Galloway-Mowat Syndrome Research Articles

A Rare Late Presentation of Galloway Mowat Syndrome (GAMOS) with Membranous Nephropathy

A Rare Late Presentation of Galloway Mowat Syndrome (GAMOS) with Membranous Nephropathy

O-Sialoglycoprotein Endopeptidase Deficiency Impairs Proteostasis and Induces Autophagy in Human Embryonic Stem Cells.

The OSGEP gene encodes O-sialoglycoprotein endopeptidase, a catalytic unit of the highly conserved KEOPS complex (Kinase, Endopeptidase, and Other Proteins of small Size) that regulates the second biosynthetic step in the formation of N-6-threonylcarbamoyladenosine (t6A). Mutations in KEOPS cause Galloway-Mowat syndrome (GAMOS), whose cellular function in mammals and underlying molecular mechanisms are not well understood. In this study, we utilized lentivirus-mediated OSGEP knockdown to generate OSGEP-deficient human embryonic stem cells (hESCs). OSGEP-knockdown hESCs exhibited reduced stemness factor expression and G2/M phase arrest, indicating a potential role of OSGEP in the regulation of hESC fate. Additionally, OSGEP silencing led to enhanced protein synthesis and increased aggregation of proteins, which further induced inappropriate autophagy, as evidenced by the altered expression of P62 and the conversion of LC3-I to LC3-II. The above findings shed light on the potential involvement of OSGEP in regulating pluripotency and differentiation in hESCs while simultaneously highlighting its crucial role in maintaining proteostasis and autophagy, which may have implications for human disease.

Prdm15 acts upstream of Wnt4 signaling in anterior neural development of Xenopus laevis.

Mutations in PRDM15 lead to a syndromic form of holoprosencephaly (HPE) known as the Galloway-Mowat syndrome (GAMOS). While a connection between PRDM15, a zinc finger transcription factor, and WNT/PCP signaling has been established, there is a critical need to delve deeper into their contributions to early development and GAMOS pathogenesis. We used the South African clawed frog Xenopus laevis as the vertebrate model organism and observed that prdm15 was enriched in the tissues and organs affected in GAMOS. Furthermore, we generated a morpholino oligonucleotide-mediated prdm15 knockdown model showing that the depletion of Prdm15 leads to abnormal eye, head, and brain development, effectively recapitulating the anterior neural features in GAMOS. An analysis of the underlying molecular basis revealed a reduced expression of key genes associated with eye, head, and brain development. Notably, this reduction could be rescued by the introduction of wnt4 RNA, particularly during the induction of the respective tissues. Mechanistically, our data demonstrate that Prdm15 acts upstream of both canonical and non-canonical Wnt4 signaling during anterior neural development. Our findings describe severe ocular and anterior neural abnormalities upon Prdm15 depletion and elucidate the role of Prdm15 in canonical and non-canonical Wnt4 signaling.

Two non-familial cases of Galloway-Mowat syndrome carrying the homozygous mutations of WDR73 and TP53RK

Galloway–Mowat syndrome (GAMOS) is a rare hereditary disease manifested as a combination of nephrotic syndrome and central nervous system impairment. To date, many GAMOS cases attributed to various gene mutations have been reported such as WHAMM, NUP107, WDR73, OSGEP, and TP53RK. We detected two novel homozygous mutations of WDR73 ‘’NM_032856:c.G287A:p.R96K‘’ and TP53RK ‘’NM_033550:c.A193O:p.K65Q‘’ in two female kids of the consanguineous parents from different families using whole exome sequencing. Both patients almost manifested similar neurodegenerative phenotypes, including developmental delay, microcephaly, hypotonia, and brain atrophy on magnetic resonance imaging during infancy. WDR73-positive GAMOS case manifested a late-onset minimal nephrotic syndrome at the age 4 years while TP53RK-positive case presented nephrotic syndrome at the age 1 which progressed to steroid-resistant nephrotic syndrome due to lack of remission after 4-6 weeks of initial treatment with prednisone. Despite the brain abnormalities and the onset time difference of renal abnormalities, both patients are still alive. Given the heterogeneity of the renal phenotype among GAMOS types, accurate recognition of expanding spectrum of phenotype findings and regular renal function screening are necessary for an early diagnosis and timely treatment.

ER stress and slit diaphragms: is there a connection?

Galloway-Mowat syndrome is a neurorenal syndrome that has beenlinked with defective transfer RNA and protein translation caused by variants in the multiprotein complex KEOPS. In the kidney,this syndrome seems to primarily affect the podocytes, butthepathogenesis has remained unclear. In this issue of KidneyInternational, Krausel etal. use Drosophila nephrocytes tolinkendoplasmic reticulum stress with defects in the slit diaphragm.

Whole-exome sequencing revealed a novel homozygous missense variant in OSGEP gene: a case report of Galloway-Mowat syndrome in Iran.

Galloway-Mowat syndrome is a rare autosomal-recessive genetic disorder that is characterized by variety of complications such as neurological abnormalities and early-onset progressive kidney disease. Studies have been shown that pathogenic mutations in genes that belong to the KEOPS complex lead to Galloway-Mowat syndrome. Several pathogenic mutations in OSGEP gene, a member of the KEOPS complex, have been detected in Galloway-Mowat syndrome. Here we describe a 12-year-old male with intellectual disability, poor speech, seizures, microcephaly, and nephrotic syndrome that were in favor of Galloway-Mowat syndrome, born to a healthy Iranian consanguineous parents. Extracted genomic DNA from blood sample was used to perform whole-exome sequencing in the patient. The mutational screening revealed a novel homozygote OSGEP gene missense variant. Our finding established whole-exome sequencing as a valuable technic for the detection of rare variants.

X-linked recessive Galloway-Mowat syndrome 2 caused by a specific LAGE3 variant.

X-linked recessive Galloway-Mowat syndrome 2 caused by a specific LAGE3 variant.

Novel TP53RK variants cause varied clinical features of Galloway-Mowat syndrome without nephrotic syndrome in three unrelated Chinese patients.

Galloway-Mowat syndrome-4 (GAMOS4) is a very rare renal-neurological disease caused by TP53RK gene mutations. GAMOS4 is characterized by early-onset nephrotic syndrome, microcephaly, and brain anomalies. To date, only nine GAMOS4 cases with detailed clinical data (caused by eight deleterious variants in TP53RK) have been reported. This study aimed to examine the clinical and genetic characteristics of three unrelated GAMOS4 patients with TP53RK gene compound heterozygous mutations. Whole-exome sequencing (WES) was used to identify four novel TP53RK variants in three unrelated Chinese children. Clinical characteristics such as biochemical parameters and image findings of patients were also evaluated. Furthermore, four studies of GAMOS4 patients with TP53RK variants were reviewed. In addition, clinical and genetic features were described after a retrospective analysis of clinical symptoms, laboratory data, and genetic test results. The three patients showed facial abnormalities, developmental delays, microcephaly, and aberrant cerebral imaging. Furthermore, patient 1 had slight proteinuria, while patient 2 had epilepsy. However, none of the individuals had nephrotic syndrome, and all were alive for more than 3 years of age. This is the first study to assess four variants in the TP53RK gene (NM_033550.4: c.15_16dup/p.A6Efs*29, c.745A > G/p.R249G, c.185G > A/p.R62H, and c.335A > G/p.Y112C). The clinical characteristics of the three children with TP53RK mutations are significantly different from the known GAMOS4 traits, including early nephrotic syndrome and mortality mainly occurring in the first year of life. This study provides insights into the pathogenic TP53RK gene mutation spectrum and clinical phenotypes of GAMOS4.

Diagnosis delay a family of Galloway-Mowat Syndrome caused by a classical splicing mutation of Lage3

BackgroundGalloway-Mowat syndrome (GAMOS) is a group of rare hereditary diseases by the combination of early onset steroid-resistant nephrotic syndrome (SRNS) and microcephaly with brain anomalies caused by WDR73, LAGE3, OSGEP, TP53RK, TPRKB, GON7, WDR4 or NUP133 mutations.Case presentationWe present the clinical and genetic features of a two-year-old boy with early nephrotic syndrome, microcephaly, growth retardation hypotonia and hypothyroidism. Genetic testing showed the presence of a canonical-splice mutation in the LAGE3 gene (NM_006014: c.188 + 1C > T). A total of nine female members of the family carried the variant. Seven male members died prematurely, and three of them suffered from nephrotic syndrome, which is consistent with the x-linked gene map of the disease. The overall symptoms of the disease due to the LAGE3 mutation were mild compared to other pathogenic genes.ConclusionAs far as we know, this is the largest family case of GAMOS2 caused by LAGE3 mutation found so far. We also compared other subtypes of GAMOS. Due to the heterogeneity of the renal phenotype, regular proteinuria screening is recommended for all patients diagnosed with GAMOS.

Wdr4 promotes cerebellar development and locomotion through Arhgap17-mediated Rac1 activation

Patients with mutations of WDR4, a substrate adaptor of the CUL4 E3 ligase complex, develop cerebellar atrophy and gait phenotypes. However, the underlying mechanisms remain unexplored. Here, we identify a crucial role of Wdr4 in cerebellar development. Wdr4 deficiency in granule neuron progenitors (GNPs) not only reduces foliation and the sizes of external and internal granular layers but also compromises Purkinje neuron organization and the size of the molecular layer, leading to locomotion defects. Mechanistically, Wdr4 supports the proliferation of GNPs by preventing their cell cycle exit. This effect is mediated by Wdr4-induced ubiquitination and degradation of Arhgap17, thereby activating Rac1 to facilitate cell cycle progression. Disease-associated Wdr4 variants, however, cannot provide GNP cell cycle maintenance. Our study identifies Wdr4 as a previously unappreciated participant in cerebellar development and locomotion, providing potential insights into treatment strategies for diseases with WDR4 mutations, such as primordial dwarfism and Galloway-Mowat syndrome.

The transcription factor ATF4 mediates endoplasmic reticulum stress-related podocyte injury and slit diaphragm defects

Mutations in OSGEP and four other genes that encode subunits of the KEOPS complex cause Galloway-Mowat syndrome, a severe, inherited kidney-neurological disease. The complex catalyzes an essential posttranscriptional modification of tRNA and its loss of function induces endoplasmic reticulum (ER) stress. Here, using Drosophila melanogaster garland nephrocytes and cultured human podocytes, we aimed to elucidate the molecular pathogenic mechanisms of KEOPS-related glomerular disease and to test pharmacological inhibition of ER stress-related signaling as a therapeutic principle. We found that ATF4, an ER stress-mediating transcription factor, or its fly orthologue Crc, were upregulated in both fly nephrocytes and human podocytes. Knockdown of Tcs3, a fly orthologue of OSGEP, caused slit diaphragm defects, recapitulating the human kidney phenotype. OSGEP cDNA with mutations found in patients lacked the capacity for rescue. Genetic interaction studies in Tcs3-deficient nephrocytes revealed that Crc mediates not only cell injury, but surprisingly also slit diaphragm defects, and that genetic or pharmacological inhibition of Crc activation attenuates both phenotypes. These findings are conserved in human podocytes where ATF4 inhibition improved the viability of podocytes with OSGEP knockdown, with chemically induced ER stress, and where ATF4 target genes and pro-apoptotic gene clusters are upregulated upon OSGEP knockdown. Thus, our data identify ATF4-mediated signaling as a molecular link among ER stress, slit diaphragm defects, and podocyte injury, and our data suggest that modulation of ATF4 signaling may be a potential therapeutic target for certain podocyte diseases.

Conservation and Diversification of tRNA t6A-Modifying Enzymes across the Three Domains of Life.

The universal N6-threonylcarbamoyladenosine (t6A) modification occurs at position 37 of tRNAs that decipher codons starting with adenosine. Mechanistically, t6A stabilizes structural configurations of the anticodon stem loop, promotes anticodon-codon pairing and safeguards the translational fidelity. The biosynthesis of tRNA t6A is co-catalyzed by two universally conserved protein families of TsaC/Sua5 (COG0009) and TsaD/Kae1/Qri7 (COG0533). Enzymatically, TsaC/Sua5 protein utilizes the substrates of L-threonine, HCO3-/CO2 and ATP to synthesize an intermediate L-threonylcarbamoyladenylate, of which the threonylcarbamoyl-moiety is subsequently transferred onto the A37 of substrate tRNAs by the TsaD-TsaB -TsaE complex in bacteria or by the KEOPS complex in archaea and eukaryotic cytoplasm, whereas Qri7/OSGEPL1 protein functions on its own in mitochondria. Depletion of tRNA t6A interferes with protein homeostasis and gravely affects the life of unicellular organisms and the fitness of higher eukaryotes. Pathogenic mutations of YRDC, OSGEPL1 and KEOPS are implicated in a number of human mitochondrial and neurological diseases, including autosomal recessive Galloway-Mowat syndrome. The molecular mechanisms underscoring both the biosynthesis and cellular roles of tRNA t6A are presently not well elucidated. This review summarizes current mechanistic understandings of the catalysis, regulation and disease implications of tRNA t6A-biosynthetic machineries of three kingdoms of life, with a special focus on delineating the structure-function relationship from perspectives of conservation and diversity.

WDR73 Depletion Destabilizes PIP4K2C Activity and Impairs Focal Adhesion Formation in Galloway-Mowat Syndrome.

Simple SummaryGalloway–Mowat syndrome is a rare genetic disease, classically characterized by a combination of various neurological symptoms and nephrotic syndrome. WDR73 is the pathogenic gene responsible for Galloway–Mowat syndrome. However, the pathological and molecular mechanisms of Galloway–Mowat syndrome, especially nephrotic syndrome caused by WDR73 deficiency, remains unknown. In this study, we knocked out the WDR73 in human embryonic kidney 293 cells to observe the morphological characteristics of the cells and elucidate the functions of WDR73. Additionally, we used a combination of proteomics, transcriptomics, and biochemical assays to identify the regulated targets of WDR73. We aimed to discover directly interacting molecules and the regulatory pathway of WDR73 and to illustrate the molecular mechanism between the WDR73 pathway and nephrotic disease in Galloway–Mowat syndrome. From the molecular mechanism we found in vitro, we draw a hypothesis that the damage to focal adhesion of podocytes caused by WDR73 defect is the key issue of kidney dysfunction. Finally, we verified the hypothesis in a podocyte-specific conditional knockout Wdr73 mouse model.(1) Background: Galloway–Mowat syndrome (GAMOS) is a rare genetic disease, classically characterized by a combination of various neurological symptoms and nephrotic syndrome. WDR73 is the pathogenic gene responsible for GAMOS1. However, the pathological and molecular mechanisms of GAMOS1, especially nephrotic syndrome caused by WDR73 deficiency, remain unknown. (2) Methods and Results: In this study, we first observed remarkable cellular morphological changes including impaired cell adhesion, decreased pseudopodia, and G2/M phase arrest in WDR73 knockout (KO) HEK 293 cells. The differentially expressed genes in WDR73 KO cells were enriched in the focal adhesion (FA) pathway. Additionally, PIP4K2C, a phospholipid kinase also involved in the FA pathway, was subsequently validated to interact with WDR73 via protein microarray and GST pulldown. WDR73 regulates PIP4K2C protein stability through the autophagy–lysosomal pathway. The stability of PIP4K2C was significantly disrupted by WDR73 KO, leading to a remarkable reduction in PIP2 and thus weakening the FA formation. In addition, we found that podocyte-specific conditional knockout (Wdr73 CKO) mice showed high levels of albuminuria and podocyte foot process injury in the ADR-induced model. FA formation was impaired in primary podocytes derived from Wdr73 CKO mice. (3) Conclusions: Since FA has been well known for its critical roles in maintaining podocyte structures and function, our study indicated that nephrotic syndrome in GAMOS1 is associated with disruption of FA caused by WDR73 deficiency.

Genomic, Proteomic, and Phenotypic Spectrum of Novel O-Sialoglycoprotein Endopeptidase Variant in Four Affected Individuals With Galloway-Mowat Syndrome.

Galloway-Mowat syndrome is a rare autosomal recessive disease characterized by a unique combination of renal and neurological manifestations, including early-onset steroid-resistant nephrotic syndrome, microcephaly, psychomotor delay, and gyral abnormalities of the brain. Most patients die during early childhood. Here, we identified a novel homozygous O-sialoglycoprotein endopeptidase (OSGEP) variant, NM_017807.3:c.973C>G (p.Arg325Gly), in four affected individuals in an extended consanguineous family from Saudi Arabia. We have described the detailed clinical characterization, brain imaging results, and muscle biopsy findings. The described phenotype varied from embryonic lethality to early pregnancy loss or death at the age of 9. Renal disease is often the cause of death. Protein modeling of this OSGEP variant confirmed its pathogenicity. In addition, proteomic analysis of the affected patients proposed a link between the KEOPS complex function and human pathology and suggested potential pathogenic mechanisms.

Commonality and diversity in tRNA substrate recognition in t6A biogenesis by eukaryotic KEOPSs.

N 6-Threonylcarbamoyladenosine (t6A) is a universal and pivotal tRNA modification. KEOPS in eukaryotes participates in its biogenesis, whose mutations are connected with Galloway-Mowat syndrome. However, the tRNA substrate selection mechanism by KEOPS and t6A modification function in mammalian cells remain unclear. Here, we confirmed that all ANN-decoding human cytoplasmic tRNAs harbor a t6A moiety. Using t6A modification systems from various eukaryotes, we proposed the possible coevolution of position 33 of initiator tRNAMet and modification enzymes. The role of the universal CCA end in t6A biogenesis varied among species. However, all KEOPSs critically depended on C32 and two base pairs in the D-stem. Knockdown of the catalytic subunit OSGEP in HEK293T cells had no effect on the steady-state abundance of cytoplasmic tRNAs but selectively inhibited tRNAIle aminoacylation. Combined with in vitro aminoacylation assays, we revealed that t6A functions as a tRNAIle isoacceptor-specific positive determinant for human cytoplasmic isoleucyl-tRNA synthetase (IARS1). t6A deficiency had divergent effects on decoding efficiency at ANN codons and promoted +1 frameshifting. Altogether, our results shed light on the tRNA recognition mechanism, revealing both commonality and diversity in substrate recognition by eukaryotic KEOPSs, and elucidated the critical role of t6A in tRNAIle aminoacylation and codon decoding in human cells.

シクロスポリン投与によりステロイド抵抗性ネフローゼ症候群の長期寛解を維持しているGalloway-Mowat症候群の1例

シクロスポリン投与によりステロイド抵抗性ネフローゼ症候群の長期寛解を維持しているGalloway-Mowat症候群の1例

A suite of in vitro and in vivo assays for monitoring the activity of the pseudokinase Bud32.

Bud32 is a member of the protein kinase superfamily that is invariably conserved in all eukaryotic and archaeal organisms. In both of these kingdoms, Bud32 forms part of the KEOPS (Kinase, Endopeptidase and Other Proteins of Small size) complex together with the three other core subunits Kae1, Cgi121 and Pcc1. KEOPS functions to generate the universal and essential tRNA post-transcriptional modification N6-theronylcarbamoyl adenosine (t6A), which is present at position A37 in all tRNAs that bind to codons with an A in the first position (ANN decoding tRNAs) and is essential for the fidelity of translation. Mutations in KEOPS genes in humans underlie the severe genetic disease Galloway-Mowat syndrome, which results in childhood death. KEOPS activity depends on two major functions of Bud32. Firstly, Bud32 facilitates efficient tRNA substrate recruitment to KEOPS and helps in positioning the A37 site of the tRNA in the active site of Kae1, which carries out the t6A modification reaction. Secondly, the enzymatic activity of Bud32 is required for the ability of KEOPS to modify tRNA. Unlike conventional protein kinases, which employ their enzymatic activity for phosphorylation of protein substrates, Bud32 employs its enzymatic activity to function as an ATPase. Herein, we present a comprehensive suite of assays to monitor the activity of Bud32 in KEOPS in vitro and in vivo. We present protocols for the purification of the archaeal KEOPS proteins and of a tRNA substrate, as well as protocols for monitoring the ATPase activity of Bud32 and for analyzing its role in tRNA binding. We further present a complementary protocol for monitoring the role Bud32 has in cell growth in yeast.

The Role of Mutations on Gene WDR73 in Galloway-Mowat Syndrome

Galloway-Mowat syndrome is a very rare genetic disorder characterized by a variety of physical and developmental abnormalities, especially neurological abnormalities and progressive primary kidney disease. Physical characteristics may include microcephaly (a condition that indicates that the size of the head circumference is significantly smaller than expected for the child’s age and sex) and, in some cases, protrusion of part of the stomach through an abnormal opening in the diaphragm. Galloway-Mowat syndrome is caused by changes (mutations) in the WDR73 gene in a subset of cases.

Late-onset nephrotic syndrome with thyroid hypoplasia and nup85 mutation in Galloway-Mowat syndrome: A case report

Galloway-Mowat syndrome is an autosomal recessive rare hereditary disorder with progressively worsening renal function, neurological and psychomotor abnormalities, microcephaly, facial dysmorphism, and thyroid, adrenal, and ovarian hypoplasia/agenesis. Here, we present the case of a 9-year-old girl who presented with late-onset steroid-resistant nephrotic syndrome with rapid worsening of renal function, microcephaly, hypertelorism, high-arched palate, delayed speech and developmental milestones, poor intellectual function, short stature, hypertension, and hypothyroidism. Magnetic resonance imaging brain was suggestive of cerebral and cerebellar atrophy, hypomyelination, and optic atrophy. Renal biopsy was suggestive of focal segmental glomerulosclerosis. Whole-genome exon sequencing revealed a homozygous mutation in the NUP85 gene. The clinicians should be aware of this rare syndrome and consider it as a possibility in any patient presenting with nephrotic syndrome, microcephaly, and neurological abnormality.

Novel variants in OSGEP leading to Galloway-Mowat syndrome by altering its subcellular localization

Galloway-Mowat syndrome (GAMOS) is an extremely rare clinically heterogeneous autosomal or X-linked inherited recessive disease characterized by early-onset steroid-resistant nephrotic syndrome (SRNS), microcephaly and neurological impairment. In this study, two siblings mainly presenting with decreased head circumference, hypotonia, gross motor delay, and dysmorphic features were initially detected without pathogenic variants by karyotyping, SNP-array and WES. After a 3 year’s follow-up, the proband manifested additional proteinuria, hematuria and “deeper sulci” with a sign of brain atrophy. By reanalysis on the proband’s previous WES data, two novel compound heterozygous variants of OSGEP (c.133dupA; c.608C > T) were identified. Furthermore, functional studies showed that the variants reduced the expression of OSGEP protein and activated the DNA damage response (DDR) signaling in the lymphoblastoid cell lines (LCLs) obtained from the patient. The analysis of protein localization with confocal microscopy revealed that the EGFP-tagged/HA-tagged mutant OSGEP proteins were abnormal aggregation or retained inside the cytosol, respectively. Our study not only expanded the pathogenic variant spectrum of OSGEP but also carried on regular follow-up for kidney involvement and established a strategy for evaluation on the function of mutant OSGFP by subcellular localization assay.