Biology subjects

Yee, Z.

Publications and source records attributed to Yee, Z..

3 recordsLinked to original sources

bioRxiv2020

Inhibition of mTOR decreases insoluble protein burden by reducing translation in C. elegans

Aging animals accumulate insoluble protein as a consequence of a decline of proteostatic maintenance with age. In Caenorhabditis elegans, for instance, levels of detergent-insoluble protein increase with age. In longer-lived strains of C. elegans, this accumulation occurs more slowly, implying a link to lifespan determination. We further explored this link, and found that detergent-insoluble protein accumulates more rapidly at higher temperatures, a condition where lifespan is short. We employed a C. elegans strain carrying a GFP transcriptional reporter under the control of a heat shock (hsp-16.2) promoter to investigate the dynamics of proteostatic failure in individual nematodes. We found that early, sporadic activation of hsp-16.2 was predictive of shorter remaining lifespan in individual nematodes. Exposure to rapamycin, resulting in reduced mTOR signaling, delayed spurious expression, extended lifespan, and delayed accumulation of insoluble protein, suggesting that targets downstream of the mTOR pathway regulate the accumulation of insoluble protein. We specifically explored ribosomal S6 kinase (rsks-1) as one such candidate and found that RNAi against rsks-1 also resulted in less age-dependent accumulation of insoluble protein and extended lifespan. Our results demonstrate that inhibition of protein translation via reduced mTOR signaling resulted in slower accumulation of insoluble protein, delayed proteostatic crisis and extended lifespan in C. elegans.

biochemistry↗

bioRxiv2018

Clonal expansion of mitochondrial DNA deletions is a private mechanism of ageing in long-lived animals

Disruption of mitochondrial metabolism and loss of mitochondrial DNA (mtDNA) integrity are widely considered as evolutionarily conserved (public) mechanisms of ageing (Lopez-Otin et al. 2013). Human ageing is associated with loss in skeletal muscle mass and function (Sarcopenia), contributing significantly to morbidity and mortality. Muscle ageing is associated with loss of mtDNA integrity. In humans, clonally expanded mtDNA deletions co-localize with sites of fiber-breakage and atrophy in skeletal muscle. mtDNA deletions may therefore play an important, possibly causal role in sarcopenia. The nematode Caenorhabditis elegans also exhibits age-dependent decline in mitochondrial function and a form of sarcopenia. However, it is unclear if mtDNA deletions play a role in C. elegans ageing. Here we report identification of 266 novel mtDNA deletions in ageing nematodes. Analysis of the mtDNA mutation spectrum and quantification of mutation burden indicates that (1) mtDNA deletions in nematode is extremely rare, (2) there is no significant age-dependent increase in mtDNA deletions and (3) there is little evidence for clonal expansion driving mtDNA deletion dynamics. Thus, mtDNA deletions are unlikely to drive the age-dependent functional decline commonly observed in C. elegans. Computational modelling of mtDNA dynamics in C. elegans indicates that the lifespan of short-lived animals such as C. elegans is likely too short to allow for significant clonal expansion of mtDNA deletions. Together, these findings suggest that clonal expansion of mtDNA deletions is likely a private mechanism of ageing predominantly relevant in long-lived animals such as humans and rhesus monkey and possibly in rodents.

genetics↗

bioRxiv2018

Thermodynamic analysis of mitochondrial DNA breakpoints reveals mechanistic details of deletion mutagenesis

Broad evidence support double-strand breaks (DSBs) as initiators of mitochondrial DNA (mtDNA) deletion mutations. But the mechanism of DSB-induced deletions, including the DSB repair pathway(s) involved, remains to be established. Here, we used DNA hybridization thermodynamics to analyze misalignment lengths surrounding deletion breakpoints. Our analysis of 9,655 previously reported mammalian mtDNA deletions and 1,307 novel Caenorhabditis elegans mtDNA deletions, indicates a significant role of 0-25bp misalignments, supporting the role of erroneous non-homologous and micro-homology dependent DSB repair in deletion formation. Based on these insights we propose that DSB-induced mtDNA deletions occur via the misjoining of DSB ends and/or strand invasion of open mtDNA regions by DSB ends.

systems biology↗