Nuclear speckles are involved in nuclear aggregation of PABPN1 and in the pathophysiology of oculopharyngeal muscular dystrophy

Neurobiology of Disease

María T. Berciano¹  Olga Tapia²  Miguel Lafarga²  Iñigo Casafont²  Rocío Bengoechea²  José Berciano³ 

[1] Corresponding author at: Department of Anatomy and Cell Biology, Faculty of Medicine, Avd. Cardenal Herrera Oria s/n, 39011 Santander, Spain. Fax: [phone].;Department of Anatomy and Cell Biology and “Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED)”, University of Cantabria (UC), Santander, Spain;Service of Neurology, University Hospital “Marqués de Valdecilla” (IFIMAV), University of Cantabria, CIBERNED and UC, Santander, Spain;

关键词: Oculopharyngeal muscular dystrophy;    Skeletal myofibers;    Intranuclear inclusions;    Nuclear speckles;    Pre-mRNA processing;    Poly(A)-binding protein nuclear 1;   

DOI  :  

来源: DOAJ

【 摘 要 】

Nuclear speckles are essential nuclear compartments involved in the assembly, delivery and recycling of pre-mRNA processing factors, and in the post-transcriptional processing of pre-mRNAs. Oculopharyngeal muscular dystrophy (OPMD) is caused by a small expansion of the polyalanine tract in the poly(A)-binding protein nuclear 1 (PABPN1). Aggregation of expanded PABPN1 into intranuclear inclusions (INIs) in skeletal muscle fibers is the pathological hallmark of OPMD. In this study what we have analyzed in muscle fibers of OPMD patients and in primary cultures of human myoblasts are the relationships between nuclear speckles and INIs, and the contribution of the former to the biogenesis of the latter. While nuclear speckles concentrate snRNP splicing factors and PABPN1 in control muscle fibers, they are depleted of PABPN1 and appear closely associated with INIs in muscle fibers of OPMD patients. The induction of INI formation in human myoblasts expressing either wild type GFP-PABPN1 or expanded GFP-PABPN1-17ala demonstrates that the initial aggregation of PABPN1 proteins and their subsequent growth in INIs occurs at the edges of the nuclear speckles. Moreover, the growing of INIs gradually depletes PABPN1 proteins and poly(A) RNA from nuclear speckles, although the existence of these nuclear compartments is preserved. Time-lapse experiments in cultured myoblasts confirm nuclear speckles as biogenesis sites of PABPN1 inclusions. Given the functional importance of nuclear speckles in the post-transcriptional processing of pre-mRNAs, the INI-dependent molecular reorganization of these nuclear compartments in muscle fibers may cause a severe dysfunction in nuclear trafficking and processing of polyadenylated mRNAs, thereby contributing to the molecular pathophysiology of OPMD. Our results emphasize the potential importance of nuclear speckles as nuclear targets of neuromuscular disorders.

【 授权许可】

Unknown