Browsing by Author "Kleefstra, Tjitske"

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    Missense variants in ANKRD11 cause KBG syndrome by impairment of stability or transcriptional activity of the encoded protein
    (Elsevier, 2022-10) de Boer, Elke; Ockeloen, Charlotte W.; Kampen, Rosalie A.; Hampstead, Juliet E.; Dingemans, Alexander J. M.; Rots, Dmitrijs; Lütje, Lukas; Ashraf, Tazeen; Baker, Rachel; Barat-Houari, Mouna; Angle, Brad; Chatron, Nicolas; Denommé-Pichon, Anne-Sophie; Devinsky, Orrin; Dubourg, Christèle; Elmslie, Frances; Elloumi, Houda Zghal; Faivre, Laurence; Fitzgerald-Butt, Sarah; Geneviève, David; Goos, Jacqueline A. C.; Helm, Benjamin M.; Kini, Usha; Lasa-Aranzasti, Amaia; Lesca, Gaetan; Lynch, Sally A.; Mathijssen, Irene M. J.; McGowan, Ruth; Monaghan, Kristin G.; Odent, Syvie; Pfundt, Rolph; Putoux, Audrey; van Reeuwijk, Jeroen; Santen, Gijs W. E.; Sasaki, Erina; Sorlin, Arthur; van der Spek, Peter J.; Stegmann, Alexander P. A.; Swagemakers, Sigrid M. A.; Valenzuela, Irene; Viora-Dupont, Eléonore; Vitobello, Antonio; Ware, Stephanie M.; Wéber, Mathys; Gilissen, Christian; Low, Karen J.; Fisher, Simon E.; Vissers, Lisenka E. L. M.; Wong, Maggie M. K.; Kleefstra, Tjitske; Pediatrics, School of Medicine
    Purpose Although haploinsufficiency of ANKRD11 is among the most common genetic causes of neurodevelopmental disorders, the role of rare ANKRD11 missense variation remains unclear. We characterized clinical, molecular, and functional spectra of ANKRD11 missense variants. Methods We collected clinical information of individuals with ANKRD11 missense variants and evaluated phenotypic fit to KBG syndrome. We assessed pathogenicity of variants through in silico analyses and cell-based experiments. Results We identified 20 unique, mostly de novo, ANKRD11 missense variants in 29 individuals, presenting with syndromic neurodevelopmental disorders similar to KBG syndrome caused by ANKRD11 protein truncating variants or 16q24.3 microdeletions. Missense variants significantly clustered in repression domain 2 at the ANKRD11 C-terminus. Of the 10 functionally studied missense variants, 6 reduced ANKRD11 stability. One variant caused decreased proteasome degradation and loss of ANKRD11 transcriptional activity. Conclusion Our study indicates that pathogenic heterozygous ANKRD11 missense variants cause the clinically recognizable KBG syndrome. Disrupted transrepression capacity and reduced protein stability each independently lead to ANKRD11 loss-of-function, consistent with haploinsufficiency. This highlights the diagnostic relevance of ANKRD11 missense variants, but also poses diagnostic challenges because the KBG-associated phenotype may be mild and inherited pathogenic ANKRD11 (missense) variants are increasingly observed, warranting stringent variant classification and careful phenotyping.
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    WDR26 Haploinsufficiency Causes a Recognizable Syndrome of Intellectual Disability, Seizures, Abnormal Gait, and Distinctive Facial Features
    (Elsevier, 2017-07-06) Skraban, Cara M.; Wells, Constance F.; Markose, Preetha; Cho, Megan T.; Nesbitt, Addie I.; Au, P.Y. Billie; Begtrup, Amber; Bernat, John A.; Bird, Lynne M.; Cao, Kajia; de Brouwer, Arjan P.M.; Denenberg, Elizabeth H.; Douglas, Ganka; Gibson, Kristin M.; Grand, Katheryn; Goldenberg, Alice; Innes, A. Micheil; Juusola, Jane; Kempers, Marlies; Kinning, Esther; Markie, David M.; Owens, Martina M.; Payne, Katelyn; Person, Richard; Pfundt, Rolph; Stocco, Amber; Turner, Claire L.S.; Verbeek, Nienke E.; Walsh, Laurence E.; Warner, Taylor C.; Wheeler, Patricia G.; Wieczorek, Dagmar; Wilkens, Alisha B.; Zonneveld-Huijssoon, Evelien; Deciphering Developmental Disorders Study; Kleefstra, Tjitske; Robertson, Stephen P.; Santani, Avni; van Gassen, Koen L.I.; Deardorf, Matthew A.; Pediatrics, School of Medicine
    We report 15 individuals with de novo pathogenic variants in WDR26. Eleven of the individuals carry loss-of-function mutations, and four harbor missense substitutions. These 15 individuals comprise ten females and five males, and all have intellectual disability with delayed speech, a history of febrile and/or non-febrile seizures, and a wide-based, spastic, and/or stiff-legged gait. These subjects share a set of common facial features that include a prominent maxilla and upper lip that readily reveal the upper gingiva, widely spaced teeth, and a broad nasal tip. Together, these features comprise a recognizable facial phenotype. We compared these features with those of chromosome 1q41q42 microdeletion syndrome, which typically contains WDR26, and noted that clinical features are consistent between the two subsets, suggesting that haploinsufficiency of WDR26 contributes to the pathology of 1q41q42 microdeletion syndrome. Consistent with this, WDR26 loss-of-function single-nucleotide mutations identified in these subjects lead to nonsense-mediated decay with subsequent reduction of RNA expression and protein levels. We derived a structural model of WDR26 and note that missense variants identified in these individuals localize to highly conserved residues of this WD-40-repeat-containing protein. Given that WDR26 mutations have been identified in ∼1 in 2,000 of subjects in our clinical cohorts and that WDR26 might be poorly annotated in exome variant-interpretation pipelines, we would anticipate that this disorder could be more common than currently appreciated.