Eve A (2021) Development "An interview with Swathi Arur."

Eve A

[Development, 2021]

Swathi Arur is an Associate Professor for the Department of Genetics at the MD Anderson Cancer Center, USA, where she uses multidisciplinary approaches to understand female germline development and fertility. She has received numerous accolades, including the MD Anderson Distinguished Research Faculty Mentor Award in 2017. In 2020, she was elected to the American Association for the Advancement of Science (AAAS). Swathi joined the team at Development as an Academic Editor in 2020, and we met with her over Zoom to hear more about her life, her career and her love for <i>C. elegans</i>.

Dixon JR (2019) Dev Cell "TADs for Life: Chromatin Domain Organization Regulates Lifespan in C.elegans."

Dixon JR

[Dev Cell, 2019]

In this issue of Developmental Cell, Anderson etal. (2019) show that chromatin domain structure on the X chromosome in C.elegans is dispensable for dosage compensation but regulates longevity and thermotolerance. This study sheds light on the mechanisms of domain formation in C.elegans and how these features affect physiology.

Mikoshiba K (2011) Cell Calcium "Role of IP receptor in development."

Mikoshiba K

[Cell Calcium, 2011]

IP receptor is a Ca(2+) release channel localized on the endoplasmic reticulum. IP(3) receptor is composed of three isoforms, which are expressed in various cells and tissues, and play variety of roles throughout development. I here describe the role of IP receptor from oogenesis, meiotic maturation and fertilization. I also describe the Ca(2+) signaling at meiosis and mitosis, and especially the role in early embryogenesis to determine dorso-ventral axis formation. Loss of function mutation of type 1 IP receptor in mouse, both by gene targeting and spontaneous mutations shows severe ataxia and other phenotypes. Interestingly, double knockouts of type 1 and type 2 exhibit cardiogenesis arrest and that of type 2 and type 3 results in exocrine secretion deficit. IPR of Drosophila or Caenorhabditis elegans is single gene and mutation results severe phenotype of behavior. All the data described here show that IPRs are essential for life and abnormality of IP(3)Rs results in severe abnormality in its structure and function of organism.

Xu X et al. (2007) Exp Cell Res "Role of phosphatidylinositol-4-phosphate 5' kinase (ppk-1) in ovulation of Caenorhabditis elegans."

Lee M, Wycuff DL, Guo H, Xu X

[Exp Cell Res, 2007]

During Caenorhabditis elegans ovulation, the somatic gonad integrates signals from germ cells and propels a mature oocyte into the spermatheca for fertilization. Previous work suggests that phosphoinositide signaling plays important roles in C. elegans fertility. To fully understand inositol-1,4,5-trisphosphate (IP(3)) signaling in ovulation, we have examined the function of phosphatidylinositol-4-phosphate 5'' kinase (PIP5K) in C. elegans. Our results show that the C. elegans PIP5K homolog, ppk-1, is essential for ovulation in C. elegans; ppk-1 is mainly expressed in somatic gonad, and depletion of ppk-1 expression causes defective ovulation, reduced gonad sheath contractility, and sterility. Increased IP(3) signaling compensates for ppk-1 (RNAi)-induced sterility, suggesting that ppk-1 is linked to IP(3) signaling. These results demonstrate that ppk-1 plays an essential role in IP(3) signaling and cytoskeleton organization in somatic gonad.

Xing J et al. (2010) Am J Physiol Cell Physiol "Phosphatidylinositol 4,5-bisphosphate and loss of PLCgamma activity inhibit TRPM channels required for oscillatory Ca2+ signaling."

Xing J, Strange K

[Am J Physiol Cell Physiol, 2010]

The Caenorhabditis elegans intestinal epithelium generates rhythmic inositol 1,4,5-trisphosphate (IP(3))-dependent Ca(2+) oscillations that control muscle contractions required for defecation. Two highly Ca(2+)-selective transient receptor potential (TRP) melastatin (TRPM) channels, GON-2 and GTL-1, function with PLCgamma in a common signaling pathway that regulates IP(3)-dependent intracellular Ca(2+) release. A second PLC, PLCbeta, is also required for IP(3)-dependent Ca(2+) oscillations, but functions in an independent signaling mechanism. PLCgamma generates IP(3) that regulates IP(3) receptor activity. We demonstrate here that PLCgamma via hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP(2)) also regulates GON-2/GTL-1 function. Knockdown of PLCgamma but not PLCbeta activity by RNA interference (RNAi) inhibits channel activity approximately 80%. Inhibition is fully reversed by agents that deplete PIP(2) levels. PIP(2) added to the patch pipette has no effect on channel activity in PLCgamma RNAi cells. However, in control cells, 10 microM PIP(2) inhibits whole cell current approximately 80%. Channel inhibition by phospholipids is selective for PIP(2) with an IC(50) value of 2.6 microM. Elevated PIP(2) levels have no effect on channel voltage and Ca(2+) sensitivity and likely inhibit by reducing channel open probability, single-channel conductance, and/or trafficking. We conclude that hydrolysis of PIP(2) by PLCgamma functions in the activation of both the IP(3) receptor and GON-2/GTL-1 channels. GON-2/GTL-1 functions as the major intestinal cell Ca(2+) influx pathway. Calcium influx through the channel feedback regulates its activity and likely functions to modulate IP(3) receptor function. PIP(2)-dependent regulation of GON-2/GTL-1 may provide a mechanism to coordinate plasma membrane Ca(2+) influx with PLCgamma and IP(3) receptor activity as well as intracellular Ca(2+) store depletion.

Davies L et al. (2007) Proteins "An unsuspected ecdysteroid/steroid phosphatase activity in the key T-cell regulator, Sts-1: surprising relationship to insect ecdysteroid phosphate phosphatase."

Anderson IP, Rigden DJ, Rees HH, Davies L, Shirras AD, Turner PC

[Proteins, 2007]

The insect enzyme ecdysteroid phosphate phosphatase (EPP) mobilizes active ecdysteroids from an inactive phosphorylated pool. Previously assigned to a novel class, it is shown here that it resides in the large histidine phosphatase superfamily related to cofactor-dependent phosphoglycerate mutase, a superfamily housing notably diverse catalytic activities. Molecular modeling reveals a plausible substrate-binding mode for EPP. Analysis of genomic and transcript data for a number of insect species shows that EPP may exist in both the single domain form previously characterized and in a longer, multidomain form. This latter form bears a quite unexpected relationship in sequence and domain architecture to vertebrate proteins, including Sts-1, characterized as a key regulator of T-cell activity. Long form Drosophila melanogaster EPP, human Sts-1, and a related protein from Caenorhabditis elegans have all been cloned, assayed, and shown to catalyse the hydrolysis of ecdysteroid and steroid phosphates. The surprising relationship described and explored here between EPP and Sts-1 has implications for our understanding of the function(s) of both. Proteins 2007. (c) 2007 Wiley-Liss, Inc.

Lee M-H et al. (1997) International C. elegans Meeting "TOWARD THE IDENTIFICATION OF IN VIVO RNA TARGETS OF GLD-1."

Lee M-H, Schedl TB

[International C. elegans Meeting, 1997]

gld-1 is a female germ cell specific tumor suppressor gene that is essential for normal oocyte differentiation and meiotic prophase progression (Francis et al., 1995a,b). GLD-1 is a member of a small family of proteins, including the mouse/human Sam68 and Quaking proteins, that are highly related over an ~ 200 amino acid region which contains a 70 to 100 amino acid RNA binding domain called the KH motif (Jones and Schedl, 1995). Extensive mutational analysis of gld-1 has demonstrated the importance of conserved sequences for its in vivo function. GLD-1 is a cytoplasmic protein and therefore is likely to control mRNA translation or RNA stability in the cytoplasm (Jones et al., 1996). Currently, no obvious RNA targets have been identified from genetic analysis. We have employed a biochemical approach to identify in vivo RNA targets of GLD-1. The strategy is based on the ability of anti GLD-1 antibodies to immunoprecipitate (IP) GLD-1 from a worm lysate and the strong likelihood that GLD-1 present in the lysate is functional and bound to RNAs. GLD-1 was IPed with affinity purified polyclonal antibodies from a cytosol extract of adult hermaphrodites or with rabbit IgG as a control. RNAs co-IP with GLD-1, as well as with rabbit IgG, were converted into cDNAs. Non-specifically trapped RNAs from the GLD-1 IP were eliminated by subtracting cDNAs from the GLD-1 IP with cDNAs from the control IP. The difference product after 4 rounds of subtraction (DP4) was used to screen a Lambda ZAP II cDNA library constructed with the cDNAs from the GLD-1 IP. Duplicate filters were also screened with a probe made from control IP cDNA. Clones that are positive only with the DP4 probe are currently being characterized. Francis et al., 1995a Genetics 139, 579-606; Francis et al., 1995b Genetics 139, 607-630; Jones and Schedl, 1995 Genes Dev. 9, 1491-1504; Jones et al., 1996 Dev. Biol. 180, 165-183. This work was supported by NIH Grant HD25614.

P Dal Santo et al. (1999) International C. elegans Meeting "The IP3 Receptor is a Timekeeper for the Defecation Cycle Rhythm"

EM Jorgensen, P Dal Santo, MA Logan, AD Chisholm

[International C. elegans Meeting, 1999]

The C. elegans defecation cycle is characterized by the activation of three distinct muscle contractions every 45-50 seconds. How is cycle time maintained? To address this question we identified and characterized mutants with abnormal cycle times. Specifically, we cloned the dec-4 gene and demonstrated that it encodes the inositol trisphosphate receptor (IP 3 receptor). Mutations in the IP 3 receptor alter the timing of the defecation cycle. Null mutations eliminate the cycle, hypomorphic mutants have a slow cycle, and overexpression of the protein results in a fast cycle time. The IP 3 receptor is expressed in several different tissues including the pharynx, the somatic gonad, and the intestine. Using mosaic analysis we demonstrated that IP 3 receptor expression in the intestine is necessary and sufficient for normal timing of the cycle. This indicates that the periodic muscle contractions can be controlled non-autonomously from the intestine. IP 3 receptors are localized to the endoplasmic reticulum and are known to function as calcium release channels. Activation of the channel by a phospholipid signaling pathway leads to the production of temporally and spatially regulated calcium oscillations. Our current data predicts a model in which calcium oscillations in the intestine trigger the defecation motor program. To test this model we injected calcium-sensitive dyes into the posterior intestinal cells of adult animals. Our results demonstrate that calcium oscillations occur in the intestine. The frequency of calcium oscillations are consistent with the timing of the defecation cycle and peak calcium levels occur just before the onset of the muscle program. We conclude that periodic calcium release in the intestinal cells initiates the muscle contractions of the defecation cycle and that the IP 3 receptor is a central component of the timekeeping mechanism that regulates this behavioral rhythm.

Oh WC et al. (2011) Mol Cells "ANK repeat-domain of SHN-1 Is indispensable for in vivo SHN-1 function in C. elegans."

Cho JH, Song HO, Park BJ, Oh WC

[Mol Cells, 2011]

Shank protein is one of the postsynaptic density (PSD) proteins which play a major role in proper localization of proteins at membranes. The shn-1, a homolog of Shank in Caenorhabditis elegans, is expressed in neurons, pharynx, intestine, vulva and sperm. We have previously reported a possible genetic interaction between Shank and IP receptor by examining shn-1 RNAi in IP receptor (itr-1) mutant background. In order to show the direct interaction of Shank and IP receptor as well as to show the direct in vivo function of Shank, we have characterized two different mutant alleles of shn-1, which have different deletions in the different domains. shn-1 mutants were observed for Ca+-related behavioral defects with itr-1 mutants. We found that only shn-1 mutant defective in ANK repeat-domain showed significant defects in defecation, pharyngeal pumping and fertility. In addition, we found that shn-1 regulates defecation, pharyngeal pumping and probably male fertility with itr-1. Thus, we suggest that Shank ANK repeat-domain along with PDZ may play a crucial role in regulating Ca+-signaling with IP receptor.

Xu X et al. (2005) FEBS Lett "Linking integrin to IP(3) signaling is important for ovulation in Caenorhabditis elegans."

Lee M, Shih HY, Seo S, Xu X, Ahn J, Lee D

[FEBS Lett, 2005]

Signals from germ and myoepithelial sheath cells initiate ovulation in Caenorhabditis elegans. The coordinated dilation and contraction of spermatheca lead to subsequent fertilization of oocyte. Either the dominant negative mutant pat-3 beta integrin or disruption of talin expression block ovulation [Cram, E.J., Clark, S.G. and Schwarzbauer, J.E. (2003) Talin loss-of-function uncovers roles in cell contractility and migration in C. elegans. J. Cell. Sci. 116, 3871-3878; Lee, M., Cram, E.J., Shen, B. and Schwarzbauer, J.E. (2001) Role of beta pat-3 integrins in development and function of Caenorhabditis elegans muscles and gonads. J. Biol. Chem. 276, 36404-36410], suggesting that the interaction between the cell and the extracellular matrix (ECM) is also important for ovulation. Here, we report that integrin plays an essential role in fertility via IP(3) signaling. Sterility caused by RNAi of pat-3 and ECM molecules was suppressed by increased IP(3) signaling. Our data suggest that the cell-ECM interaction controls ovulation via IP(3) signaling.