Speaker
Description
Background/Objectives. ADLD is a rare neurodegenerative disorder caused by LMNB1 overexpression due to gene duplications (classical ADLD) or noncoding deletions in the locus (atypical ADLD). Our group collected > 20 families worldwide carrying structural variants (SVs) in the LMNB1 locus and reported strong clinical variability, even among patients carrying duplications of the entire LMNB1 gene, ranging from classical and atypical ADLD to asymptomatic carriers. We performed Hi-C and RNA sequencing on ADLD fibroblasts, providing preliminary insights into ADLD pathomechanisms and the genotype/phenotype correlation of SVs at the LMNB1 locus. Here, we aim to validate these findings in disease-relevant cellular models, namely hiPSC-derived astrocytes.
Methods. We generated hiPSC-derived astrocytes from four subjects carrying a SV in the LMNB1 locus (a classical ADLD and two atypical ADLD patients, and a asymptomatic carrier) and an healthy control. Hi-C were performed on 1 million astrocytes per sample following standard protocols. Statistically significant contacts have been highlighted using Fit-Hi-C v.2.0.8 (FitHiC2).
Results. We validate that: classical ADLD is due to an intra-TAD duplication, resulting in a simple gene dose gain; atypical ADLD is caused by LMNB1 forebrain-specific misexpression due to SVs encompassing a TAD boundary. Finally, in the asymptomatic subject we identified an inter-TAD duplication, which extends centromerically and crosses two boundaries. FitHiC2 has detected a significant physiological regulatory contact between the LMNB1 promoter and the LMNB1 regulatory element at genomic coordinates chr5:125995687-125996125 (hg19), previously reported by our group in the control cell line.
Conclusion. Our results highlight the importance of considering the effects of SVs at the LMNB1 locus on the TAD structure before assuming their pathogenicity and corroborate that a duplication encompassing the LMNB1 gene is not sufficient per se to diagnose ADLD, with implications for ADLD diagnosis and genetic counseling.
| Author(s) | Anna Basile*(1), Ingrid Battistella (2), Mariia Zadorozhna (1)(3), Malte Spielmann (4)(5)(6), Luciano Conti(2), Elisa Giorgio(1)(3) |
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| Affiliation(s) | (1)Department of Molecular Medicine, University of Pavia, Pavia, Italy, (2)Laboratory of Stem Cell Biology, Department of Cellular, Computational and Integrative Biology-CIBIO, University of Trento, 38123 Trento, Italy, (3)Neurogenetics Research Centre, IRCCS Mondino Foundation, Pavia, Italy, (4) Institute of Human Genetics, Universitätsklinikum Schleswig Holstein, University of Lübeck and University of Kiel, Lübeck, Germany, (5) Max Planck Institute for Molecular Genetics, Human Molecular Genomics Group, Berlin, Germany, (6) Institute of Human Genetics, Universitätsklinikum Schleswig Holstein Campus Kiel and Christian-Albrechts-Universität, Kiel, Germany |
