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SLC35F1 is a member of the sugar-like carrier (SLC) superfamily that is expressed in the mammalian brain. Malfunction of SLC35F1 in humans is associated with neurodevelopmental disorders. To get insight into the possible roles of Slc35f1 in the brain, we generated Slc35f1-deficient mice. The Slc35f1-deficient mice are viable and survive into adulthood, which allowed examining adult Slc35f1-deficient mice on the anatomical as well as behavioral level. In humans, mutation in the SLC35F1 gene can induce a Rett syndrome-like phenotype accompanied by intellectual disability (Fede et al. Am J Med Genet A 185:2238–2240, 2021). The Slc35f1-deficient mice, however, display only a very mild phenotype and no obvious deficits in learning and memory as, e.g., monitored with the novel object recognition test or the Morris water maze test. Moreover, neuroanatomical parameters of neuronal plasticity (as dendritic spines and adult hippocampal neurogenesis) are also unaltered. Thus, Slc35f1-deficient mice display no major alterations that resemble a neurodevelopmental phenotype.
Niemann–Pick type C1 (NPC1) is a lysosomal storage disorder, inherited as an
autosomal-recessive trait. Mutations in the Npc1 gene result in malfunction of the NPC1 protein,
leading to an accumulation of unesterified cholesterol and glycosphingolipids. Beside visceral
symptoms like hepatosplenomegaly, severe neurological symptoms such as ataxia occur. Here,
we analyzed the sphingosine-1-phosphate (S1P)/S1P receptor (S1PR) axis in different brain regions
of Npc1−/− mice and evaluated specific effects of treatment with 2-hydroxypropyl-β-cyclodextrin
(HPβCD) together with the iminosugar miglustat. Using high-performance thin-layer chromatography
(HPTLC), mass spectrometry, quantitative real-time PCR (qRT-PCR) and western blot analyses, we
Int. J. Mol. Sci. 2020, 21, 4502; doi:10.3390/ijms21124502 www.mdpi.com/journal/ijms
Int. J. Mol. Sci. 2020, 21, 4502 2 of 31
studied lipid metabolism in an NPC1 mouse model and human skin fibroblasts. Lipid analyses
showed disrupted S1P metabolism in Npc1−/− mice in all brain regions, together with distinct changes
in S1pr3/S1PR3 and S1pr5/S1PR5 expression. Brains of Npc1−/− mice showed only weak treatment
effects. However, side effects of the treatment were observed in Npc1+/+ mice. The S1P/S1PR axis
seems to be involved in NPC1 pathology, showing only weak treatment effects in mouse brain. S1pr
expression appears to be affected in human fibroblasts, induced pluripotent stem cells (iPSCs)-derived
neural progenitor and neuronal differentiated cells. Nevertheless, treatment-induced side effects
make examination of further treatment strategies indispensable
80% of chronic kidney diseases are caused by the loss and the damage of a differentiated and postmitotic cell type, the podocytes. The size-selectivity of the blood filtration barrier is highly dependent on the complex interdigitation of the podocyte foot processes as well as of the slit membrane which is spanned in between. Changes of this specific morphology as well as a detachment of podocytes lead to the clinical hallmark of a nephrotic syndrome e.g. proteinuria and oedema formation.
Since specific drugs or therapies are usually not available, patients are often dependent on dialysis and transplantation. Therefore, intensive studies are necessary to understand the pathogenesis of glomerulopathies as well as to identify specific drugs. In the past, it was already demonstrated that the zebrafish is an ideal model to study kidney function and to screen for drugs, since the larvae quickly develop a simple glomerulus that is comparable to the glomeruli of mice, rat and human.
In the present work, a zebrafish model was established to study a specific glomerulopathy named focal segmental glomerulosclerosis (FSGS). FSGS is mainly characterized by histology of the glomeruli which shows segmental scar formation and matrix deposition due to an activation of parietal epithelial cells (PEC) lining the Bowman’s capsule. For this purpose, we used the nitroreductase/metronidazole (NTR/MTZ) system, in which a cytotoxic agent is exclusively generated in podocytes by the enzyme NTR resulting in apoptosis of cells. Firstly, the parameters for development of an FSGS-like disease were evaluated and the glomerular response to podocyte depletion was examined during three days after the induction of podocyte damage. Using classic histological techniques, immunofluorescence staining and transmission electron microscopy, it was possible to demonstrate that zebrafish larvae phenocopy human FSGS in important characteristics after partial podocyte depletion. Secondly, by intravascular injection of fluorescence-labeled high molecular weight dextran, we found that the filtration barrier became leaky. Moreover, we identified a severe podocyte foot process effacement, formation of subpodocyte space pseudocysts and loss of the slit membrane protein podocin. Morphometrical, histological and ultrastructural analysis revealed an enlargement of the glomerulus, proliferation of cuboidal PECs and intraglomerular deposition of extracellular matrix components, all typical hallmarks of FSGS. Further, we observed adhesions between the parietal and the visceral glomerular cell layer forming sclerotic lesions. However, it remains still unclear whether an inflammatory response is involved in the development of sclerotic lesions. Our microscopic analysis provided some evidence for immigration of immunocompetent cells like neutrophils, presumably due to induction of apoptosis in our model.
Taken together, in the present work a zebrafish model was established with characteristics of mammals FSGS which will be useful for pathomechanism studies as well as for drug screening.
Chronic alcohol abuse is one of the most common addictions and one of the most substantial public health problems as it affects millions of people physically as well as mentally around the world. Globally more than 3 million deaths are assignable to alcohol intake each year. Chronic alcoholism is a multi-component disease and its development is associated with both environmental as well as genetic factors. However, the key mechanisms underlying an addiction, especially on a cellular and physiological basis, are still unknown. Bio-medically an influence of chronic alcohol consumption on synaptic plasticity in the brain of humans as well as rodents has been proven.
On the dendritic shaft of nervous brain cells, small membrane protrusions called dendritic spines can be found. These spines possess the capacity to change their morphology and quantity and are thought to play an important role in learning and memory forming, and seem to be impaired in multiple neurological disorders. These dynamics are called synaptic plasticity. Most of these studies however, were carried out on the cortex. These previous observations raise the question whether such alterations in synaptic plasticity can also be observed in regions of the brain that contribute to the limbic system and therefore to the processing of emotional responses, learning and decision making. The amygdala is of special interest when trying to understand the neurobiology and pathophysiology that lead to the emergence and up keeping of an alcohol addiction. In this thesis a closer look has been taken at possible alterations in synaptic plasticity within different amygdaloid nuclei by the help of a rat model. These rats were put into the so called postdependent state, one of the most common animal models to investigate excessive ethanol intake in rodents. The postdependent state is a model in which the key driving force to obtain alcohol as part of a preserved addiction cycle is based on negative affect. Studies showed differences in the behavioural outcome of those animals that were exposed to chronic intermittent alcohol consumption compared to a control group, so it was of special interest to see whether those behavioural changes also show on a cellular basis.
In the study, a morphological comparison of the spine length as well as the spine density of alcohol dependent rats with a comparable control group has been made. The medial, the central, the lateral and the basolateral amygdaloid nucleus were of special interest in this research project.
The results showed no significant difference of the spine densities in any of the four amygdaloid regions. When comparing the spine morphology within the ethanol and the control group, differences showed in the lateral amygdaloid nucleus. In this region the spines of the ethanol group were significantly smaller. This leads to the conclusion that chronic alcohol intake can have an influence on the spine morphology and hence alter anatomical brain structures.
Morphological changes of the complex 3-D architecture of podocytes as well as the loss of these post-mitotic cells often result in severe kidney disease. Since currently, there are no curative drugs, we focused on the identification of non-invasive biomarkers, allowing an early detection of the onset of such diseases. Therefore, we analyzed the cellular- and the cell-free fractions of urine samples from patients suffering from chronic kidney disease (CKD), especially for injury markers as well as for exosome-derived miRNAs.
We identified the mRNA of the neuronal protein brain-derived neurotrophic factor (BDNF) in the cellular fraction of 120 CKD patients and found that the expression was highly correlated with the mRNA expression of the kidney injury marker molecule 1 (KIM-1). Furthermore, we found that both were correlated with the mRNA expression of the podocyte-specific gene Nephrin (NPHS1), suggesting that podocytes are very likely the cellular source.
Beside this, we observed that BDNF is upregulated in biopsies of diabetic patients and seems to be involved in the differentiation of podocytes. Immunofluorescence staining clearly showed that BDNF is localized in the cell body and major processes of podocytes within the glomerulus. Knockdown experiments in zebrafish larvae, a well-established animal model to study kidney function, showed the importance of BDNF on kidney function, morphology and filtration in vivo.
Additionally, we analyzed circulating exosomal microRNAs (miRs) isolated from the cell-free urine fraction. After the optimization of a column-based isolation protocol for exosomes, we identified miR-16 from a pre-selected set of candidates as a suitable endogenous reference gene for data normalization. Subsequently, we analyzed the exosomal levels of miR-21, miR-30a-5p and miR-92a in urine samples of 41 CKD patients and 5 healthy controls. We found significantly enhanced levels of miR-21 in CKD patients that were also negatively correlated with the eGFR, suggesting a negative influence on kidney function. MiR-21 was also highly upregulated in de-differentiated glomeruli and in kidneys of nephrotoxic serum- (NTS-) treated mice as an in vivo kidney injury model.
To summarize, we identified two promising new and non-invasive biomarkers for CKD in the urine of patients which may also have a functional relevance on kidney function.
Chronic kidney disease is a major public health burden associated with a drastically reduced quality of living and life span that lacks suitable, individualized therapeutic strategies. Here we present a human induced pluripotent stem cell line (iPSC, UMGACBi001-A) reprogrammed from urine cells of an acute septic dialysis patient suffering from chronic kidney disease using non-integrating administration of RNAs. The generated iPSCs were positively characterized for typical morphology, pluripotency marker expression, directed differentiation potential, non-contamination, chromosomal consistency and donor identity. This iPSC-line can be a useful source for in vitro disease modelling and individualized therapeutic approaches.