Consequence of FA2H Deficiency and FA2H Interaction Partners Revealed by Proteomic Analyses

Fatty acid-2 hydroxylase (FA2H) is a 43 kDa transmembrane protein residing in the endoplasmic reticulum. As a monooxygenase it is responsible for the alpha–hydroxylation of fatty acids, which are later incorporated into sphingolipids, thereby generating 2-OH sphingolipids. FA2H and 2-OH sphingolipids show a quite ubiquitous tissue distribution, with high amounts detectable in brain, spinal cord, skin, testis, ovary, kidney, stomach and intestine. Especially important is their role in myelin, where up to 60% of the total amount of galactoylceramide and sulfatide are alpha- hydroxylated. The importance of this modification is emphasized by the observation that humans with a FA2H deficiency develop a spastic paraplegia (autosomal recessive spastic paraplegia 35 (SPG35)). Moreover, aged FA2H-KO mice present with a similar phenotype, showing an axonal and myelin sheath degeneration in spinal cord and later also in sciatic nerves. While the symptoms of FA2H deficiency have been well described, so far almost nothing is known about the exact disease mechanisms. Furthermore, there is no knowledge about the proteins biological regulation and its protein microenvironment. Thus, in the first part of the thesis FA2H-KO mice of different ages (6, 13 & 17 months) were examined for changes in their CNS- and PNS-myelin protein composition, which might help to better understand the observed pathology. This was achieved using a TMT 6-plex gel-free quantitative mass spectrometry approach. In the CNS this led to the identification of various protein alterations, of which some were already present in 6-month-old mice. The most prominent ones, which were also verified by Western blot, were upregulations of C1qb, C4b, ApoE, GFAP, tau protein, hinting at previously unknown roles of inflammation, astrogliosis and tau aggregation in the pathology of FA2H deficiency. In addition, a strong upregulation of one structural myelin membrane protein, Opalin/TMEM10, was observed as well. Because not much is known about this protein’s function so far, its possible role in the pathology of FA2H deficiency should be elucidated by further experiments. The PNS-myelin analysis also allowed for the identification of various protein changes. Those were mainly restricted to 13- and 17-month-old animals, which is in line with the late onset of PNS- demyelination. Unfortunately, because many of the measured changes were not consistent and thus less confident, further experiments are still needed for verification. The second part of this thesis concentrated on the discovery of protein interaction partners of FA2H. This was done, because the pathology may not be caused by the absence of 2-OH sphingolipids, but rather the loss of certain protein interactions of FA2H. For the identification, two complementary affinity purification-based screening strategies were applied in combination with quantitative mass spectrometry (SILAC-lP). In addition, a selection of the interaction partners was afterwards successfully verified by Western blotting and bimolecular fluorescence complementation (BiFC). Finally, this for the first time allowed a description of FA2H interaction partners in mammals. Interestingly, many are involved in metabolism, transport and regulation of synthesis of sphingolipids, indicating a tight coupling of enzymes participating in these processes. Furthermore, with PGRMC1 and 2, two promising regulators of FA2H’s activity were identified

Modeling Gully Erosion Susceptibility to Evaluate Human Impact on a Local Landscape System in Tigray, Ethiopia

In recent years, modeling gully erosion susceptibility has become an increasingly popular approach for assessing the impact of different land degradation factors. However, different forms of human influence have so far not been identified in order to form an independent model. We investigate the spatial relation between gully erosion and distance to settlements and footpaths, as typical areas of human interaction, with the natural environment in rural African areas. Gullies are common features in the Ethiopian Highlands, where they often hinder agricultural productivity. Within a catchment in the north Ethiopian Highlands, 16 environmental and human-related variables are mapped and categorized. The resulting susceptibility to gully erosion is predicted by applying the Random Forest (RF) machine learning algorithm. Human-related and environmental factors are used to generate independent susceptibility models and form an additional inclusive model. The resulting models are compared and evaluated by applying a change detection technique. All models predict the locations of most gullies, while 28% of gully locations are exclusively predicted using human-related factors

Late Quaternary formation of the Miaoli Tableland in northwest Taiwan, an interplay of tectonic uplift and fluvial processes dated by OSL

The “tablelands” in Taiwan are sedimentary terraces occurring in the foreland basin west of the Neogene mountain ranges. The Miaoli Tableland consists of elevated Late Quaternary sedimentary successions, representing a change from tidal to coastal and fluvial to eolian depositional environments. The present-day morphology is a result of combined processes, including differential tectonic uplift, ongoing fluvial aggradation, and incision. Selected deposits in 10 outcrops were sampled and studied by optical dating. The deposition of fluvial sediments started after the last interglacial (<100 ka) in the southeast of the tablelands. Uplift and sea-level lowering caused a base-level fall, resulting in a stepwise redeposition of the fluvial sediments. Additionally, enhanced remobilization of fluvial sediments occurred during the cold/dry climate during Marine Oxygen Isotope Stages (MIS) 4 and 2. The depositional ages of the coastal sediments enabled the estimation of long-term uplift rates of ca. 0.5 to 3.5 mm/yr. The eolian cover sediments yielded MIS 3 (east) to Holocene ages (west). Our results provide new insight into the interplay of climate, sea-level changes, remobilization of sediments, and tectonism leading to tableland formation during the Late Quaternary

Real Homotopy Theory of Semi-Algebraic Sets

We complete the details of a theory outlined by Kontsevich and Soibelman that associates to a semi-algebraic set a certain graded commutative differential algebra of "semi-algebraic differential forms" in a functorial way. This algebra encodes the real homotopy type of the semi-algebraic set in the spirit of the DeRham algebra of differential forms on a smooth manifold. Its development is needed for Kontsevich's proof of the formality of the little cubes operad.Comment: 58 pages. Cosmetic changes with respect to previous version. Submitte

Salmonella Typhimurium Strain ATCC14028 Requires H-2-Hydrogenases for Growth in the Gut, but Not at Systemic Sites

Salmonella enterica is a common cause of diarrhea. For eliciting disease, the pathogen has to colonize the gut lumen, a site colonized by the microbiota. This process/initial stage is incompletely understood. Recent work established that one particular strain, Salmonella enterica subspecies 1 serovar Typhimurium strain SL1344, employs the hyb H-2-hydrogenase for consuming microbiota-derived H-2 to support gut luminal pathogen growth: Protons from the H-2-splitting reaction contribute to the proton gradient across the outer bacterial membrane which can be harvested for ATP production or for import of carbon sources. However, it remained unclear, if other Salmonella strains would use the same strategy. In particular, earlier work had left unanswered if strain ATCC14028 might use H-2 for growth at systemic sites. To clarify the role of the hydrogenases, it seems important to establish if H-2 is used at systemic sites or in the gut and if Salmonella strains may differ with respect to the host sites where they require H-2 in vivo. In order to resolve this, we constructed a strain lacking all three H-2-hydrogenases of ATCC14028 (14028(hyd3)) and performed competitive infection experiments. Upon intragastric inoculation, 14028(hyd3) was present at 100-fold lower numbers than 14028(WT) in the stool and at systemic sites. In contrast, i.v. inoculation led to equivalent systemic loads of 14028(hyd3) and the wild type strain. However, the pathogen population spreading to the gut lumen featured again up to 100-fold attenuation of 14028(hyd3). Therefore, ATCC14028 requires H-2-hydrogenases for growth in the gut lumen and not at systemic sites. This extends previous work on ATCC14028 and supports the notion that H-2-utilization might be a general feature of S. Typhimurium gut colonization

Salmonella Typhimurium Strain ATCC14028 Requires H-2-Hydrogenases for Growth in the Gut, but Not at Systemic Sites

Salmonella enterica is a common cause of diarrhea. For eliciting disease, the pathogen has to colonize the gut lumen, a site colonized by the microbiota. This process/initial stage is incompletely understood. Recent work established that one particular strain, Salmonella enterica subspecies 1 serovar Typhimurium strain SL1344, employs the hyb H-2-hydrogenase for consuming microbiota-derived H-2 to support gut luminal pathogen growth: Protons from the H-2-splitting reaction contribute to the proton gradient across the outer bacterial membrane which can be harvested for ATP production or for import of carbon sources. However, it remained unclear, if other Salmonella strains would use the same strategy. In particular, earlier work had left unanswered if strain ATCC14028 might use H-2 for growth at systemic sites. To clarify the role of the hydrogenases, it seems important to establish if H-2 is used at systemic sites or in the gut and if Salmonella strains may differ with respect to the host sites where they require H-2 in vivo. In order to resolve this, we constructed a strain lacking all three H-2-hydrogenases of ATCC14028 (14028(hyd3)) and performed competitive infection experiments. Upon intragastric inoculation, 14028(hyd3) was present at 100-fold lower numbers than 14028(WT) in the stool and at systemic sites. In contrast, i.v. inoculation led to equivalent systemic loads of 14028(hyd3) and the wild type strain. However, the pathogen population spreading to the gut lumen featured again up to 100-fold attenuation of 14028(hyd3). Therefore, ATCC14028 requires H-2-hydrogenases for growth in the gut lumen and not at systemic sites. This extends previous work on ATCC14028 and supports the notion that H-2-utilization might be a general feature of S. Typhimurium gut colonization

On Human Predictions with Explanations and Predictions of Machine Learning Models: A Case Study on Deception Detection

Humans are the final decision makers in critical tasks that involve ethical and legal concerns, ranging from recidivism prediction, to medical diagnosis, to fighting against fake news. Although machine learning models can sometimes achieve impressive performance in these tasks, these tasks are not amenable to full automation. To realize the potential of machine learning for improving human decisions, it is important to understand how assistance from machine learning models affects human performance and human agency. In this paper, we use deception detection as a testbed and investigate how we can harness explanations and predictions of machine learning models to improve human performance while retaining human agency. We propose a spectrum between full human agency and full automation, and develop varying levels of machine assistance along the spectrum that gradually increase the influence of machine predictions. We find that without showing predicted labels, explanations alone slightly improve human performance in the end task. In comparison, human performance is greatly improved by showing predicted labels (>20% relative improvement) and can be further improved by explicitly suggesting strong machine performance. Interestingly, when predicted labels are shown, explanations of machine predictions induce a similar level of accuracy as an explicit statement of strong machine performance. Our results demonstrate a tradeoff between human performance and human agency and show that explanations of machine predictions can moderate this tradeoff.Comment: 17 pages, 19 figures, in Proceedings of ACM FAT* 2019, dataset & demo available at https://deception.machineintheloop.co