Biology subjects

Snodgrass, R.

Publications and source records attributed to Snodgrass, R..

3 recordsLinked to original sources

bioRxiv2021

Synergistic TOR and ERK inhibition mitigates the hereditary haemorrhagic telangiectasia-like phenotype and excess kugel formation in endoglin mutant zebrafish

RationaleHereditary haemorrhagic telangiectasia (HHT) is an inherited bleeding disorder characterised by arteriovenous malformations (AVMs). Such AVMs affect lungs, liver and brain, whilst telangiectases in mucocutaneous tissues are prone to haemorrhage. HHT type I is caused by loss-of-function endoglin (ENG) mutations. Evidence suggests AVMs result from abnormal responses to VEGF signalling. ObjectiveWe therefore characterised the vascular abnormalities in eng mutant zebrafish and investigated whether these are prevented by inhibiting different pathways downstream of VEGF signalling. Methods and ResultsWe used light sheet fluorescence microscopy to visualise the vasculature in engmu130 mutant zebrafish. In addition to previously described significantly enlarged dorsal aorta and posterior cardinal vein at 3d post fertilisation, engmu130 embryos had an enlarged basilar artery (BA), and increased formation of endothelial "kugeln" on cerebral vessels. Adult engmu130 fish developed skin AVMs, retinal vascular abnormalities, and an enlarged heart. Tivozanib (AV951), a VEGF receptor tyrosine kinase inhibitor, prevented development of the abnormally enlarged major vessels and normalised the number of kugeln in engmu130 embryos. Inhibiting discrete signalling pathways downstream of VEGFR2 in engmu130 embryos gave further insights. Inhibiting TOR or MEK prevented the abnormal trunk and cerebral vasculature phenotype, whilst targeting NOS and MAPK had no effect. Combining subtherapeutic TOR and MEK inhibition prevented the vascular phenotype, suggesting synergy between TOR and MEK/ERK signalling pathways. ConclusionsThese results indicate the HHT-like phenotype in zebrafish endoglin mutants can be mitigated through modulation of VEGF signalling, and implicate combination low dose ERK and TOR pathway inhibitors as a therapeutic strategy in HHT. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

developmental biology↗

bioRxiv2021

Interferon-α subtype treatment induces the repression of SRSF1 in HIV-1 target cells and affects HIV-1 post integration steps

Efficient replication of HIV-1 depends on balanced levels of host cell components, including cellular splicing factors. Type I interferons (IFN-I), playing a crucial role in the innate immune defense against viral infections, are well known to induce the transcription of IFN-stimulated genes (ISGs) including potent host restriction factors. Not so well known is, that IFN-repressed genes (IRepGs) also affect viral infections by downregulating host dependency factors that are essential for viral replication. So far, knowledge about IRepGs involved in HIV-1 infection is very limited. Here, we demonstrate that expression levels of the serine/arginine-rich splicing factor 1 (SRSF1) were repressed upon treatment with IFN subtypes in HIV-1 susceptible cell lines as well as primary cells. Furthermore, we could demonstrate in two independent patient cohorts that HIV-1 infection and the concomitant inflammation during the acute and chronic phase, resulted in the strong induction of ISGs, but at the same time significantly repressed SRSF1. 4sU-labeling of newly transcribed mRNAs revealed that IFN-mediated repression of SRSF1 originated from a transcriptional shutdown. Experimental downregulation as well as overexpression of SRSF1 expression levels resulted in crucial changes in HIV-1 LTR-transcription, alternative splice site usage and virus production. While lower SRSF1 levels resulted in low vif mRNA levels and thus severely reduced viral infectivity, higher levels of SRSF1 impaired LTR-Tat-activity and HIV-1 particle production. Our data highlight the so far undescribed role of SRSF1 acting as an IFN-repressed cellular dependency factor decisively regulating HIV-1 post integration steps. Author SummaryIFN-I play a central role in the innate immune defense against viral infections by regulating the expression of interferon stimulated genes (ISGs) and interferon repressed genes (IRepGs). The stimulation of host restriction factors and the reduction of host dependency factors decisively affects the efficiency of HIV-1 replication. After the stable integration of the provirus into the host chromosome, HIV-1 exploits the host cell transcription and splicing machinery for its replication. A network of conserved splice sites and splicing regulatory elements maintain balanced levels of viral transcripts essential for virus production and immune evasion. We demonstrate the so far undescribed role of the splicing factor SRSF1 as an IRepG crucially involved in HIV-1 RNA processing. In HIV-1 infected individuals, we observed inversely proportional expression of high ISG15 and low SRSF1 levels, which were restored in ART treated patients. We could demonstrate, that IFN-I stimulation of HIV-1 target cells resulted in a significant repression of SRSF1 RNA and protein levels. Since low SRSF1 expression decisively reduced HIV-1 vif mRNA levels, a severe impairment of viral replication was observed in APOBEC3G expressing cells. As overexpression negatively affected HIV-1 LTR transcription and virus production, balanced levels of SRSF1 are indispensable for efficient replication.

microbiology↗

bioRxiv2020

The effect of absent blood flow on the zebrafish cerebral and trunk vasculature

The role of blood flow is complex and context-dependent. In this study, we quantify the effect of the lack of blood flow on vascular development and compare its impact in two vascular beds, namely the cerebral and trunk vasculature, using zebrafish as preclinical model. We performed this by analysing vascular topology, endothelial cell number, apoptosis, and inflammatory response in animals with normal blood flow or absent blood flow. We find that absent blood flow reduced vascular area and endothelial cell number significantly in both examined vascular beds, but the effect is more severe in the cerebral vasculature. Similarly, while stereotypic vascular patterning in the trunk is maintained, intra-cerebral vessels show altered patterning. Absent blood flow lead to an increase in non-EC-specific apoptosis without increasing tissue inflammation, as quantified by cerebral immune cell numbers and nitric oxide. In conclusion, blood flow is essential for cellular survival in both the trunk and cerebral vasculature, but particularly intra-cerebral vessels are affected by the lack of blood flow, suggesting that responses to blood flow differ between these two vascular beds. Key pointsO_LIWe here use zebrafish as a model to quantitatively assess the impact of the lack of blood flow in development and compare its impact in two vascular beds, namely the cerebral to trunk vasculature. C_LIO_LIIn both vascular beds, vascular growth and endothelial cell number are reduced by lack of blood flow, with increasing effect size from 2-5 days post fertilisation. C_LIO_LIExamination of vascular patterning shows that while stereotypic patterning in the trunk is preserved, the intra-cerebral vasculature patterning is altered. C_LIO_LIWe found non-EC-specific cell death to be increased in both vascular beds, with a larger effect size in the brain, but that this cell death occurs without triggering tissue inflammation. C_LI

developmental biology↗