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Published on: May 17, 2013
Pathogenetic basis of Takenouchi-Kosaki syndrome: Electron microscopy study using platelets in patients and
Tomoko Uehara1, Hidenori Suzuki2, Nobuhiko Okamoto3
1Center for Medical Genetics, Keio University School of Medicine, Tokyo, Japan.
The combined phenotype of thrombocytopenia accompanied by intellectual disability in patients with a de novo heterozygous mutation, i.e., p.Tyr64Cys in CDC42, signifies a clinically recognizable novel syndrome that has been eponymized as "Takenouchi-Kosaki syndrome" (OMIM #616737). In the present study, a detailed phenotypic analysis performed for a total of five patients with Takenouchi-Kosaki syndrome revealed that intellectual disability, macrothrombocytopenia, camptodactyly, structural brain abnormalities with sensorineural deafness, hypothyroidism, and frequent infections comprise the cardinal features of this condition. A morphologic analysis of platelets derived from three affected individuals was performed using electron microscopy. The platelets of the three patients were large and spherical in shape. Furthermore, platelet α-granules were decreased, while vacuoles were increased. We further performed a functional analysis of p.Tyr64Cys in CDC42 through CRISPR/Cas9-mediated gene editing in a Caenorhabditis elegans model. This functional analysis suggested that the mutant allele has hypomorphic effects. Takenouchi-Kosaki syndrome is clinically recognizable by the combined phenotype of intellectual disability, macrothrombocytopenia, camptodactyly, structural brain abnormalities with sensorineural deafness, hypothyroidism, and frequent infections as well as the identification of a heterozygous de novo mutation in CDC42, i.e., p.Tyr64Cys.
The combined phenotype of thrombocytopenia accompanied by intellectual disability in patients with a de novo heterozygous mutation, i.e., p.Tyr64Cys in CDC42, signifies a clinically recognizable novel syndrome that has been eponymized as "Takenouchi-Kosaki syndrome" (OMIM #616737). In the present study, a detailed phenotypic analysis performed for a total of five patients with Takenouchi-Kosaki syndrome revealed that intellectual disability, macrothrombocytopenia, camptodactyly, structural brain abnormalities with sensorineural deafness, hypothyroidism, and frequent infections comprise the cardinal features of this condition. A morphologic analysis of platelets derived from three affected individuals was performed using electron microscopy. The platelets of the three patients were large and spherical in shape. Furthermore, platelet α-granules were decreased, while vacuoles were increased. We further performed a functional analysis of p.Tyr64Cys in CDC42 through CRISPR/Cas9-mediated gene editing in a Caenorhabditis elegans model. This functional analysis suggested that the mutant allele has hypomorphic effects. Takenouchi-Kosaki syndrome is clinically recognizable by the combined phenotype of intellectual disability, macrothrombocytopenia, camptodactyly, structural brain abnormalities with sensorineural deafness, hypothyroidism, and frequent infections as well as the identification of a heterozygous de novo mutation in CDC42, i.e., p.Tyr64Cys.
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