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De Boer, E., Ockeloen, C. W., Kampen, R. A., Hampstead, J. E., Dingemans, A. J. M., Rots, D., Lütje, L., Ashraf, T., Baker, R., Barat-Houari, M., Angle, B., Chatron, N., Denommé-Pichon, A.-S., Devinsky, O., Dubourg, C., Elmslie, F., Elloumi, H. Z., Faivre, L., Fitzgerald-Butt, S., Geneviève, D. and 30 moreDe Boer, E., Ockeloen, C. W., Kampen, R. A., Hampstead, J. E., Dingemans, A. J. M., Rots, D., Lütje, L., Ashraf, T., Baker, R., Barat-Houari, M., Angle, B., Chatron, N., Denommé-Pichon, A.-S., Devinsky, O., Dubourg, C., Elmslie, F., Elloumi, H. Z., Faivre, L., Fitzgerald-Butt, S., Geneviève, D., Goos, J. A. C., Helm, B. M., Kini, U., Lasa-Aranzasti, A., Lesca, G., Lynch, S. A., Mathijssen, I. M. J., McGowan, R., Monaghan, K. G., Odent, S., Pfundt, R., Putoux, A., Van Reeuwijk, J., Santen, G. W. E., Sasaki, E., Sorlin, A., Van der Spek, P. J., Stegmann, A. P. A., Swagemakers, S. M. A., Valenzuela, I., Viora-Dupont, E., Vitobello, A., Ware, S. M., Wéber, M., Gilissen, C., Low, K. J., Fisher, S. E., Vissers, L. E. L. M., Wong, M. M. K., & Kleefstra, T. (2022). Missense variants in ANKRD11 cause KBG syndrome by impairment of stability or transcriptional activity of the encoded protein. Genetics in Medicine, 24(10), 2051-2064. doi:10.1016/j.gim.2022.06.007.
Abstract
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. -
Wong, M. M. K., Watson, L. M., & Becker, E. B. E. (2017). Recent advances in modelling of cerebellar ataxia using induced pluripotent stem cells. Journal of Neurology & Neuromedicine, 2(7), 11-15. doi:10.29245/2572.942X/2017/7.1134.
Abstract
The cerebellar ataxias are a group of incurable brain disorders that are caused primarily by the progressive dysfunction and degeneration of cerebellar Purkinje cells. The lack of reliable disease models for the heterogeneous ataxias has hindered the understanding of the underlying pathogenic mechanisms as well as the development of effective therapies for these devastating diseases. Recent advances in the field of induced pluripotent stem cell (iPSC) technology offer new possibilities to better understand and potentially reverse disease pathology. Given the neurodevelopmental phenotypes observed in several types of ataxias, iPSC-based models have the potential to provide significant insights into disease progression, as well as opportunities for the development of early intervention therapies. To date, however, very few studies have successfully used iPSC-derived cells to cerebellar ataxias. In this review, we focus on recent breakthroughs in generating human iPSC-derived Purkinje cells. We also highlight the future challenges that will need to be addressed in order to fully exploit these models for the modelling of the molecular mechanisms underlying cerebellar ataxias and the development of effective therapeutics.
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