title: Calreticulin secures calcium-dependent nuclear pore competency required for cardiogenesis.
abstract: Calreticulin deficiency causes myocardial developmental defects that culminate in an embryonic lethal phenotype. Recent studies have linked loss of this calcium binding chaperone to failure in myofibrillogenesis through an as yet undefined mechanism. The purpose of the present study was to identify cellular processes corrupted by calreticulin deficiency that precipitate dysregulation of cardiac myofibrillogenesis related to acquisition of cardiac phenotype. In an embryonic stem cell knockout model, calreticulin deficit (crt(-/-)) compromised nucleocytoplasmic transport of nuclear localization signal-dependent and independent pathways, disrupting nuclear import of the cardiac transcription factor MEF2C. The expression of nucleoporins and associated nuclear transport proteins in derived crt(-/-) cardiomyocytes revealed an abnormal nuclear pore complex (NPC) configuration. Altered protein content in crt(-/-) cells resulted in remodeled NPC architecture that caused decreased pore diameter and diminished probability of central channel occupancy versus wild type counterparts. Ionophore treatment of impaired calcium handling in crt(-/-) cells corrected nuclear pore microarchitecture and rescued nuclear import resulting in normalized myofibrillogenesis. Thus, calreticulin deficiency alters nuclear pore function and structure, impeding myofibrillogenesis in nascent cardiomyocytes through a calcium dependent mechanism. This essential role of calreticulin in nucleocytoplasmic communication competency ties its regulatory action with proficiency of cardiac myofibrillogenesis essential for proper cardiac development.
authors.affiliation: Center for Regenerative Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.
authors.forename: Randolph S
authors.initials: RS
authors.lastname: Faustino
authors.affiliation: Center for Regenerative Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.
authors.forename: Atta
authors.initials: A
authors.lastname: Behfar
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Jody
authors.initials: J
authors.lastname: Groenendyk
authors.affiliation: Center for Regenerative Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.
authors.forename: Saranya P
authors.initials: SP
authors.lastname: Wyles
authors.affiliation: Center for Regenerative Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Niederlander
authors.affiliation: Center for Regenerative Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.
authors.forename: Santiago
authors.initials: S
authors.lastname: Reyes
authors.affiliation: INSERM UMR910, Marseille, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Puceat
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Marek
authors.initials: M
authors.lastname: Michalak
authors.affiliation: Center for Regenerative Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA.
authors.forename: Andre
authors.initials: A
authors.lastname: Terzic
authors.affiliation: Center for Regenerative Medicine, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN, USA; Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN, USA; Rehabilitation Research Center, Rochester, MN, USA. Electronic address: terzic.carmen@mayo.edu.
authors.forename: Carmen
authors.initials: C
authors.lastname: Perez-Terzic
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000235:genetics; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000235:genetics; D037282:Calreticulin / Q000172:deficiency / Q000235:genetics*; D009202:Cardiomyopathies / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation / Q000235:genetics; D053595:Embryonic Stem Cells / Q000378:metabolism / Q000473:pathology; D055786:Gene Knockout Techniques; D006801:Humans; D064326:MEF2 Transcription Factors / Q000235:genetics; D051379:Mice; D024510:Muscle Development / Q000235:genetics*; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D022022:Nuclear Pore / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D037282:Calreticulin; D064326:MEF2 Transcription Factors; D002118:Calcium
keywords: Calreticulin; Cardiac differentiation; Embryonic stem cells; Nuclear transport