Emerging Role of Environmental Epitranscriptomics and RNA Modifications in Parkinson's Disease.

Environmental risk factors and gene-environment interactions play a critical role in Parkinson's disease (PD). However, the relatively large contribution of environmental risk factors in the overwhelming majority of PD cases has been widely neglected in the field. A "PD prevention agenda" proposed in this journal laid out a set of research priorities focused on preventing PD through modification of environmental risk factors. This agenda includes a call for preclinical studies to employ new high-throughput methods for analyzing transcriptomics and epigenomics to provide a deeper understanding of the effects of exposures linked to PD. Here, we focus on epitranscriptomics as a novel area of research with the potential to add to our understanding of the interplay between genes and environmental exposures in PD. Both epigenetics and epitranscriptomics have been recognized as potential mediators of the complex relationship between genes, environment, and disease. Multiple studies have identified epigenetic alterations, such as DNA methylation, associated with PD and PD-related exposures in human studies and preclinical models. In addition, recent technological advancements have made it possible to study epitranscriptomic RNA modifications, such as RNA N6-methyladenosine (m6A), and a handful of recent studies have begun to explore epitranscriptomics in PD-relevant exposure models. Continued exploration of epitranscriptomic mechanisms in environmentally relevant PD models offers the opportunity to identify biomarkers, pre-degenerative changes that precede symptom onset, and potential mitigation strategies for disease prevention and treatment.

Histopathology of the cerebellar cortex in essential tremor and other neurodegenerative motor disorders: comparative analysis of 320 brains.

In recent years, numerous morphologic changes have been identified in the essential tremor (ET) cerebellar cortex, distinguishing ET from control brains. These findings have not been fully contextualized within a broader degenerative disease spectrum, thus limiting their interpretability. Building off our prior study and now doubling the sample size, we conducted comparative analyses in a postmortem series of 320 brains on the severity and patterning of cerebellar cortex degenerative changes in ET (n = 100), other neurodegenerative disorders of the cerebellum [spinocerebellar ataxias (SCAs, n = 47, including 13 SCA3 and 34 SCA1, 2, 6, 7, 8, 14); Friedreich's ataxia (FA, n = 13); multiple system atrophy (MSA), n = 29], and other disorders that may involve the cerebellum [Parkinson's disease (PD), n = 62; dystonia, n = 19] versus controls (n = 50). We generated data on 37 quantitative morphologic metrics, grouped into 8 broad categories: Purkinje cell (PC) loss, heterotopic PCs, PC dendritic changes, PC axonal changes (torpedoes), PC axonal changes (other than torpedoes), PC axonal changes (torpedo-associated), basket cell axonal hypertrophy, and climbing fiber-PC synaptic changes. Principal component analysis of z scored raw data across all diagnoses (11,651 data items) revealed that diagnostic groups were not uniform with respect to pathology. Dystonia and PD each differed from controls in only 4/37 and 5/37 metrics, respectively, whereas ET differed in 21, FA in 10, SCA3 in 10, MSA in 21, and SCA1/2/6/7/8/14 in 27. Pathological changes were generally on the milder end of the degenerative spectrum in ET, FA and SCA3, and on the more severe end of that spectrum in SCA1/2/6/7/8/14. Comparative analyses across morphologic categories demonstrated differences in relative expression, defining distinctive patterns of changes in these groups. In summary, we present a robust and reproducible method that identifies somewhat distinctive signatures of degenerative changes in the cerebellar cortex that mark each of these disorders.

Pituitary corticotroph tumour with adrenocortical cells: A distinct clinicopathologic entity with unique morphology and methylation profile.

We describe a rare TPIT-positive corticotroph PitNET that is admixed with SF1-positive adrenocortical cells. This dimorphous population of cells showed no colocalisation between TPIT and SF1 by immunofluorescence, and an adrenocortical choristoma was favoured. Methylation array analysis revealed a novel methylation profile in relation to other pituitary neoplasms.

Essential Tremor versus "ET-plus": A Detailed Postmortem Study of Cerebellar Pathology.

Essential tremor (ET) is among the most prevalent movement disorders, and by some accounts, the most common form of cerebellar degeneration. Over the past 15 years, we have carefully documented a large number of postmortem changes within the cerebellum; these cerebellar changes differ significantly between ET and controls. A recent Consensus Classification of tremor proposed that ET patients with other neurological signs aside from action tremor (e.g., parkinsonism, ataxia, cognitive changes, dystonia) should be segregated off as "ET-plus". This diagnostic concept has raised considerable controversy and its validity is not yet established. Indeed, "ET-plus" has not been distinguished from ET based on differences in genetics, pathology or prognosis. Here we determine whether ET cases differ from "ET-plus" cases in underlying pathological changes in the postmortem brain. We examined postmortem brains from 50 ET cases (24 ET and 26 ET-plus), using a set of 14 quantitative metrics of cerebellar pathology determined by histologic and immunohistochemical methods. These metrics reflect changes across the Purkinje cell (PC) body (PC counts, empty baskets, heterotopias), PC dendrites (swellings), PC axon (torpedoes and associated axonal changes), basket cell axonal hypertrophy and climbing fiber-PC dendrite synaptic changes. ET and ET-plus were similar with respect to 13 of 14 cerebellar pathologic metrics (p > 0.05). Only one metric, the linear density of thickened PC axon profiles, differed between these groups (ET = 0.529 ± 0.397, ET-plus = 0.777 ± 0.477, p = 0.013), although after correcting for multiple comparisons, there were no differences. If ET-plus were indeed a different entity, then the underlying pathological basis should be distinct from that of ET. This study demonstrated there were no pathological differences in cerebellar cortex between ET versus ET-plus cases. These data do not support the notion that ET and ET-plus represent distinct clinical-pathological entities.