDS) and vesicular trafficking alterations (Waisman syndrome). However, in other cases it still remains poorly defined. Recognition of the phenotypic and genetic heterogeneity of X-linked parkinsonism has important implications for diagnosis, management, and genetic counseling. \ua9 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Morphological analysis of genetic modulation of PINK1 on mitochondrial alterations, autophagy and cell death

Mutations in the PTEN-induced putative kinase1 (PINK1) represent the second most common cause of autosomal recessive Parkinson’s disease. The PINK1 protein has a mitochondrial localization and interacts with a variety of proteins, including the pro-autophagy protein beclin1 and the ubiquitin-ligase parkin. In particular, PINK1 is able to recruit parkin to the surface of dysfunctional mitochondria, to promote the ubiquitination of several mitochondrial proteins and the subsequent activation of the mitophagy cascade. Aim of this study was to use a dopaminergic cell model and transmission electron microscopy to characterize whether the modulation of PINK1 expression: (i) modifies the number and morphology of mitochondria and of autophagy organelles (autophagosomes); (ii) alters the recruitment of beclin1, parkin and ubiquitin to the mitochondria; (iii) affects cell survival. We used PC12 cells transfected either with the empty vector (pcDNA), or vectors expressing wild type PINK1 (PINK1wt), a pathogenic mutant (PINK1W437X), shRNA against rat PINK1 (shPINK1) or scramble (shSCR). Samples were analyzed both in baseline conditions and following methamphetamine (METH) treatment to provide a neurotoxic, autophagy-dependent stimulation. We showed that, especially upon METH exposure, the modulation of PINK1 levels dramatically affected the morphology and clearance of mitochondria. In fact, the number of abnormal mitochondria was reduced in PINK1wt, while it was significantly increased upon shPINK1 and also, to a lesser extent, in PINK1W437X cells. In keeping with this, mitochondrial ubiquitin clusters and mitochondrial levels of parkin and beclin1 were increased in PINK1wt cells while they were reduced both in PINK1 silenced and PINK1W437X cells. Interestingly, the number of autophagic vacuoles was unaffected by PINK1 modulation in baseline conditions, and was significantly reduced only in cells lacking functional PINK1 and upon METH exposure. All these effects were significantly associated with a modulation of apoptotic cell death. Our data provide robust sub-cellular evidence that PINK1 counteracts neurodegeneration by simultaneously recruiting beclin1, parkin and ubiquitin and thus enhancing the clearance of damaged mitochondria. In the absence of functional PINK1 and upon autophagy stress, we observed a failure of the autophagy system at large, with marked accumulation of dysfunctional mitochondria and dramatic increase in apoptotic cell death

Genetic modulation of PINK1 differentially affects mitophagy compared with autophagy disclosing common mechanisms of genetic and environmental parkinsonism

The second most frequent cause of autosomal recessive Parkinson’s disease is represented by mutations in the PTEN-induced putative kinase1 (PINK1). The PINK1 protein mainly localizes to mitochondria which are considered the target organelles mainly affected in Parkinson’s disease. In fact, parkinsonism-inducing neurotoxins such as rotenone, MPTP and methamphetamine all damage mitochondria. Therefore, the ability to counteract mitochondrial toxicity and promoting mitochondrial renewal by mithophagy and mitochondrial biogenesis is critical to cure Parkinsonism. For instance the autophagy-dependent removal of altered mitochondria known as mitophagy is supposed to be key in conteracting mitochondrial toxicity. Interestingly mitochondrial PINK1 is known to interact with autophagy proteins such as beclin1 and the ubiquitin-ligase parkin. Therefore, in the present study we evaluated whether such an interaction produced downstream effects leading to autophagy activation. This was evaluated through the simultaneous analysis of co-localization of parkin and beclin1 with the autophagy initiator ubiquitin. These phenomena were analyzed both at mitochondrial level and throughout the cytosol by analyzing autophagy-like vacuoles and LC3-II positive structures. Interestingly, despite increased mitophagy PINK1 overexpression did not produce a general activation of the autophagy pathway. It is likely that such a selective fashion of autophagy activation only limited to mitochondrial removal could explain the relevance of PINK1 for Parkinson’s disease but not for other neurodegenerative, autophagy-related disorders. The present data were obtained through several experimental settings featuring PINK1 overexpression, mutation, deletion and silencing of the gene. The effects were analyzed in baseline conditions but were supplemented by experiments in the presence of methamphetamine used here both as a mitochondrial neurotoxin and an autophagy-dependent Parkinsonism inducing compound. Data revealed that PINK1 was critical for mitochondria and cell viability already in baseline conditions though such an effect was magnified upon methamphetamine exposure. The present findings while explaining the molecular interactions which are likely to induce PINK1-dependent genetic Parkinsonism, provide a further evidence on the critical role of genetic and environmental alterations in the genesis of Parkinson’s disease

Delineation and Diagnostic Criteria of Oral-Facial-Digital Syndrome Type VI

Oral-Facial-Digital Syndrome type VI (OFD VI) represents a rare phenotypic subtype of Joubert syndrome and related disorders (JSRD). In the original report polydactyly, oral findings, intellectual disability, and absence of the cerebellar vermis at post-mortem characterized the syndrome. Subsequently, the molar tooth sign (MTS) has been found in patients with OFD VI, prompting the inclusion of OFD VI in JSRD. We studied the clinical, neurodevelopmental, neuroimaging, and genetic findings in a cohort of 16 patients with OFD VI. We derived the following inclusion criteria from the literature: 1) MTS and one oral finding and polydactyly, or 2) MTS and more than one typical oral finding. The OFD VI neuroimaging pattern was found to be more severe than in other JSRD subgroups and includes severe hypoplasia of the cerebellar vermis, hypoplastic and dysplastic cerebellar hemispheres, marked enlargement of the posterior fossa, increased retrocerebellar collection of cerebrospinal fluid, abnormal brainstem, and frequently supratentorial abnormalities that occasionally include characteristic hypothalamic hamartomas. Additionally, two new JSRD neuroimaging findings (ascending superior cerebellar peduncles and fused thalami) have been identified. Tongue hamartomas, additional frenula, upper lip notch, and mesoaxial polydactyly are specific findings in OFD VI, while cleft lip/palate and other types of polydactyly of hands and feet are not specific. Involvement of other organs may include ocular findings, particularly colobomas. The majority of the patients have absent motor development and profound cognitive impairment. In OFD VI, normal cognitive functions are possible, but exceptional. Sequencing of known JSRD genes in most patients failed to detect pathogenetic mutations, therefore the genetic basis of OFD VI remains unknown. Compared with other JSRD subgroups, the neurological findings and impairment of motor development and cognitive functions in OFD VI are significantly worse, suggesting a correlation with the more severe neuroimaging findings. Based on the literature and this study we suggest as diagnostic criteria for OFD VI: MTS and one or more of the following: 1) tongue hamartoma(s) and/or additional frenula and/or upper lip notch; 2) mesoaxial polydactyly of one or more hands or feet; 3) hypothalamic hamartoma

Healthcare recommendations for Joubert syndrome

Joubert syndrome (JS) is a recessive neurodevelopmental disorder defined by a characteristic cerebellar and brainstem malformation recognizable on axial brain magnetic resonance imaging as the "Molar Tooth Sign". Although defined by the neurological features, JS is associated with clinical features affecting many other organ systems, particularly progressive involvement of the retina, kidney, and liver. JS is a rare condition; therefore, many affected individuals may not have easy access to subspecialty providers familiar with JS (e.g., geneticists, neurologists, developmental pediatricians, ophthalmologists, nephrologists, hepatologists, psychiatrists, therapists, and educators). Expert recommendations can enable practitioners of all types to provide quality care to individuals with JS and know when to refer for subspecialty care. This need will only increase as precision treatments targeting specific genetic causes of JS emerge. The goal of these recommendations is to provide a resource for general practitioners, subspecialists, and families to maximize the health of individuals with JS throughout the lifespan

RFC1 expansions are a common cause of idiopathic sensory neuropathy

After extensive evaluation, one-third of patients affected by polyneuropathy remain undiagnosed and are labelled as having chronic idiopathic axonal polyneuropathy, which refers to a sensory or sensory-motor, axonal, slowly progressive neuropathy of unknown origin. Since a sensory neuropathy/neuronopathy is identified in all patients with genetically confirmed RFC1 cerebellar ataxia, neuropathy, vestibular areflexia syndrome, we speculated that RFC1 expansions could underlie a fraction of idiopathic sensory neuropathies also diagnosed as chronic idiopathic axonal polyneuropathy. We retrospectively identified 225 patients diagnosed with chronic idiopathic axonal polyneuropathy (125 sensory neuropathy, 100 sensory-motor neuropathy) from our general neuropathy clinics in Italy and the UK. All patients underwent full neurological evaluation and a blood sample was collected for RFC1 testing. Biallelic RFC1 expansions were identified in 43 patients (34%) with sensory neuropathy and in none with sensory-motor neuropathy. Forty-two per cent of RFC1-positive patients had isolated sensory neuropathy or sensory neuropathy with chronic cough, while vestibular and/or cerebellar involvement, often subclinical, were identified at examination in 58%. Although the sensory ganglia are the primary pathological target of the disease, the sensory impairment was typically worse distally and symmetric, while gait and limb ataxia were absent in two-thirds of the cases. Sensory amplitudes were either globally absent (26%) or reduced in a length-dependent (30%) or non-length dependent pattern (44%). A quarter of RFC1-positive patients had previously received an alternative diagnosis, including Sj\uf6gren's syndrome, sensory chronic inflammatory demyelinating polyneuropathy and paraneoplastic neuropathy, while three cases had been treated with immune therapies

Pontine tegmental cap dysplasia: developmental and cognitive outcome in three adolescent patients

Pontine Tegmental Cap Dysplasia (PTCD) is a recently described, rare disorder characterized by a peculiar cerebellar and brainstem malformation. Nineteen patients have been reported to date, of which only one in the adolescent age, and data on the clinical, cognitive and behavioural outcome of this syndrome are scarce

LIPAD (LRRK2/Luebeck International Parkinson's Disease) Study Protocol:Deep Phenotyping of an International Genetic Cohort

Background: Pathogenic variants in the Leucine-rich repeat kinase 2 (LRRK2) gene are the most common known monogenic cause of Parkinson's disease (PD). LRRK2-linked PD is clinically indistinguishable from idiopathic PD and inherited in an autosomal dominant fashion with reduced penetrance and variable expressivity that differ across ethnicities and geographic regions.Objective: To systematically assess clinical signs and symptoms including non-motor features, comorbidities, medication and environmental factors in PD patients, unaffected LRRK2 pathogenic variant carriers, and controls. A further focus is to enable the investigation of modifiers of penetrance and expressivity of LRRK2 pathogenic variants using genetic and environmental data.Methods: Eligible participants are invited for a personal or online examination which comprises completion of a detailed eCRF and collection of blood samples (to obtain DNA, RNA, serum/plasma, immune cells), urine as well as household dust. We plan to enroll 1,000 participants internationally: 300 with LRRK2-linked PD, 200 with LRRK2 pathogenic variants but without PD, 100 PD patients with pathogenic variants in the GBA or PRKN genes, 200 patients with idiopathic PD, and 200 healthy persons without pathogenic variants.Results: The eCRF consists of an investigator-rated (1 h) and a self-rated (1.5 h) part. The first part includes the Movement Disorder Society Unified Parkinson's Disease Rating, Hoehn &Yahr, and Schwab & England Scales, the Brief Smell Identification Test, and Montreal Cognitive Assessment. The self-rating part consists of a PD risk factor, food frequency, autonomic dysfunction, and quality of life questionnaires, the Pittsburgh Sleep Quality Inventory, and the Epworth Sleepiness as well as the Hospital Anxiety and Depression Scales. The first 15 centers have been initiated and the first 150 participants enrolled (as of March 25th, 2021).Conclusions: LIPAD is a large-scale international scientific effort focusing on deep phenotyping of LRRK2-linked PD and healthy pathogenic variant carriers, including the comparison with additional relatively frequent genetic forms of PD, with a future perspective to identify genetic and environmental modifiers of penetrance and expressivityClinical Trial Registration:ClinicalTrials.gov, NCT04214509