Genetic analysis of daf-18/PTEN missense mutants for starvation resistance and developmental regulation during Caenorhabditis elegans L1 arrest

Abstract

Mutations in the well-known tumor suppressor PTEN are observed in many cancers. PTEN is a dual-specificity phosphatase that harbors lipid and protein-phosphatase activities. The Caenorhabditis elegans PTEN ortholog is daf-18, which has pleiotropic effects on dauer formation, aging, starvation resistance, and development. Function of three daf-18 point-mutants, G174E, D137A and C169S, had previously been investigated using high-copy transgenes in a daf-18 null background. These alleles were generated based on their mammalian counterparts and were treated as though they specifically disrupt lipid or protein-phosphatase activity, or both, respectively. Here, we investigated these alleles using genome editing of endogenous daf-18. We assayed three traits relevant to L1 starvation resistance, and we show that each point mutant is essentially as starvation-sensitive as a daf-18 null mutant. Furthermore, we show that G174E and D137A do not complement each other, suggesting overlapping effects on lipid and protein-phosphatase activity. We also show that each allele has strong effects on nucleocytoplasmic localization of DAF-16/FoxO and dauer formation, both of which are regulated by PI3K signaling, similar to a daf-18 null allele. In addition, each allele also disrupts M-cell quiescence during L1 starvation, though D137A has a weaker effect than the other alleles, including the null. Our results confirm that daf-18/PTEN is important for promoting starvation resistance and developmental arrest and that it is a potent regulator of PI3K signaling, and they highlight challenges of using genetic analysis to link specific DAF-18/PTEN enzymatic activities to particular phenotypes.

Developmental and conditional regulation of DAF-2/INSR ubiquitination inCaenorhabditis elegans

“…2a; Baugh & Sternberg, 2006). In contrast, there were substantial M cell divisions in daf-18(ok480) mutants, as expected with increased IIS (Chen et al 2022). Over-expression of agonistic insulin-like peptides during L1 starvation drives M cell division (Chen and Baugh 2014), but there were very few M cell divisions in daf-2(gk390525), consistent with this allele not appreciably increasing IIS during L1 arrest (Fig.…”

Using population selection and sequencing to characterize natural variation of starvation resistance in Caenorhabditis elegans

“…Larvae that hatch in the absence of food arrest development in the first larval stage (L1 arrest) and can survive starvation for weeks ( Baugh, 2013 ). In addition to causing mortality, extended starvation reduces growth and reproductive success upon feeding ( Jobson et al, 2015 ; Jordan et al, 2019 ), and these effects can be uncoupled by genotype or condition ( Roux et al, 2016 ; Kaplan et al, 2018 ; Chen et al, 2022 and reviewed in Baugh and Hu, 2020 ). Starvation resistance therefore integrates survival, growth rate, and reproductive success, and different genes and conditions can affect these phenotypes independently.…”

“…When IIS is reduced, such as during starvation, DAF-16 moves to the nucleus and regulates transcription ( Henderson and Johnson, 2001 ; Lee et al, 2001 ; Lin et al, 2001 ), promoting starvation resistance ( Muñoz and Riddle, 2003 ; Baugh and Sternberg, 2006 ; Hibshman et al, 2017 ). ( Roux et al, 2016 ; Kaplan et al, 2018 ; Baugh and Hu, 2020 ; Chen et al, 2022 ).…”

Natural variation in theirldgene family affects starvation resistance inC. elegans

“…2018). In addition, daf-18/PTEN mutant worms display reduced L1 starvation survival and growth upon recovery, but their reproduction is particularly sensitive to starvation, with only 12 hours of L1 starvation causing dramatic decline in brood size, including sterility in some individuals (C hen et al . 2022).…”

“…Likewise, sensory perception of food during L1 starvation does not affect survival but causes irreversible developmental arrest (KAPLAN et al 2018). In addition, daf-18/PTEN mutant worms display reduced L1 starvation survival and growth upon recovery, but their reproduction is particularly sensitive to starvation, with only 12 hours of L1 starvation causing dramatic decline in brood size, including sterility in some individuals (CHEN et al 2022). Starvation resistance therefore integrates survival, growth rate, and reproductive success, and different genes and conditions can affect these three phenotypes independently.…”