Loss-of-function mutations in PTPRJ cause a new form of inherited thrombocytopenia

Caterina Marconi, Christian A. DI Buduo, Kellie LeVine, Serena Barozzi, Michela Faleschini, Valeria Bozzi, Flavia Palombo, Spencer McKinstry, Giuseppe Lassandro, Paola Giordano, Patrizia Noris, Carlo L. Balduini, Anna Savoia, Alessandra Balduini, Tommaso Pippucci, Marco Seri*, Elias Nicholas Katsanis, Alessandro Pecci

*Corresponding author for this work

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

Inherited thrombocytopenias (ITs) are a heterogeneous group of disorders characterized by low platelet count that may result in bleeding tendency. Despite progress being made in defining the genetic causes of ITs, nearly 50% of patients with familial thrombocytopenia are affected with forms of unknown origin. Here, through exome sequencing of 2 siblings with autosomal-recessive thrombocytopenia, we identified biallelic loss-offunction variants in PTPRJ. This gene encodes for a receptor-like PTP, PTPRJ (or CD148), which is expressed abundantly in platelets and megakaryocytes. Consistent with the predicted effects of the variants, both probands have an almost complete loss of PTPRJ at the messenger RNA and protein levels. To investigate the pathogenic role of PTPRJ deficiency in hematopoiesis in vivo, we carried out CRISPR/Cas9-mediated ablation of ptprja (the ortholog of human PTPRJ) in zebrafish, which induced a significantly decreased number of CD41+ thrombocytes in vivo. Moreover, megakaryocytes of our patients showed impaired maturation and profound defects in SDF1-driven migration and formation of proplatelets in vitro. Silencing of PTPRJ in a human megakaryocytic cell line reproduced the functional defects observed in patients' megakaryocytes. The disorder caused by PTPRJ mutations presented as a nonsyndromic thrombocytopenia characterized by spontaneous bleeding, small-sized platelets, and impaired platelet responses to the GPVI agonists collagen and convulxin. These platelet functional defects could be attributed to reduced activation of Src family kinases. Taken together, our data identify a new form of IT and highlight a hitherto unknown fundamental role for PTPRJ in platelet biogenesis.

Original languageEnglish (US)
Pages (from-to)1346-1357
Number of pages12
JournalBlood
Volume133
Issue number12
DOIs
StatePublished - Jan 1 2019

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

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    Marconi, C., DI Buduo, C. A., LeVine, K., Barozzi, S., Faleschini, M., Bozzi, V., Palombo, F., McKinstry, S., Lassandro, G., Giordano, P., Noris, P., Balduini, C. L., Savoia, A., Balduini, A., Pippucci, T., Seri, M., Katsanis, E. N., & Pecci, A. (2019). Loss-of-function mutations in PTPRJ cause a new form of inherited thrombocytopenia. Blood, 133(12), 1346-1357. https://doi.org/10.1182/blood-2018-07-859496