Functional analysis of PTPN11/SHP-2 mutants identified in Noonan syndrome and childhood leukemia |
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Authors: | Tetsuya Niihori Yoko Aoki Hirofumi Ohashi Kenji Kurosawa Tatsuro Kondoh Satoshi Ishikiriyama Hiroshi Kawame Hotaka Kamasaki Tsutomu Yamanaka Fumio Takada Kimio Nishio Masahiro Sakurai Hiroshi Tamai Tatsuro Nagashima Yoichi Suzuki Shigeo Kure Kunihiro Fujii Masue Imaizumi Yoichi Matsubara |
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Affiliation: | (1) Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Sendai 980-8574, Japan;(2) Division of Medical Genetics, Saitama Childrens Medical Center, Saitama, Japan;(3) Division of Medical Genetics, Kanagawa Childrens Medical Center, Yokohama, Japan;(4) Department of Pediatrics, Nagasaki University of Medicine, Nagasaki, Japan;(5) Division of Clinical Genetics and Cytogenetics, Shizuoka Childrens Hospital, Shizuoka, Japan;(6) Division of Medical Genetics, Nagano Childrens Hospital, Nagano, Japan;(7) Department of Pediatrics, Sapporo Medical University, Sapporo, Japan;(8) Okazaki Womens Junior College, Okazaki, Japan;(9) Department of Medical Genetics, Kitasato University Graduate School of Medical Sciences, Sagamihara, Japan;(10) Department of Pediatrics, Seirei Hamamatsu General Hospital, Hamamatsu, Japan;(11) Department of Cardiovascular Surgery, Tohoku University School of Medicine, Sendai, Japan;(12) Department of Pediatrics, Osaka Medical College, Osaka, Japan;(13) Department of Pediatrics, Jikei University Hospital, Tokyo, Japan;(14) Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan;(15) Department of Hematology and Oncology, Miyagi Childrens Hospital, Sendai, Japan |
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Abstract: | Noonan syndrome (NS) is characterized by short stature, characteristic facial features, and heart defects. Recently, missense mutations of PTPN11, the gene encoding protein tyrosine phosphatase (PTP) SHP-2, were identified in patients with NS. Further, somatic mutations in PTPN11 were detected in childhood leukemia. Recent studies showed that the phosphatase activities of five mutations identified in NS and juvenile myelomonocytic leukemia (JMML) were increased. However, the functional properties of the other mutations remain unidentified. In this study, in order to clarify the differences between the mutations identified in NS and leukemia, we examined the phosphatase activity of 14 mutants of SHP-2. We identified nine mutations, including a novel F71I mutation, in 16 of 41 NS patients and two mutations, including a novel G503V mutation, in three of 29 patients with leukemia. Immune complex phosphatase assays of individual mutants transfected in COS7 cells showed that ten mutants identified in NS and four mutants in leukemia showed 1.4-fold to 12.7-fold increased activation compared with wild-type SHP-2. These results suggest that the pathogenesis of NS and leukemia is associated with enhanced phosphatase activity of mutant SHP-2. A comparison of the phosphatase activity in each mutant and a review of previously reported cases showed that high phosphatase activity observed in mutations at codons 61, 71, 72, and 76 was significantly associated with leukemogenesis. |
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Keywords: | Tyrosine phosphatase SHP-2 SHP2 PTPN11 Noonan syndrome Leukemia |
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