PIEZO1 and PIEZO2 are newly identified mechanosensitive ion channels that exhibit a preference for calcium in response to mechanical stimuli. In this study, we discovered the vital roles of pezo-1, the sole PIEZO ortholog in Caenorhabditiselegans, in regulating reproduction. A number of deletion alleles, as well as a putative gain-of-function mutant, of PEZO-1 caused a severe reduction in brood size. In vivo observations showed that oocytes undergo a variety of transit defects as they enter and exit the spermatheca during ovulation. Post-ovulation oocytes were frequently damaged during spermathecal contraction. However, the calcium signaling was not dramatically changed in the pezo-1 mutants during ovulation. Loss of PEZO-1 also led to an inability of self-sperm to navigate back to the spermatheca properly after being pushed out of the spermatheca during ovulation. These findings suggest that PEZO-1 acts in different reproductive tissues to promote proper ovulation and fertilization in C. elegans.

Methylation of histone H3 on lysine 79 (H3K79) by DOT1L is associated with actively transcribed genes. Earlier, we described that DOT-1.1, the Caenorhabditis elegans homolog of mammalian DOT1L, cooperates with the chromatin-binding protein ZFP-1 (AF10 homolog) to negatively modulate transcription of highly and widely expressed target genes. Also, the reduction of ZFP-1 levels has consistently been associated with lower efficiency of RNA interference (RNAi) triggered by exogenous double-stranded RNA (dsRNA), but the reason for this is not clear. Here, we demonstrate that the DOT1L complex suppresses transcription originating from enhancer elements and antisense transcription, thus potentiating the expression of enhancer-regulated genes. We also show that worms lacking H3K79 methylation do not survive, and this lethality is suppressed by a loss of caspase-3 or Dicer complex components that initiate gene silencing response to exogenous dsRNA. Our results suggest that ectopic elevation of endogenous dsRNA directly or indirectly resulting from global misregulation of transcription in DOT1L complex mutants may engage the Dicer complex and, therefore, limit the efficiency of exogenous RNAi.

Objective Animal lifespan is controlled through genetic pathways that are conserved from nematodes to humans. Lifespan-promoting conditions in nematodes include fasting and a reduction of insulin/IGF signaling. Here we aimed to investigate the input of the Caenorhabditis elegans homologue of the mammalian rate-limiting lipolytic enzyme Adipose Triglyceride Lipase, ATGL-1, in longevity control. Methods We used a combination of genetic and biochemical approaches to determine the role of ATGL-1 in accumulation of triglycerides and regulation of longevity. Results We found that expression of ATGL is increased in the insulin receptor homologue mutant daf-2 in a FoxO/DAF-16-dependent manner. ATGL-1 is also up-regulated by fasting and in the eat-2 loss-of-function mutant strain. Overexpression of ATGL-1 increases basal and maximal oxygen consumption rate and extends lifespan in C. elegans . Reduction of ATGL-1 function suppresses longevity of the long-lived mutants eat-2 and daf-2 . Conclusion Our results demonstrate that ATGL is required for extended lifespan downstream of both dietary restriction and reduced insulin/IGF signaling.

26The PIEZO proteins are involved in a wide range of developmental and 27 physiological processes. Human PIEZO1 and PIEZO2 are newly identified excitatory 28 mechano-sensitive proteins; they are non-selective ion channels that exhibit a 29 preference for calcium in response to mechanical stimuli. To further understand the 30 function of these proteins, we investigated the roles of pezo-1, the sole PIEZO ortholog 31 in C. elegans. pezo-1 is expressed throughout development in C. elegans, with strong 32 expression in reproductive tissues. A number of deletion alleles as well as a putative 33 gain-of-function mutant caused severe defects in reproduction. A reduced brood size 34 was observed in the strains depleted of PEZO-1. In vivo observations show that oocytes 35 undergo a variety of transit defects as they enter and exit the spermatheca during 36 ovulation. Post ovulation oocytes were frequently damaged during spermathecal 37 contraction. Calcium signaling in the spermatheca is normal during ovulation in pezo-1 38 mutants, however, pezo-1 interacts genetically with known regulators of calcium 39 signaling. Lastly, loss of PEZO-1 caused defective sperm navigation after being pushed 40 out of the spermatheca during ovulation. Mating with males rescued these reproductive 41 deficiencies in our pezo-1 mutants. These findings suggest that PEZO-1 may act in 42 different reproductive tissues to promote proper ovulation and fertilization in C. elegans. 43 Zarychanski et al., 2012). Loss-of-function mutations in the PIEZO1 gene cause 67 autosomal recessive congenital lymphatic dysplasia while gain-of-function mutations led 68 to autosomal dominant stomatocytosis (Alper, 2017). However, the cellular and 69 molecular mechanisms of PIEZO dysfunction in these diseases are not well understood. 70 71Caenorhabditis elegans is an attractive model system to study 72 mechanotransduction in vivo. C. elegans contains multiple tubular tissues, including the 73 reproductive system, which experience mechanical stimulation throughout the life cycle 74 (Cram, 2014(Cram, , 2015 Voglis and Tavernarakis, 2005). The C. elegans reproductive 75 system consists of two U-shaped gonad arms, each ending with a spermatheca and 76 joined in the center by a shared uterus. C. elegans hermaphrodites produce sperm 77 during the L4 larval stage and then shift to produce oocytes during the adult stage. 78About 150 sperm are stored in each spermatheca while the oocytes form in the oviduct 79 in each gonad arm. The oocyte adjacent to the spermatheca undergoes oocyte 80 maturation ~25 minutes before being ovulated into the spermatheca (Greenstein, 2005). 81Oocyte maturation is triggered by sperm derived polypeptides known as major sperm 82 proteins (MSPs), which activate the oocyte mitogen-activated protein kinase (MPK-1) 83 (Miller, 2001; Yang et al., 2010). Once the oocyte matures, five pairs of contractile 84 myoepithelial cells, named sheath cells, which make up the somatic gonad and encase 85 the germline, push the matured oocyte into the spermatheca...

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