title: Expression of myotubularins in blood platelets: Characterization and potential diagnostic of X-linked myotubular myopathy.
abstract: Phosphoinositides play a key role in the spatiotemporal control of central intracellular processes and several specific kinases and phosphatases regulating the level of these lipids are implicated in human diseases. Myotubularins are a family of 3-phosphatases acting specifically on phosphatidylinositol 3-monophosphate and phosphatidylinositol 3,5 bisphosphate. Members of this family are mutated in genetic diseases including myotubularin 1 (MTM1) and myotubularin-related protein 2 (MTMR2) which mutations are responsible of X-linked centronuclear myopathy and Charcot-Marie-Tooth neuropathy, respectively. Here we show that MTM1 is expressed in blood platelets and that hundred microliters of blood is sufficient to detect the protein by western blotting. Since the most severe cases of pathogenic mutations of MTM1 lead to loss of expression of the protein, we propose that a minimal amount of blood can allow a rapid diagnostic test of X-linked myotubular myopathy, which is currently based on histopathology of muscle biopsy and molecular genetic testing. In platelets, MTM1 is a highly active 3-phosphatase mainly associated to membranes and found on the dense granules and to a lesser extent on alpha-granules. However, deletion of MTM1 in mouse had no significant effect on platelet count and on platelet secretion and aggregation induced by thrombin or collagen stimulation. Potential compensation by other members of the myotubularin family is conceivable since MTMR2 was easily detectable by western blotting and the mRNA of several members of the family increased during in vitro differentiation of human megakaryocytes and MEG-01 cells. In conclusion, we show the presence of several myotubularins in platelets and propose that minimal amounts of blood can be used to develop a rapid diagnostic test for genetic pathologies linked to loss of expression of these phosphatases.
authors.affiliation: INSERM, U1048 and Université Toulouse 3, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Toulouse, France.
authors.forename: Rana
authors.initials: R
authors.lastname: Mansour
authors.affiliation: INSERM, U1048 and Université Toulouse 3, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Toulouse, France.
authors.forename: Sonia
authors.initials: S
authors.lastname: Severin
authors.affiliation: INSERM, U1048 and Université Toulouse 3, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Toulouse, France.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Xuereb
authors.affiliation: INSERM, U1048 and Université Toulouse 3, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Toulouse, France.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Gratacap
authors.affiliation: Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR710, Strasbourg University, Ilkirch, France.
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Laporte
authors.affiliation: Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC), INSERM U964, CNRS UMR710, Strasbourg University, Ilkirch, France.
authors.forename: Ana
authors.initials: A
authors.lastname: Buj-Bello
authors.affiliation: INSERM, U1048 and Université Toulouse 3, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Toulouse, France. Electronic address: helene.tronchere@inserm.fr.
authors.forename: Hélène
authors.initials: H
authors.lastname: Tronchère
authors.affiliation: INSERM, U1048 and Université Toulouse 3, Institut des Maladies Métaboliques et Cardiovasculaires (I2MC), Toulouse, France; CHU de Toulouse, Laboratoire d'Hématologie, Toulouse, France. Electronic address: bernard.payrastre@inserm.fr.
authors.forename: Bernard
authors.initials: B
authors.lastname: Payrastre
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000378:metabolism / Q000473:pathology*; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020914:Myopathies, Structural, Congenital / Q000097:blood / Q000175:diagnosis* / Q000235:genetics; D010974:Platelet Aggregation; D054558:Protein Tyrosine Phosphatases, Non-Receptor / Q000032:analysis* / Q000097:blood / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C099588:myotubularin
keywords: Blood platelets; Diagnostic; Myotubularins; Phosphoinositides; X-linked myotubular myopathy