Biology subjects

Swanson, M.

Publications and source records attributed to Swanson, M..

8 recordsLinked to original sources

bioRxiv2026

Thoracoabdominal pressure transmission during prone and supine cardiopulmonary resuscitation in fresh-frozen human cadavers

Background: Prone cardiopulmonary resuscitation (CPR) may be necessary when turning a prone patient supine would delay chest compressions. Although prone compressions can generate arterial pressures comparable with or greater than supine CPR, the pathway of pressure transmission is uncertain. We examined synchronized intrathoracic, intra-abdominal, and central arterial pressures in both supine and prone positions. Methods: Two thawed fresh-frozen adult cadavers underwent three, 2-minute mechanical CPR trials per position in a counterbalanced crossover sequence. Solid-state catheters recorded pleural, peritoneal, and central arterial pressures simultaneously. Trial-level outcomes included peak pressure, mean pressure, pressure-time area, and the mean peritoneal-to-pleural pressure gradient. Exploratory fixed-effects models included position, cadaver, and their interaction. Results: Prone CPR increased peak intrathoracic pressure by 7.04 mmHg, peak intra-abdominal pressure by 21.69 mmHg, and peak arterial pressure by 15.40 mmHg. Mean intra-abdominal and arterial pressures increased by 16.22 and 9.90 mmHg, respectively. The mean peritoneal-to-pleural gradient reversed direction from -8.46 mmHg supine to 4.85 mmHg prone. Intrathoracic pressure-time area increased 3.4-fold, from 1.62 to 5.46 mmHg{middle dot}s, and arterial pressure-time area increased 2.2-fold, from 2.96 to 6.42 mmHg{middle dot}s. Conclusions: Compared to supine, prone mechanical CPR generated higher arterial pressures and reversed the pressure relationship across the thoracoabdominal boundary in both cadavers. Higher abdominal pressure coincided with a larger intrathoracic pressure-time area, a pattern compatible with reduced caudal pressure dissipation.

physiology↗

bioRxiv2024

Removal of the catalytic subunit of DNA-protein kinase in the proximal tubules promotes DNA and tubular damage during kidney injury

Tubular epithelial cell damage can be repaired through a series of complex signaling pathways. An early event in many forms of tubular damage is the observation of DNA damage, which can be repaired by specific pathways depending upon the type of genomic alteration.. In this study, we report that the catalytic subunit of DNA protein kinase (DNA-PKcs), a central DNA repair enzyme involved in sensing DNA damage and performing double stranded DNA break repair, plays an important role in the extent of tubular epithelial cell damage following exposure to injurious acute and chronic stimuli. Selective loss of DNA-PKcs in the proximal tubules led to increased markers of kidney dysfunction, DNA damage, and tubular epithelial cell injury in multiple models of acute kidney injury, specifically bilateral renal ischemia-reperfusion injury and single dose of cisplatin (15 mg/kg IP). In contrast, in a mouse model of kidney fibrosis and chronic kidney disease (UUO),the protective effects of DNA-PKcs was not as obvious histologically from the tissue sections. In the absence of proximal tubular DNA-PKcs, there was reduced levels of fibrotic markers, -SMA and fibronectin, which suggests that there may be a biphasic role of DNA-PKcs depending upon the conditions exerted upon the kidney. In conclusion, this study demonstrates that the catalytic subunit of DNA-PKcs plays a context-dependent role in the kidney to reduce DNA damage during exposure to various types of acute, but not chronic forms of injurious stimuli.

physiology↗

bioRxiv2023

Heterogeneous Nuclear Ribonucleoprotein C is an Indispensable Target in Acute Myeloid Leukemia

Refractory disease is the greatest challenge in acute myeloid leukaemia (AML). Previously, we found vascular-associated AML cells as a source for refractory disease. In this study we use a bioassay of AML cells co-cultured on bone marrow-derived endothelial cells (BMECs) to screen 31 million compounds within a mixture-based synthetic combinatorial library followed by deconvolution leading to the identification of a novel polyamine sulfonamide that is selectively toxic to AML. Using three distinct proteomics methods we identified heterogeneous nuclear ribonucleoprotein C (HNRNPC) as the compound target. Depleting HNRNPC reduces AML cell proliferation, viability, colony formation and fails to establish AML in mice. In contrast, no changes in cell proliferation, survival, or colony outgrowth were observed when depleting HNRNPC in normal hematopoietic or stromal cells. Clinical data show that lower HNRNPC expression independently associates with prolonged survival times in 554 adult and pediatric AML patients. We show that HNRNPC regulates DNA replication initiation and the Myc transcriptional program. Using differential isoform expression and differential alternative splicing analyses, we show significant alternative splicing of MAX after HNRNPC depletion, resulting in MAX transcript isoforms that lack Myc-interacting domains, which we term non-activating MAX isoforms. These Myc-interacting domains are necessary for the obligate heterodimerization of Myc and Max and are critical for Myc transcriptional activation. We further analyzed the alternative splicing landscapes of 538 AML patients and 33 specimens from healthy individuals and show substantial alternative splicing of mRNA in AML patients despite the absence of splicing factor gene mutations. Moreover, we found significantly high expression of non-activating MAX isoforms in healthy individuals, while AML patients highly expressed fully functional MAX isoforms, suggesting that MAX splicing may serve an important functional role in AML. Together, these data show HNRNPC as an indispensable splicing repressor in AML that is necessary for supporting deregulated Myc-Max activity and suggest HNRNPC as a potential therapeutic target for AML.

cancer biology↗

bioRxiv2021

The X-linked splicing regulator MBNL3 has been co-opted to restrict placental growth in eutherians

The eutherian placenta is a major site for parental genetic conflict. Here, we identify the X-linked Mbnl3 gene as a novel player in this dispute. Mbnl3 belongs to an RNA binding protein family whose members regulate alternative splicing and other aspects of RNA metabolism in association with cellular differentiation. We find that, in eutherians, Mbnl3 has become specifically expressed in placenta and has undergone accelerated sequence evolution leading to changes in its RNA binding specificities. Although its molecular roles are partly redundant with those of Mbnl2, Mbnl3 has also acquired novel biological functions. In particular, whereas Mbnl2;Mbnl3 double knockout mice display severe placental maturation defects leading to strong histological and functional abnormalities, Mbnl3 knockout alone results in increased placental growth and favors placental and fetal resource allocation during limiting conditions.

evolutionary biology↗

bioRxiv2021

Cryo-EM reveals new species-specific proteins and symmetry elements in the Legionella pneumophila Dot/Icm T4SS

Legionella pneumophila is an opportunistic pathogen that causes the potentially fatal pneumonia known as Legionnaires Disease. The pathology associated with infection depends on bacterial delivery of effector proteins into the host via the membrane spanning Dot/Icm type IV secretion system (T4SS). We have determined sub-3.0 [A] resolution maps of the Dot/Icm T4SS core complex by single particle cryo-EM. The high-resolution structural analysis has allowed us to identify proteins encoded outside the Dot/Icm genetic locus that contribute to the core T4SS structure. We can also now define two distinct areas of symmetry mismatch, one that connects the C18 periplasmic ring (PR) and the C13 outer membrane cap (OMC) and one that connects the C13 OMC with a 16-fold symmetric dome. Unexpectedly the connection between the PR and OMC is DotH, with five copies sandwiched between the OMC and PR to accommodate the symmetry mismatch. Finally, we observe multiple conformations in the reconstructions that indicate flexibility within the structure. We hypothesize this conformational flexibility is likely to facilitate the Dot/Icm T4SSs ability to translocate a remarkably large set of [~]300 putative substrates across the inner and outer membranes of the bacterial cell.

microbiology↗

bioRxiv2020

Identification and Characterization of a Residual Host Cell Protein Hexosaminidase B Associated with N-glycan Degradation During the Stability Study of a Therapeutic Recombinant Monoclonal Antibody Product

Host cell proteins (HCPs) are process-related impurities derived from host organisms, which need to be controlled to ensure adequate product quality and safety. In this study, product quality attributes were tracked for several mAbs under the intended storage and accelerated stability conditions. One product quality attribute not expected to be stability indicating is the N-glycan heterogeneity profile. However, significant N-glycan degradation was observed for one mAbs under accelerated and stressed stability conditions. The root cause for this instability was attributed to Hexosaminidase B (HEXB), an enzyme known to remove terminal N-acetylglucosamine (GlcNAc). HEXB was identified by liquid chromatography-mass spectrometry (LC-MS) based proteomics approach to be enriched in the impacted stability batches from mAb-1. Subsequently, enzymatic and targeted multiple reaction monitoring (MRM) MS assays were developed to support process and product characterization. A potential interaction between HEXB and mAb-1 was initially observed from the analysis of process intermediates by proteomics among several mAbs and later supported by computational modeling. An improved bioprocess was developed to significantly reduce HEXB levels in the final drug substance. A risk assessment was conducted by evaluating the in silico immunogenicity risk and the impact on product quality. To the best of our knowledge, HEXB is the first residual HCP reported to have impact on the glycan profile of a formulated drug product. The combination of different analytical tools, mass spectrometry and computational modeling provide a general strategy on how to study residual HCP for biotherapeutics development.

biochemistry↗

bioRxiv2020

Structural analysis of the Legionella pneumophila Dot/Icm Type IV Secretion System Core Complex

Legionella pneumophila is an opportunistic pathogen that causes the potentially fatal pneumonia Legionnaires Disease. This infection and subsequent pathology require the Dot/Icm Type IV Secretion System (T4SS) to deliver effector proteins into host cells. Compared to prototypical T4SSs, the Dot/Icm assembly is much larger, containing ~27 different components including a core complex reported to be composed of five proteins: DotC, DotD, DotF, DotG, and DotH. Using single particle cryo-electron microscopy (cryo-EM), we report reconstructions of the core complex of the Dot/Icm T4SS that includes a symmetry mismatch between distinct structural features of the outer membrane cap (OMC) and periplasmic ring (PR). We present models of known core complex proteins, DotC, DotD, and DotH, and two structurally similar proteins within the core complex, DotK and Lpg0657. This analysis reveals the stoichiometry and contact interfaces between the key proteins of the Dot/Icm T4SS core complex and provides a framework for understanding a complex molecular machine.

microbiology↗

bioRxiv2017

Impeding transcription of expanded microsatellite repeats by deactivated Cas9

Transcription of expanded microsatellite repeats is associated with multiple human diseases, including myotonic dystrophy, Fuchs endothelial corneal dystrophy, and C9orf72-ALS/FTD. Eliminating or reducing production of RNA and proteins arising from these expanded loci holds therapeutic benefit. Here, we tested the hypothesis that a deactivated form of the Cas9 enzyme impedes transcription across expanded microsatellites. We observed a repeat length-, PAM-, and strand-dependent reduction in the abundance of repeat-containing RNAs upon targeting dCas9 directly to repeat sequences. Aberrant splicing patterns were rescued in DM1 cells, and production of RAN peptides characteristic of DM1, DM2, and C9orf72-ALS/FTD cells was drastically decreased. Systemic delivery of dCas9/gRNA by adeno-associated virus led to reductions in pathological RNA foci, rescue of chloride channel 1 protein expression, and decreased myotonia. These observations suggest that transcription of microsatellite repeat-containing RNAs is more sensitive to perturbation than transcription of other RNAs, indicating potentially viable strategies for therapeutic intervention.

molecular biology↗