Steinert, Hannah et al. (2015) International Worm Meeting "Male hypersensitivity to dauer entry: a model for sex differences in larval physiology."

Portman, Douglas, Steinert, Hannah

[International Worm Meeting, 2015]

Across the animal kingdom, males and females differ in stress responses and aging. This natural variation provides interesting opportunities to better understand these responses and to identify the points at which they are regulated by sex determination. In C. elegans, entry into the dauer stage is a well-studied developmental response to juvenile stress. Interestingly, there are several indications that males are more sensitive than hermaphrodites to dauer-entry signals (Vowels and Thomas, 1992, Genetics 130:105-123; Ailion and Thomas, 2000, Genetics 156:1047-1067). Consistent with these results, we find that males carrying a mutation in the TGFbeta ligand daf-7 virtually always enter dauer at 20degC, while only a small fraction of hermaphrodites do so. In contrast, animals lacking the insulin receptor daf-2 appear to form dauers with no obvious sex bias, suggesting that sex differences act at a specific early stage in the dauer decision pathway. Using sexually mosaic animals, we are currently working to identify the cellular focus of sexual dimorphism in this mechanism. In addition, we are interested in the possibility that signals promoting dauer exit may be interpreted differently in males and hermaphrodites. While multiple sex differences in late larval and adult physiology have been described, these differences in dauer entry indicate the existence of uncharacterized sexual dimorphism in the physiology of early larvae. .

Steinert, Hannah et al. (2017) International Worm Meeting "Heterochronic regulation of the sex-specific maturation of the C. elegans nervous system."

Steinert, Hannah, Portman, Douglas S.

[International Worm Meeting, 2017]

Structural and functional remodeling of the nervous system is a pervasive feature of adolescence in many animals. One critical purpose of this remodeling is to enable adult-specific sex differences in behaviors, such as mate-searching and parental care. While some of these changes involve neurogenesis and changes in connectivity, others occur through gene expression changes in existing neural circuits. In C. elegans, several pre-existing neural circuits undergo gene expression changes during the juvenile-to-adult transition, particularly in males. In one important example, juvenile males and hermaphrodites have similar levels of the food-associated chemoreceptor odr-10 in the sensory neuron AWA; however, upon maturation males specifically downregulate expression of this chemoreceptor, reducing food sensitivity and facilitating mate-searching behavior. tra-1, the master regulator of C. elegans sex-determination, acts cell-autonomously to repress male development, allowing us to alter the sexual identity of single cells by manipulating its expression. Feminizing AWA by inducing tra-1 is sufficient to generate high, hermaphrodite-like odr-10 expression in adult males, demonstrating odr-10 expression is dependent on genetic sex. This raises the question of how genetic sex and developmental timing intersect to regulate neural maturation. The heterochronic pathway is known to control developmental timing by regulating stage-specific events in the hypodermis; however, its functions in the nervous system are less well understood. Using developmentally regulated genes, such as odr-10, as markers for nervous system maturity, we investigated whether the heterochronic pathway mediates nervous system maturation. Consistent with this hypothesis the "precocious" lin-28 and "retarded" let-7 mutants have early and delayed maturation, respectively, while the retarded lep-5 and lep-2 mutants retain larval gene expression patterns as adults. For example, lep-5 and lep-2 mutants exhibit high levels of odr-10 expression in AWA. Like larvae, they also fail to exhibit food-leaving behavior. Surprisingly, our results suggest that other important heterochronic genes, such as daf-12 and lin-41, may not be important for this process. Currently we are determining where the heterochronic pathway acts to time neural maturation by performing cell-specific rescue. One interesting possibility that we are currently considering is that the male nervous system adopts a masculinized state at the juvenile-to-adult transition by heterochronic regulation of the sex-determination pathway.

Chen X et al. (2015) Mol Neurodegener "Erratum to: Ethosuximide ameliorates neurodegenerative disease phenotypes by modulating DAF-16/FOXO target gene expression."

McCue HV, Chen X, Morgan A, Kashyap SS, Barclay JW, Kraemer BC, Burgoyne RD, Wong SQ

[Mol Neurodegener, 2015]

The original version of this article [1] unfortunately contained a mistake. The author list contained a spelling error for the author Hannah V. McCue. The original article has been corrected for this error. The corrected author list is given below:Xi Chen, Hannah V. McCue, Shi Quan Wong, Sudhanva S. Kashyap, Brian C. Kraemer, Jeff W. Barclay, Robert D. Burgoyne and Alan Morgan

Mintzer EA et al. (2002) FEBS Lett "Behavior of a photoactivatable analog of cholesterol, 6-photocholesterol, in model membranes."

Mintzer EA, Wilschut J, Waarts BL, Bittman R

[FEBS Lett, 2002]

6-Photocholesterol, a new photoactivatable analog of cholesterol in which a diazirine functionality replaces the 5,6-double bond in the steroid nucleus, was used recently to identify cholesterol-binding proteins in neuroendocrine cells [Thiele, C., Hannah, M.J., Farenholz, F. and Huttner, W.B. (2000) Nat. Cell Biol. 2, 42-49], to track the distribution and transport of cholesterol in Caenorhabditis elegans [Matyash, V., Geier, C., Henske, A., Mukherjee, S., Hirsh, D., Thiele, C., Grant, B., Maxfield, F.R. and Kurzchalia, T.V. (2001) Mol. Biol. Cell 12, 1725-1736], and to probe lipid-protein interactions in oligodendrocytes [Simons, M., Kramer, E.M., Thiele, C., Stoffel, W. and Trotter, J. (2000) J. Cell Biol. 151, 143-154]. To determine whether 6-photocholesterol is a faithful mimetic of cholesterol we analyzed the ability of this probe, under conditions in which it is not photoactivated to a carbene, to substitute for cholesterol in two unrelated assays: (1) to condense 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine monomolecular films and (2) to mediate the fusion of two alphaviruses (Semliki Forest and Sindbis) with liposomes. The results suggest that this analog is a suitable photoprobe of cholesterol.

Tang LZ et al. (1991) International C. elegans Meeting "THE UNC-44 SITE B TRANSCRIPT ENCODES A PUTATIVE ACIDIC PROTEIN."

Tang LZ, Franco R, Otsuka AJ

[International C. elegans Meeting, 1991]

Mutations in the unc-44 gene result in defective targeting of several axons to their appropriate partners [Hedgecock, E. M. et. al., Devel. Biol., 111, 158-170 (1985)]. The six characterized insertion mutations are found in two transcriptional regions, designated sites A and B [Otsuka, A. et al., WBG, 11(5) 39 (1991)]. Four alleles (mn259, mn339, rhlO42, and st200) are insertions at site B. Three independently isolated cDNA clones (approx. 3.4 kb) with similar restriction maps were obtained from the Barstead and Waterston cDNA clone bank. One of these, DD#PA013, has been sequenced. The 821-amino acid open reading frame present on DD#PA013 appears to extend beyond the cloned cDNA. The predicted protein product of DD#PA013 is acidic (pI = approx. 4). The central portion of the predicted protein (612 amino acid residues) lacks cysteine residues. The protein contains two copies of the sequence SL(Q/A)EFERLEKE. The Tcl insertion in the rhlO42 allele occurs between these repeats. A region of 9 related tandem repeats, including the two just noted, can be surmised from the sequence, although the similarity is very poor in some of the repeats. The limited number of cysteine residues, the hydrophilic character of the predicted protein, and the high predicted alpha-helical content suggest an acidic protein with an extended central domain. In searches of Genbank with the predicted DD#PA013 protein sequence, the intermediate filament proteins are selected, but the core domain of the intermediate filament proteins [Steinert, P. M. and Roop, D. R., Ann. Rev. Biochem., 57, 593-625 (1988)] is not obvious in the sequence of the predicted DD#PA013 product.

Hannah L. Craig et al. (2006) European Worm Meeting "Understanding the Role of a Non-Peptidase Member of the ACE Family in Nematode Moulting"

R.Elwyn Isaac, Hannah L. Craig, Clare Hunton, Darren R. Brooks

[European Worm Meeting, 2006]

Hannah L. Craig1, Clare Hunton1, Darren R. Brooks2, R.Elwyn Isaac1 Analysis of the large number of protease-like genes present in animal genomes has shown that a considerable proportion of these genes code for proteins that are structurally related to peptidases, but lack key catalytic residues. These proteins are classified as non-peptidase family members. One such protein is the single member of the angiotensin-converting enzyme (ACE) family of zinc metallopeptidases found in C. elegans. ACN-1 (ACE-like non-metallopeptidase) shares considerable identity with ACE from other organisms, but lacks the conserved active site residues required for proteolytic activity. ACN-1 also differs from other ACEs in having a proline/glutamic acid-rich domain, and, towards the C-terminus, a cysteine-rich region, a proline and threonine/serine rich region and a potential GPI anchor attachment site. It has recently become apparent that an alternatively-spliced form of acn-1 may be expressed at low levels. A single EST with 5 and 3 sequence identical to acn-1, but missing a major portion of the central ACE-like domain, has been identified. Sequences showing considerable similarity to acn-1 are also present in EST and genomic datasets from several parasitic nematodes.. ACN-1 has an essential role in C. elegans development and morphogenesis. GFP-tagged ACN-1 expression was observed in the hypodermal cells and developing vulva of hermaphrodites and also the ray papillae of the male tail. Deletion of a 692 bp fragment (strain tm844, provided by Shohei Mitani, Tokyo Womens Medical College) comprising part of exon 7 and all of exons 8 and 9 resulted in arrested embryonic development and acn-1 RNAi resulted in larval arrest due to a moulting defect. Further examination showed that acn-1 RNAi-treated adults had disrupted alae, an incomplete seam syncytium and a protruding vulva. SEM images of arrested larvae showed a failure to shed the old cuticle after RNAi. Adult males displayed similar hypodermal defects, including a severely disrupted tail. The nuclear hormone receptors nhr-23 and nhr-25 were shown by RNAi to regulate expression of acn-1::gfp, hence positioning acn-1 downstream of these nuclear hormone receptors in the genetic cascade controlling moulting.