3D imaging in Myotonic Dystrophy Type 1: linking molecular alterations with disease phenotype

3D imaging in Myotonic Dystrophy Type 1: linking molecular alterations with disease phenotype

Online publication: 21/07/2020 Printed publication: 21 July 2020 Journal: Neurology Genetics


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

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.

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]).

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.

Authors: Ballester-Lopez A, Núñez-Manchón J, Koehorst E, Linares-Pardo I, Almendrote M, Lucente G, Guanyabens N, Lopez-Osias M, Suárez-Mesa A, Hanick SA, Chojnacki J, Lucia A, Pintos-Morell G, Coll-Cantí J, Martínez-Piñeiro A, Ramos-Fransi A, Nogales-Gadea G

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