The Mitochondrial Chaperone Protein TRAP1 Mitigates α-Synuclein Toxicity

Overexpression or mutation of α-Synuclein is associated with protein aggregation and interferes with a number of cellular processes, including mitochondrial integrity and function. We used a whole-genome screen in the fruit fly Drosophila melanogaster to search for novel genetic modifiers of human [A53T]α-Synuclein–induced neurotoxicity. Decreased expression of the mitochondrial chaperone protein tumor necrosis factor receptor associated protein-1 (TRAP1) was found to enhance age-dependent loss of fly head dopamine (DA) and DA neuron number resulting from [A53T]α-Synuclein expression. In addition, decreased TRAP1 expression in [A53T]α-Synuclein–expressing flies resulted in enhanced loss of climbing ability and sensitivity to oxidative stress. Overexpression of human TRAP1 was able to rescue these phenotypes. Similarly, human TRAP1 overexpression in rat primary cortical neurons rescued [A53T]α-Synuclein–induced sensitivity to rotenone treatment. In human (non)neuronal cell lines, small interfering RNA directed against TRAP1 enhanced [A53T]α-Synuclein–induced sensitivity to oxidative stress treatment. [A53T]α-Synuclein directly interfered with mitochondrial function, as its expression reduced Complex I activity in HEK293 cells. These effects were blocked by TRAP1 overexpression. Moreover, TRAP1 was able to prevent alteration in mitochondrial morphology caused by [A53T]α-Synuclein overexpression in human SH-SY5Y cells. These results indicate that [A53T]α-Synuclein toxicity is intimately connected to mitochondrial dysfunction and that toxicity reduction in fly and rat primary neurons and human cell lines can be achieved using overexpression of the mitochondrial chaperone TRAP1. Interestingly, TRAP1 has previously been shown to be phosphorylated by the serine/threonine kinase PINK1, thus providing a potential link of PINK1 via TRAP1 to α-Synuclein

The influence of sperm competition and parasites on reproductive strategies in simultaneously hermaphroditic land snails

Sexual selection is a concept of selection and subject of numerous studies on reproduction and sexual dimorphism in secondary sexual characteristics. In simultaneous hermaphrodites both the female and male function within the same individual compete for resources. Complex behaviours and mechanisms optimize the reproductive investment in these species. These behaviours and mechanisms might also be affected by internal factors and external conditions. In former studies researchers started to disentangle different factors and conditions in order to understand the major drivers of reproduction success. In my thesis I focused on reproductive strategies of the model organism Arianta arbustorum, a hermaphroditic land snail, and the influence on reproduction and winter survival of its parasite Riccardoella limacum, a blood- sucking mite that lives in the mantle cavity of the snail. For a better understanding of the fragile host-parasite interaction, further details about the life-history of R. limacum were explored. Hibernation is a crucial period in the annual cycle of a parasite and its host. Hibernation has a strong impact on the fitness of both species and consequently affects their life-history and reproduction. Temperature, for example, can be a limiting factor for parasite development. Low temperatures over a long period could influence the life cycle of R. limacum. Three experiments were performed to examine the influence of hibernation duration on the survival of the parasitic mite R. limacum and its eggs. The intensity of mite infection of hosts decreased with increasing hibernation duration. R. limacum survived the winter in the egg stage in the host’s lung. Winter survival of the host itself was negatively affected. It could be hypothesised that low temperature and a longer winter period at high elevation may limit the occurrence of R. limacum. The variation in sperm morphology of the land snail Arianta arbustorum in relation to parasitic mite infection was investigated. Variation in total sperm length and sperm head length was assessed in 23 populations sampled across the distributional range of the species in Central and Northern Europe. Results showed a variation in total sperm length among populations, which increased significantly with the geographic distance between the populations. Additionally, a minimal adequate model revealed that mite-infected individuals of A. arbustorum produced longer sperm than uninfected snails and total sperm length decreased from west to east across Europe. Moreover, total sperm length in a subsample of 12 alpine populations decreased with increasing elevation. Differences among populations explained 62.9% of the variance in total sperm length, differences among individual snails within population 23.4% and differences within individual snails 13.7%. These results suggest that selection pressures acting among populations may differ from those acting within. To examine the principles of selection pressures on sperm traits on a larger scale, a comparative approach was used considering 57 stylommatophoran snail species of Europe and South America. The hypothesis that cross-fertilizing species have longer sperm than self- fertilizing species as a consequence of sperm competition risk was tested. Sperm length, sperm head length and shell traits of these species were measured and analysed. Information on the breeding system and life-history characters including habitat preferences was gathered. Results showed that both total sperm length and sperm head length varied significantly between species and indicated that risk of sperm competition as well as shell size account for the variation across species. Sperm competition is an important part of sexual selection and considered as a driving force in the evolution of sperm traits. Furthermore, sperm competition is regarded as principal determinant of male fitness in promiscuous species. The last project of this thesis deals with the question, whether the risk of sperm competition leads to a preference for mating with virgin individuals. In promiscuous species with sperm storage and multiple paternity, males are expected to prefer mating with a virgin partner to assure an exclusive paternity. In a series of mate-choice tests I examined whether virgin and nonvirgin individuals of A. arbustorum discriminate between virgin and nonvirgin mates. I also measured the sperm number of the ejaculates delivered to virgin or nonvirgin partners to see whether the snails adjust sperm delivery. In all experiments mate-choice was random and the number of sperm delivered was not adjusted to the mating status of the partner. The mating success seemed to be determined by the activity of the individual snail and its partner. Random mating does not imply a random fertilization of eggs. The presence of a sperm-digesting organ and the morphology of the sperm storage organ allow a selective storage and use of sperm in A. arbustorum. This thesis showed that reproductive strategies and sperm traits in simultaneously hermaphrodites are influenced by species’ morphology, environmental conditions and parasitic infection

Data from: Breeding system, shell size and age at sexual maturity affect sperm length in stylommatophoran gastropods

Background: Sperm size and quality are key factors for fertilization success. There is increasing empirical evidence demonstrating that sperm form and function are influenced by selective pressures. Theoretical models predict that sperm competition could favour the evolution of longer sperm. In hermaphrodites, self-fertilizing species are expected to have shorter sperm than cross-fertilizing species, which use sperm stored from several mating partners for the fertilization of their eggs and thus are exposed to intense sperm competition. We tested this hypothesis by comparing original data on sperm length in 57 species of simultaneously hermaphroditic stylommatophoran gastropods from Europe and South America with respect to the species’ breeding system. We used 28S rRNA nuclear and COI mitochondrial sequence data to construct a molecular phylogeny. Phylogenetic generalized linear models were applied to examine the potential influence of morphological and life-history characters. Results: The best-fit model revealed that the breeding system and age at sexual maturity influence sperm length in gastropods. In general, species with predominant cross-fertilization had longer sperm than species with predominant self-fertilization or a mixed breeding system. Across species with shells (snails), sperm length also increased with shell size. Conclusions: Our study provides evidence that sperm length in stylommatophoran gastropods is influenced by the risk of sperm competition, as well as by age at sexual maturity and shell size. This finding extends present knowledge of sperm evolution to a group of so far poorly studied simultaneous hermaphrodites

Sperm measurements

Sperm measurements: total sperm length (Sperm length), head length (Head) and tail length (Tail) of sperms

Data from: Breeding system, shell size and age at sexual maturity affect sperm length in stylommatophoran gastropods

Background: Sperm size and quality are key factors for fertilization success. There is increasing empirical evidence demonstrating that sperm form and function are influenced by selective pressures. Theoretical models predict that sperm competition could favour the evolution of longer sperm. In hermaphrodites, self-fertilizing species are expected to have shorter sperm than cross-fertilizing species, which use sperm stored from several mating partners for the fertilization of their eggs and thus are exposed to intense sperm competition. We tested this hypothesis by comparing original data on sperm length in 57 species of simultaneously hermaphroditic stylommatophoran gastropods from Europe and South America with respect to the species’ breeding system. We used 28S rRNA nuclear and COI mitochondrial sequence data to construct a molecular phylogeny. Phylogenetic generalized linear models were applied to examine the potential influence of morphological and life-history characters. Results: The best-fit model revealed that the breeding system and age at sexual maturity influence sperm length in gastropods. In general, species with predominant cross-fertilization had longer sperm than species with predominant self-fertilization or a mixed breeding system. Across species with shells (snails), sperm length also increased with shell size. Conclusions: Our study provides evidence that sperm length in stylommatophoran gastropods is influenced by the risk of sperm competition, as well as by age at sexual maturity and shell size. This finding extends present knowledge of sperm evolution to a group of so far poorly studied simultaneous hermaphrodites

The effect of local heating on air quality in a small settlement

Concentrations of PM10 and Black Smoke (BS) were measured during one winter and two summer periods in small village Albrechtice v Jizerských horách. Major source of aerosol in this village is domestic use of coal and wood burning. 15 minute concentrations of PM10 were measured by DustTrak and 24-h concentrations of PM10 were measured by Harvard impactor. 24-h concentrations of BS were measured too. Concentrations of PM10 and 24-h concentrations of BS were highly correlated during the heating season (0,89). The correlation dropped to 0,68 during the second summer period. Concentrations of PM10 were negatively correlated with average daily temperature during the winter season (-0,41). Positive correlation between PM10 and temperature was found during the first summer period (0,34) and no correlation was found during the second summer period (-0,01). Concentrations of BS were negatively correlated with average daily temperature during all the three seasons. Negative correlation between PM10 and wind velocity was found during the winter season (-0,43). Daily maximums were found mainly between 4 and 12 pm. Comparison of PM10 data from Albrechtice with PM10 data from two urban areas Jablonec nad Nisou and Liberec and one background area Souš showed that average PM10 concentrations in Albrechtice were the..

Expression of the Wnt Receptor Frizzled-4 in the Human Enteric Nervous System of Infants

The Wnt signalling pathway plays a crucial role in the development of the nervous system. This signalling cascade is initiated upon binding of the secreted Wnt ligand to a member of the family of frizzled receptors. In the present study, we analysed the presence of frizzled-4 in the enteric nervous system of human infants. Frizzled-4 could be identified by immunohistochemistry in a subpopulation of enteric neuronal and glial cells in the small and large intestine. Detection of frizzled-4 in the tunica muscularis by RT-PCR confirmed this receptor’s expression on the mRNA level. Interestingly, we observed distinct cell populations that co-expressed frizzled-4 with the intermediate filament protein nestin and the neurotrophin receptor p75NTR, which have been reported to be expressed in neural progenitor cells. Flow cytometry analysis revealed that 60% of p75NTR positive cells of the tunica muscularis were positive for frizzled-4. Additionally, in pathological samples of Hirschsprung’s disease, the expression of this Wnt receptor correlated with the number of myenteric ganglion cells and decreased from normoganglionic to aganglionic areas of large intestine. The expression pattern of frizzled-4 indicates that this Wnt receptor could be involved in postnatal development and/or function of the enteric nervous system