Parkinson’s disease (PD) is a complex neurodegenerative disorder with diverse molecular signatures that extend beyond the central nervous system. Peripheral blood serves as a minimally invasive source of transcriptomic biomarkers reflecting systemic inflammation, mitochondrial dysfunction, lysosomal impairment, and disrupted RNA processing—key pathways involved in PD. Long-read RNA sequencing with Oxford Nanopore Technologies (ONT) offers unprecedented detail of full-length transcripts, alternative isoforms, and RNA modifications, enabling more accurate detection of disease-related transcriptional changes. We conducted high-throughput ONT long-read RNA sequencing on blood samples from 145 individuals, including PD patients and age-matched healthy controls. RNA libraries were prepared using a cDNA-based protocol optimised for high-accuracy PromethION sequencing. Transcriptomes were quantified with ONT-specific pipelines, and analyses of differential gene expression (DGE), differential transcript expression (DEX), differential transcript usage (DTU), and alternative splicing were performed using ONT-aware tools such as DRIMSeq, DEXSeq, and stageR. Pathway enrichment linked disease-related changes to mitochondrial, lysosomal, and vesicle-trafficking pathways. Our analysis identified highly significant PD-associated transcriptional signatures in peripheral blood (SNCA, VPS13C, LRRK2, GRN, STAU1, NPTN, PARK7). Long-read sequencing uncovered extensive isoform-level dysregulation, including novel transcript variants (e.g., BCL2L2-PABPN1, SQSTM1) in pathways relevant to PD, such as autophagy and endolysosomal trafficking. DTU analyses revealed shifts in isoforms of LRRK2 and GBA1, indicating widespread disturbances in RNA processing. Enrichment analysis showed activation of molecular pathways linked to neurodegeneration. This study provides the largest long-read blood transcriptomic dataset in PD to date, demonstrating that ONT sequencing can resolve isoform-level changes and reveal systemic molecular signatures of PD. Our findings support the development of blood-based RNA biomarkers and the establishment of long-read transcriptomics as a transformative approach for genomic pathology in PD.

SINE-VNTR-Alus (SVAs) are the youngest retrotransposon family in the human genome. Their ongoing mobilization has generated genetic variation within the human population. At least 24 insertions to date, detailed in this review, have been associated with disease. The predominant mechanisms through which this occurs are alterations to normal splicing patterns, exonic insertions causing loss-of-function mutations, and large genomic deletions. Dissecting the functional impact of these SVAs and the mechanism through which they cause disease provides insight into the consequences of their presence in the genome and how these elements could influence phenotypes. Many of these disease-associated SVAs have been difficult to characterize and would not have been identified through routine analyses. However, the number identified has increased in recent years as DNA and RNA sequencing data became more widely available. Therefore, as the search for complex structural variation in disease continues, it is likely to yield further disease-causing SVA insertions.

The pathophysiology of Parkinson's disease (PD) is a complex process of the interaction between genetic and environmental factors. Studies on the genetic component of PD have predominantly focused on single nucleotide polymorphisms (SNPs) using a cross-sectional case-control design in large genome-wide association studies. This approach while giving insight into a significant portion of the genetics of PD does not fully account for all the genetic components resulting in missing heritability. In this study, we approached this problem by focusing on the non-reference genome transposable elements (TEs) and their impact on the progression of PD using a longitudinal study design within the Parkinson's progression markers initiative (PPMI) cohort. We analyzed 2886 Alu repeats, 360 LINE1 and 128 SINE-VNTR-Alus (SVAs) that were called from the whole-genome sequence data which are not within the reference genome. The presence or absence of these non-reference TE variants is known as a retrotransposon insertion polymorphism, and measuring this polymorphism describes the impact of TEs on the traits. The variations for the presence or absence of the non-reference TE elements were modeled to align with the changes in the 114 outcome measures during the five-year follow-up period of the PPMI cohort. Linear mixed-effects models were used, and many TEs were found to have a highly significant effect on the longitudinal changes in the clinically important PD outcomes such as UPDRS subscale II, UPDRS total scores, and modified Schwab and England ADL scale. In addition, the progression of several imaging and functional measures, including the Caudate/Putamen ratio and levodopa equivalent daily dose (LEDD) were also significantly affected by the TEs. In conclusion, this study identified the overwhelming effect of the non-reference TEs on the progression of PD and is a good example of the impact the variations in the "junk DNA" have on complex diseases.

Transposable elements (TEs) form a large proportion of many eukaryotic genomes and we are beginning to develop an understanding of their function. TEs are a large and diverse family of elements forming part of the repetitive genome or genomic dark matter that has not been addressed in detail in the majority of genetic studies. These repetitive and large elements are impossible to call from SNP-based genotyping data, and this is the main factor limiting research in this field thus far. However, the increasing availability of whole genome sequencing data provides the necessary data structure and quality needed for correct calling of TEs. Here we focus on the calling of variation of the composite element SINE-VNTR-Alu (SVA) which is the youngest TE family present in the human genome. Utilizing high-coverage whole genome sequencing data, we address the presence/absence and size variation of these elements. These data can be combined with whole transcriptome data to provide potential functional importance of SVAs in the regulation of the transcriptome and the pathophysiology of diseases. We recently applied this technology to analyze the effect of SVAs on the longitudinal course of Parkinson’s disease in the Parkinson’s Progression Markers Initiative cohort. This chapter briefly describes the background of transposable elements with the emphasis on SVAs and the available methods to study SVAs in genetic analysis of complex diseases.

Parkinson’s disease (PD) is associated with neuronal damage in the brain and gut. This work compares changes in the enteric nervous system (ENS) of commonly used mouse models of PD that exhibit central neuropathy and a gut phenotype. Enteric neuropathy was assessed in five mouse models: peripheral injection of MPTP; intracerebral injection of 6-OHDA; oral rotenone; and mice transgenic for A53T variant human α-synuclein with and without rotenone. Changes in the ENS of the colon were quantified using pan-neuronal marker, Hu, and neuronal nitric oxide synthase (nNOS) and were correlated with GI function. MPTP had no effect on the number of Hu+ neurons but was associated with an increase in Hu+ nuclear translocation (P < 0.04). 6-OHDA lesioned mice had significantly fewer Hu+ neurons/ganglion (P < 0.02) and a reduced proportion of nNOS+ neurons in colon (P < 0.001). A53T mice had significantly fewer Hu+ neurons/area (P < 0.001) and exhibited larger soma size (P < 0.03). Treatment with rotenone reduced the number of Hu+ cells/mm 2 in WT mice (P < 0.006) and increased the proportion of Hu+ translocated cells in both WT (P < 0.02) and A53T mice (P < 0.04). All PD models exhibited a degree of enteric neuropathy, the extent and type of damage to the ENS, however, was dependent on the model.