Publications by authors named "Verena Klämbt"

15 Publications

  • Page 1 of 1

Recessive Mutations in as a Candidate of Monogenic Nephrotic Syndrome.

Kidney Int Rep 2021 Feb 10;6(2):472-483. Epub 2020 Nov 10.

Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.

Introduction: Most of the approximately 60 genes that if mutated cause steroid-resistant nephrotic syndrome (SRNS) are highly expressed in the glomerular podocyte, rendering SRNS a "podocytopathy."

Methods: We performed whole-exome sequencing (WES) in 1200 nephrotic syndrome (NS) patients.

Results: We discovered homozygous truncating and homozygous missense mutation in (synaptopodin-2) (p.Lys1124∗ and p.Ala1134Thr) in 2 patients with childhood-onset NS. We found SYNPO2 expression in both podocytes and mesangial cells; however, notably, immunofluorescence staining of adult human and rat kidney cryosections indicated that SYNPO2 is localized mainly in mesangial cells. Subcellular localization studies reveal that in these cells SYNPO2 partially co-localizes with α-actinin and filamin A-containing F-actin filaments. Upon transfection in mesangial cells or podocytes, EGFP-SYNPO2 co-localized with α-actinin-4, which gene is mutated in autosomal dominant SRNS in humans. SYNPO2 overexpression increases mesangial cell migration rate (MMR), whereas shRNA knockdown reduces MMR. Decreased MMR was rescued by transfection of wild-type mouse cDNA but only partially by cDNA representing mutations from the NS patients. The increased mesangial cell migration rate (MMR) by SYNPO2 overexpression was inhibited by ARP complex inhibitor CK666. shRNA knockdown in podocytes decreased active Rac1, which was rescued by transfection of wild-type cDNA but not by cDNA representing any of the 2 mutant variants.

Conclusion: We show that SYNPO2 variants may lead to Rac1-ARP3 dysregulation, and may play a role in the pathogenesis of nephrotic syndrome.
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http://dx.doi.org/10.1016/j.ekir.2020.10.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7879128PMC
February 2021

Generation of Monogenic Candidate Genes for Human Nephrotic Syndrome Using 3 Independent Approaches.

Kidney Int Rep 2021 Feb 3;6(2):460-471. Epub 2020 Dec 3.

Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.

Introduction: Steroid-resistant nephrotic syndrome (SRNS) is the second most common cause of chronic kidney disease during childhood. Identification of 63 monogenic human genes has delineated 12 distinct pathogenic pathways.

Methods: Here, we generated 2 independent sets of nephrotic syndrome (NS) candidate genes to augment the discovery of additional monogenic causes based on whole-exome sequencing (WES) data from 1382 families with NS.

Results: We first identified 63 known monogenic causes of NS in mice from public databases and scientific publications, and 12 of these genes overlapped with the 63 known human monogenic SRNS genes. Second, we used a set of 64 genes that are regulated by the transcription factor Wilms tumor 1 (WT1), which causes SRNS if mutated. Thirteen of these WT1-regulated genes overlapped with human or murine NS genes. Finally, we overlapped these lists of murine and WT1 candidate genes with our list of 120 candidate genes generated from WES in 1382 NS families, to identify novel candidate genes for monogenic human SRNS. Using this approach, we identified 7 overlapping genes, of which 3 genes were shared by all datasets, including . We show that loss-of-function of leads to decreased CDC42 activity and reduced podocyte migration rate, both of which are rescued by overexpression of wild-type complementary DNA (cDNA), but not by cDNA representing the patient mutation.

Conclusion: Thus, we identified 3 novel candidate genes for human SRNS using 3 independent, nonoverlapping hypotheses, and generated functional evidence for as a novel potential monogenic cause of NS.
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http://dx.doi.org/10.1016/j.ekir.2020.11.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7879125PMC
February 2021

Mutations in Are a Novel Cause of Galloway-Mowat Syndrome.

J Am Soc Nephrol 2021 Mar 16;32(3):580-596. Epub 2021 Feb 16.

Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts

Background: Galloway-Mowat syndrome (GAMOS) is characterized by neurodevelopmental defects and a progressive nephropathy, which typically manifests as steroid-resistant nephrotic syndrome. The prognosis of GAMOS is poor, and the majority of children progress to renal failure. The discovery of monogenic causes of GAMOS has uncovered molecular pathways involved in the pathogenesis of disease.

Methods: Homozygosity mapping, whole-exome sequencing, and linkage analysis were used to identify mutations in four families with a GAMOS-like phenotype, and high-throughput PCR technology was applied to 91 individuals with GAMOS and 816 individuals with isolated nephrotic syndrome. and studies determined the functional significance of the mutations identified.

Results: Three biallelic variants of the transcriptional regulator were detected in six families with proteinuric kidney disease. Four families with a variant in the protein's zinc-finger (ZNF) domain have additional GAMOS-like features, including brain anomalies, cardiac defects, and skeletal defects. All variants destabilize the PRDM15 protein, and the ZNF variant additionally interferes with transcriptional activation. Morpholino oligonucleotide-mediated knockdown of Prdm15 in embryos disrupted pronephric development. Human wild-type RNA rescued the disruption, but the three variants did not. Finally, CRISPR-mediated knockout of in human podocytes led to dysregulation of several renal developmental genes.

Conclusions: Variants in can cause either isolated nephrotic syndrome or a GAMOS-type syndrome on an allelic basis. PRDM15 regulates multiple developmental kidney genes, and is likely to play an essential role in renal development in humans.
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http://dx.doi.org/10.1681/ASN.2020040490DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7920168PMC
March 2021

Recessive variants impair actin remodeling and cause glomerulopathy in humans and mice.

Sci Adv 2021 Jan 1;7(1). Epub 2021 Jan 1.

Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.

Nephrotic syndrome (NS) is a leading cause of chronic kidney disease. We found recessive variants in two families with early-onset NS by exome sequencing. Overexpression of wild-type (WT) , but not cDNA constructs bearing patient variants, increased active CDC42 and promoted filopodia and podosome formation. Pharmacologic inhibition of CDC42 or its effectors, formin proteins, reduced NOS1AP-induced filopodia formation. knockdown reduced podocyte migration rate (PMR), which was rescued by overexpression of WT but not by constructs bearing patient variants. PMR in knockdown podocytes was also rescued by constitutively active or the formin Modeling a patient variant in knock-in human kidney organoids revealed malformed glomeruli with increased apoptosis. mice recapitulated the human phenotype, exhibiting proteinuria, foot process effacement, and glomerulosclerosis. These findings demonstrate that recessive variants impair CDC42/DIAPH-dependent actin remodeling, cause aberrant organoid glomerulogenesis, and lead to a glomerulopathy in humans and mice.
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http://dx.doi.org/10.1126/sciadv.abe1386DOI Listing
January 2021

De novo TRIM8 variants impair its protein localization to nuclear bodies and cause developmental delay, epilepsy, and focal segmental glomerulosclerosis.

Am J Hum Genet 2021 02 27;108(2):357-367. Epub 2021 Jan 27.

Division of Nephrology, Columbia University, New York, NY 10032, USA. Electronic address:

Focal segmental glomerulosclerosis (FSGS) is the main pathology underlying steroid-resistant nephrotic syndrome (SRNS) and a leading cause of chronic kidney disease. Monogenic forms of pediatric SRNS are predominantly caused by recessive mutations, while the contribution of de novo variants (DNVs) to this trait is poorly understood. Using exome sequencing (ES) in a proband with FSGS/SRNS, developmental delay, and epilepsy, we discovered a nonsense DNV in TRIM8, which encodes the E3 ubiquitin ligase tripartite motif containing 8. To establish whether TRIM8 variants represent a cause of FSGS, we aggregated exome/genome-sequencing data for 2,501 pediatric FSGS/SRNS-affected individuals and 48,556 control subjects, detecting eight heterozygous TRIM8 truncating variants in affected subjects but none in control subjects (p = 3.28 × 10). In all six cases with available parental DNA, we demonstrated de novo inheritance (p = 2.21 × 10). Reverse phenotyping revealed neurodevelopmental disease in all eight families. We next analyzed ES from 9,067 individuals with epilepsy, yielding three additional families with truncating TRIM8 variants. Clinical review revealed FSGS in all. All TRIM8 variants cause protein truncation clustering within the last exon between residues 390 and 487 of the 551 amino acid protein, indicating a correlation between this syndrome and loss of the TRIM8 C-terminal region. Wild-type TRIM8 overexpressed in immortalized human podocytes and neuronal cells localized to nuclear bodies, while constructs harboring patient-specific variants mislocalized diffusely to the nucleoplasm. Co-localization studies demonstrated that Gemini and Cajal bodies frequently abut a TRIM8 nuclear body. Truncating TRIM8 DNVs cause a neuro-renal syndrome via aberrant TRIM8 localization, implicating nuclear bodies in FSGS and developmental brain disease.
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http://dx.doi.org/10.1016/j.ajhg.2021.01.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7895901PMC
February 2021

DAAM2 Variants Cause Nephrotic Syndrome via Actin Dysregulation.

Am J Hum Genet 2020 12 23;107(6):1113-1128. Epub 2020 Nov 23.

Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

The discovery of >60 monogenic causes of nephrotic syndrome (NS) has revealed a central role for the actin regulators RhoA/Rac1/Cdc42 and their effectors, including the formin INF2. By whole-exome sequencing (WES), we here discovered bi-allelic variants in the formin DAAM2 in four unrelated families with steroid-resistant NS. We show that DAAM2 localizes to the cytoplasm in podocytes and in kidney sections. Further, the variants impair DAAM2-dependent actin remodeling processes: wild-type DAAM2 cDNA, but not cDNA representing missense variants found in individuals with NS, rescued reduced podocyte migration rate (PMR) and restored reduced filopodia formation in shRNA-induced DAAM2-knockdown podocytes. Filopodia restoration was also induced by the formin-activating molecule IMM-01. DAAM2 also co-localizes and co-immunoprecipitates with INF2, which is intriguing since variants in both formins cause NS. Using in vitro bulk and TIRF microscopy assays, we find that DAAM2 variants alter actin assembly activities of the formin. In a Xenopus daam2-CRISPR knockout model, we demonstrate actin dysregulation in vivo and glomerular maldevelopment that is rescued by WT-DAAM2 mRNA. We conclude that DAAM2 variants are a likely cause of monogenic human SRNS due to actin dysregulation in podocytes. Further, we provide evidence that DAAM2-associated SRNS may be amenable to treatment using actin regulating compounds.
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http://dx.doi.org/10.1016/j.ajhg.2020.11.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820625PMC
December 2020

Mutations in transcription factor CP2-like 1 may cause a novel syndrome with distal renal tubulopathy in humans.

Nephrol Dial Transplant 2021 01;36(2):237-246

Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.

Background: An underlying monogenic cause of early-onset chronic kidney disease (CKD) can be detected in ∼20% of individuals. For many etiologies of CKD manifesting before 25 years of age, >200 monogenic causative genes have been identified to date, leading to the elucidation of mechanisms of renal pathogenesis.

Methods: In 51 families with echogenic kidneys and CKD, we performed whole-exome sequencing to identify novel monogenic causes of CKD.

Results: We discovered a homozygous truncating mutation in the transcription factor gene transcription factor CP2-like 1 (TFCP2L1) in an Arabic patient of consanguineous descent. The patient developed CKD by the age of 2 months and had episodes of severe hypochloremic, hyponatremic and hypokalemic alkalosis, seizures, developmental delay and hypotonia together with cataracts. We found that TFCP2L1 was localized throughout kidney development particularly in the distal nephron. Interestingly, TFCP2L1 induced the growth and development of renal tubules from rat mesenchymal cells. Conversely, the deletion of TFCP2L1 in mice was previously shown to lead to reduced expression of renal cell markers including ion transporters and cell identity proteins expressed in different segments of the distal nephron. TFCP2L1 localized to the nucleus in HEK293T cells only upon coexpression with its paralog upstream-binding protein 1 (UBP1). A TFCP2L1 mutant complementary DNA (cDNA) clone that represented the patient's mutation failed to form homo- and heterodimers with UBP1, an essential step for its transcriptional activity.

Conclusion: Here, we identified a loss-of-function TFCP2L1 mutation as a potential novel cause of CKD in childhood accompanied by a salt-losing tubulopathy.
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http://dx.doi.org/10.1093/ndt/gfaa215DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7834595PMC
January 2021

Mutations of the Transcriptional Corepressor ZMYM2 Cause Syndromic Urinary Tract Malformations.

Authors:
Dervla M Connaughton Rufeng Dai Danielle J Owen Jonathan Marquez Nina Mann Adda L Graham-Paquin Makiko Nakayama Etienne Coyaud Estelle M N Laurent Jonathan R St-Germain Lot Snijders Blok Arianna Vino Verena Klämbt Konstantin Deutsch Chen-Han Wilfred Wu Caroline M Kolvenbach Franziska Kause Isabel Ottlewski Ronen Schneider Thomas M Kitzler Amar J Majmundar Florian Buerger Ana C Onuchic-Whitford Mao Youying Amy Kolb Daanya Salmanullah Evan Chen Amelie T van der Ven Jia Rao Hadas Ityel Steve Seltzsam Johanna M Rieke Jing Chen Asaf Vivante Daw-Yang Hwang Stefan Kohl Gabriel C Dworschak Tobias Hermle Mariëlle Alders Tobias Bartolomaeus Stuart B Bauer Michelle A Baum Eva H Brilstra Thomas D Challman Jacob Zyskind Carrie E Costin Katrina M Dipple Floor A Duijkers Marcia Ferguson David R Fitzpatrick Roger Fick Ian A Glass Peter J Hulick Antonie D Kline Ilona Krey Selvin Kumar Weining Lu Elysa J Marco Ingrid M Wentzensen Heather C Mefford Konrad Platzer Inna S Povolotskaya Juliann M Savatt Natalia V Shcherbakova Prabha Senguttuvan Audrey E Squire Deborah R Stein Isabelle Thiffault Victoria Y Voinova Michael J G Somers Michael A Ferguson Avram Z Traum Ghaleb H Daouk Ankana Daga Nancy M Rodig Paulien A Terhal Ellen van Binsbergen Loai A Eid Velibor Tasic Hila Milo Rasouly Tze Y Lim Dina F Ahram Ali G Gharavi Heiko M Reutter Heidi L Rehm Daniel G MacArthur Monkol Lek Kristen M Laricchia Richard P Lifton Hong Xu Shrikant M Mane Simone Sanna-Cherchi Andrew D Sharrocks Brian Raught Simon E Fisher Maxime Bouchard Mustafa K Khokha Shirlee Shril Friedhelm Hildebrandt

Am J Hum Genet 2020 10 4;107(4):727-742. Epub 2020 Sep 4.

Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

Congenital anomalies of the kidney and urinary tract (CAKUT) constitute one of the most frequent birth defects and represent the most common cause of chronic kidney disease in the first three decades of life. Despite the discovery of dozens of monogenic causes of CAKUT, most pathogenic pathways remain elusive. We performed whole-exome sequencing (WES) in 551 individuals with CAKUT and identified a heterozygous de novo stop-gain variant in ZMYM2 in two different families with CAKUT. Through collaboration, we identified in total 14 different heterozygous loss-of-function mutations in ZMYM2 in 15 unrelated families. Most mutations occurred de novo, indicating possible interference with reproductive function. Human disease features are replicated in X. tropicalis larvae with morpholino knockdowns, in which expression of truncated ZMYM2 proteins, based on individual mutations, failed to rescue renal and craniofacial defects. Moreover, heterozygous Zmym2-deficient mice recapitulated features of CAKUT with high penetrance. The ZMYM2 protein is a component of a transcriptional corepressor complex recently linked to the silencing of developmentally regulated endogenous retrovirus elements. Using protein-protein interaction assays, we show that ZMYM2 interacts with additional epigenetic silencing complexes, as well as confirming that it binds to FOXP1, a transcription factor that has also been linked to CAKUT. In summary, our findings establish that loss-of-function mutations of ZMYM2, and potentially that of other proteins in its interactome, as causes of human CAKUT, offering new routes for studying the pathogenesis of the disorder.
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http://dx.doi.org/10.1016/j.ajhg.2020.08.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7536580PMC
October 2020

Different approaches to long-term treatment of aHUS due to MCP mutations: a multicenter analysis.

Pediatr Nephrol 2021 Feb 26;36(2):463-471. Epub 2020 Jul 26.

Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Center, University of Freiburg, Faculty of Medicine, Mathildenstr. 1, 79106 Freiburg, Germany.

Background: Atypical hemolytic uremic syndrome (aHUS) is a rare, life-threatening microangiopathy, frequently causing kidney failure. Inhibition of the terminal complement complex with eculizumab is the only licensed treatment but mostly requires long-term administration and risks severe side effects. The underlying genetic cause of aHUS is thought to influence the severity of initial and recurring episodes, with milder courses in patients with mutations in membrane cofactor protein (MCP).

Methods: Twenty pediatric cases of aHUS due to isolated heterozygous MCP mutations were reported from 12 German pediatric nephrology centers to describe initial presentation, timing of relapses, treatment, and kidney outcome.

Results: The median age of onset was 4.6 years, with a female to male ratio of 1:3. Without eculizumab maintenance therapy, 50% (9/18) of the patients experienced a first relapse after a median period of 3.8 years. Kaplan-Meier analysis showed a relapse-free survival of 93% at 1 year. Four patients received eculizumab long-term treatment, while 3 patients received short courses. We could not show a benefit from complement blockade therapy on long term kidney function, independent of short-term or long-term treatment. To prevent 1 relapse with eculizumab, the theoretical number-needed-to-treat (NNT) was 15 for the first year and 3 for the first 5 years after initial presentation.

Conclusion: Our study shows that heterozygous MCP mutations cause aHUS with a risk of first relapse of about 10% per year, resulting in large NNTs for prevention of relapses with eculizumab. More studies are needed to define an optimal treatment schedule for patients with MCP mutations to minimize the risks of the disease and treatment.
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http://dx.doi.org/10.1007/s00467-020-04714-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7815604PMC
February 2021

Phenotype expansion of heterozygous FOXC1 pathogenic variants toward involvement of congenital anomalies of the kidneys and urinary tract (CAKUT).

Genet Med 2020 10 1;22(10):1673-1681. Epub 2020 Jun 1.

Department of Pediatrics, Boston Children's Hospital/Harvard Medical School, Boston, MA, USA.

Purpose: Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney disease in childhood and adolescence. We aim to identify novel monogenic causes of CAKUT.

Methods: Exome sequencing was performed in 550 CAKUT-affected families.

Results: We discovered seven FOXC1 heterozygous likely pathogenic variants within eight CAKUT families. These variants are either never reported, or present in <5 alleles in the gnomAD database with ~141,456 controls. FOXC1 is a causal gene for Axenfeld-Rieger syndrome type 3 and anterior segment dysgenesis 3. Pathogenic variants in FOXC1 have not been detected in patients with CAKUT yet. Interestingly, mouse models for Foxc1 show severe CAKUT phenotypes with incomplete penetrance and variable expressivity. The FOXC1 variants are enriched in the CAKUT cohort compared with the control. Genotype-phenotype correlations showed that Axenfeld-Rieger syndrome or anterior segment dysgenesis can be caused by both truncating and missense pathogenic variants, and the missense variants are located at the forkhead domain. In contrast, for CAKUT, there is no truncating pathogenic variant, and all variants except one are located outside the forkhead domain.

Conclusion: We thereby expanded the phenotype of FOXC1 pathogenic variants toward involvement of CAKUT, which can potentially be explained by allelism.
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http://dx.doi.org/10.1038/s41436-020-0844-zDOI Listing
October 2020

A CRISPR-based assay for the detection of opportunistic infections post-transplantation and for the monitoring of transplant rejection.

Nat Biomed Eng 2020 06 13;4(6):601-609. Epub 2020 Apr 13.

Institute for Medical Engineering and Science and Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.

In organ transplantation, infection and rejection are major causes of graft loss. They are linked by the net state of immunosuppression. To diagnose and treat these conditions earlier, and to improve long-term patient outcomes, refined strategies for the monitoring of patients after graft transplantation are needed. Here, we show that a fast and inexpensive assay based on CRISPR-Cas13 accurately detects BK polyomavirus DNA and cytomegalovirus DNA from patient-derived blood and urine samples, as well as CXCL9 messenger RNA (a marker of graft rejection) at elevated levels in urine samples from patients experiencing acute kidney transplant rejection. The assay, which we adapted for lateral-flow readout, enables-via simple visualization-the post-transplantation monitoring of common opportunistic viral infections and of graft rejection, and should facilitate point-of-care post-transplantation monitoring.
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http://dx.doi.org/10.1038/s41551-020-0546-5DOI Listing
June 2020

Whole exome sequencing identified ATP6V1C2 as a novel candidate gene for recessive distal renal tubular acidosis.

Kidney Int 2020 03 22;97(3):567-579. Epub 2019 Oct 22.

Division of Nephrology, Department of Pediatrics, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA. Electronic address:

Distal renal tubular acidosis is a rare renal tubular disorder characterized by hyperchloremic metabolic acidosis and impaired urinary acidification. Mutations in three genes (ATP6V0A4, ATP6V1B1 and SLC4A1) constitute a monogenic causation in 58-70% of familial cases of distal renal tubular acidosis. Recently, mutations in FOXI1 have been identified as an additional cause. Therefore, we hypothesized that further monogenic causes of distal renal tubular acidosis remain to be discovered. Panel sequencing and/or whole exome sequencing was performed in a cohort of 17 families with 19 affected individuals with pediatric onset distal renal tubular acidosis. A causative mutation was detected in one of the three "classical" known distal renal tubular acidosis genes in 10 of 17 families. The seven unsolved families were then subjected to candidate whole exome sequencing analysis. Potential disease causing mutations in three genes were detected: ATP6V1C2, which encodes another kidney specific subunit of the V-type proton ATPase (1 family); WDR72 (2 families), previously implicated in V-ATPase trafficking in cells; and SLC4A2 (1 family), a paralog of the known distal renal tubular acidosis gene SLC4A1. Two of these mutations were assessed for deleteriousness through functional studies. Yeast growth assays for ATP6V1C2 revealed loss-of-function for the patient mutation, strongly supporting ATP6V1C2 as a novel distal renal tubular acidosis gene. Thus, we provided a molecular diagnosis in a known distal renal tubular acidosis gene in 10 of 17 families (59%) with this disease, identified mutations in ATP6V1C2 as a novel human candidate gene, and provided further evidence for phenotypic expansion in WDR72 mutations from amelogenesis imperfecta to distal renal tubular acidosis.
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http://dx.doi.org/10.1016/j.kint.2019.09.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7039771PMC
March 2020

CAKUT and Autonomic Dysfunction Caused by Acetylcholine Receptor Mutations.

Am J Hum Genet 2019 12 7;105(6):1286-1293. Epub 2019 Nov 7.

Department of Pediatrics, Boston Children's Hospital, Boston, MA 02115, USA. Electronic address:

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney disease in the first three decades of life, and in utero obstruction to urine flow is a frequent cause of secondary upper urinary tract malformations. Here, using whole-exome sequencing, we identified three different biallelic mutations in CHRNA3, which encodes the α3 subunit of the nicotinic acetylcholine receptor, in five affected individuals from three unrelated families with functional lower urinary tract obstruction and secondary CAKUT. Four individuals from two families have additional dysautonomic features, including impaired pupillary light reflexes. Functional studies in vitro demonstrated that the mutant nicotinic acetylcholine receptors were unable to generate current following stimulation with acetylcholine. Moreover, the truncating mutations p.Thr337Asnfs81 and p.Ser340 led to impaired plasma membrane localization of CHRNA3. Although the importance of acetylcholine signaling in normal bladder function has been recognized, we demonstrate for the first time that mutations in CHRNA3 can cause bladder dysfunction, urinary tract malformations, and dysautonomia. These data point to a pathophysiologic sequence by which monogenic mutations in genes that regulate bladder innervation may secondarily cause CAKUT.
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http://dx.doi.org/10.1016/j.ajhg.2019.10.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6904809PMC
December 2019

Ribavirin therapy of hepatitis E infection may cause hyporegenerative anemia in pediatric renal transplant patients.

Pediatr Transplant 2018 06 17;22(4):e13195. Epub 2018 Apr 17.

Faculty of Medicine, Department of General Pediatrics, Adolescent Medicine and Neonatology, Medical Center - University Freiburg, University of Freiburg, Freiburg, Germany.

HEV infection can lead to chronic hepatitis in immunosuppressed patients; extrahepatic manifestations are rarely seen. Here, we report a 13-year-old renal transplant patient with chronic hepatitis E and renal involvement. Ribavirin therapy led to temporary virus clearance and amelioration of kidney function. However, ribavirin therapy caused severe hyporegenerative anemia, which has so far only been reported in patients treated with a combination of ribavirin and interferon alpha.
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http://dx.doi.org/10.1111/petr.13195DOI Listing
June 2018

A Novel Function for P2Y2 in Myeloid Recipient-Derived Cells during Graft-versus-Host Disease.

J Immunol 2015 Dec 4;195(12):5795-804. Epub 2015 Nov 4.

Department of Hematology and Oncology, University Medical Center Freiburg, 79106 Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, Albert Ludwigs University of Freiburg, 79104 Freiburg, Germany

Acute graft-versus-host disease (GvHD) is a life-threatening complication of allogeneic hematopoietic cell transplantation. During the initiation phase of acute GvHD, endogenous danger signals such as ATP are released and inform the innate immune system via activation of the purinergic receptor P2X7 that a noninfectious damage has occurred. A second ATP-activated purinergic receptor involved in inflammatory diseases is P2Y2. In this study, we used P2y2(-/-) mice to test the role of this receptor in GvHD. P2y2(-/-) recipients experienced reduced GvHD-related mortality, IL-6 levels, enterocyte apoptosis, and histopathology scores. Chimeric mice with P2y2 deficiency restricted to hematopoietic tissues survived longer after GvHD induction than did wild-type mice. P2y2 deficiency of the recipient was connected to lower levels of myeloperoxidase in the intestinal tract of mice developing GvHD and a reduced myeloid cell signature. Selective deficiency of P2Y2 in inflammatory monocytes decreased GvHD severity. Mechanistically, P2y2(-/-) inflammatory monocytes displayed defective ERK activation and reactive oxygen species production. Compatible with a role of P2Y2 in human GvHD, the frequency of P2Y2(+) cells in inflamed GvHD lesions correlated with histopathological GvHD severity. Our findings indicate a novel function for P2Y2 in ATP-activated recipient myeloid cells during GvHD, which could be exploited when targeting danger signals to prevent GvHD.
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http://dx.doi.org/10.4049/jimmunol.1501357DOI Listing
December 2015