RESUMEN
Myotonic dystrophy type 1 (DM1) is a form of muscular dystrophy causing progressive muscle loss and weakness. Although clinical features can manifest at any age, it is the most common form of muscular dystrophy with onset in adulthood. DM1 is an autosomal dominant condition, resulting from an unstable CTG expansion in the 3'-untranslated region of the myotonic dystrophy protein kinase (DMPK) gene. The age of onset and the severity of the phenotype are roughly correlated with the size of the CTG expansion. Multiple methodologies can be used to diagnose affected individuals with DM1, including polymerase chain reaction, Southern blot, and triplet repeat-primed polymerase chain reaction. Recently, triplet repeat interruptions have been described, which may affect clinical outcomes of a fully-variable allele in DMPK. This document supersedes the Technical Standards and Guidelines for Myotonic Dystrophy originally published in 2009 and reaffirmed in 2015. It is designed for genetic testing professionals who are already familiar with the disease and the methods of analysis.
Asunto(s)
Pruebas Genéticas , Genética Médica , Genómica , Distrofia Miotónica , Proteína Quinasa de Distrofia Miotónica , Expansión de Repetición de Trinucleótido , Distrofia Miotónica/genética , Distrofia Miotónica/diagnóstico , Humanos , Proteína Quinasa de Distrofia Miotónica/genética , Pruebas Genéticas/normas , Pruebas Genéticas/métodos , Genética Médica/normas , Genética Médica/métodos , Expansión de Repetición de Trinucleótido/genética , Genómica/métodos , Genómica/normas , Estados UnidosRESUMEN
The aortic root is the predominant site for development of aneurysm caused by heterozygous loss-of-function mutations in positive effectors of the transforming growth factor-ß (TGF-ß) pathway. Using a mouse model of Loeys-Dietz syndrome (LDS) that carries a heterozygous kinase-inactivating mutation in TGF-ß receptor I, we found that the effects of this mutation depend on the lineage of origin of vascular smooth muscle cells (VSMCs). Secondary heart field-derived (SHF-derived), but not neighboring cardiac neural crest-derived (CNC-derived), VSMCs showed impaired Smad2/3 activation in response to TGF-ß, increased expression of angiotensin II (AngII) type 1 receptor (Agtr1a), enhanced responsiveness to AngII, and higher expression of TGF-ß ligands. The preserved TGF-ß signaling potential in CNC-derived VSMCs associated, in vivo, with increased Smad2/3 phosphorylation. CNC-, but not SHF-specific, deletion of Smad2 preserved aortic wall architecture and reduced aortic dilation in this mouse model of LDS. Taken together, these data suggest that aortic root aneurysm predisposition in this LDS mouse model depends both on defective Smad signaling in SHF-derived VSMCs and excessive Smad signaling in CNC-derived VSMCs. This work highlights the importance of considering the regional microenvironment and specifically lineage-dependent variation in the vulnerability to mutations in the development and testing of pathogenic models for aortic aneurysm.
