Three-dimensional imaging in myotonic dystrophy type 1: Linking molecular alterations with disease phenotype

Alfonsina Ballester-Lopez; Judit Núñez-Manchón; Emma Koehorst; Ian Linares-Pardo; Miriam Almendrote; Giuseppe Lucente; Nicolau Guanyabens; Marta Lopez-Osias; Adrián Suárez-Mesa; Shaliza Ann Hanick; Jakub Chojnacki; Alejandro Lucia; Guillem Pintos-Morell; Jaume Coll-Cantí; Alicia Martínez-Piñeiro; Alba Ramos-Fransi; Gisela Nogales-Gadea

doi:10.1212/NXG.0000000000000484

Three-dimensional imaging in myotonic dystrophy type 1: Linking molecular alterations with disease phenotype

Neurol Genet. 2020 Jul 21;6(4):e484. doi: 10.1212/NXG.0000000000000484. eCollection 2020 Aug.

Authors

Alfonsina Ballester-Lopez¹, Judit Núñez-Manchón¹, Emma Koehorst¹, Ian Linares-Pardo¹, Miriam Almendrote¹, Giuseppe Lucente¹, Nicolau Guanyabens¹, Marta Lopez-Osias¹, Adrián Suárez-Mesa¹, Shaliza Ann Hanick¹, Jakub Chojnacki¹, Alejandro Lucia¹, Guillem Pintos-Morell¹, Jaume Coll-Cantí¹, Alicia Martínez-Piñeiro¹, Alba Ramos-Fransi¹, Gisela Nogales-Gadea¹

Affiliation

¹ Neuromuscular and Neuropediatric Research Group (A.B.-L., J.N.-M., E.K., I.L.-P., M.A., G.L., M.L.-O., A.S.-M., S.A.H., G.P.-M., J.C.-C., A.M.-P., A.R.-F., G.N.-G.), Institut d'Investigació en Ciències de la Salut Germans Trias i Pujol, Campus Can Ruti, Universitat Autònoma de Barcelona, Badalona; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER) (A.B.-L., G.P.-M., J.C.-C., G.N.-G.), Instituto de Salud Carlos III, Madrid; Neuromuscular Pathology Unit. Neurology Service. Neuroscience department (M.A., G.L., N.G., J.C.-C., A.M.-P., A.R.-F.), Hospital Universitari Germans Trias i Pujol, Badalona, Barcelona; IrsiCaixa AIDS Research Institute (J.C.), Badalona, Spain; Faculty of Sport Sciences (A.L.), Universidad Europea de Madrid; Instituto de Investigación Hospital 12 de Octubre (i+12) (A.L.), Madrid; and Division of Rare Diseases. University Hospital Vall d'Hebron (G.P.-M.), Barcelona, Spain.

Abstract

Objective: We aimed to determine whether 3D imaging reconstruction allows identifying molecular:clinical associations in myotonic dystrophy type 1 (DM1).

Methods: We obtained myoblasts from 6 patients with DM1 and 6 controls. We measured cytosine-thymine-guanine (CTG) expansion and detected RNA foci and muscleblind like 1 (MBNL1) through 3D reconstruction. We studied dystrophia myotonica protein kinase (DMPK) expression and splicing alterations of MBNL1, insulin receptor, and sarcoplasmic reticulum Ca(2+)-ATPase 1.

Results: Three-dimensional analysis showed that RNA foci (nuclear and/or cytoplasmic) were present in 45%-100% of DM1-derived myoblasts we studied (range: 0-6 foci per cell). RNA foci represented <0.6% of the total myoblast nuclear volume. CTG expansion size was associated with the number of RNA foci per myoblast (r = 0.876 [95% confidence interval 0.222-0.986]) as well as with the number of cytoplasmic RNA foci (r = 0.943 [0.559-0.994]). Although MBNL1 colocalized with RNA foci in all DM1 myoblast cell lines, colocalization only accounted for 1% of total MBNL1 expression, with the absence of DM1 alternative splicing patterns. The number of RNA foci was associated with DMPK expression (r = 0.967 [0.079-0.999]). On the other hand, the number of cytoplasmic RNA foci was correlated with the age at disease onset (r = -0.818 [-0.979 to 0.019]).

Conclusions: CTG expansion size modulates RNA foci number in myoblasts derived from patients with DM1. MBNL1 sequestration plays only a minor role in the pathobiology of the disease in these cells. Higher number of cytoplasmic RNA foci is related to an early onset of the disease, a finding that should be corroborated in future studies.