Characterization of RAN Translation and Antisense Transcription in Primary Cell Cultures of Patients with Myotonic Dystrophy Type 1

Abstract

Traducció RAN; Transcripció antisentit; Moduladors fenotípics

Traducción RAN; Transcripción antisentido; Moduladores fenotípicos

RAN translation; Antisense transcription; Phenotypic modulators

Myotonic Dystrophy type 1 (DM1) is a muscular dystrophy with a multi-systemic nature. It was one of the first diseases in which repeat associated non-ATG (RAN) translation was described in 2011, but has not been further explored since. In order to enhance our knowledge of RAN translation in DM1, we decided to study the presence of DM1 antisense (DM1-AS) transcripts (the origin of the polyglutamine (polyGln) RAN protein) using RT-PCR and FISH, and that of RAN translation via immunoblotting and immunofluorescence in distinct DM1 primary cell cultures, e.g., myoblasts, skin fibroblasts and lymphoblastoids, from ten patients. DM1-AS transcripts were found in all DM1 cells, with a lower expression in patients compared to controls. Antisense RNA foci were found in the nuclei and cytoplasm of a subset of DM1 cells. The polyGln RAN protein was undetectable in all three cell types with both approaches. Immunoblots revealed a 42 kD polyGln containing protein, which was most likely the TATA-box-binding protein. Immunofluorescence revealed a cytoplasmic aggregate, which co-localized with the Golgi apparatus. Taken together, DM1-AS transcript levels were lower in patients compared to controls and a small portion of the transcripts included the expanded repeat. However, RAN translation was not present in patient-derived DM1 cells, or was in undetectable quantities for the available methods.

The research of G. Nogales-Gadea and A. Ramos-Fransi is funded by Instituto de Salud Carlos III (grant numbers PI15/01756 and PI18/00713) and co-financed by Fondos FEDER. G. Nogales-Gadea is supported by a Miguel Servet research contract (ISCIII CD14/00032, ISCIII CPII19/00021, and FEDER) and by a Trampoline Grant #21108 from AFM Telethon. E. Koehorst is funded by the La Caixa Foundation (ID 100010434), fellowship code LCF/BQ/IN18/11660019, cofunded by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 713673. The research of M. Suelves is funded by Ministerio de Ciencia e Innovación (grant number PID2020-118730RB-I00) and co-financed by Fondos FEDER. J. Núñez-Manchón is funded by Instituto de Salud Carlos III I-PFIS fellowship (grant number IFI20/00022). G. Lucente is supported by a Rio Hortega contract (ISCIII CM16/00016 and FEDER). J. Chojnacki is supported by European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 793830. The work of A.P. Gómez-Escribano and R.P. Vázquez-Manrique is funded by the ISCIII (CPII16/00004, PI17/00011 and PI20/00114) and the Fundación Ramón Areces (CIVP19S8119). This work was supported by the CERCA program/ Government of Catalonia. The funding bodies had no role in the design of the study and the collection, analysis, and interpretation of data.