Graziano, Bianca et al. (2021) International Worm Meeting "Glial KQT-2 K+ channels are needed for aversive response to octanol"

Graziano, Bianca, Wang, Lei, Bianchi, Laura, Encalada, Nicole, Fernandez-Abascal, Jesus

[International Worm Meeting, 2021]

KCNQ channels are members of a family of voltage-gated potassium channels that are encoded by five human genes and are evolutionarily conserved across species. KCNQ2 through 5 subunits are primarily expressed in the nervous system, where they modulate cellular excitability. Epilepsy, autism and other neuropsychiatric conditions have been associated with mutations in the KCNQ channels genes expressed in the nervous system. Although strong evidence supports the expression of KCNQ channels both in neurons and in glia, the role of these channels in glial cells is still unknown. In this study, we use C. elegans to investigate the glial function of the nematode KQT channels, which are the homologs of the human KCNQ channels. By RNA sequencing we found that the amphid glia, that encapsulate sensory neurons in the amphid sensory organ, are enriched in kqt-2. Using kqt-2 knock-out and glial-specific knock-down, we found that glial KQT-2 is needed for aversive response to octanol. Furthermore, we showed that the kqt-2 reduced octanol response is rescued by glial-specific expression not only of the nematode KQT-2 but also of the human KCNQ2 and KCNQ3 subunits. Our data support that KCNQ channels function in glia to promote neuronal activity suggesting that diseases associated with mutations in these channels might be contributed by glial KCNQ channels as well. Ca2+ imaging and behavioral experiments with worm and human genes wild type and mutants are in progress to establish via what mechanism glial KCNQ channels regulate neuronal output and behavior.

Wang, Lei et al. (2021) International Worm Meeting "Glial mediators of K+ and Cl- transport shape C. elegans olfaction and taste"

Bianchi, Laura, Wang, Lei, Encalada, Nicole, Graziano, Bianca

[International Worm Meeting, 2021]

Anosmia is among the most prevalent symptom of SARS-CoV-2 infection. Interestingly though, the SARS-CoV-2 virus infects the olfactory supporting cells, rather than the primary sensory neurons themselves. These recent findings have underscored the importance of the supporting cells in olfaction. However, very little is known about the mechanisms underlying the regulation of olfaction by the supporting cells. In C. elegans, the Amphid sheath (Amsh) glial cells are the supportive cells of the amphid sensory apparatus, sharing with mammalian olfactory supporting cells general function and expression of the homologs of the SARS-CoV-2 viral entry proteins ACE2 and TMPRSS2. To understand the contribution of the Amsh glia to sensory function, our lab has taken the unbiased approach of sequencing the mRNA extracted from these cells. Among the ~1,000 glial-enriched genes, we identified 14 ion channel and transporter genes with 2.7- to 29.6-fold mRNA enrichment in Amsh glia as compared to other cells. To determine whether these channels and transporter genes are needed for sensory behaviors, we performed behavioral assays on knock-outs and Amsh cell specific knock-downs. Our results support the predominant requirement of glial K+ and Cl- channels and transporters for the response to isoamyl alcohol, octanol, diacetyl, and NaCl. Given, the recent report that Amsh glia function as odorant receptor cells, Ca2+ imaging experiments are underway to determine whether these channels and transporters alter the response of Amsh glia or sensory neurons (or both) to these sensory cues. Taken together, our findings expand on our understanding of the mechanisms underlying the contribution of Amsh glia to sensory perception in C. elegans; mechanisms that might be conserved from worm to man.

Fernandez, Jesus et al. (2021) International Worm Meeting "A glial Cl- channel is the master regulator of ASH neurons' response to touch"

Bianchi, Laura, Wang, Lei, Fernandez, Jesus, Graziano, Bianca, Encalada, Nicole

[International Worm Meeting, 2021]

In mammalian touch receptors, accessory cells, including glia, play a key role in mechanosensation. However, the mechanisms underlying such regulation are not fully understood. We show here that knock-out or amphid glia specific knock-down of Cl- channel clh-1 causes nose touch insensitivity in C. elegans. Analysis of ASH nose touch neurons' dendrites in clh-1 mutants show no structural abnormality. However, Ca2+ transients in ASH neurons upon consecutive touch stimulations are altered in clh-1 knock-out. More specifically, while in wild type ASH neurons the second touch elicits smaller transients, this adaptation is absent in clh-1 knock-out animals. We further show that Ca2+ transients' adaptation is also lost in animals in which GABA transmission from amphid glia is inhibited or in which GABAA channel lgc-38 is knocked down in ASH neurons. Importantly, this phenotype is rescued in clh-1 mutants by expression of Cl- channels clh-3 and rat ClC-2 in amphid glia, as well as by growth in high Cl- plates. These results support that Cl- excreted by glia via CLH-1 permeates through LGC-38 in ASH to mediate inactivation in these neurons upon consecutive touches. We also demonstrate for the first time that cAMP in ASH neurons favors Ca2+ transients' adaptation upon touch stimulation. Indeed, using both pharmacological and genetic approaches, we show that the lack of adaptation in clh-1 is rescued by hyperactivation of adenylyl cyclase (acy-1) or by inactivation of phosphodiesterase (pde-4). Parallel behavioral experiments demonstrate that mutations and conditions in which adaptation of Ca2+ transients is lost, cause nose touch insensitivity, while mutations and conditions that restore Ca2+ transients' adaptation restore nose touch sensitivity. Taken together our data support that reduction in Ca2+ transients in ASH upon consecutive touches is essential for maintaining nose touch sensitivity and that both neuronal cAMP and glial Cl- channel CLH-1 are required for this molecular mechanism. We suggest that this Cl- mediated mechanism of functional interaction between glia and neurons might be conserved across species in touch receptors and elsewhere in the nervous system.

Eugeni V. Entchev et al. (2006) European Worm Meeting "Identifying Monomethyl Branched Fatty Acids as a Critical Product Of let-767, A Short Chain Dehydrogenase"

Eugeni V. Entchev, Teymuras V. Kurzchalia, Michaela Wilsch-Brninger, Vitali Matyash, Andrej Shevchenko, Dominik Schwudke, Bianca Abermann

[European Worm Meeting, 2006]

Eugeni V. Entchev, Dominik Schwudke, Vitali Matyash, Bianca Abermann, Michaela Wilsch-Bruninger, Andrej Shevchenko and Teymuras V. Kurzchalia. Recently, metabolic studies in C.elegans are catching considerable attention. However, the small molecule products of many enzymes are not known. Generally in a genetic system such as C.elegans, these molecules can be identified based on two approaches: i) by analyzing metabolites in mutants; ii) by complementing mutants with downstream products. We have exploited these two approaches in order to study the function of let-767, a short chain dehydrogenase/ reductase involved either in sterols or fatty acids metabolism. By complementing let-767 (RNAi) developmental arrest with hydrophobic extract from wild type worms, we found that the critical missing products in let-767 (RNAi) were the monomethyl branched chain fatty acids (mmBCFA). Consistently, the amount of mmBCFA in triacylglycerols from let-767 (RNAi) worms was highly reduced. In addition, we studied the cellular requirements of LET-767 and showed that its activity was important for the apical structure of the intestinal cells. Thus, identification of the product of LET-767 allowed to connect its cellular functions with a class of lipids, products of this enzyme. Our combination of approaches can be used in order to study other metabolic enzymes.