title: SPEG interacts with myotubularin, and its deficiency causes centronuclear myopathy with dilated cardiomyopathy.
abstract: Centronuclear myopathies (CNMs) are characterized by muscle weakness and increased numbers of central nuclei within myofibers. X-linked myotubular myopathy, the most common severe form of CNM, is caused by mutations in MTM1, encoding myotubularin (MTM1), a lipid phosphatase. To increase our understanding of MTM1 function, we conducted a yeast two-hybrid screen to identify MTM1-interacting proteins. Striated muscle preferentially expressed protein kinase (SPEG), the product of SPEG complex locus (SPEG), was identified as an MTM1-interacting protein, confirmed by immunoprecipitation and immunofluorescence studies. SPEG knockout has been previously associated with severe dilated cardiomyopathy in a mouse model. Using whole-exome sequencing, we identified three unrelated CNM-affected probands, including two with documented dilated cardiomyopathy, carrying homozygous or compound-heterozygous SPEG mutations. SPEG was markedly reduced or absent in two individuals whose muscle was available for immunofluorescence and immunoblot studies. Examination of muscle samples from Speg-knockout mice revealed an increased frequency of central nuclei, as seen in human subjects. SPEG localizes in a double line, flanking desmin over the Z lines, and is apparently in alignment with the terminal cisternae of the sarcoplasmic reticulum. Examination of human and murine MTM1-deficient muscles revealed similar abnormalities in staining patterns for both desmin and SPEG. Our results suggest that mutations in SPEG, encoding SPEG, cause a CNM phenotype as a result of its interaction with MTM1. SPEG is present in cardiac muscle, where it plays a critical role; therefore, individuals with SPEG mutations additionally present with dilated cardiomyopathy.
authors.affiliation: Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Division of Newborn Medicine, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA. Electronic address: pagrawal@enders.tch.harvard.edu.
authors.forename: Pankaj B
authors.initials: PB
authors.lastname: Agrawal
authors.affiliation: Department of Pathology and Laboratory Medicine, Nationwide Children's Hospital and the Ohio State University College of Medicine, Columbus, OH 43205, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Pierson
authors.affiliation: Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Mugdha
authors.initials: M
authors.lastname: Joshi
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Boston MA 02115, USA.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Liu
authors.affiliation: Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Nedlands, WA 6009, Australia.
authors.forename: Gianina
authors.initials: G
authors.lastname: Ravenscroft
authors.affiliation: Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Behzad
authors.initials: B
authors.lastname: Moghadaszadeh
authors.affiliation: Research Institute, Nationwide Children's Hospital and the Ohio State University College of Medicine, Columbus, OH 43205, USA.
authors.forename: Tiffany
authors.initials: T
authors.lastname: Talabere
authors.affiliation: Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Marissa
authors.initials: M
authors.lastname: Viola
authors.affiliation: Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Lindsay C
authors.initials: LC
authors.lastname: Swanson
authors.affiliation: Neurology Unit, Department of Pediatrics, Hacettepe University Children's Hospital, Ankara 06100, Turkey.
authors.forename: Göknur
authors.initials: G
authors.lastname: Haliloğlu
authors.affiliation: Pathology Unit, Department of Pediatrics, Hacettepe University Children's Hospital, Ankara 06100, Turkey.
authors.forename: Beril
authors.initials: B
authors.lastname: Talim
authors.affiliation: Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Nedlands, WA 6009, Australia.
authors.forename: Kyle S
authors.initials: KS
authors.lastname: Yau
authors.affiliation: Lotterywest State Biomedical Facility Genomics and School of Pathology and Laboratory Medicine, University of Western Australia, Perth, WA 6009, Australia.
authors.forename: Richard J N
authors.initials: RJ
authors.lastname: Allcock
authors.affiliation: Harry Perkins Institute of Medical Research and the Centre for Medical Research, University of Western Australia, Nedlands, WA 6009, Australia.
authors.forename: Nigel G
authors.initials: NG
authors.lastname: Laing
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Boston MA 02115, USA; Department of Newborn Medicine, Brigham and Women's Hospital, Boston MA 02115, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Perrella
authors.affiliation: Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA; Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA 02115, USA. Electronic address: beggs@enders.tch.harvard.edu.
authors.forename: Alan H
authors.initials: AH
authors.lastname: Beggs
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009206:Myocardium / Q000166:cytology; D009210:Myofibrils / Q000235:genetics; D020914:Myopathies, Structural, Congenital / Q000235:genetics*; D018129:Phosphatidylinositol Phosphates / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D054558:Protein Tyrosine Phosphatases, Non-Receptor / Q000235:genetics* / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000235:genetics / Q000473:pathology; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014421:Turkey; D020798:Two-Hybrid System Techniques
chemical_list: D009124:Muscle Proteins; D018129:Phosphatidylinositol Phosphates; C055525:phosphatidylinositol 3-phosphate; D017346:Protein Serine-Threonine Kinases; C100675:SPEG protein, human; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C099588:myotubularin
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