Biology subjects

Daw, J.

Publications and source records attributed to Daw, J..

6 recordsLinked to original sources

bioRxiv2026

VCP is a critical component for TDP-43 disaggregase activity in skeletal muscle

TDP-43 aggregates are a unifying pathological feature between several neurodegenerative diseases and myopathies. Mutations in the AAA ATPase protein VCP have been linked to TDP-43 proteinopathies in both brain and skeletal muscle including frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), and inclusion body myopathy (IBM). In the case of multisystem proteinopathy (MSP), patients with VCP mutations may present with combinations of these phenotypes. Of these MSP phenotypes IBM is the most common, affecting around 90% of patients. However, it is not well understood how mutations in VCP contribute to the accumulation of insoluble TDP-43 aggregates in the context of skeletal muscle. To study this further, we used in vitro and in vivo models of TDP-43 aggregation in skeletal muscle in the presence of VCP mutation or inhibition to study its effects on the ability to clear TDP-43 aggregates. Across multiple model systems we found that VCP disease mutations or inhibition causes a reduced capacity to clear insoluble TDP-43, suggesting a VCP loss of function in patients with VCP-related MSP.

pathology↗

bioRxiv2025

Mutations in Hsp40 co-chaperone change the unique canonical inter-domain interactions stimulating LGMDD1 myopathy

Limb-girdle muscular dystrophy D1 (LGMDD1) is a rare, dominantly inherited neuromuscular disorder caused by mutations in the HSP40 co-chaperone DNAJB6, primarily in the GF or J-domains. Currently, no treatments are available, and a challenge in understanding the disease is identifying a specific client protein for DNAJB6 in skeletal muscle. Our previous research indicated that LGMDD1 GF domain mutants in Sis1 exhibit substrate-specific effects, influenced by HSP70 activity. Herein, we found that novel mutations in the J-domain similarly affected chaperone function. The J-domain mutants exhibited variable substrate processing, reduced binding affinity to client-substrate, and decreased stimulation of Ssa1 ATP hydrolysis, with these effects being substrate-conformer-specific. Our simulation studies noted differences in inter-domain interactions linked to the mutants, which influence the Hsp40-Hsp70 ATPase cycle. These mechanistic insights enhance our understanding of LGMDD1 myopathy and help to identify potential treatment strategies in the future. TeaserRecalibrating the inter-domain interface of the mutant protein could potentially serve as a key therapeutic strategy for LGMDD1 myopathy.

biochemistry↗

bioRxiv2024

Seeding competent TDP-43 persists in human patient and mouse muscle

TAR DNA-binding protein 43 (TDP-43) is an RNA binding protein that accumulates as aggregates in the central nervous system of some neurodegenerative diseases. However, TDP-43 aggregation is also a sensitive and specific pathologic feature found in a family of degenerative muscle diseases termed inclusion body myopathy (IBM). TDP-43 aggregates from ALS and FTD brain lysates may serve as self-templating aggregate seeds in vitro and in vivo, supporting a prion-like spread from cell to cell. Whether a similar process occurs in IBM patient muscle is not clear. We developed a mouse model of inducible, muscle-specific cytoplasmic localized TDP-43. These mice develop muscle weakness with robust accumulation of insoluble and phosphorylated sarcoplasmic TDP-43, leading to eosinophilic inclusions, altered proteostasis and changes in TDP-43-related RNA processing that resolve with the removal of doxycycline. Skeletal muscle lysates from these mice also have seeding competent TDP-43, as determined by a FRET-based biosensor, that persists for weeks upon resolution of TDP-43 aggregate pathology. Human muscle biopsies with TDP-43 pathology also contain TDP-43 aggregate seeds. Using lysates from muscle biopsies of patients with IBM, IMNM and ALS we found that TDP-43 seeding capacity was specific to IBM. Surprisingly, TDP-43 seeding capacity anti-correlated with TDP-43 aggregate and vacuole abundance. These data support that TDP-43 aggregate seeds are present in IBM skeletal muscle and represent a unique TDP-43 pathogenic species not previously appreciated in human muscle disease. SummaryTDP-43 aggregate seeds persist in mouse and human skeletal muscle independent of large TDP-43 inclusions.

pathology↗

bioRxiv2022

Loss of function variants in DNAJB4 cause a myopathy with early respiratory failure

DNAJ/HSP40 co-chaperones are integral to the chaperone network, bind client proteins and recruit them to HSP70 for folding. We performed exome sequencing on patients with a presumed hereditary muscle disease and no genetic diagnosis. This identified four individuals from three unrelated families carrying an unreported homozygous stop gain (c.856A>T; p.Lys286Ter), or homozygous missense variants (c.74G>A; p.Arg25Gln and c.785T>C; p.Leu262Ser) in DNAJB4. Affected patients presented with axial rigidity and early respiratory failure requiring ventilator support between the 1st and 4th decade of life. Selective involvement of the semitendinosus and biceps femoris muscles was seen on MRI scans of the thigh. On biopsy, muscle was myopathic with angular fibers, protein inclusions and occasional rimmed vacuoles. DNAJB4 normally localizes to the Z-disc and was absent from muscle and fibroblasts of affected patients supporting a loss of function. Functional studies confirmed that the p.Lys286Ter and p.Leu262Ser mutant proteins are rapidly degraded in cells. In contrast, the p.Arg25Gln mutant protein is stable but failed to complement for DNAJB function in yeast, disaggregate client proteins or protect from heat shock induced cell death consistent with its loss of function. DNAJB4 knockout mice had muscle weakness and fiber atrophy with prominent diaphragm involvement and kyphosis. DNAJB4 knockout muscle and myotubes had myofibrillar disorganization and accumulated Z-disc proteins and protein chaperones. These data demonstrate a novel chaperonopathy associated with DNAJB4 causing a myopathy with early respiratory failure. DNAJB4 loss of function variants may lead to the accumulation of DNAJB4 client proteins resulting in muscle dysfunction and degeneration.

genetics↗

bioRxiv2021

Improving long-read consensus sequencing accuracy with deep learning

The PacBio HiFi sequencing technology combines less accurate, multi-read passes from the same molecule (subreads) to yield consensus sequencing reads that are both long (averaging 10-25 kb) and highly accurate. However, these reads can retain residual sequencing error, predominantly insertions or deletions at homopolymeric regions. Here, we train deep learning models to polish HiFi reads by recognizing and correcting sequencing errors. We show that our models are effective at reducing these errors by 25-40% in HiFi reads from human as well as E. coli genomes.

genomics↗

bioRxiv2020

Inhibition of DNAJ-HSP70 interaction improves strength in muscular dystrophy

Dominant mutations in the HSP70 co-chaperone DNAJB6 cause a late onset muscle disease termed limb girdle muscular dystrophy type 1D (LGMD1D), which is characterized by protein aggregation and vacuolar myopathology. Disease mutations reside within the G/F domain of DNAJB6, but the molecular mechanisms underlying dysfunction are not well understood. Using yeast, cell culture, and mouse models of LGMD1D, we find that the toxicity associated with disease-associated DNAJB6 requires its interaction with HSP70, and that abrogating this interaction genetically or with small molecules is protective. In skeletal muscle, DNAJB6 localizes to the Z-disc with HSP70. Whereas HSP70 normally diffuses rapidly between the Z-disc and sarcoplasm, the rate of HSP70s diffusion in LGMD1D mouse muscle is diminished likely because it has an unusual affinity for the Z-disc and mutant DNAJB6. Treating LGMD1D mice with a small molecule inhibitor of the DNAJ-HSP70 complex re-mobilizes HSP70, improves strength and corrects myopathology. These data support a model in which LGMD1D mutations in DNAJB6 are a gain-of-function disease that is, counter-intuitively, mediated via HSP70 binding. Thus, therapeutic approaches targeting HSP70:DNAJB6 may be effective in treating this inherited muscular dystrophy.

cell biology↗