The inner centromere is a biomolecular condensate scaffolded by the chromosomal passenger complex.

The inner centromere is a region on every mitotic chromosome that enables specific biochemical reactions that underlie properties, such as the maintenance of cohesion, the regulation of kinetochores and the assembly of specialized chromatin, that can resist microtubule pulling forces. The chromosomal passenger complex (CPC) is abundantly localized to the inner centromeres and it is unclear whether it is involved in non-kinase activities that contribute to the generation of these unique chromatin properties. We find that the borealin subunit of the CPC drives phase separation of the CPC in vitro at concentrations that are below those found on the inner centromere. We also provide strong evidence that the CPC exists in a phase-separated state at the inner centromere. CPC phase separation is required for its inner-centromere localization and function during mitosis. We suggest that the CPC combines phase separation, kinase and histone code-reading activities to enable the formation of a chromatin body with unique biochemical activities at the inner centromere

Genetic studies of hypertrophic cardiomyopathy in Singaporeans identify variants in TNNI3 and TNNT2 that are common in Chinese patients

Background - To assess the genetic architecture of hypertrophic cardiomyopathy (HCM) in patients of predominantly Chinese ancestry. Methods - We sequenced HCM disease genes in Singaporean patients (n=224) and Singaporean controls (n=3,634), compared findings with additional populations and Caucasian HCM cohorts (n=6,179) and performed in vitro functional studies. Results - Singaporean HCM patients had significantly fewer confidently interpreted HCM disease variants (Pathogenic (P)/Likely Pathogenic (LP):18%, p<0.0001) but an excess of variants of unknown significance (exVUS: 24%, p<0.0001), as compared to Caucasians (P/LP: 31%, exVUS: 7%). Two missense variants in thin filament encoding genes were commonly seen in Singaporean HCM (TNNI3:p.R79C, disease allele frequency (AF)=0.018; TNNT2:p.R286H, disease AF=0.022) and are enriched in Singaporean HCM when compared with Asian controls (TNNI3:p.R79C, Singaporean controls AF=0.0055, p=0.0057, gnomAD-East Asian (gnomAD-EA) AF=0.0062, p=0.0086; TNNT2:p.R286H, Singaporean controls AF=0.0017, p<0.0001, gnomAD-EA AF=0.0009, p<0.0001). Both these variants have conflicting annotations in ClinVar and are of low penetrance (TNNI3:p.R79C, 0.7%; TNNT2:p.R286H, 2.7%) but are predicted to be deleterious by computational tools. In population controls, TNNI3:p.R79C carriers had significantly thicker left ventricular walls compared to non-carriers while its etiological fraction is limited (0.70, 95% CI: 0.35-0.86) and thus TNNI3:p.R79C is considered a VUS. Mutant TNNT2:p.R286H iPSC-CMs show hypercontractility, increased metabolic requirements and cellular hypertrophy and the etiological fraction (0.93, 95% CI: 0.83-0.97) support the likely pathogenicity of TNNT2:p.R286H. Conclusions - As compared to Caucasians, Chinese HCM patients commonly have low penetrance risk alleles in TNNT2 or TNNI3 but exhibit few clinically actionable HCM variants overall. This highlights the need for greater study of HCM genetics in non-Caucasian populations

1-phenyl 2-thiourea (PTU) activates autophagy in zebrafish embryos

202207 bcwwAccepted ManuscriptOthersHMRFPublishe

Neurons reduce glial responses to lipopolysaccharide (LPS) and prevent injury of microglial cells from over-activation by LPS

The microenvironment of the CNS has been considered to tonically inhibit glial activities. It has been shown that glia become activated where neuronal death occurs in the aging brain. We have previously demonstrated that neurons tonically inhibit glial activities including their responses to the bacterial endotoxin lipopolysaccharide (LPS). It is not clear whether activation of glia, especially microglia in the aging brain, is the consequence of disinhibition due to neuronal death. This study was designed to determine if glia regain their responsiveness to LPS once the neurons have died in aged cultures. When cultured alone, glia from postnatal day one rat mesencephalons stimulated with LPS (0.1-1000 ng/mL) produced both nitric oxide (NO) and tumor necrosis factor α (TNFα), yielding a sigmoid and a bell-shaped curve, respectively. When neuron-containing cultures were prepared from embryonic day 14/15 mesencephalons, the shape of the dose-response curve for NO was monotonic and the bell-shaped curve for TNFα production was shifted to the right. After 1 month of culture under conditions where neurons die, the production curves for NO and TNFα in LPS-stimulated glia shifted back to the left compared to mixed neuron-glia cultures. Immunostaining of rat microglia for the marker CR3 (the receptor for complement component C3) demonstrated that high concentrations of LPS (1 μg/mL) reduced the number of microglia in mixed-glial cultures. In contrast, reduction of CR3 immunostaining was not observed in LPS-stimulated mixed neuron-glia cultures. Taken together, the results demonstrate that disinhibition of the glial response to LPS occurs after neurons die in aged cultures. Once neurons have died, the responsiveness of glia to LPS is restored. Neurons prevented injury to microglia by reducing their responsiveness to LPS. This study broadens our understanding of the ways in which the CNS microenvironment affects cerebral inflammation.link_to_subscribed_fulltex

Leukocyte invasion of the brain after peripheral trauma in zebrafish (Danio rerio)

202309 bcvcVersion of RecordOthersFish Model Translational Research Laboratory; University of Hong KongPublishe