Mendoza, A.D. et al. (2017) International Worm Meeting "Zinc regulates germline viability through dynamic zinc fluxes in Caenorhabditis elegans."

Vogt, S, Mendoza, A.D., Wignall, S.M., Woodruff, T.K., O'Halloran, T.V.

[International Worm Meeting, 2017]

Infertility affects 6.7 million women between the ages of 15 and 44 in the US. Our approach to solving the infertility problem is multidisciplinary; drawing from cell biology, chemistry, and physics to define how the transition metal zinc, maintains healthy female eggs. Zinc is critical in regulating mammalian egg development through large-scale, dynamic zinc fluxes. To expand on these findings, we utilize the model system Caenorhabditis elegans to further uncover zinc's role in egg viability maintenance. Many regulatory factors involved in the reproductive tract formation in C.elegans are conserved in higher organisms. Therefore, C.elegans are an excellent model to study zinc. We aim to uncover if zinc fluxes are conserved and characterize how zinc affects egg viability. We hypothesize that zinc fluxes are conserved and that proper zinc levels maintains oocyte viability. We sequestered zinc utilizing the chemical TPEN in the worm's growth environment. Results demonstrated that zinc insufficient (ZI) hermaphrodites yielded smaller broods and contained fewer unfertilized oocytes compared to controls, whether self-mated or not. By time-lapse confocal imaging, we discovered that zygotes exposed to low TPEN concentrations (10 uM) displayed improper polar body extrusion, hyperploidy, lagging chromosomes and improper cytoplasmic cleavage. Combined, these results suggest that zinc insufficiency impacts unfertilized eggs within the reproductive tract and not sperm from hermaphrodites or males. Moreover, zygotes remain sensitive after fertilization to changes in cytoplasmic zinc concentrations. Because we determined that zinc insufficiency impacts the maturing egg, we next performed X-Ray Fluorescence Microscopy (XFM) at Argonne National Laboratory to determine total zinc content during oocyte maturation. Total zinc is all of the zinc in the cell, bound and unbound. We discovered that total zinc content sharply increases after fertilization up to the zygote stage, and decreases after meiosis. This indicates that large-scale zinc fluxes in C.elegans occur similarly as mammals. We similarly examined labile zinc dynamics during oocyte maturation. Labile zinc is zinc that is accessible to our probes. Utilizing the zinc sensor ZincBy-1, we determined that after fertilization, labile zinc steadily increases in the cytoplasm up to Anaphase II. Then, labile zinc content declines steadily and remains at low levels through 2-cell. Labile zinc from the cytoplasm relocates to the extra embryonic matrix (EEM), and is visible beginning at pronuclear migration. Future experiments will allow us to understand the mechanism behind zinc fluctuations within maturing oocytes. Work with C.elegans can provide insight for the conserved mechanisms for zinc action during fertilization and proper egg formation. We will then be closer to understanding human infertility issues we face today.

Cutter, Asher D. et al. (2011) International Worm Meeting "The evolution and genetics of speciation between C. briggsae and C. sp. 9."

Cutter, Asher D., Kozlowska, Joanna L.

[International Worm Meeting, 2011]

The recent discovery that the new species C. sp. 9 could hybridize with C. briggsae to generate viable and fertile F1 female progeny opens the door, for the first time, to applying the power of the Caenorhabditis model system to what Darwin called the "mystery of mysteries": speciation (Woodruff et al. 2010). We have begun exploiting this system to investigate the evolution and genetics of reproductive isolation between these species in several dimensions: pre-mating isolation, post-mating pre-zygotic isolation, and post-zygotic isolation. At the pre-mating level, we are using chemotaxis assays to determine the extent of species-specificity in attraction to female mating pheromone produced by C. sp. 9. While we find that male attraction appears to attenuate as a function of evolutionary divergence across the phylogeny, this "love potion no. 9" may not provide a species-specific mating signal. Post-zygotically, we confirm that inter-species crosses conform to Haldane's rule in that males are disproportionately detrimentally affected in hybrids and that parent-of-origin asymmetries are rampant, in accord with Darwin's corollary to Haldane's rule (Woodruff et al. 2010). In addition, we document significant within-species heritable variation for between-species hybrid incompatibility. This phenomenon of "variable reproductive isolation" is emerging as a general pattern in many organisms, and C. briggsae provides an exceptional system to dissect its genetic causes. We are now applying QTL mapping approaches with recombinant inbred lines (RILs) to determine the genetic basis to this intra-specific variation in hybrid incompatibility. I will also discuss a potentially new incipient speciation system involving C. remanei and strains from China. Woodruff GC, Eke O, Baird SE, Felix MA, Haag ES (2010). Insights into species divergence and the evolution of hermaphroditism from fertile interspecies hybrids of Caenorhabditis nematodes. Genetics 186: 997-1012.

Karin Kiontke et al. (2008) Development & Evolution Meeting "New Phylogeny Of Caenorhabditis Including Recently Discovered Species"

David Fitch, Karin Kiontke, Marie-Anne FELIX

[Development & Evolution Meeting, 2008]

Recently, seven new Caenorhabditis have been discovered, bringing the number of Caenorhabditis species in culture to 17, 10 of which are undescribed. To elucidate the relationships of the new species to the five species with sequenced genomes, we have used sequence data from two rRNA genes and several protein-coding genes for reconstructing the phylogenetic tree of Caenorhabditis. Four new species (spp. 5, 9, 10, 11) group within the so-called Elegans group of Caenorhabditis, with C. elegans being the first branch. Whereas none of them is likely to be the sister species of C. elegans, we now know of two close relatives of C. briggsae-C. sp. 5 and C. sp. 9. C. sp. 9 can hybridize with C. briggsae in the laboratory [see abstract by Woodruff et al.]. Of the remaining new species, C. sp. 7 branches off between C. elegans and C. japonica. This species is easier to cultivate than C. japonica and may be a better candidate for comparative experimental work. Two of the new species branch off before C. japonica as sister species of C. sp. 3 and C. drosophilae+C. sp. 2, respectively. Only one of the new species, C. sp. 11, is hermaphroditic. The position of C. sp. 11 in the phylogeny suggests that hermaphroditism evolved three times within the Elegans group. Two of the new species were isolated from rotting leaves and flowers, and five from rotting fruit. Rotting fruit is also the habitat in which C. elegans has been found to proliferate (Barriere and Felix, Genetics 2007) and from which C. briggsae, C. brenneri and C. remanei were repeatedly isolated. This suggests that the habitat of the stem species of Caenorhabditis after the divergence of the earliest branches (C. plicata, C. sonorae and C. sp. 1) was rotting fruit. The rate of discovery of new Caenorhabditis species has steadily increased since the description of C. elegans in 1899, with a leap in the last two years. There is no indication that we are even close to knowing all species in this genus.

Olahova M et al. (2010) Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI "Modulation of DAF-16 Activity by a Peroxiredoxin Antioxidant Enzyme with Tissue-Specific Effects on Stress Resistance and Ageing"

Crook H M, Veal E A, Olahova M

[Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI, 2010]

Over the past few years several studies have suggested that links between oxidative stress and ageing may be more complex than initially proposed by oxidative damage theories. For instance, although many long-lived mutant C. elegans have increased stress resistance there is limited evidence that increased antioxidant defences are responsible for their increased lifespan. 2-Cys Peroxiredoxins (Prx) are abundant, conserved thioredoxin peroxidases, which have been shown to have important roles in responses to hydrogen peroxide and in normal longevity. For instance, C. elegans lacking PRDX-2, the ortholog of the Prdx1 tumor suppressor, are highly sensitive to hydrogen peroxide and short-lived. Consistent with an antioxidant role, intestinal PRDX-2 protects against oxidative stress. However, unexpectedly, non-intestinal PRDX-2 acts to reduce the resistance of C. elegans to some forms of oxidative stress, such as arsenite[1]. Here we will present data suggesting that the increased arsenite resistance associated with loss of PRDX-2 from non-intestinal tissues is dependent on the FOXO transcription factor DAF-16. Indeed, we find that DAF-16 is partially activated in PRDX-2-deficient animals. Our preliminary data indicate that reduced insulin/IGF-1-like signaling can increase still further the arsenite resistance of PRDX-2-deficient animals, but only partially rescue the progeric phenotypes associated with PRDX-2-deficiency. Similarly, although intestinal expression of PRDX-2 increases the oxidative stress resistance of prdx-2 mutants beyond that of wild-type animals, it does not increase their lifespan [1]. Together these data suggest that the accelerated ageing associated with loss of PRDX-2 from non-intestinal tissues is not a consequence of reduced resistance to oxidative stress. Moreover, these data demonstrate the importance of taking into consideration tissue-specific activities when assessing how stress-defences may influence the stress resistance and ageing of the whole animal. [1] Olahova, M., Taylor, S.R., Khazaipoul, S., Wang, J., Morgan, B.A., Matsumoto, K., Blackwell, T.K., and Veal, E.A. (2008). A redox-sensitive peroxiredoxin that is important for longevity has tissue- and stress-specific roles in stress resistance. PNAS, 105, 19839-19844.