Congenital myopathies (CM) are a heterogeneous group of skeletal muscle disorders that manifest as hypotonia as well as breathing and feeding difficulties early in life, and can often be fatal. Centronuclear myopathy (CNM) is a common CM subtype characterized by the mislocalization of nuclei from the periphery to the center of myofibers. X-linked myotubular myopathy, the most frequent and severe form of CNM, is caused by MTM1 mutations. Myotubularin or MTM1 is a lipid phosphatase, and little is known about its interacting partners. To determine MTM1-interacting proteins, we conducted a yeast two-hybrid screen and found striated preferentially expressed gene (SPEG) to be an interacting partner. Concurrently, whole exome sequencing to determine genetic basis of CNM revealed recessive SPEG mutations in probands from three unrelated CNM families. Two of the three were also diagnosed with dilated cardiomyopathy (DCM), one of which had spontaneous resolution by a year. Our results suggest that mutations in SPEG cause a CNM phenotype, but the underlying basis for skeletal muscle dysfunction is unknown. Knocking out Speg in a mouse model has been associated with severe DCM, an increased number of central nuclei, and death by postnatal day two. SPEG and desmin genes are tandemly arrayed on the genome, and a common locus control region in mammals regulates their expression. Immunofluorescence studies have shown that SPEG localizes with the terminal cisternae of the sarcoplasmic reticulum (SR). We propose that SPEG may maintain terminal SR structure for efficient excitation-contraction coupling.
In Aim 1, we will decipher the molecular mechanisms responsible for poor skeletal muscle function associated with lack of SPEG and its differential role in skeletal and cardiac muscles.
In Aim 2, we will investigate SPEG's involvement in skeletal muscle growth and differentiation, with special focus on central nucleation.
In Aim 3, we will determine the relationship between SPEG, MTM1, and desmin. The overall goals of the proposal are to understand how lack of SPEG affects muscle function, its role in muscle growth and differentiation, and relationship with MTM1 and desmin. When completed, this work will provide clear insights into the molecular functions of SPEG in skeletal muscle, and how its deficiency causes CNM. The findings will help determine therapeutic approaches against such devastating muscle diseases.

Public Health Relevance

Congenital myopathies (CM) are genetic disorders of muscle that may affect normal ambulation, feeding and breathing. They are poorly understood with no available cures. We have identified SPEG protein deficiency in a few CM patients. The function of this protein is unknown, and we propose to determine disease mechanisms using cell and mouse models. This will help us better understand CM and devise appropriate future therapies.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR068429-05
Application #
9733129
Study Section
Skeletal Muscle and Exercise Physiology Study Section (SMEP)
Program Officer
Boyce, Amanda T
Project Start
2015-09-14
Project End
2021-06-30
Budget Start
2019-07-01
Budget End
2021-06-30
Support Year
5
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Boston Children's Hospital
Department
Type
DUNS #
076593722
City
Boston
State
MA
Country
United States
Zip Code
02115
Lo, Mindy S; Towne, Meghan; VanNoy, Grace E et al. (2018) Monogenic Hashimoto thyroiditis associated with a variant in the thyroglobulin (TG) gene. J Autoimmun 86:116-119
Katwa, Umakanth; D'Gama, Alissa M; Qualls, Anita E et al. (2018) Atypical presentations associated with non-polyalanine repeat PHOX2B mutations. Am J Med Genet A 176:1627-1631
O'Connell, Amy E; Zhou, Fanny; Shah, Manasvi S et al. (2018) Neonatal-Onset Chronic Diarrhea Caused by Homozygous Nonsense WNT2B Mutations. Am J Hum Genet 103:131-137
Wojcik, Monica H; Schwartz, Talia S; Yamin, Inbar et al. (2018) Genetic disorders and mortality in infancy and early childhood: delayed diagnoses and missed opportunities. Genet Med 20:1396-1404
Rodan, Lance H; Hauptman, Marissa; D'Gama, Alissa M et al. (2018) Novel founder intronic variant in SLC39A14 in two families causing Manganism and potential treatment strategies. Mol Genet Metab 124:161-167
Huntoon, Virginia; Widrick, Jeffrey J; Sanchez, Colline et al. (2018) SPEG-deficient skeletal muscles exhibit abnormal triad and defective calcium handling. Hum Mol Genet 27:1608-1617
Wojcik, Monica H; Wierenga, Klaas J; Rodan, Lance H et al. (2018) Beta-Ketothiolase Deficiency Presenting with Metabolic Stroke After a Normal Newborn Screen in Two Individuals. JIMD Rep 39:45-54
Fan, Xin; Xie, Bobo; Zou, Jun et al. (2018) Novel ETFDH mutations in four cases of riboflavin responsive multiple acyl-CoA dehydrogenase deficiency. Mol Genet Metab Rep 16:15-19
Schwartz, Talia S; Wojcik, Monica H; Pelletier, Renee C et al. (2018) Expanding the phenotypic spectrum associated with OPHN1 variants. Eur J Med Genet :
Shu, Chang; Huang, He; Xu, Ying et al. (2018) Pressure Overload in Mice With Haploinsufficiency of Striated Preferentially Expressed Gene Leads to Decompensated Heart Failure. Front Physiol 9:863

Showing the most recent 10 out of 23 publications