Person:

Steinbaugh, Michael

In Caenorhabditis elegans, ablation of germline stem cells (GSCs) extends lifespan, but also increases fat accumulation and alters lipid metabolism, raising the intriguing question of how these effects might be related. Here, we show that a lack of GSCs results in a broad transcriptional reprogramming in which the conserved detoxification regulator SKN-1/Nrf increases stress resistance, proteasome activity, and longevity. SKN-1 also activates diverse lipid metabolism genes and reduces fat storage, thereby alleviating the increased fat accumulation caused by GSC absence. Surprisingly, SKN-1 is activated by signals from this fat, which appears to derive from unconsumed yolk that was produced for reproduction. We conclude that SKN-1 plays a direct role in maintaining lipid homeostasis in which it is activated by lipids. This SKN-1 function may explain the importance of mammalian Nrf proteins in fatty liver disease and suggest that particular endogenous or dietary lipids might promote health through SKN-1/Nrf. DOI: http://dx.doi.org/10.7554/eLife.07836.001

The discovery that TDP-43 mutations cause familial ALS and that many patients display pathological TDP-43 mislocalization has nominated altered RNA metabolism as a potential disease mechanism. Despite its importance, the identity of RNAs regulated by TDP-43 in motor neurons remains poorly understood. Here, we report transcripts whose abundances in human motor neurons are sensitive to TDP-43 depletion. Notably, we found STMN2, which encodes a microtubule regulator, declined after TDP-43 knockdown, in patient-specific motor neurons, following TDP-43 mislocalization, and in the postmortem patient spinal cords. Loss of STMN2 upon reduced TDP-43 function was due to the emergence of a cryptic exon, which is of substantial functional importance, as we further demonstrate that STMN2 is necessary for both axonal outgrowth and repair. Importantly, post-translational stabilization of STMN2 could rescue neurite outgrowth and axon regeneration deficits induced by TDP-43 depletion. We propose restoring STMN2 expression warrants future examination as an ALS therapeutic strategy.