Publications by authors named "Bettina Lorenz-Depiereux"

28 Publications

  • Page 1 of 1

A novel homozygous variant in exon 10 of the gene causing hyperphosphatemic familial tumoral calcinosis in a family from North India.

Intractable Rare Dis Res 2021 Feb;10(1):55-57

Institute of Human Genetics, Technische Universität München, Munich, Germany.

Hyperphosphatemic familial tumoral calcinosis (HFTC) is an extremely rare autosomal recessive disorder caused by variants in the (N-acetylgalactosaminyltransferase 3), (Fibroblast Growth Factor-23) and (α-Klotho) genes, which results in progressive calcification of soft tissues. We describe the case of a 9-year-old girl who presented with recurrent hard nodular swellings on her feet and knees which intermittently discharged chalky white material. Her younger brother also had a similar condition. Both siblings showed hyperphosphatemia, but the parentsbiochemical parameters were normal. The histological features of the material aspirated from a skin lesion were consistent with tumoral calcinosis. Sanger sequencing identified a novel homozygous non-synonymous sequence variant in exon 10 of the gene (NM_004482.3:c.[1681T>A];[1681T>A], NP_004473.2:p. [Cys561Ser];[Cys561Ser] in the proband and her affected brother. The parents were heterozygous carriers for the same sequence variant. In conclusion, we report a new variant in the gene that caused HFTC in a North Indian family.
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http://dx.doi.org/10.5582/irdr.2020.03084DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7882081PMC
February 2021

Systemic Jak1 activation provokes hepatic inflammation and imbalanced FGF23 production and cleavage.

FASEB J 2021 Feb;35(2):e21302

Institute of Physiology, University of Zurich (UZH), and National Center of Competence in Research NCCR Kidney.CH, Zurich, Switzerland.

Fibroblast growth factor 23 (FGF23) is a main regulator of mineral homeostasis. Low and high circulating FGF23 levels are associated with bone, renal, cardiovascular diseases, and increased mortality. Understanding the factors and signaling pathways affecting FGF23 levels is crucial for the management of these diseases and their complications. Here, we show that activation of the Jak1/Stat3 signaling pathway leads to inflammation in liver and to an increase in hepatic FGF23 synthesis, a key hormone in mineral metabolism. This increased synthesis leads to massive C-terminal FGF23 circulating levels, the inactive C-terminal fragment, and increased intact FGF23 levels, the active form, resulting in imbalanced production and cleavage. Liver inflammation does not lead to activation of the calcineurin-NFAT pathway, and no signs of systemic inflammation could be observed. Despite the increase of active intact FGF23, excessive C-terminal FGF23 levels block the phosphaturic activity of FGF23. Therefore, kidney function and renal αKlotho expression are normal and no activation of the MAPK pathway was detected. In addition, activation of the Jak1/Stat3 signaling pathway leads to high calcitriol levels and low parathyroid hormone production. Thus, JAK1 is a central regulator of mineral homeostasis. Moreover, this study also shows that in order to assess the impact of high FGF23 levels on disease and kidney function, the source and the balance in FGF23 production and cleavage are critical.
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http://dx.doi.org/10.1096/fj.202002113RDOI Listing
February 2021

Regulatory myeloid cells paralyze T cells through cell-cell transfer of the metabolite methylglyoxal.

Nat Immunol 2020 05 23;21(5):555-566. Epub 2020 Apr 23.

Institute of Molecular Immunology, School of Life Sciences, TUM, Munich, Germany.

Regulatory myeloid immune cells, such as myeloid-derived suppressor cells (MDSCs), populate inflamed or cancerous tissue and block immune cell effector functions. The lack of mechanistic insight into MDSC suppressive activity and a marker for their identification has hampered attempts to overcome T cell inhibition and unleash anti-cancer immunity. Here, we report that human MDSCs were characterized by strongly reduced metabolism and conferred this compromised metabolic state to CD8 T cells, thereby paralyzing their effector functions. We identified accumulation of the dicarbonyl radical methylglyoxal, generated by semicarbazide-sensitive amine oxidase, to cause the metabolic phenotype of MDSCs and MDSC-mediated paralysis of CD8 T cells. In a murine cancer model, neutralization of dicarbonyl activity overcame MDSC-mediated T cell suppression and, together with checkpoint inhibition, improved the efficacy of cancer immune therapy. Our results identify the dicarbonyl methylglyoxal as a marker metabolite for MDSCs that mediates T cell paralysis and can serve as a target to improve cancer immune therapy.
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http://dx.doi.org/10.1038/s41590-020-0666-9DOI Listing
May 2020

Diagnostic exome sequencing in non-acquired focal epilepsies highlights a major role of GATOR1 complex genes.

J Med Genet 2020 09 21;57(9):624-633. Epub 2020 Feb 21.

Department of Neurology, Medical University of Vienna, Vienna, Austria

Background: The genetic architecture of non-acquired focal epilepsies (NAFEs) becomes increasingly unravelled using genome-wide sequencing datasets. However, it remains to be determined how this emerging knowledge can be translated into a diagnostic setting. To bridge this gap, we assessed the diagnostic outcomes of exome sequencing (ES) in NAFE.

Methods: 112 deeply phenotyped patients with NAFE were included in the study. Diagnostic ES was performed, followed by a screen to detect variants of uncertain significance (VUSs) in 15 well-established focal epilepsy genes. Explorative gene prioritisation was used to identify possible novel candidate aetiologies with so far limited evidence for NAFE.

Results: ES identified pathogenic or likely pathogenic (ie, diagnostic) variants in 13/112 patients (12%) in the genes , , , , and . Two pathogenic variants were microdeletions involving and . Nine of the 13 diagnostic variants (69%) were found in genes of the GATOR1 complex, a potentially druggable target involved in the mammalian target of rapamycin (mTOR) signalling pathway. In addition, 17 VUSs in focal epilepsy genes and 6 rare variants in candidate genes (, and ) were detected. Five patients with reported variants had double hits in different genes, suggesting a possible (oligogenic) role of multiple rare variants.

Conclusion: This study underscores the molecular heterogeneity of NAFE with GATOR1 complex genes representing the by far most relevant genetic aetiology known to date. Although the diagnostic yield is lower compared with severe early-onset epilepsies, the high rate of VUSs and candidate variants suggests a further increase in future years.
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http://dx.doi.org/10.1136/jmedgenet-2019-106658DOI Listing
September 2020

Mitochondrial DNA mutation analysis from exome sequencing-A more holistic approach in diagnostics of suspected mitochondrial disease.

J Inherit Metab Dis 2019 09 11;42(5):909-917. Epub 2019 Jun 11.

Institute of Human Genetics, Technical University München, Munich, Germany.

Diagnostics for suspected mitochondrial disease (MD) can be challenging and necessitate invasive procedures like muscle biopsy. This is due to the extremely broad genetic and phenotypic spectrum, disease genes on both nuclear and mitochondrial DNA (mtDNA), and the tissue specificity of mtDNA variants. Exome sequencing (ES) has revolutionized the diagnostics for MD. However, the nuclear and mtDNA are investigated with separate tests, increasing costs and duration of diagnostics. The full potential of ES is often not exploited as the additional analysis of "off-target reads" deriving from the mtDNA can be used to analyze both genomes. We performed mtDNA analysis by ES of 2111 cases in a clinical setting. We further assessed the recall rate and precision as well as the estimation of heteroplasmy by ES data by comparison with targeted mtDNA next generation sequencing in 49 cases. ES identified known pathogenic mtDNA point mutations in 38 individuals, increasing the diagnostic yield by nearly 2%. Analysis of mtDNA variants by ES had a high recall rate (96.2 ± 5.6%) and an excellent precision (99.5 ± 2.2%) when compared to the gold standard of targeted mtDNA next generation sequencing. ES estimated heteroplasmy levels with an average difference of 6.6 ± 3.8%, sufficient for clinical decision making. Taken together, the mtDNA analysis from ES is of sufficient quality for clinical diagnostics. We therefore propose ES, investigating both nuclear and mtDNA, as first line test in individuals with suspected MD. One should be aware, that a negative result does not exclude MD and necessitates further test (in additional tissues).
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http://dx.doi.org/10.1002/jimd.12109DOI Listing
September 2019

The elevation of circulating fibroblast growth factor 23 without kidney disease does not increase cardiovascular disease risk.

Kidney Int 2018 07 5;94(1):49-59. Epub 2018 May 5.

Institute of Physiology, University of Zurich, and National Center for Competence in Research NCCR Kidney.CH, Zurich, Switzerland. Electronic address:

High circulating fibroblast growth factor 23 (FGF23) levels are probably a major risk factor for cardiovascular disease in chronic kidney disease. FGF23 interacts with the receptor FGFR4 in cardiomyocytes inducing left ventricular hypertrophy. Moreover, in the liver FGF23 via FGFR4 increases the risk of inflammation which is also found in chronic kidney disease. In contrast, X-linked hypophosphatemia is characterized by high FGF23 circulating levels due to loss of function mutations of the phosphate-regulating gene with homologies to an endopeptidase on the X chromosome (PHEX), but is not characterized by high cardiovascular morbidity. Here we used a novel murine X-linked hypophosphatemia model, the Phex mouse line, bearing an amino acid substitution (p.Cys733Arg) to test whether high circulating FGF23 in the absence of renal injury would trigger cardiovascular disease. As X-linked hypophosphatemia patient mimics, these mice show high FGF23 levels, hypophosphatemia, normocalcemia, and low/normal vitamin D levels. Moreover, these mice show hyperparathyroidism and low circulating soluble αKlotho levels. At the age of 27 weeks we found no left ventricular hypertrophy and no alteration of cardiac function as assessed by echocardiography. These mice also showed no activation of the calcineurin/NFAT pathway in heart and liver and no tissue and systemic signs of inflammation. Importantly, blood pressure, glomerular filtration rate and urea clearance were similar between genotypes. Thus, the presence of high circulating FGF23 levels alone in the absence of renal impairment and normal/high phosphate levels is not sufficient to cause cardiovascular disease.
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http://dx.doi.org/10.1016/j.kint.2018.02.017DOI Listing
July 2018

The First Scube3 Mutant Mouse Line with Pleiotropic Phenotypic Alterations.

G3 (Bethesda) 2016 12 7;6(12):4035-4046. Epub 2016 Dec 7.

German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany

The vertebrate Scube (Signal peptide, CUB, and EGF-like domain-containing protein) family consists of three independent members, Scube1-3, which encode secreted cell surface-associated membrane glycoproteins. Limited information about the general function of this gene family is available, and their roles during adulthood. Here, we present the first Scube3 mutant mouse line (Scube3), which clearly shows phenotypic alterations by carrying a missense mutation in exon 8, and thus contributes to our understanding of SCUBE3 functions. We performed a detailed phenotypic characterization in the German Mouse Clinic (GMC). Scube3 mutants showed morphological abnormalities of the skeleton, alterations of parameters relevant for bone metabolism, changes in renal function, and hearing impairments. These findings correlate with characteristics of the rare metabolic bone disorder Paget disease of bone (PDB), associated with the chromosomal region of human SCUBE3 In addition, alterations in energy metabolism, behavior, and neurological functions were detected in Scube3 mice. The Scube3 mutant mouse line may serve as a new model for further studying the effect of impaired SCUBE3 gene function.
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http://dx.doi.org/10.1534/g3.116.033670DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5144972PMC
December 2016

Viable Ednra mice feature human mandibulofacial dysostosis with alopecia (MFDA) syndrome due to the homologue mutation.

Mamm Genome 2016 12 26;27(11-12):587-598. Epub 2016 Sep 26.

Institute of Experimental Genetics and German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Ingolstädter Landstr.1, 85764, Neuherberg, Germany.

Animal models resembling human mutations are valuable tools to research the features of complex human craniofacial syndromes. This is the first report on a viable dominant mouse model carrying a non-synonymous sequence variation within the endothelin receptor type A gene (Ednra c.386A>T, p.Tyr129Phe) derived by an ENU mutagenesis program. The identical amino acid substitution was reported recently as disease causing in three individuals with the mandibulofacial dysostosis with alopecia (MFDA, OMIM 616367) syndrome. We performed standardized phenotyping of wild-type, heterozygous, and homozygous Ednra mice within the German Mouse Clinic. Mutant mice mimic the craniofacial phenotypes of jaw dysplasia, micrognathia, dysplastic temporomandibular joints, auricular dysmorphism, and missing of the squamosal zygomatic process as described for MFDA-affected individuals. As observed in MFDA-affected individuals, mutant Ednra mice exhibit hearing impairment in line with strong abnormalities of the ossicles and further, reduction of some lung volumetric parameters. In general, heterozygous and homozygous mice demonstrated inter-individual diversity of expression of the craniofacial phenotypes as observed in MFDA patients but without showing any cleft palates, eyelid defects, or alopecia. Mutant Ednra mice represent a valuable viable model for complex human syndromes of the first and second pharyngeal arches and for further studies and analysis of impaired endothelin 1 (EDN1)-endothelin receptor type A (EDNRA) signaling. Above all, Ednra mice model the recently published human MFDA syndrome and may be helpful for further disease understanding and development of therapeutic interventions.
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http://dx.doi.org/10.1007/s00335-016-9664-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5110705PMC
December 2016

Exome sequencing identifies a nonsense mutation in Fam46a associated with bone abnormalities in a new mouse model for skeletal dysplasia.

Mamm Genome 2016 Apr 23;27(3-4):111-21. Epub 2016 Jan 23.

Institute of Human Genetics, German Research Center for Environmental Health (GmbH), Helmholtz Zentrum München, Ingolstädter Landstr. 1, 85764, Neuherberg, Germany.

We performed exome sequencing for mutation discovery of an ENU (N-ethyl-N-nitrosourea)-derived mouse model characterized by significant elevated plasma alkaline phosphatase (ALP) activities in female and male mutant mice, originally named BAP014 (bone screen alkaline phosphatase #14). We identified a novel loss-of-function mutation within the Fam46a (family with sequence similarity 46, member A) gene (NM_001160378.1:c.469G>T, NP_001153850.1:p.Glu157*). Heterozygous mice of this mouse line (renamed Fam46a (E157*Mhda)) had significantly high ALP activities and apparently no other differences in morphology compared to wild-type mice. In contrast, homozygous Fam46a (E157*Mhda) mice showed severe morphological and skeletal abnormalities including short stature along with limb, rib, pelvis, and skull deformities with minimal trabecular bone and reduced cortical bone thickness in long bones. ALP activities of homozygous mutants were almost two-fold higher than in heterozygous mice. Fam46a is weakly expressed in most adult and embryonic tissues with a strong expression in mineralized tissues as calvaria and femur. The FAM46A protein is computationally predicted as a new member of the superfamily of nucleotidyltransferase fold proteins, but little is known about its function. Fam46a (E157*Mhda) mice are the first mouse model for a mutation within the Fam46a gene.
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http://dx.doi.org/10.1007/s00335-016-9619-xDOI Listing
April 2016

Development of A Cell-Based Assay to Identify Small Molecule Inhibitors of FGF23 Signaling.

Assay Drug Dev Technol 2015 Oct;13(8):476-87

1 German Research Center for Environmental Health, Institute of Human Genetics , HelmholtzZentrum München, Neuherberg, Bavaria, Germany .

Fibroblast growth factor 23 (FGF23) is a bone-derived endocrine key regulator of phosphate homeostasis. It inhibits renal tubular phosphate reabsorption by activating receptor complexes composed of FGF receptor 1c (FGFR1c) and the co-receptor Klotho. As a major signaling pathway mitogen-activated protein kinase (MAPK) pathway is employed. In this study, we established an FGF23-inducible cell model by stably expressing human Klotho in HEK293 cells (HEK293-KL cells) containing endogenous FGF receptors. To identify novel small molecule compounds that modulate FGF23/FGFR1c/Klotho signaling, we developed and optimized a cell-based assay that is suited for high-throughput screening. The assay monitors the phosphorylation of endogenous extracellular signal-regulated kinase 1 and 2 in cellular lysates of HEK293-KL cells after induction with FGF23. This cell-based assay was highly robust (Z' factor >0.5) and the induction of the system is strictly dependent on the presence of FGF23. The inhibitor response curves generated using two known MAPK pathway inhibitors correlate well with data obtained by another assay format. This assay was further used to identify small molecule modulators of the FGF23 signaling cascade by screening the 1,280 food and drug administration-approved small molecule library of Prestwick Chemical. The primary hit rate was 2% and false positives were efficiently identified by retesting the hits in primary and secondary validation screening assays and in western blot analysis. Intriguingly, by using a basic FGF (bFGF)/FGFR counterscreening approach, one validated hit compound retained specificity toward FGF23 signaling, while bFGF signaling was not affected. Since increased plasma concentrations of FGF23 are the main cause of many hypophosphatemic disorders, a modulation of its effect could be a potential novel strategy for therapeutic intervention. Moreover, this strategy may be valuable for other disorders affecting phosphate homeostasis.
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http://dx.doi.org/10.1089/adt.2015.653DOI Listing
October 2015

Biallelic Mutations of Methionyl-tRNA Synthetase Cause a Specific Type of Pulmonary Alveolar Proteinosis Prevalent on Réunion Island.

Am J Hum Genet 2015 May 23;96(5):826-31. Epub 2015 Apr 23.

Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany; Institute of Human Genetics, Technische Universität München, 81675 Munich, Germany. Electronic address:

Methionyl-tRNA synthetase (MARS) catalyzes the ligation of methionine to tRNA and is critical for protein biosynthesis. We identified biallelic missense mutations in MARS in a specific form of pediatric pulmonary alveolar proteinosis (PAP), a severe lung disorder that is prevalent on the island of Réunion and the molecular basis of which is unresolved. Mutations were found in 26 individuals from Réunion and nearby islands and in two families from other countries. Functional consequences of the mutated alleles were assessed by growth of wild-type and mutant strains and methionine-incorporation assays in yeast. Enzyme activity was attenuated in a liquid medium without methionine but could be restored by methionine supplementation. In summary, identification of a founder mutation in MARS led to the molecular definition of a specific type of PAP and will enable carrier screening in the affected community and possibly open new treatment opportunities.
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http://dx.doi.org/10.1016/j.ajhg.2015.03.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4570277PMC
May 2015

Early onset hearing loss in autosomal recessive hypophosphatemic rickets caused by loss of function mutation in ENPP1.

J Pediatr Endocrinol Metab 2015 Jul;28(7-8):967-70

Autosomal recessive hypophosphatemic rickets 2 (ARHR2) is a rare form of renal tubular phosphate wasting disorder. Loss of function mutations of the ecto-nucleotide pyrophosphatase/pyrophosphodiesterase 1 gene (ENPP1) causes a wide spectrum of phenotypes, ranging from lethal generalized arterial calcification of infancy to hypophosphatemic rickets with hypertension. Hearing loss was not previously thought to be one of the features of the disease entities and was merely regarded as a complication rather than a part of the disease. We report two children who presented in mid to late childhood with progressive varus deformity of their legs due to hypophosphatemic rickets caused by mutations in the ENPP1 gene. Both children had evidence of progressive hearing loss requiring the use of hearing aids. This report of two unrelated infants with compound heterozygous mutations in ENPP1 and previously published cases confirms that mild to moderate hearing loss is frequently associated with ARHR2. Early onset conductive hearing loss may further distinguish the autosomal recessive ENPP1 related type from other types of hypophosphatemia.
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http://dx.doi.org/10.1515/jpem-2014-0531DOI Listing
July 2015

Unusually severe hypophosphatemic rickets caused by a novel and complex re-arrangement of the PHEX gene.

Am J Med Genet A 2014 Nov 13;164A(11):2931-7. Epub 2014 Aug 13.

Division of Endocrinology, Department of Medicine, Helsinki University Central Hospital, Vantaa, Finland.

X-linked hypophosphatemia (XLH) is caused by mutations in PHEX. Several other genetic forms of hypophosphatemia have also been described. These disorders share variable clinical presentation ranging from mild hypophosphatemia to severe lower extremity bowing. We report on a 43-year-old woman with short stature, painful leg deformities, and poor dentation. Her biochemical profile showed hypophosphatemia with renal phosphate wasting. Due to unusually severe clinical presentation and absence of mutations in Sanger sequencing of the PHEX gene, quantitative multiplex ligation-dependent probe amplification was performed. A large deletion within the PHEX gene encompassing exons 8 to 11 was identified. We generated a specific junction fragment using long-range PCR and sequenced the junction fragment to determine the exact deletion breakpoints. We found a heterozygous novel complex re-arrangement involving gross deletions, insertions, and inversion of PHEX (hg19:g.22,115,003_22,141,395del;g:22,145,536_22,150,789delinsCins22,114,640_22,114,698invinsA). Thus, the complex re-arrangement including a deletion of coding exons 8 to 11 of the PHEX can be regarded as the cause of XLH in the patient reported here. Phosphate and active vitamin D treatment was initiated with subsequent relief in bone pain and physical improvement. This report expands the spectrum of clinical severity underlying genetic defects in XLH and highlights the importance of conventional medical therapy even at adult age. Furthermore, our findings underscore the importance of search for gene deletions in patients with suspected XLH.
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http://dx.doi.org/10.1002/ajmg.a.36721DOI Listing
November 2014

An ENU mutagenesis-derived mouse model with a dominant Jak1 mutation resembling phenotypes of systemic autoimmune disease.

Am J Pathol 2013 Aug 19;183(2):352-68. Epub 2013 Jun 19.

Institute of Experimental Genetics and the German Mouse Clinic, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany.

Within the Munich, Germany, N-ethyl-N-nitrosourea mouse mutagenesis program, we isolated a dominant Jak1 mouse model resembling phenotypic characteristics related to autoimmune disease. Chromosomal sequencing revealed a new Jak1 (p.Ser645Pro) point mutation at the conserved serine of the pseudokinase domain, corresponding to a somatic human mutation (p.Ser646Phe) inducing a constitutive activation of the Janus kinase (JAK)/STAT pathway. Morphologically, all Jak1(S645P+/-) mice showed a progressive structural deterioration of ears starting at the age of 4 months, with mononuclear cell infiltration into the dermis. Female mutant mice, in particular, developed severe skin lesions in the neck from 7 months of age. The IHC analysis of these lesions showed an activation of Stat3 downstream to Jak1(S645P) and elevated tissue levels of IL-6. Histopathological analysis of liver revealed a nodular regenerative hyperplasia. In the spleen, the number of Russell bodies was doubled, correlating with significant increased levels of all immunoglobulin isotypes and anti-DNA antibodies in serum. Older mutant mice developed thrombocytopenia and altered microcytic red blood cell counts. Jak1(S645P+/-) mice showed phenotypes related to impaired bone metabolism as increased carboxy-terminal collagen cross-link-1 levels and alkaline phosphatase activities in plasma, hypophosphatemia, and strongly decreased bone morphometric values. Taken together, Jak1(S645P+/-) mice showed an increased activation of the IL-6-JAK-STAT pathway leading to a systemic lupus erythematosus-like phenotype and offering a new valuable tool to study the role of the JAK/STAT pathway in disease development.
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http://dx.doi.org/10.1016/j.ajpath.2013.04.027DOI Listing
August 2013

New mouse models for metabolic bone diseases generated by genome-wide ENU mutagenesis.

Mamm Genome 2012 Aug 21;23(7-8):416-30. Epub 2012 Apr 21.

Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.

Metabolic bone disorders arise as primary diseases or may be secondary due to a multitude of organ malfunctions. Animal models are required to understand the molecular mechanisms responsible for the imbalances of bone metabolism in disturbed bone mineralization diseases. Here we present the isolation of mutant mouse models for metabolic bone diseases by phenotyping blood parameters that target bone turnover within the large-scale genome-wide Munich ENU Mutagenesis Project. A screening panel of three clinical parameters, also commonly used as biochemical markers in patients with metabolic bone diseases, was chosen. Total alkaline phosphatase activity and total calcium and inorganic phosphate levels in plasma samples of F1 offspring produced from ENU-mutagenized C3HeB/FeJ male mice were measured. Screening of 9,540 mice led to the identification of 257 phenodeviants of which 190 were tested by genetic confirmation crosses. Seventy-one new dominant mutant lines showing alterations of at least one of the biochemical parameters of interest were confirmed. Fifteen mutations among three genes (Phex, Casr, and Alpl) have been identified by positional-candidate gene approaches and one mutation of the Asgr1 gene, which was identified by next-generation sequencing. All new mutant mouse lines are offered as a resource for the scientific community.
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http://dx.doi.org/10.1007/s00335-012-9397-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3401305PMC
August 2012

Identification of FOXP1 deletions in three unrelated patients with mental retardation and significant speech and language deficits.

Hum Mutat 2010 Nov;31(11):E1851-60

Institute of Medical Genetics, Charité, University Medicine of Berlin, Berlin, Germany.

Mental retardation affects 2-3% of the population and shows a high heritability.Neurodevelopmental disorders that include pronounced impairment in language and speech skills occur less frequently. For most cases, the molecular basis of mental retardation with or without speech and language disorder is unknown due to the heterogeneity of underlying genetic factors.We have used molecular karyotyping on 1523 patients with mental retardation to detect copy number variations (CNVs) including deletions or duplications. These studies revealed three heterozygous overlapping deletions solely affecting the forkhead box P1 (FOXP1) gene. All three patients had moderate mental retardation and significant language and speech deficits. Since our results are consistent with a de novo occurrence of these deletions, we considered them as causal although we detected a single large deletion including FOXP1 and additional genes in 4104 ancestrally matched controls. These findings are of interest with regard to the structural and functional relationship between FOXP1 and FOXP2. Mutations in FOXP2 have been previously related to monogenic cases of developmental verbal dyspraxia. Both FOXP1 and FOXP2 are expressed in songbird and human brain regions that are important for the developmental processes that culminate in speech and language.
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http://dx.doi.org/10.1002/humu.21362DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049153PMC
November 2010

Loss-of-function ENPP1 mutations cause both generalized arterial calcification of infancy and autosomal-recessive hypophosphatemic rickets.

Am J Hum Genet 2010 Feb 4;86(2):267-72. Epub 2010 Feb 4.

Institute of Human Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.

The analysis of rare genetic disorders affecting phosphate homeostasis led to the identification of several proteins that are essential for the renal regulation of phosphate homeostasis; for example, fibroblast growth factor 23 (FGF23), which inhibits renal phosphate reabsorption and 1,25-dihydroxyvitamin D synthesis. Here, we report presumable loss-of-function mutations in the ENPP1 gene (ectonucleotide pyrophosphatase/phosphodiesterase) in members of four families affected with hypophosphatemic rickets. We provide evidence for the conclusion that ENPP1 is the fourth gene-in addition to PHEX, FGF23, and DMP1-that, if mutated, causes hypophosphatemic rickets resulting from elevated FGF23 levels. Surprisingly, ENPP1 loss-of-function mutations have previously been described in generalized arterial calcification of infancy, suggesting an as yet elusive mechanism that balances arterial calcification with bone mineralization.
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http://dx.doi.org/10.1016/j.ajhg.2010.01.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2820166PMC
February 2010

Evaluation of [18F]fluoro-L-DOPA positron emission tomography-computed tomography for surgery in focal congenital hyperinsulinism.

J Clin Endocrinol Metab 2008 Mar 11;93(3):869-75. Epub 2007 Dec 11.

Clinic for Pediatric Surgery, Institute for Pathology, Charité University Medicine Berlin, Campus Virchow Klinikum, Augustenburger Platz 1, Mittelallee 8, D-13353 Berlin, Germany.

Context: In congenital hyperinsulinism (CHI), the identification and precise localization of a focal lesion is essential for successful surgery.

Objective: Our objective was to evaluate the predictive value and accuracy of integrated [18F]fluoro-L-DOPA ([18F]FDOPA) positron emission tomography (PET)-computed tomography (CT) for the surgical therapy of CHI.

Design: This was an observational study.

Setting: The study was performed in the Department of Pediatric Surgery at a university hospital.

Patients: From February 2005 to September 2007, 10 children with the clinical signs of CHI and an increased radiotracer uptake in a circumscribed area of the pancreas in the [18F]FDOPA PET-CT were evaluated.

Interventions: Guided by the [18F]FDOPA PET-CT report, all children underwent partial pancreatic resection, in two cases twice.

Main Outcome Measures: Correlation of the anatomical findings at surgery with the report of the [18F]FDOPA PET-CT, and the results of surgery and clinical outcome were determined.

Results: In nine children the intraoperative situation corresponded exactly to the description of the [18F]FDOPA PET-CT. A limited resection of the pancreas was curative in eight cases at the first surgery, in one case at the second intervention. We observed no diabetes mellitus or exocrine insufficiency in the follow up so far. In one child, hypoglycemia persisted even after two partial resections of the pancreatic head. Histological analysis finally revealed an atypical intermediate form of CHI.

Conclusions: The integrated [18F]FDOPA PET-CT is accurate to localize the lesion in focal CHI and is a valuable tool to guide the surgeon in limited pancreatic resection.
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http://dx.doi.org/10.1210/jc.2007-2036DOI Listing
March 2008

Copy-number variations measured by single-nucleotide-polymorphism oligonucleotide arrays in patients with mental retardation.

Am J Hum Genet 2007 Oct 28;81(4):768-79. Epub 2007 Aug 28.

Institute of Human Genetics, GSF National Research Center for Environment and Health, Munich-Neuherberg, Germany.

Whole-genome analysis using high-density single-nucleotide-polymorphism oligonucleotide arrays allows identification of microdeletions, microduplications, and uniparental disomies. We studied 67 children with unexplained mental retardation with normal karyotypes, as assessed by G-banded chromosome analyses. Their DNAs were analyzed with Affymetrix 100K arrays. We detected 11 copy-number variations that most likely are causative of mental retardation, because they either arose de novo (9 cases) and/or overlapped with known microdeletions (2 cases). The eight deletions and three duplications varied in size from 200 kb to 7.5 Mb. Of the 11 copy-number variations, 5 were flanked by low-copy repeats. Two of those, on chromosomes 15q25.2 and Xp22.31, have not been described before and have a high probability of being causative of new deletion and duplication syndromes, respectively. In one patient, we found a deletion affecting only a single gene, MBD5, which codes for the methyl-CpG-binding domain protein 5. In addition to the 67 children, we investigated 4 mentally retarded children with apparent balanced translocations and detected four deletions at breakpoint regions ranging in size from 1.1 to 14 Mb.
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http://dx.doi.org/10.1086/521274DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2227926PMC
October 2007

DMP1 mutations in autosomal recessive hypophosphatemia implicate a bone matrix protein in the regulation of phosphate homeostasis.

Nat Genet 2006 Nov 8;38(11):1248-50. Epub 2006 Oct 8.

Institute of Human Genetics, GSF National Research Center for Environment and Health, 85764 Munich-Neuherberg, Germany.

Hypophosphatemia is a genetically heterogeneous disease. Here, we mapped an autosomal recessive form (designated ARHP) to chromosome 4q21 and identified homozygous mutations in DMP1 (dentin matrix protein 1), which encodes a non-collagenous bone matrix protein expressed in osteoblasts and osteocytes. Intact plasma levels of the phosphaturic protein FGF23 were clearly elevated in two of four affected individuals, providing a possible explanation for the phosphaturia and inappropriately normal 1,25(OH)2D levels and suggesting that DMP1 may regulate FGF23 expression.
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http://dx.doi.org/10.1038/ng1868DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5942547PMC
November 2006

Polypeptide GalNAc-transferase T3 and familial tumoral calcinosis. Secretion of fibroblast growth factor 23 requires O-glycosylation.

J Biol Chem 2006 Jul 25;281(27):18370-7. Epub 2006 Apr 25.

Department of Medical Biochemistry and Genetics, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark.

Mutations in the gene encoding the glycosyltransferase polypeptide GalNAc-T3, which is involved in initiation of O-glycosylation, were recently identified as a cause of the rare autosomal recessive metabolic disorder familial tumoral calcinosis (OMIM 211900). Familial tumoral calcinosis is associated with hyperphosphatemia and massive ectopic calcifications. Here, we demonstrate that the secretion of the phosphaturic factor fibroblast growth factor 23 (FGF23) requires O-glycosylation, and that GalNAc-T3 selectively directs O-glycosylation in a subtilisin-like proprotein convertase recognition sequence motif, which blocks processing of FGF23. The study suggests a novel posttranslational regulatory model of FGF23 involving competing O-glycosylation and protease processing to produce intact FGF23.
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http://dx.doi.org/10.1074/jbc.M602469200DOI Listing
July 2006

Hereditary hypophosphatemic rickets with hypercalciuria is caused by mutations in the sodium-phosphate cotransporter gene SLC34A3.

Am J Hum Genet 2006 Feb 9;78(2):193-201. Epub 2005 Dec 9.

Institute of Human Genetics, GSF National Research Center for Environment and Health, Munich-Neuherberg, Germany.

Hypophosphatemia due to isolated renal phosphate wasting results from a heterogeneous group of disorders. Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is an autosomal recessive form that is characterized by reduced renal phosphate reabsorption, hypophosphatemia, and rickets. It can be distinguished from other forms of hypophosphatemia by increased serum levels of 1,25-dihydroxyvitamin D resulting in hypercalciuria. Using SNP array genotyping, we mapped the disease locus in two consanguineous families to the end of the long arm of chromosome 9. The candidate region contained a sodium-phosphate cotransporter gene, SLC34A3, which has been shown to be expressed in proximal tubulus cells. Sequencing of this gene revealed disease-associated mutations in five families, including two frameshift and one splice-site mutation. Loss of function of the SLC34A3 protein presumably results in a primary renal tubular defect and is compatible with the HHRH phenotype. We also show that the phosphaturic factor FGF23 (fibroblast growth factor 23), which is increased in X-linked hypophosphatemic rickets and carries activating mutations in autosomal dominant hypophosphatemic rickets, is at normal or low-normal serum levels in the patients with HHRH, further supporting a primary renal defect. Identification of the gene mutated in a further form of hypophosphatemia adds to the understanding of phosphate homeostasis and may help to elucidate the interaction of the proteins involved in this pathway.
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http://dx.doi.org/10.1086/499410DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1380229PMC
February 2006

Mutation in the neuronal voltage-gated sodium channel SCN1A in familial hemiplegic migraine.

Lancet 2005 Jul 30-Aug 5;366(9483):371-7

Department of Neurology, Klinikum Grosshadern, Ludwig-Maximilians-Universität, 81377 München, Germany.

Background: Familial hemiplegic migraine is an autosomal dominant severe subtype of migraine with aura characterised by some degree of hemiparesis during the attacks. So far, mutations in two genes regulating ion translocation-CACNA1A and ATP1A2-have been identified in pedigrees with this disease.

Methods: To identify additional genes for familial hemiplegic migraine, we did a genome-wide linkage analysis of two disease pedigrees without mutations in CACNA1A and ATP1A2. Ion channel genes in the candidate interval were analysed for mutations, and the functional consequences of the recorded sequence alteration were determined.

Findings: We identified a novel locus for familial hemiplegic migraine on chromosome 2q24. Sequencing of candidate genes in this region revealed a heterozygous missense mutation (Gln1489Lys) in the neuronal voltage-gated sodium channel gene SCN1A, mutations of which have been associated with epilepsy. This same mutation was present in three families with familial hemiplegic migraine. It results in a charge-altering aminoacid exchange in the so-called hinged-lid domain of the protein, which is critical for fast inactivation of the channel. Whole-cell recordings in transiently transfected tsA201 cells expressing the highly homologous SCN5A sodium channel showed that the mutation induces a two-fold to four-fold accelerated recovery from fast inactivation without altering any of the other channel parameters investigated.

Interpretation: Dysfunction of the neuronal sodium channel SCN1A can cause familial hemiplegic migraine. Our findings have implications for the understanding of migraine aura. Moreover, our study reinforces the molecular links between migraine and epilepsy, two common paroxysmal disorders.
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http://dx.doi.org/10.1016/S0140-6736(05)66786-4DOI Listing
October 2005

An FGF23 missense mutation causes familial tumoral calcinosis with hyperphosphatemia.

Hum Mol Genet 2005 Feb 8;14(3):385-90. Epub 2004 Dec 8.

Institute of Human Genetics, GSF National Research Center for Environment and Health, Ingolstädter Landstr. 1, 85764 Munich-Neuherberg, Germany.

Familial tumoral calcinosis (FTC) is an autosomal recessive disorder characterized by ectopic calcifications and elevated serum phosphate levels. Recently, mutations in the GALNT3 gene have been described to cause FTC. The FTC phenotype is regarded as the metabolic mirror image of hypophosphatemic conditions, where causal mutations are known in genes FGF23 or PHEX. We investigated an individual with FTC who was negative for GALNT3 mutations. Sequencing revealed a homozygous missense mutation in the FGF23 gene (p.S71G) at an amino acid position which is conserved from fish to man. Wild-type FGF23 is secreted as intact protein and processed N-terminal and C-terminal fragments. Expression of the mutated protein in HEK293 cells showed that only the C-terminal fragment is secreted, whereas the intact protein is retained in the Golgi complex. In addition, determination of circulating FGF23 in the affected individual showed a marked increase in the C-terminal fragment. These results suggest that the FGF23 function is decreased by absent or extremely reduced secretion of intact FGF23. We conclude that FGF23 mutations in hypophosphatemic rickets and FTC have opposite effects on phosphate homeostasis.
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http://dx.doi.org/10.1093/hmg/ddi034DOI Listing
February 2005

FGF23 is processed by proprotein convertases but not by PHEX.

Bone 2004 Aug;35(2):455-62

Institute of Human Genetics, GSF National Research Center, 85764 München-Neuherberg, Germany.

X-linked hypophosphatemia (XLH) and autosomal dominant hypophosphatemic rickets (ADHR) are characterized by renal phosphate wasting, rickets, and osteomalacia. ADHR is caused by gain of function mutations in the fibroblast growth factor 23 gene (FGF23). During secretion, FGF23 is processed at the C-terminus between amino acids 179 and 180. The cleavage site is mutated in ADHR, preventing processing of FGF23. Here, we show that FGF23 is likely to be cleaved by subtilisin-like proprotein convertases (SPC) as cleavage can be inhibited by a specific SPC inhibitor in HEK293 cells. SPCs, which are widely expressed, were demonstrated to be also present in HEK293 cells as well as in osteoblasts. XLH is caused by loss of function mutations in the putative endopeptidase PHEX. It was tempting to speculate that FGF23 is a substrate of PHEX, but studies have been inconclusive so far. Here, we used a secreted form of PHEX (secPHEX) and tagged and untagged FGF23 constructs for co-incubation experiments. These experiments provided evidence against cleavage of intact FGF23(25-251) as well as of N-terminal (FGF23(25-179)) and C-terminal (FGF23(180-251)) fragments by the endopeptidase PHEX.
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http://dx.doi.org/10.1016/j.bone.2004.04.002DOI Listing
August 2004

New intragenic deletions in the Phex gene clarify X-linked hypophosphatemia-related abnormalities in mice.

Mamm Genome 2004 Mar;15(3):151-61

Institute of Human Genetics, GSF National Research Center, München-Neuherberg, Germany.

X-linked hypophosphatemic rickets (XLH) in humans is caused by mutation in the PHEX gene. Previously, three mutations in the mouse Phex gene have been reported: Phex(Hyp), Gy, and Phex(Ska1). Here we report analysis of two new spontaneous mutation in the mouse Phex gene, Phex(Hyp-2J) and Phex(Hyp-Duk). Phex(Hyp-2J) and Phex(Hyp-Duk) involve intragenic deletions of at least 7.3 kb containing exon 15, and 30 kb containing exons 13 and 14, respectively. Both mutations cause similar phenotypes in males, including shortened hind legs and tail, a shortened square trunk, hypophosphatemia, hypocalcemia, and rachitic bone disease. In addition, mice carrying the Phex(Hyp-Duk) mutation exhibit background-dependent variable expression of deafness, circling behavior, and cranial dysmorphology, demonstrating the influence of modifying genes on Phex-related phenotypes. Cochlear cross-sections from Phex(Hyp-2J)/Y and Phex(Hyp-Duk)/Y males reveal a thickening of the temporal bones surrounding the cochlea with the presence of a precipitate in the scala tympani. Evidence of the degeneration of the organ of Corti and spiral ganglion also are present in the hearing-impaired Phex(Hyp-Duk)/Y mice, but not in the normal-hearing Phex(Hyp-2J)/Y mice. Analysis of the phenotypes noted in Phex(Hyp-Duk)/Y and Phex(Hyp-2J)/Y males, together with those noted in Phex(Ska1)/Y and Phex(Hyp)/Y males, now allow XLH-related phenotypes to be separated from non-XLH-related phenotypes, such as those noted in Gy/Y males. Also, identification of the genetic modifiers of hearing and craniofacial dysmorphology in Phex(Hyp-Duk)/Y mice could provide insight into the phenotypic variation of XLH in humans.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2859190PMC
http://dx.doi.org/10.1007/s00335-003-2310-zDOI Listing
March 2004

The epsilon-sarcoglycan gene (SGCE), mutated in myoclonus-dystonia syndrome, is maternally imprinted.

Eur J Hum Genet 2003 Feb;11(2):138-44

Institute of Human Genetics, GSF National Research Center, D-85764 München-Neuherberg, Germany.

Myoclonus-dystonia syndrome (MDS) is a non-degenerative neurological disorder that has been described to be inherited in an autosomal dominant mode with incomplete penetrance. MDS is caused by loss of function mutations in the epsilon-sarcoglycan gene. Reinvestigation of MDS pedigrees provided evidence for a maternal imprinting mechanism. As differential methylated regions (DMRs) are a characteristic feature of imprinted genes, we studied the methylation pattern of CpG dinucleotides within the CpG island containing the promoter region and the first exon of the SGCE gene by bisulphite genomic sequencing. Our findings revealed that in peripheral blood leukocytes the maternal allele is methylated, while the paternal allele is unmethylated. We also showed that most likely the maternal allele is completely methylated in brain tissue. Furthermore, CpG dinucleotides in maternal and paternal uniparental disomy 7 (UPD7) lymphoblastoid cell lines show a corresponding parent-of-origin specific methylation pattern. The effect of differential methylation on the expression of the SGCE gene was tested in UPD7 cell lines with only a weak RT-PCR signal observed in matUPD7 and a strong signal in patUPD7. These results provide strong evidence for a maternal imprinting of the SGCE gene. The inheritance pattern in MDS families is in agreement with such an imprinting mechanism with the exception of a few cases. We investigated one affected female that inherited the mutated allele from her mother. Surprisingly, we found the paternal wild type allele expressed whereas the mutated maternal allele was not detectable in peripheral blood cDNA.
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http://dx.doi.org/10.1038/sj.ejhg.5200938DOI Listing
February 2003