Biology subjects

Shaw, E. D.

Publications and source records attributed to Shaw, E. D..

3 recordsLinked to original sources

bioRxiv2023

Blood DDIT4 and TRIM13 transcript levels mark the early stages of Machado-Joseph disease

Machado-Joseph disease (MJD) is a rare late-onset polyglutamine neurodegenerative disease caused by the expansion of a CAG repeat in the ATXN3 gene encoding the ataxin- 3 (ATXN3) protein. Several studies have identified changes in the abundance of select transcripts and proteins in blood samples of MJD mutation carriers. Here, we aimed to: 1) identify blood transcriptional changes that could be potential biomarkers of MJD from preclinical to symptomatic disease stages; 2) correlate levels of differentially expressed transcripts in blood of MJD carriers with demographic, genetics, and clinical features; and 3) evaluate whether the identified differential abundance of selected transcripts in blood of MJD subjects is preserved in post-mortem brains of MJD patients. Using real- time quantitative PCR, we observed consistent dysregulation of DDIT4, TRIM13 and P2RY13 transcript levels in blood samples of MJD subjects from different disease stages (from preclinical to symptomatic), and of patients from two cohorts with different backgrounds (Azores and Brazil). Importantly, combined blood DDIT4 and TRIM13 transcript levels display a very high accuracy to discriminate MJD carriers in preclinical stage, early-stage patients, and patients with more than five years of disease duration from respective controls (AUC=1.00, AUC=0.96, and AUC=0.90, respectively). Moreover, in the combined group of Azorean and Brazilian patients, blood levels of P2RY13 transcript correlate with age at onset, and abundance of DDIT4 and TRIM13 transcripts correlate with the CAG repeat size of the expanded ATXN3 allele. In the subgroup of early-stage Azorean patients, blood levels of TRIM13 transcripts correlate with age at disease onset. Interestingly, abundance of DDIT4, TRIM13 and P2RY13 proteins is also altered in brains of MJD patients. In summary, this work shows that blood DDIT4 and TRIM13 transcript levels are potentially blood-based biomarkers of MJD of special usefulness in marking preclinical and early stages of the disease, and points for common dysregulated processes involving DDIT4, TRIM13 and P2RY13 in the blood and the brain of MJD subjects.

neuroscience↗

bioRxiv2023

Tissue-specific vulnerability to apoptosis in Machado-Joseph disease

Machado-Joseph disease (MJD) is a dominant neurodegenerative disease caused by an expanded CAG repeat in the ATXN3 gene encoding the ataxin-3 protein. Several cellular processes, including transcription and apoptosis, are disrupted in MJD. To gain further insights into the extent of dysregulation of mitochondrial apoptosis in MJD, and to evaluate if expression alterations of specific apoptosis genes/proteins could be used as transcriptional biomarkers of disease, the levels of BCL2, BAX and TP53 and the BCL2/BAX ratio, an indicator of susceptibility to apoptosis, were assessed in blood and post-mortem brain samples from MJD subjects and MJD transgenic mice and controls. While patients show reduced levels of blood BCL2 transcripts, this measurement displays low accuracy to discriminate patients from matched controls. However, increased levels of blood BAX transcripts and decreased BCL2/BAX ratio are associated with earlier onset, indicating a possible association with MJD pathogenesis. Post-mortem MJD brains show increased BCL2/BAX transcript ratio in the dentate cerebellar nucleus (DCN) and increased BCL2/BAX insoluble protein ratio in the DCN and pons, suggesting that in these regions, severely affected by degeneration in MJD, cells show signs of apoptosis resistance. Interestingly, a follow-up study of 18 patients further shows that blood BCL2 and TP53 transcript levels increase over time in MJD patients. Furthermore, while the similar levels of blood BCL2, BAX, and TP53 transcripts observed in preclinical subjects and controls is mimicked by pre-symptomatic MJD mice, the expression profile of these genes in patient brains is partially replicated by symptomatic MJD mice. Globally, our findings indicate that there is tissue-specific vulnerability to apoptosis in MJD subjects and that this tissue dependent behavior is partially replicated in a MJD mouse model.

neuroscience↗

bioRxiv2019

Druggable genome screen identifies new regulators of the abundance and toxicity of ATXN3, the Spinocerebellar Ataxia Type 3 disease protein

BackgroundSpinocerebellar Ataxia type 3 (SCA3, also known as Machado-Joseph disease) is a neurodegenerative disorder caused by a CAG repeat expansion encoding an abnormally long polyglutamine (polyQ) tract in the disease protein, ataxin-3 (ATXN3). No preventive treatment is yet available for SCA3. Because SCA3 is likely caused by a toxic gain of ATXN3 function, a rational therapeutic strategy is to reduce mutant ATXN3 levels by targeting pathways that control its production or stability. Here, we sought to identify genes that modulate ATXN3 levels as potential therapeutic targets in this fatal disorder.\n\nMethodsWe screened a collection of siRNAs targeting 2742 druggable human genes using a cell-based assay based on luminescence readout of polyQ-expanded ATXN3. From 317 candidate genes identified in the primary screen, 100 genes were selected for validation. Among the 33 genes confirmed in secondary assays, 15 were validated in an independent cell model as modulators of pathogenic ATXN3 protein levels. Ten of these genes were then assessed in a Drosophila model of SCA3, and one was confirmed as a key modulator of physiological ATXN3 abundance in SCA3 neuronal progenitor cells.\n\nResultsAmong the 15 genes shown to modulate ATXN3 in mammalian cells, orthologs of CHD4, FBXL3, HR and MC3R regulate mutant ATXN3-mediated toxicity in fly eyes. Further mechanistic studies of one of these genes, FBXL3, encoding a F-box protein that is a component of the SKP1-Cullin-F-box (SCF) ubiquitin ligase complex, showed that it reduces levels of normal and pathogenic ATXN3 in SCA3 neuronal progenitor cells, primarily via a SCF complex-dependent manner. Bioinformatic analysis of the 15 genes revealed a potential molecular network with connections to tumor necrosis factor-/nuclear factor-kappa B (TNF/NF-kB) and extracellular signal-regulated kinases 1 and 2 (ERK1/2) pathways.\n\nConclusionsWe identified 15 druggable genes with diverse functions to be suppressors or enhancers of pathogenic ATXN3 abundance. Among identified pathways highlighted by this screen, the FBXL3/SCF axis represents a novel molecular pathway that regulates physiological levels of ATXN3 protein.

neuroscience↗