Publications by authors named "Hannah Hugo"

10 Publications

  • Page 1 of 1

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

variants are associated with multiple congenital anomalies including ciliopathy phenotypes.

J Med Genet 2020 Jul 6. Epub 2020 Jul 6.

Pediatric Genomics Discovery Program, Department of Pediatrics and Genetics, Yale University School of Medicine, New Haven, Connecticut, USA

Background: Cilia are dynamic cellular extensions that generate and sense signals to orchestrate proper development and tissue homeostasis. They rely on the underlying polarisation of cells to participate in signalling. Cilia dysfunction is a well-known cause of several diseases that affect multiple organ systems including the kidneys, brain, heart, respiratory tract, skeleton and retina.

Methods: Among individuals from four unrelated families, we identified variants in ( that manifested in a variety of pathologies. In our proband, we also examined patient tissues. We depleted in frog embryos to generate a loss-of-function model. Finally, we tested the pathogenicity of patient variants through rescue experiments in the frog model.

Results: Patients with variants of were found to have a variety of phenotypes including cystic kidneys, nephrotic syndrome, hydrocephalus, limb abnormalities, congenital heart disease and craniofacial malformations. We also observed a loss of cilia in cystic kidney tissue of our proband. Knockdown of in embryos recapitulated many of these phenotypes and resulted in a loss of cilia in multiple tissues. Unlike introduction of wildtype in frog embryos depleted of introduction of patient variants was largely ineffective in restoring proper ciliation and tissue morphology in the kidney and brain suggesting that the variants were indeed detrimental to function.

Conclusion: These findings in both patient tissues and shed light on how mutations in may lead to tissue-specific manifestations of disease. DLG5 is essential for cilia and many of the patient phenotypes are in the ciliopathy spectrum.
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http://dx.doi.org/10.1136/jmedgenet-2019-106805DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7785698PMC
July 2020

ADCK4 Deficiency Destabilizes the Coenzyme Q Complex, Which Is Rescued by 2,4-Dihydroxybenzoic Acid Treatment.

J Am Soc Nephrol 2020 06 7;31(6):1191-1211. Epub 2020 May 7.

Departments of Pharmacology, Yonsei University College of Medicine, Seoul, Korea

Background: Mutations in (aarF domain containing kinase 4) generally manifest as steroid-resistant nephrotic syndrome and induce coenzyme Q (CoQ) deficiency. However, the molecular mechanisms underlying steroid-resistant nephrotic syndrome resulting from mutations are not well understood, largely because the function of ADCK4 remains unknown.

Methods: To elucidate the ADCK4's function in podocytes, we generated a podocyte-specific, -knockout mouse model and a human podocyte cell line featuring knockout of . These knockout mice and podocytes were then treated with 2,4-dihydroxybenzoic acid (2,4-diHB), a CoQ precursor analogue, or with a vehicle only. We also performed proteomic mass spectrometry analysis to further elucidate ADCK4's function.

Results: Absence of in mouse podocytes caused FSGS and albuminuria, recapitulating features of nephrotic syndrome caused by mutations. studies revealed that ADCK4-knockout podocytes had significantly reduced CoQ concentration, respiratory chain activity, and mitochondrial potential, and subsequently displayed an increase in the number of dysmorphic mitochondria. However, treatment of 3-month-old knockout mice or ADCK4-knockout cells with 2,4-diHB prevented the development of renal dysfunction and reversed mitochondrial dysfunction in podocytes. Moreover, ADCK4 interacted with mitochondrial proteins such as COQ5, as well as cytoplasmic proteins such as myosin and heat shock proteins. Thus, ADCK4 knockout decreased the COQ complex level, but overexpression of ADCK4 in ADCK4-knockout podocytes transfected with wild-type ADCK4 rescued the COQ5 level.

Conclusions: Our study shows that ADCK4 is required for CoQ biosynthesis and mitochondrial function in podocytes, and suggests that ADCK4 in podocytes stabilizes proteins in complex Q in podocytes. Our study also suggests a potential treatment strategy for nephrotic syndrome resulting from mutations.
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http://dx.doi.org/10.1681/ASN.2019070756DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7269352PMC
June 2020

Mutations in KIRREL1, a slit diaphragm component, cause steroid-resistant nephrotic syndrome.

Kidney Int 2019 10 10;96(4):883-889. Epub 2019 Jul 10.

Department of Medicine, Nephrology Division, Medical University of South Carolina, Charleston, South Carolina, USA. Electronic address:

Steroid-resistant nephrotic syndrome is a frequent cause of chronic kidney disease almost inevitably progressing to end-stage renal disease. More than 58 monogenic causes of SRNS have been discovered and majority of known steroid-resistant nephrotic syndrome causing genes are predominantly expressed in glomerular podocytes, placing them at the center of disease pathogenesis. Herein, we describe two unrelated families with steroid-resistant nephrotic syndrome with homozygous mutations in the KIRREL1 gene. One mutation showed high frequency in the European population (minor allele frequency 0.0011) and this patient achieved complete remission following treatment, but later progressed to chronic kidney disease. We found that mutant KIRREL1 proteins failed to localize to the podocyte cell membrane, indicating defective trafficking and impaired podocytes function. Thus, the KIRREL1 gene product has an important role in modulating the integrity of the slit diaphragm and maintaining glomerular filtration function.
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http://dx.doi.org/10.1016/j.kint.2019.06.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6756928PMC
October 2019

Treatment with 2,4-Dihydroxybenzoic Acid Prevents FSGS Progression and Renal Fibrosis in Podocyte-Specific Knockout Mice.

J Am Soc Nephrol 2019 Feb 8. Epub 2019 Feb 8.

Division of Nephrology, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts;

Background: Although studies have identified >55 genes as causing steroid-resistant nephrotic syndrome (SRNS) and localized its pathogenesis to glomerular podocytes, the disease mechanisms of SRNS remain largely enigmatic. We recently reported that individuals with mutations in COQ6, a coenzyme Q (also called CoQ, CoQ, or ubiquinone) biosynthesis pathway enzyme, develop SRNS with sensorineural deafness, and demonstrated the beneficial effect of CoQ for maintenace of kidney function.

Methods: To study function in podocytes, we generated a podocyte-specific knockout mouse ( ) model and a transient siRNA-based knockdown in a human podocyte cell line. Mice were monitored for development of proteinuria and assessed for development of glomerular sclerosis. Using a podocyte migration assay, we compared motility in knockdown podocytes and control podocytes. We also randomly assigned 5-month-old mice and controls to receive no treatment or 2,4-dihydroxybenzoic acid (2,4-diHB), an analog of a CoQ precursor molecule that is classified as a food additive by health authorities in Europe and the United States.

Results: Abrogation of in mouse podocytes caused FSGS and proteinuria (>46-fold increases in albuminuria). studies revealed an impaired podocyte migration rate in knockdown human podocytes. Treating mice or cells with 2,4-diHB prevented renal dysfunction and reversed podocyte migration rate impairment. Survival of mice given 2,4diHB was comparable to that of control mice and significantly higher than that of untreated mice, half of which died by 10 months of age.

Conclusions: These findings reveal a potential novel treatment strategy for those cases of human nephrotic syndrome that are caused by a primary dysfunction in the CoQ biosynthesis pathway.
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http://dx.doi.org/10.1681/ASN.2018060625DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6405149PMC
February 2019

Whole-Exome Sequencing Enables a Precision Medicine Approach for Kidney Transplant Recipients.

J Am Soc Nephrol 2019 02 17;30(2):201-215. Epub 2019 Jan 17.

Division of Nephrology,

Background: Whole-exome sequencing (WES) finds a CKD-related mutation in approximately 20% of patients presenting with CKD before 25 years of age. Although provision of a molecular diagnosis could have important implications for clinical management, evidence is lacking on the diagnostic yield and clinical utility of WES for pediatric renal transplant recipients.

Methods: To determine the diagnostic yield of WES in pediatric kidney transplant recipients, we recruited 104 patients who had received a transplant at Boston Children's Hospital from 2007 through 2017, performed WES, and analyzed results for likely deleterious variants in approximately 400 genes known to cause CKD.

Results: By WES, we identified a genetic cause of CKD in 34 out of 104 (32.7%) transplant recipients. The likelihood of detecting a molecular genetic diagnosis was highest for patients with urinary stone disease (three out of three individuals), followed by renal cystic ciliopathies (seven out of nine individuals), steroid-resistant nephrotic syndrome (nine out of 21 individuals), congenital anomalies of the kidney and urinary tract (ten out of 55 individuals), and chronic glomerulonephritis (one out of seven individuals). WES also yielded a molecular diagnosis for four out of nine individuals with ESRD of unknown etiology. The WES-related molecular genetic diagnosis had implications for clinical care for five patients.

Conclusions: Nearly one third of pediatric renal transplant recipients had a genetic cause of their kidney disease identified by WES. Knowledge of this genetic information can help guide management of both transplant patients and potential living related donors.
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http://dx.doi.org/10.1681/ASN.2018060575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6362619PMC
February 2019

Mutations in multiple components of the nuclear pore complex cause nephrotic syndrome.

J Clin Invest 2018 10 4;128(10):4313-4328. Epub 2018 Sep 4.

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

Steroid-resistant nephrotic syndrome (SRNS) almost invariably progresses to end-stage renal disease. Although more than 50 monogenic causes of SRNS have been described, a large proportion of SRNS remains unexplained. Recently, it was discovered that mutations of NUP93 and NUP205, encoding 2 proteins of the inner ring subunit of the nuclear pore complex (NPC), cause SRNS. Here, we describe mutations in genes encoding 4 components of the outer rings of the NPC, namely NUP107, NUP85, NUP133, and NUP160, in 13 families with SRNS. Using coimmunoprecipitation experiments, we showed that certain pathogenic alleles weakened the interaction between neighboring NPC subunits. We demonstrated that morpholino knockdown of nup107, nup85, or nup133 in Xenopus disrupted glomerulogenesis. Re-expression of WT mRNA, but not of mRNA reflecting mutations from SRNS patients, mitigated this phenotype. We furthermore found that CRISPR/Cas9 knockout of NUP107, NUP85, or NUP133 in podocytes activated Cdc42, an important effector of SRNS pathogenesis. CRISPR/Cas9 knockout of nup107 or nup85 in zebrafish caused developmental anomalies and early lethality. In contrast, an in-frame mutation of nup107 did not affect survival, thus mimicking the allelic effects seen in humans. In conclusion, we discovered here that mutations in 4 genes encoding components of the outer ring subunits of the NPC cause SRNS and thereby provide further evidence that specific hypomorphic mutations in these essential genes cause a distinct, organ-specific phenotype.
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http://dx.doi.org/10.1172/JCI98688DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6159964PMC
October 2018

Whole-Exome Sequencing Identifies Causative Mutations in Families with Congenital Anomalies of the Kidney and Urinary Tract.

J Am Soc Nephrol 2018 09 24;29(9):2348-2361. Epub 2018 Aug 24.

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

Background: Congenital anomalies of the kidney and urinary tract (CAKUT) are the most prevalent cause of kidney disease in the first three decades of life. Previous gene panel studies showed monogenic causation in up to 12% of patients with CAKUT.

Methods: We applied whole-exome sequencing to analyze the genotypes of individuals from 232 families with CAKUT, evaluating for mutations in single genes known to cause human CAKUT and genes known to cause CAKUT in mice. In consanguineous or multiplex families, we additionally performed a search for novel monogenic causes of CAKUT.

Results: In 29 families (13%), we detected a causative mutation in a known gene for isolated or syndromic CAKUT that sufficiently explained the patient's CAKUT phenotype. In three families (1%), we detected a mutation in a gene reported to cause a phenocopy of CAKUT. In 15 of 155 families with isolated CAKUT, we detected deleterious mutations in syndromic CAKUT genes. Our additional search for novel monogenic causes of CAKUT in consanguineous and multiplex families revealed a potential single, novel monogenic CAKUT gene in 19 of 232 families (8%).

Conclusions: We identified monogenic mutations in a known human CAKUT gene or CAKUT phenocopy gene as the cause of disease in 14% of the CAKUT families in this study. Whole-exome sequencing provides an etiologic diagnosis in a high fraction of patients with CAKUT and will provide a new basis for the mechanistic understanding of CAKUT.
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http://dx.doi.org/10.1681/ASN.2017121265DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6115658PMC
September 2018

Mutations in WDR4 as a new cause of Galloway-Mowat syndrome.

Am J Med Genet A 2018 11 6;176(11):2460-2465. Epub 2018 Aug 6.

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

Galloway-Mowat syndrome (GAMOS) is a phenotypically heterogeneous disorder characterized by neurodevelopmental defects combined with renal-glomerular disease, manifesting with proteinuria. To identify additional monogenic disease causes, we here performed whole exome sequencing (WES), linkage analysis, and homozygosity mapping in three affected siblings of an Indian family with GAMOS. Applying established criteria for variant filtering, we identify a novel homozygous splice site mutation in the gene WDR4 as the likely disease-causing mutation in this family. In line with previous reports, we observe growth deficiency, microcephaly, developmental delay, and intellectual disability as phenotypic features resulting from WDR4 mutations. However, the newly identified allele additionally gives rise to proteinuria and nephrotic syndrome, a phenotype that was never reported in patients with WDR4 mutations. Our data thus expand the phenotypic spectrum of WDR4 mutations by demonstrating that, depending on the specific mutated allele, a renal phenotype may be present. This finding suggests that GAMOS may occupy a phenotypic spectrum with other microcephalic diseases. Furthermore, WDR4 is an additional example of a gene that encodes a tRNA modifying enzyme and gives rise to GAMOS, if mutated. Our findings thereby support the recent observation that, like neurons, podocytes of the renal glomerulus are particularly vulnerable to cellular defects resulting from altered tRNA modifications.
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http://dx.doi.org/10.1002/ajmg.a.40489DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6289609PMC
November 2018

Genetic variants in the LAMA5 gene in pediatric nephrotic syndrome.

Nephrol Dial Transplant 2019 03;34(3):485-493

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

Background: Nephrotic syndrome (NS), a chronic kidney disease, is characterized by significant loss of protein in the urine causing hypoalbuminemia and edema. In general, ∼15% of childhood-onset cases do not respond to steroid therapy and are classified as steroid-resistant NS (SRNS). In ∼30% of cases with SRNS, a causative mutation can be detected in one of 44 monogenic SRNS genes. The gene LAMA5 encodes laminin-α5, an essential component of the glomerular basement membrane. Mice with a hypomorphic mutation in the orthologous gene Lama5 develop proteinuria and hematuria.

Methods: To identify additional monogenic causes of NS, we performed whole exome sequencing in 300 families with pediatric NS. In consanguineous families we applied homozygosity mapping to identify genomic candidate loci for the underlying recessive mutation.

Results: In three families, in whom mutations in known NS genes were excluded, but in whom a recessive, monogenic cause of NS was strongly suspected based on pedigree information, we identified homozygous variants of unknown significance (VUS) in the gene LAMA5. While all affected individuals had nonsyndromic NS with an early onset of disease, their clinical outcome and response to immunosuppressive therapy differed notably.

Conclusion: We here identify recessive VUS in the gene LAMA5 in patients with partially treatment-responsive NS. More data will be needed to determine the impact of these VUS in disease management. However, familial occurrence of disease, data from genetic mapping and a mouse model that recapitulates the NS phenotypes suggest that these genetic variants may be inherited factors that contribute to the development of NS in pediatric patients.
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http://dx.doi.org/10.1093/ndt/gfy028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6399483PMC
March 2019