Gallagher, T. J. | Search bioRxiv

bioRxiv2021

S. pombe wtf genes use dual transcriptional regulation and selective protein exclusion from spores to cause meiotic drive

Meiotic drivers bias gametogenesis to ensure their transmission into more than half the offspring of a heterozygote. In Schizosaccharomyces pombe, wtf meiotic drivers destroy the meiotic products (spores) that do not inherit the driver from a heterozygote, thereby reducing fertility. wtf drivers encode both a Wtfpoison protein and a Wtfantidote protein using alternative transcriptional start sites. Here, we analyze how the expression and localization of the Wtf proteins are regulated to achieve drive. We show that transcriptional timing and selective protein exclusion from developing spores ensure that all spores are exposed to Wtf4poison, but only the spores that inherit wtf4 receive a dose of Wtf4antidote sufficient for survival. In addition, we show that the Mei4 transcription factor, a master regulator of meiosis, controls the expression of the wtf4poison transcript. This dual transcriptional regulation, which includes the use of a critical meiotic transcription factor, likely complicates the universal suppression of wtf genes without concomitantly disrupting spore viability. We propose that these features contribute to the evolutionary success of the wtf drivers. Author SummaryKiller meiotic drivers are one type of selfish DNA sequence. When only one copy of a killer meiotic driver is found in a genome, the driver is expected to be transmitted to only half of the gametes (e.g. eggs or sperm). Killer meiotic drivers, however, kill developing gametes that do not inherit them, giving the driver a transmission advantage into the next generation. The molecular mechanisms used by these killers are not well understood. In this work, we analyzed how one killer meiotic driver, wtf4 from fission yeast, ensures targeted gamete (spore) killing. Previous work showed that wtf meiotic drivers encode a poison protein that is transmitted to all spores and an antidote protein that rescues only spores that inherit the locus. Here, we show that different timing of the expression of the two proteins, combined with differential inclusion of the proteins in developing spores, both contribute to targeted spore killing. We also demonstrate that wtf4 exploits an essential gene expression pathway, making it difficult for the genome to prevent this locus from being expressed and killing. This extends our knowledge both of how these genetic parasites act and how they are equipped to evade host suppression mechanisms.

genetics↗

bioRxiv2020

Exogenous L-lactate promotes astrocyte plasticity but is not sufficient for enhancing striatal synaptogenesis or motor learning in mice

L-lactate is an energetic and signaling molecule that is key to the metabolic and neuroplastic connection between astrocytes and neurons and may be involved in exercise-induced neuroplasticity. This study sought to explore the role of L-lactate in astrocyte reactivity and neuroplasticity. Using in vitro cultures of primary astrocytes, we show L-lactate increased expression of plasticity-related genes, including neurotrophic factors, Bdnf, Gdnf, Cntf and the immediate early gene cFos. L-lactates promotion of neurotrophic factor expression may be mediated in part by the lactate receptor HCAR1 since application of the HCAR1 agonist 3,5-DHBA also increased expression of Bdnf in primary astrocytes. In vivo L-lactate administration to healthy mice caused a similar increase in the expression of plasticity-related genes as well as increased astrocyte morphological complexity in a region-specific manner, with increased astrocytic response found in the striatum but not the ectorhinal cortex, regions of the brain where increases in regional cerebral blood flow are increased or unaltered, respectively, with motor behavior. Additionally, L-lactate administration did not cause synaptogenesis or improve motor behavior based on the latency to fall on the accelerating rotarod, suggesting that L-lactate administration can initiate astrocyte-specific gene expression, but the activation of motor circuits is necessary to initiate striatal neuroplasticity. These results suggest that peripheral L-lactate is likely an important molecular component of exercise-induced neuroplasticity by acting in an astrocyte-specific manner to prime the brain for neuroplasticity.

neuroscience↗