Ralph Krätzner - Academia.edu (original) (raw)

Papers by Ralph Krätzner

Biomolecules

Severe aortic stenosis (AS) is a common pathological condition in an ageing population imposing s... more Severe aortic stenosis (AS) is a common pathological condition in an ageing population imposing significant morbidity and mortality. Based on distinct hemodynamic features, i.e., ejection fraction (EF), transvalvular gradient and stroke volume, four different AS subtypes can be distinguished: (i) normal EF and high gradient, (ii) reduced EF and high gradient, (iii) reduced EF and low gradient, and (iv) normal EF and low gradient. These subtypes differ with respect to pathophysiological mechanisms, cardiac remodeling, and prognosis. However, little is known about metabolic changes in these different hemodynamic conditions of AS. Thus, we carried out metabolomic analyses in serum samples of 40 AS patients (n = 10 per subtype) and 10 healthy blood donors (controls) using ultrahigh-performance liquid chromatography–tandem mass spectroscopy. A total of 1293 biochemicals could be identified. Principal component analysis revealed different metabolic profiles in all of the subgroups of AS (...

Die Inhibitor-Cystinknoten-Familie enthält eine große Anzahl von kleinen, nur ca. 30 Aminosäuren ... more Die Inhibitor-Cystinknoten-Familie enthält eine große Anzahl von kleinen, nur ca. 30 Aminosäuren umfassenden Mikroproteinen, die eine hohe Diversität hinsichtlich ihrer inhibitorischen Eigenschaften zeigen. Das charakteristische Strukturmerkmal dieser Naturstoffe ist der sogenannte Cystinknoten, durch den die Polypeptidkette über drei Cystinbrücken fixiert wird. Er ersetzt den hydrophoben Kern größerer Proteine und ermöglicht somit eine Faltung im konformationellen Sinne. Hierbei ist das erste Cystein mit dem vierten, das zweite mit dem fünften und das dritte mit dem sechsten Cysteinrest der Polypeptidsequenz verknüpft. Der 30 Aminosäuren lange Ecballium elaterium Trypsin Inhibitor-II (EETI-II) ist ein typischer Vertreter dieser Proteinfamilie. EETI-II wurde erstmals aus Samen des Kürbisgewächses Ecballium elaterium isoliert und hemmt Trypsin mit einer nanomolaren Dissoziationskonstante. Die hohe strukturelle Toleranz des Inhibitor-Cystinknotenmotivs gegenüber Nicht- Cystein Substit...

Metabolites

Peroxisomes are central hubs for cell metabolism and their dysfunction is linked to devastating h... more Peroxisomes are central hubs for cell metabolism and their dysfunction is linked to devastating human disorders, such as peroxisomal biogenesis disorders and single peroxisomal enzyme/protein deficiencies. For decades, biochemical diagnostics have been carried out using classical markers such as very long-chain fatty acids (VLCFA), which can be inconspicuous in milder and atypical cases. Holistic metabolomics studies revealed several potentially new biomarkers for peroxisomal disorders for advanced laboratory diagnostics including atypical cases. However, establishing these new markers is a major challenge in routine diagnostic laboratories. We therefore investigated whether the commercially available AbsoluteIDQ p180 kit (Biocrates Lifesciences), which utilizes flow injection and liquid chromatography mass spectrometry, may be used to reproduce some key results from previous global metabolomics studies. We applied it to serum samples from patients with mutations in peroxisomal targ...

Science Advances

Genetic CLN5 variants are associated with childhood neurodegeneration and Alzheimer’s disease; ho... more Genetic CLN5 variants are associated with childhood neurodegeneration and Alzheimer’s disease; however, the molecular function of ceroid lipofuscinosis neuronal protein 5 (Cln5) is unknown. We solved the Cln5 crystal structure and identified a region homologous to the catalytic domain of members of the N1pC/P60 superfamily of papain-like enzymes. However, we observed no protease activity for Cln5; and instead, we discovered that Cln5 and structurally related PPPDE1 and PPPDE2 have efficient cysteine palmitoyl thioesterase ( S -depalmitoylation) activity using fluorescent substrates. Mutational analysis revealed that the predicted catalytic residues histidine-166 and cysteine-280 are critical for Cln5 thioesterase activity, uncovering a new cysteine-based catalytic mechanism for S -depalmitoylation enzymes. Last, we found that Cln5-deficient neuronal progenitor cells showed reduced thioesterase activity, confirming live cell function of Cln5 in setting S -depalmitoylation levels. Our...

Circulation, 2007

Background - Dilated Cardiomyopathy (DCM) is a syndrome characterized by ventricular dilation, co... more Background - Dilated Cardiomyopathy (DCM) is a syndrome characterized by ventricular dilation, contractile dysfunction and symptoms of congestive heart failure. Extracellular matrix proteins such as laminins as well as endothelial cells are known to influence cardiomyocyte performance, however a molecular link between mutations in the ECM and DCM has not been provided. Methods and Results - Using a forward genetic screen in zebrafish to identify novel genes required for myocardial function we were able to identify the lost-contact (loc) mutant, encoding a nonsense mutation in the integrin-linked kinase (ILK) gene. This loc/ilk mutant is associated with both, a severe defect in cardiomyocytes as well as in endothelial cells leading to severe myocardial dysfunction. Additional experiments revealed the epistatic regulation between the ECM component laminin alpha 4 (LAMA4), integrin and ILK, which led us to screen for mutations in the human ILK and LAMA4 genes in patients with severe di...

Molecular Pharmacology, 2008

The peptide hormone glucagon stimulates hepatic glucose output, and its levels in the blood are e... more The peptide hormone glucagon stimulates hepatic glucose output, and its levels in the blood are elevated in type 2 diabetes mellitus. The nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) has essential roles in glucose homeostasis, and thiazolidinedione PPARγ agonists are clinically important antidiabetic drugs. As part of their antidiabetic effect, thiazolidinediones such as rosiglitazone have been shown to inhibit glucagon gene transcription through binding to PPARγ and inhibition of the transcriptional activity of PAX6 that is required for cell-specific activation of the glucagon gene. However, how thiazolidinediones and PPARγ inhibit PAX6 activity at the glucagon promoter remained unknown. After transient transfection of a glucagon promoter-reporter fusion gene into a glucagon-producing pancreatic islet α-cell line, ligand-bound PPARγ was found in the present study to inhibit glucagon gene transcription also after deletion of its DNA-binding domain. Like PPAR...

Inorganic Chemistry, 2001

Reaction of t-BuP(O)(OSiMe3)(OH) with Me3Al leads to the formation of [Me2Al(mu -O)(2)P(OSiMe3)(t... more Reaction of t-BuP(O)(OSiMe3)(OH) with Me3Al leads to the formation of [Me2Al(mu -O)(2)P(OSiMe3)(t-Bu)](2) (1) whereas Me2AlCl reacts with Ph2P(O)(OH) to yield [(Cl)(Me)Al(mu -O)(2)PPh2](2) (2). These compounds represent the first examples of functionalized dimeric four-ring type aluminophosphonate systems. The double four-ring type gallophosphonate, namely, [t-BuPO3GaMe](4), reacts with n-Bu4NHF2 under ambient conditions, resulting in the formation of a monomeric gallophosphonate [n-Bu4N][MeGa(t-BuPO2(OH))(3)] (3) These derivatives have been adequately characterized using various spectroscopic techniques and X-ray diffraction studies.

Journal of Inherited Metabolic Disease, 2021

X-linked adrenoleukodystrophy (X-ALD) is the most common leukodystrophy. Despite intensive resear... more X-linked adrenoleukodystrophy (X-ALD) is the most common leukodystrophy. Despite intensive research in recent years, it remains unclear, what drives the different clinical disease courses. Due to this missing pathophysiological link, therapy for the childhood cerebral disease course of X-ALD (CCALD) remains symptomatic; the allogenic hematopoietic stem cell transplantation or hematopoietic stem-cell gene therapy is an option for early disease stages. The inclusion of dried blood spot (DBS) C26:0-lysophosphatidylcholine to newborn screening in an increasing number of countries is leading to an increasing number of X-ALD patients diagnosed at risk for CCALD. Current follow-up in asymptomatic boys with X-ALD requires repetitive cerebral MRIs under sedation. A reliable and easily accessible biomarker that predicts CCALD would therefore be of great value. Here we report the application of targeted metabolomics by AbsoluteIDQ p180-Kit from Biocrates to search for suitable biomarkers in X-ALD. LysoPC a C20:3 and lysoPC a C20:4 were identified as metabolites that indicate neuroinflammation after induction of experimental autoimmune encephalitis in the serum of Abcd1 tm1Kds mice. Analysis of serum from X-ALD patients also revealed different concentrations of these lipids at different disease stages. Further studies in a larger cohort of X-ALD

Experimental and Clinical Endocrinology & Diabetes, 2006

Experimental and Clinical Endocrinology & Diabetes, 2005

American Journal of Medical Genetics Part A, 2017

Cabezas type of X-linked syndromic intellectual disability (MRXSC; MIM300354) is a rare X-linked ... more Cabezas type of X-linked syndromic intellectual disability (MRXSC; MIM300354) is a rare X-linked recessive intellectual disability characterized primarily by intellectual disability, short stature, hypogonadism, and gait abnormalities. It is caused by a wide spectrum of hemizygous variants in CUL4B. In a 10-year-old boy with an exceptional leukoencephalopathy pattern, we identified a new missense variant p.Leu329Gln in CUL4B using "Mendeliome" sequencing. However, his phenotype does not include the severe characteristics currently known for MRXSC. We discuss the divergent phenotype and propose a potential connection between the different CUL4B variants and corresponding phenotypes in the context of the current literature as well as 3D homology modeling.

Molecular pharmacology

The peptide hormone glucagon stimulates hepatic glucose output, and its levels in the blood are e... more The peptide hormone glucagon stimulates hepatic glucose output, and its levels in the blood are elevated in type 2 diabetes mellitus. The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) has essential roles in glucose homeostasis, and thiazolidinedione PPARgamma agonists are clinically important antidiabetic drugs. As part of their antidiabetic effect, thiazolidinediones such as rosiglitazone have been shown to inhibit glucagon gene transcription through binding to PPARgamma and inhibition of the transcriptional activity of PAX6 that is required for cell-specific activation of the glucagon gene. However, how thiazolidinediones and PPARgamma inhibit PAX6 activity at the glucagon promoter remained unknown. After transient transfection of a glucagon promoter-reporter fusion gene into a glucagon-producing pancreatic islet alpha-cell line, ligand-bound PPARgamma was found in the present study to inhibit glucagon gene transcription also after deletion of its D...

Genome Medicine, 2015

Background: The organic cation transporter OCT1 (SLC22A1) mediates the uptake of vitamin B1, cati... more Background: The organic cation transporter OCT1 (SLC22A1) mediates the uptake of vitamin B1, cationic drugs, and xenobiotics into hepatocytes. Nine percent of Caucasians lack or have very low OCT1 activity due to loss-of-function polymorphisms in OCT1 gene. Here we analyzed the global genetic variability in OCT1 to estimate the therapeutic relevance of OCT1 polymorphisms in populations beyond Caucasians and to identify evolutionary patterns of the common loss of OCT1 activity in humans. Methods: We applied massively parallel sequencing to screen for coding polymorphisms in 1,079 unrelated individuals from 53 populations worldwide. The obtained data was combined with the existing 1000 Genomes data comprising an additional 1,092 individuals from 14 populations. The identified OCT1 variants were characterized in vitro regarding their cellular localization and their ability to transport 10 known OCT1 substrates. Both the population genetics data and transport data were used in tandem to generate a world map of loss of OCT1 activity. Results: We identified 16 amino acid substitutions potentially causing loss of OCT1 function and analyzed them together with five amino acid substitutions that were not expected to affect OCT1 function. The variants constituted 16 major alleles and 14 sub-alleles. Six major alleles showed improper subcellular localization leading to substrate-wide loss in activity. Five major alleles showed correct subcellular localization, but substrate-specific loss of activity. Striking differences were observed in the frequency of loss of OCT1 activity worldwide. While most East Asian and Oceanian individuals had completely functional OCT1, 80 % of native South American Indians lacked functional OCT1 alleles. In East Asia and Oceania the average nucleotide diversity of the loss-of-function variants was much lower than that of the variants that do not affect OCT1 function (ratio of 0.03) and was significantly lower than the theoretically expected heterozygosity (Tajima's D = −1.64, P < 0.01). Conclusions: Comprehensive genetic analyses showed strong global variations in the frequency of loss of OCT1 activity with selection pressure for maintaining OCT1 activity in East Asia and Oceania. These results not only enable pharmacogenetically-based optimization of drug treatment worldwide, but may help elucidate the functional role of human OCT1.

Diabetologie und Stoffwechsel, 2007

Histology and histopathology, May 1, 2011

AMPK is an ubiquitously distributed multienzyme complex. It is an important energy sensor and reg... more AMPK is an ubiquitously distributed multienzyme complex. It is an important energy sensor and regulator of cellular metabolic activity. In this study we analyzed for the first time the cellular distribution of the catalytically active subunits AMPKα1 and α2 in different human tissues by immunohistochemistry. We found different expression patterns for both isoforms. AMPKα2 expression clearly dominates in skeletal myocytes and cardiomyocytes, whereas AMPKα1 dominates in a number of secreting cells, like mammary glands, islets of langerhans and cells of the colon crypts.

JIMD reports, 2011

Peroxisome biogenesis disorders (PBDs) are a group of autosomal-recessive developmental and progr... more Peroxisome biogenesis disorders (PBDs) are a group of autosomal-recessive developmental and progressive metabolic diseases leading to the Zellweger spectrum (ZS) phenotype in most instances. Diagnosis of clinically suspected cases can be difficult because of extensive genetic heterogeneity and large spectrum of disease severity. Furthermore, a second group of peroxisomal diseases caused by deficiencies of single peroxisomal enzymes can show an indistinguishable clinical phenotype. The diagnosis of these peroxisomal disorders relies on the clinical presentation, the biochemical parameters in plasma and erythrocyte membranes, and genetic testing as the final step. Analysis of patients' cells is frequently required during the diagnostic process, e.g., for complementation analysis to identify the affected gene before sequencing. In the cases with unclear clinical or biochemical presentation, patients' cells are analyzed to prove PBD or to demonstrate biochemical abnormalities th...

Acta Crystallographica Section D Biological Crystallography, 2014

Mucopolysaccharidosis type IIIA (Sanfilippo A syndrome), a fatal childhood-onset neurodegenerativ... more Mucopolysaccharidosis type IIIA (Sanfilippo A syndrome), a fatal childhood-onset neurodegenerative disease with mild facial, visceral and skeletal abnormalities, is caused by an inherited deficiency of the enzyme N-sulfoglucosamine sulfohydrolase (SGSH; sulfamidase). More than 100 mutations in the SGSH gene have been found to reduce or eliminate its enzymatic activity. However, the molecular understanding of the effect of these mutations has been confined by a lack of structural data for this enzyme. Here, the crystal structure of glycosylated SGSH is presented at 2 Å resolution. Despite the low sequence identity between this unique N-sulfatase and the group of O-sulfatases, they share a similar overall fold and active-site architecture, including a catalytic formylglycine, a divalent metal-binding site and a sulfate-binding site. However, a highly conserved lysine in O-sulfatases is replaced in SGSH by an arginine (Arg282) that is positioned to bind the N-linked sulfate substrate. ...

Organometallics, 1999

Reactions of H 2 O 2 with Cp*MoCl 4 and Cp*WCl 4 (Cp*) C 5 Me 5) yield chloro oxo-peroxo complexe... more Reactions of H 2 O 2 with Cp*MoCl 4 and Cp*WCl 4 (Cp*) C 5 Me 5) yield chloro oxo-peroxo complexes of the type Cp*MoO(O 2)Cl (1) and Cp*WO(O 2)Cl (2) in high yields. The compounds have been characterized using X-ray structural analysis. Supporting Information Available: X-ray structural data for 1 and 2, including a summary of crystallographic parameters, atomic coordinates, bond distances and angles, and anisotropic thermal parameters (10 pages). See any current masthead page for ordering and Internet access instructions. OM980732O

Nucleic Acids Research, 2012

Mutations in the gene of human RNase T2 are associated with white matter disease of the human bra... more Mutations in the gene of human RNase T2 are associated with white matter disease of the human brain. Although brain abnormalities (bilateral temporal lobe cysts and multifocal white matter lesions) and clinical symptoms (psychomotor impairments, spasticity and epilepsy) are well characterized, the pathomechanism of RNase T2 deficiency remains unclear. RNase T2 is the only member of the Rh/T2/S family of acidic hydrolases in humans. In recent years, new functions such as tumor suppressing properties of RNase T2 have been reported that are independent of its catalytic activity. We determined the X-ray structure of human RNase T2 at 1.6 Å resolution. The a+b core fold shows high similarity to those of known T2 RNase structures from plants, while, in contrast, the external loop regions show distinct structural differences. The catalytic features of RNase T2 in presence of bivalent cations were analyzed and the structural consequences of known clinical mutations were investigated. Our data provide further insight into the function of human RNase T2 and may prove useful in understanding its mode of action independent of its enzymatic activity.

Biomolecules

Severe aortic stenosis (AS) is a common pathological condition in an ageing population imposing s... more Severe aortic stenosis (AS) is a common pathological condition in an ageing population imposing significant morbidity and mortality. Based on distinct hemodynamic features, i.e., ejection fraction (EF), transvalvular gradient and stroke volume, four different AS subtypes can be distinguished: (i) normal EF and high gradient, (ii) reduced EF and high gradient, (iii) reduced EF and low gradient, and (iv) normal EF and low gradient. These subtypes differ with respect to pathophysiological mechanisms, cardiac remodeling, and prognosis. However, little is known about metabolic changes in these different hemodynamic conditions of AS. Thus, we carried out metabolomic analyses in serum samples of 40 AS patients (n = 10 per subtype) and 10 healthy blood donors (controls) using ultrahigh-performance liquid chromatography–tandem mass spectroscopy. A total of 1293 biochemicals could be identified. Principal component analysis revealed different metabolic profiles in all of the subgroups of AS (...

Die Inhibitor-Cystinknoten-Familie enthält eine große Anzahl von kleinen, nur ca. 30 Aminosäuren ... more Die Inhibitor-Cystinknoten-Familie enthält eine große Anzahl von kleinen, nur ca. 30 Aminosäuren umfassenden Mikroproteinen, die eine hohe Diversität hinsichtlich ihrer inhibitorischen Eigenschaften zeigen. Das charakteristische Strukturmerkmal dieser Naturstoffe ist der sogenannte Cystinknoten, durch den die Polypeptidkette über drei Cystinbrücken fixiert wird. Er ersetzt den hydrophoben Kern größerer Proteine und ermöglicht somit eine Faltung im konformationellen Sinne. Hierbei ist das erste Cystein mit dem vierten, das zweite mit dem fünften und das dritte mit dem sechsten Cysteinrest der Polypeptidsequenz verknüpft. Der 30 Aminosäuren lange Ecballium elaterium Trypsin Inhibitor-II (EETI-II) ist ein typischer Vertreter dieser Proteinfamilie. EETI-II wurde erstmals aus Samen des Kürbisgewächses Ecballium elaterium isoliert und hemmt Trypsin mit einer nanomolaren Dissoziationskonstante. Die hohe strukturelle Toleranz des Inhibitor-Cystinknotenmotivs gegenüber Nicht- Cystein Substit...

Metabolites

Peroxisomes are central hubs for cell metabolism and their dysfunction is linked to devastating h... more Peroxisomes are central hubs for cell metabolism and their dysfunction is linked to devastating human disorders, such as peroxisomal biogenesis disorders and single peroxisomal enzyme/protein deficiencies. For decades, biochemical diagnostics have been carried out using classical markers such as very long-chain fatty acids (VLCFA), which can be inconspicuous in milder and atypical cases. Holistic metabolomics studies revealed several potentially new biomarkers for peroxisomal disorders for advanced laboratory diagnostics including atypical cases. However, establishing these new markers is a major challenge in routine diagnostic laboratories. We therefore investigated whether the commercially available AbsoluteIDQ p180 kit (Biocrates Lifesciences), which utilizes flow injection and liquid chromatography mass spectrometry, may be used to reproduce some key results from previous global metabolomics studies. We applied it to serum samples from patients with mutations in peroxisomal targ...

Science Advances

Genetic CLN5 variants are associated with childhood neurodegeneration and Alzheimer’s disease; ho... more Genetic CLN5 variants are associated with childhood neurodegeneration and Alzheimer’s disease; however, the molecular function of ceroid lipofuscinosis neuronal protein 5 (Cln5) is unknown. We solved the Cln5 crystal structure and identified a region homologous to the catalytic domain of members of the N1pC/P60 superfamily of papain-like enzymes. However, we observed no protease activity for Cln5; and instead, we discovered that Cln5 and structurally related PPPDE1 and PPPDE2 have efficient cysteine palmitoyl thioesterase ( S -depalmitoylation) activity using fluorescent substrates. Mutational analysis revealed that the predicted catalytic residues histidine-166 and cysteine-280 are critical for Cln5 thioesterase activity, uncovering a new cysteine-based catalytic mechanism for S -depalmitoylation enzymes. Last, we found that Cln5-deficient neuronal progenitor cells showed reduced thioesterase activity, confirming live cell function of Cln5 in setting S -depalmitoylation levels. Our...

Circulation, 2007

Background - Dilated Cardiomyopathy (DCM) is a syndrome characterized by ventricular dilation, co... more Background - Dilated Cardiomyopathy (DCM) is a syndrome characterized by ventricular dilation, contractile dysfunction and symptoms of congestive heart failure. Extracellular matrix proteins such as laminins as well as endothelial cells are known to influence cardiomyocyte performance, however a molecular link between mutations in the ECM and DCM has not been provided. Methods and Results - Using a forward genetic screen in zebrafish to identify novel genes required for myocardial function we were able to identify the lost-contact (loc) mutant, encoding a nonsense mutation in the integrin-linked kinase (ILK) gene. This loc/ilk mutant is associated with both, a severe defect in cardiomyocytes as well as in endothelial cells leading to severe myocardial dysfunction. Additional experiments revealed the epistatic regulation between the ECM component laminin alpha 4 (LAMA4), integrin and ILK, which led us to screen for mutations in the human ILK and LAMA4 genes in patients with severe di...

Molecular Pharmacology, 2008

The peptide hormone glucagon stimulates hepatic glucose output, and its levels in the blood are e... more The peptide hormone glucagon stimulates hepatic glucose output, and its levels in the blood are elevated in type 2 diabetes mellitus. The nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) has essential roles in glucose homeostasis, and thiazolidinedione PPARγ agonists are clinically important antidiabetic drugs. As part of their antidiabetic effect, thiazolidinediones such as rosiglitazone have been shown to inhibit glucagon gene transcription through binding to PPARγ and inhibition of the transcriptional activity of PAX6 that is required for cell-specific activation of the glucagon gene. However, how thiazolidinediones and PPARγ inhibit PAX6 activity at the glucagon promoter remained unknown. After transient transfection of a glucagon promoter-reporter fusion gene into a glucagon-producing pancreatic islet α-cell line, ligand-bound PPARγ was found in the present study to inhibit glucagon gene transcription also after deletion of its DNA-binding domain. Like PPAR...

Inorganic Chemistry, 2001

Reaction of t-BuP(O)(OSiMe3)(OH) with Me3Al leads to the formation of [Me2Al(mu -O)(2)P(OSiMe3)(t... more Reaction of t-BuP(O)(OSiMe3)(OH) with Me3Al leads to the formation of [Me2Al(mu -O)(2)P(OSiMe3)(t-Bu)](2) (1) whereas Me2AlCl reacts with Ph2P(O)(OH) to yield [(Cl)(Me)Al(mu -O)(2)PPh2](2) (2). These compounds represent the first examples of functionalized dimeric four-ring type aluminophosphonate systems. The double four-ring type gallophosphonate, namely, [t-BuPO3GaMe](4), reacts with n-Bu4NHF2 under ambient conditions, resulting in the formation of a monomeric gallophosphonate [n-Bu4N][MeGa(t-BuPO2(OH))(3)] (3) These derivatives have been adequately characterized using various spectroscopic techniques and X-ray diffraction studies.

Journal of Inherited Metabolic Disease, 2021

X-linked adrenoleukodystrophy (X-ALD) is the most common leukodystrophy. Despite intensive resear... more X-linked adrenoleukodystrophy (X-ALD) is the most common leukodystrophy. Despite intensive research in recent years, it remains unclear, what drives the different clinical disease courses. Due to this missing pathophysiological link, therapy for the childhood cerebral disease course of X-ALD (CCALD) remains symptomatic; the allogenic hematopoietic stem cell transplantation or hematopoietic stem-cell gene therapy is an option for early disease stages. The inclusion of dried blood spot (DBS) C26:0-lysophosphatidylcholine to newborn screening in an increasing number of countries is leading to an increasing number of X-ALD patients diagnosed at risk for CCALD. Current follow-up in asymptomatic boys with X-ALD requires repetitive cerebral MRIs under sedation. A reliable and easily accessible biomarker that predicts CCALD would therefore be of great value. Here we report the application of targeted metabolomics by AbsoluteIDQ p180-Kit from Biocrates to search for suitable biomarkers in X-ALD. LysoPC a C20:3 and lysoPC a C20:4 were identified as metabolites that indicate neuroinflammation after induction of experimental autoimmune encephalitis in the serum of Abcd1 tm1Kds mice. Analysis of serum from X-ALD patients also revealed different concentrations of these lipids at different disease stages. Further studies in a larger cohort of X-ALD

Experimental and Clinical Endocrinology & Diabetes, 2006

Experimental and Clinical Endocrinology & Diabetes, 2005

American Journal of Medical Genetics Part A, 2017

Cabezas type of X-linked syndromic intellectual disability (MRXSC; MIM300354) is a rare X-linked ... more Cabezas type of X-linked syndromic intellectual disability (MRXSC; MIM300354) is a rare X-linked recessive intellectual disability characterized primarily by intellectual disability, short stature, hypogonadism, and gait abnormalities. It is caused by a wide spectrum of hemizygous variants in CUL4B. In a 10-year-old boy with an exceptional leukoencephalopathy pattern, we identified a new missense variant p.Leu329Gln in CUL4B using "Mendeliome" sequencing. However, his phenotype does not include the severe characteristics currently known for MRXSC. We discuss the divergent phenotype and propose a potential connection between the different CUL4B variants and corresponding phenotypes in the context of the current literature as well as 3D homology modeling.

Molecular pharmacology

The peptide hormone glucagon stimulates hepatic glucose output, and its levels in the blood are e... more The peptide hormone glucagon stimulates hepatic glucose output, and its levels in the blood are elevated in type 2 diabetes mellitus. The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) has essential roles in glucose homeostasis, and thiazolidinedione PPARgamma agonists are clinically important antidiabetic drugs. As part of their antidiabetic effect, thiazolidinediones such as rosiglitazone have been shown to inhibit glucagon gene transcription through binding to PPARgamma and inhibition of the transcriptional activity of PAX6 that is required for cell-specific activation of the glucagon gene. However, how thiazolidinediones and PPARgamma inhibit PAX6 activity at the glucagon promoter remained unknown. After transient transfection of a glucagon promoter-reporter fusion gene into a glucagon-producing pancreatic islet alpha-cell line, ligand-bound PPARgamma was found in the present study to inhibit glucagon gene transcription also after deletion of its D...

Genome Medicine, 2015

Background: The organic cation transporter OCT1 (SLC22A1) mediates the uptake of vitamin B1, cati... more Background: The organic cation transporter OCT1 (SLC22A1) mediates the uptake of vitamin B1, cationic drugs, and xenobiotics into hepatocytes. Nine percent of Caucasians lack or have very low OCT1 activity due to loss-of-function polymorphisms in OCT1 gene. Here we analyzed the global genetic variability in OCT1 to estimate the therapeutic relevance of OCT1 polymorphisms in populations beyond Caucasians and to identify evolutionary patterns of the common loss of OCT1 activity in humans. Methods: We applied massively parallel sequencing to screen for coding polymorphisms in 1,079 unrelated individuals from 53 populations worldwide. The obtained data was combined with the existing 1000 Genomes data comprising an additional 1,092 individuals from 14 populations. The identified OCT1 variants were characterized in vitro regarding their cellular localization and their ability to transport 10 known OCT1 substrates. Both the population genetics data and transport data were used in tandem to generate a world map of loss of OCT1 activity. Results: We identified 16 amino acid substitutions potentially causing loss of OCT1 function and analyzed them together with five amino acid substitutions that were not expected to affect OCT1 function. The variants constituted 16 major alleles and 14 sub-alleles. Six major alleles showed improper subcellular localization leading to substrate-wide loss in activity. Five major alleles showed correct subcellular localization, but substrate-specific loss of activity. Striking differences were observed in the frequency of loss of OCT1 activity worldwide. While most East Asian and Oceanian individuals had completely functional OCT1, 80 % of native South American Indians lacked functional OCT1 alleles. In East Asia and Oceania the average nucleotide diversity of the loss-of-function variants was much lower than that of the variants that do not affect OCT1 function (ratio of 0.03) and was significantly lower than the theoretically expected heterozygosity (Tajima's D = −1.64, P < 0.01). Conclusions: Comprehensive genetic analyses showed strong global variations in the frequency of loss of OCT1 activity with selection pressure for maintaining OCT1 activity in East Asia and Oceania. These results not only enable pharmacogenetically-based optimization of drug treatment worldwide, but may help elucidate the functional role of human OCT1.

Diabetologie und Stoffwechsel, 2007

Histology and histopathology, May 1, 2011

AMPK is an ubiquitously distributed multienzyme complex. It is an important energy sensor and reg... more AMPK is an ubiquitously distributed multienzyme complex. It is an important energy sensor and regulator of cellular metabolic activity. In this study we analyzed for the first time the cellular distribution of the catalytically active subunits AMPKα1 and α2 in different human tissues by immunohistochemistry. We found different expression patterns for both isoforms. AMPKα2 expression clearly dominates in skeletal myocytes and cardiomyocytes, whereas AMPKα1 dominates in a number of secreting cells, like mammary glands, islets of langerhans and cells of the colon crypts.

JIMD reports, 2011

Peroxisome biogenesis disorders (PBDs) are a group of autosomal-recessive developmental and progr... more Peroxisome biogenesis disorders (PBDs) are a group of autosomal-recessive developmental and progressive metabolic diseases leading to the Zellweger spectrum (ZS) phenotype in most instances. Diagnosis of clinically suspected cases can be difficult because of extensive genetic heterogeneity and large spectrum of disease severity. Furthermore, a second group of peroxisomal diseases caused by deficiencies of single peroxisomal enzymes can show an indistinguishable clinical phenotype. The diagnosis of these peroxisomal disorders relies on the clinical presentation, the biochemical parameters in plasma and erythrocyte membranes, and genetic testing as the final step. Analysis of patients' cells is frequently required during the diagnostic process, e.g., for complementation analysis to identify the affected gene before sequencing. In the cases with unclear clinical or biochemical presentation, patients' cells are analyzed to prove PBD or to demonstrate biochemical abnormalities th...

Acta Crystallographica Section D Biological Crystallography, 2014

Mucopolysaccharidosis type IIIA (Sanfilippo A syndrome), a fatal childhood-onset neurodegenerativ... more Mucopolysaccharidosis type IIIA (Sanfilippo A syndrome), a fatal childhood-onset neurodegenerative disease with mild facial, visceral and skeletal abnormalities, is caused by an inherited deficiency of the enzyme N-sulfoglucosamine sulfohydrolase (SGSH; sulfamidase). More than 100 mutations in the SGSH gene have been found to reduce or eliminate its enzymatic activity. However, the molecular understanding of the effect of these mutations has been confined by a lack of structural data for this enzyme. Here, the crystal structure of glycosylated SGSH is presented at 2 Å resolution. Despite the low sequence identity between this unique N-sulfatase and the group of O-sulfatases, they share a similar overall fold and active-site architecture, including a catalytic formylglycine, a divalent metal-binding site and a sulfate-binding site. However, a highly conserved lysine in O-sulfatases is replaced in SGSH by an arginine (Arg282) that is positioned to bind the N-linked sulfate substrate. ...

Organometallics, 1999

Reactions of H 2 O 2 with Cp*MoCl 4 and Cp*WCl 4 (Cp*) C 5 Me 5) yield chloro oxo-peroxo complexe... more Reactions of H 2 O 2 with Cp*MoCl 4 and Cp*WCl 4 (Cp*) C 5 Me 5) yield chloro oxo-peroxo complexes of the type Cp*MoO(O 2)Cl (1) and Cp*WO(O 2)Cl (2) in high yields. The compounds have been characterized using X-ray structural analysis. Supporting Information Available: X-ray structural data for 1 and 2, including a summary of crystallographic parameters, atomic coordinates, bond distances and angles, and anisotropic thermal parameters (10 pages). See any current masthead page for ordering and Internet access instructions. OM980732O

Nucleic Acids Research, 2012

Mutations in the gene of human RNase T2 are associated with white matter disease of the human bra... more Mutations in the gene of human RNase T2 are associated with white matter disease of the human brain. Although brain abnormalities (bilateral temporal lobe cysts and multifocal white matter lesions) and clinical symptoms (psychomotor impairments, spasticity and epilepsy) are well characterized, the pathomechanism of RNase T2 deficiency remains unclear. RNase T2 is the only member of the Rh/T2/S family of acidic hydrolases in humans. In recent years, new functions such as tumor suppressing properties of RNase T2 have been reported that are independent of its catalytic activity. We determined the X-ray structure of human RNase T2 at 1.6 Å resolution. The a+b core fold shows high similarity to those of known T2 RNase structures from plants, while, in contrast, the external loop regions show distinct structural differences. The catalytic features of RNase T2 in presence of bivalent cations were analyzed and the structural consequences of known clinical mutations were investigated. Our data provide further insight into the function of human RNase T2 and may prove useful in understanding its mode of action independent of its enzymatic activity.