@article {989, title = {Rho-GTPase Activating Protein myosin MYO9A identified as a novel candidate gene for monogenic focal segmental glomerulosclerosis.}, journal = {Kidney Int}, volume = {99}, year = {2021}, month = {2021 05}, pages = {1102-1117}, abstract = {

Focal segmental glomerulosclerosis (FSGS) is a podocytopathy leading to kidney failure, whose molecular cause frequently remains unresolved. Here, we describe a rare MYO9A loss of function nonsense heterozygous mutation (p.Arg701) as a possible contributor to disease in a sibling pair with familial FSGS/proteinuria. MYO9A variants of uncertain significance were identified by whole exome sequencing in a cohort of 94 biopsy proven patients with FSGS. MYO9A is an unconventional myosin with a Rho-GAP domain that controls epithelial cell junction assembly, crosslinks and bundles actin and deactivates the small GTPase protein encoded by the RHOA gene. RhoA activity is associated with cytoskeleton regulation of actin stress fiber formation and actomyosin contractility. Myo9A was detected in mouse and human podocytes in~vitro and in~vivo. Knockin mice carrying the p.Arg701MYO9A (Myo9A) generated by gene editing developed proteinuria, podocyte effacement and FSGS. Kidneys and podocytes from Myo9A mutant mice revealed Myo9A haploinsufficiency, increased RhoA activity, decreased Myo9A-actin-calmodulin interaction, impaired podocyte attachment and migration. Our results indicate that Myo9A is a novel component of the podocyte cytoskeletal apparatus that regulates RhoA activity and podocyte function. Thus, Myo9A knock-in mice recapitulate the proband FSGS phenotype, demonstrate that p.R701X Myo9A is an FSGS-causing mutation in mice and suggest that heterozygous loss-of-function MYO9A mutations may cause a novel form of human autosomal dominant FSGS. Hence, identification of MYO9A pathogenic variants in additional individuals with familial or sporadic FSGS is needed to ascertain the gene contribution to disease.

}, issn = {1523-1755}, doi = {10.1016/j.kint.2020.12.022}, author = {Li, Qi and Gulati, Ashima and Lemaire, Mathieu and Nottoli, Timothy and Bale, Allen and Tufro, Alda} } @article {640, title = {Characterization of a New DGKE Intronic Mutation in Genetically Unsolved Cases of Familial Atypical Hemolytic Uremic Syndrome.}, journal = {Clin J Am Soc Nephrol}, volume = {10}, year = {2015}, month = {2015 Jun 05}, pages = {1011-9}, abstract = {

BACKGROUND AND OBJECTIVES: Genetic and acquired abnormalities causing dysregulation of the complement alternative pathway contribute to atypical hemolytic uremic syndrome (aHUS), a rare disorder characterized by thrombocytopenia, nonimmune microangiopathic hemolytic anemia, and acute kidney failure. However, in a substantial proportion of patients the disease-associated alterations are still unknown.

DESIGN, SETTING, PARTICIPANTS, \& MEASUREMENTS: Whole-exome and whole-genome sequencing were performed in two unrelated families with infantile recessive aHUS. Sequencing of cDNA from affected individuals was used to test for the presence of aberrant mRNA species. Expression of mutant diacylglycerol kinase epsilon (DGKE) protein was evaluated with western blotting.

RESULTS: Whole-exome sequencing analysis with conventional variant filtering parameters did not reveal any obvious candidate mutation in the first family. The report of aHUS-associated mutations in DGKE, encoding DGKE, led to re-examination of the noncoding DGKE variants obtained from next-generation sequencing, allowing identification of a novel intronic DGKE mutation (c.888+40A>G) that segregated with disease. Sequencing of cDNA from affected individuals revealed aberrant forms of DGKE mRNA predicted to cause profound abnormalities in the protein catalytic site. By whole-genome sequencing, the same mutation was found in compound heterozygosity with a second nonsense DGKE mutation in all affected siblings of another unrelated family. Homozygous and compound heterozygous patients presented similar clinical features, including aHUS presentation in the first year of life, multiple relapsing episodes, and proteinuria, which are prototypical of DGKE-associated aHUS.

CONCLUSIONS: This is the first report of a mutation located beyond the exon-intron boundaries in aHUS. Intronic mutations such as these are underreported because conventional filtering parameters used to process next-generation sequencing data routinely exclude these regions from downstream analyses in both research and clinical settings. The results suggest that analysis of noncoding regions of aHUS-associated genes coupled with mRNA sequencing might provide a tool to explain genetically unsolved aHUS cases.

}, keywords = {Adolescent, Atypical Hemolytic Uremic Syndrome, Base Sequence, Blotting, Western, Child, Diacylglycerol Kinase, DNA Mutational Analysis, Female, Genetic Association Studies, Genetic Predisposition to Disease, Heterozygote, Homozygote, Humans, Infant, Introns, Male, Molecular Sequence Data, Mutation, Phenotype, Predictive Value of Tests, Risk Factors}, issn = {1555-905X}, doi = {10.2215/CJN.08520814}, author = {Mele, Caterina and Lemaire, Mathieu and Iatropoulos, Paraskevas and Piras, Rossella and Bresin, Elena and Bettoni, Serena and Bick, David and Helbling, Daniel and Veith, Regan and Valoti, Elisabetta and Donadelli, Roberta and Murer, Luisa and Neunh{\"a}userer, Maria and Breno, Matteo and Fremeaux-Bacchi, Veronique and Lifton, Richard and Remuzzi, Giuseppe and Noris, Marina} } @article {306, title = {Recessive mutations in DGKE cause atypical hemolytic-uremic syndrome.}, journal = {Nat Genet}, volume = {45}, year = {2013}, month = {2013 May}, pages = {531-6}, abstract = {

Pathologic thrombosis is a major cause of mortality. Hemolytic-uremic syndrome (HUS) features episodes of small-vessel thrombosis resulting in microangiopathic hemolytic anemia, thrombocytopenia and renal failure. Atypical HUS (aHUS) can result from genetic or autoimmune factors that lead to pathologic complement cascade activation. Using exome sequencing, we identified recessive mutations in DGKE (encoding diacylglycerol kinase ɛ) that co-segregated with aHUS in nine unrelated kindreds, defining a distinctive Mendelian disease. Affected individuals present with aHUS before age 1 year, have persistent hypertension, hematuria and proteinuria (sometimes in the nephrotic range), and develop chronic kidney disease with age. DGKE is found in endothelium, platelets and podocytes. Arachidonic acid-containing diacylglycerols (DAG) activate protein kinase C (PKC), which promotes thrombosis, and DGKE normally inactivates DAG signaling. We infer that loss of DGKE function results in a prothrombotic state. These findings identify a new mechanism of pathologic thrombosis and kidney failure and have immediate implications for treating individuals with aHUS.

}, keywords = {Acute Kidney Injury, Atypical Hemolytic Uremic Syndrome, Child, Child, Preschool, Diacylglycerol Kinase, Exome, Female, Genes, Recessive, Hemolytic-Uremic Syndrome, Humans, Immunoenzyme Techniques, Infant, Male, Molecular Sequence Data, Mutation, Renal Insufficiency, Chronic, Thrombocytopenia, Thrombotic Microangiopathies}, issn = {1546-1718}, doi = {10.1038/ng.2590}, author = {Lemaire, Mathieu and Fremeaux-Bacchi, Veronique and Schaefer, Franz and Choi, Murim and Tang, Wai Ho and Le Quintrec, Moglie and Fakhouri, Fadi and Taque, Sophie and Nobili, Fran{\c c}ois and Martinez, Frank and Ji, Weizhen and Overton, John D and Mane, Shrikant M and N{\"u}rnberg, Gudrun and Altm{\"u}ller, Janine and Thiele, Holger and Morin, Denis and Deschenes, Georges and Baudouin, V{\'e}ronique and Llanas, Brigitte and Collard, Laure and Majid, Mohammed A and Simkova, Eva and N{\"u}rnberg, Peter and Rioux-Leclerc, Nathalie and Moeckel, Gilbert W and Gubler, Marie Claire and Hwa, John and Loirat, Chantal and Lifton, Richard P} }