De novo Variants Affecting DNM1 Exon 10a Cause Severe Developmental and Epileptic Encephalopathy
Abstract number :
1.02
Submission category :
1. Basic Mechanisms / 1B. Epileptogenesis of genetic epilepsies
Year :
2022
Submission ID :
2205010
Source :
www.aesnet.org
Presentation date :
12/3/2022 12:00:00 PM
Published date :
Nov 22, 2022, 05:27 AM
Authors :
Shridhar Parthasarathy, – Children's Hospital of Philadelphia; Sarah Ruggiero, MS, CGC – Children's Hospital of Philadelphia; Antoinette Gelot, MD, PhD – Hopital Armand-Trousseau; Fernanda Soardi, PhD – Universidade Federal de Minas Gerais; Bethania FR Ribeiro, PhD – Secretaria Estadual de Saude do Estado do Acre; Douglas EV Pires, PhD – University of Melbourne; David Ascher, PhD – University of Melbourne; Alain Schmitt, PhD – Institut Cochin; Caroline Rambaud, MD – Hopital Raymond-Poincare; Hongbo Xie, PhD – Children's Hospital of Philadelphia; Laina Lusk, MS, CGC – Children's Hospital of Philadelphia; Olivia Wilmarth, BS – Children's Hospital of Philadelphia; Pamela McDonnell, MD – Children's Hospital of Philadelphia; Olivia Juarez, MMSc, CGC – Children's Hospital of San Antonio; Alexandra Grace, PNP, PC – Children's Hospital of San Antonio; Julien Buratti, PhD – Hopital de la Pitie Salpetriere; Cyril Mignot, MD – Hopital de la Pitie Salpetriere; Domitille Gras, MD – Hopital Robert Debre; Caroline Nava, MD – Hopital de la Pitie Salpetriere; Samuel Pierce, PT, PhD – Children's Hospital of Philadelphia; Boris Keren, MD – Hopital de la Pitie Salpetriere; Benjamin Kennedy, MD – Children's Hospital of Philadelphia; Sergio DJ Pena, PhD – Universidade Federal de Minas Gerais; Ingo Helbig, MD – Children's Hospital of Philadelphia; Vishnu Cuddapah, MD, PhD – Children's Hospital of Philadelphia
This abstract is a recipient of the Young Investigator Award
This abstract has been invited to present during the Basic Mechanisms platform session
Rationale: The developmental and epileptic encephalopathies are a group of severe childhood epilepsies, frequently with identifiable monogenic etiology. DNM1, encoding dynamin-1, is one of several synapse-related genes associated with a DEE phenotype. Pathogenic, heterozygous missense variants in DNM1 cause dominant-negative effects, which occur when the mutant copy of dynamin-1 blocks the function of the normal copy as well, impairing the function of dynamin-1 oligomers in vesicle recycling. Thus far, pathogenic variants in DNM1 have been identified using a single transcript containing the alternatively spliced exon 10b. Here, we identify individuals with variants exclusively affecting exon 10a or 10b, including one intronic variant recurrent in eight individuals,
Methods: We reviewed medical records in 11 individuals diagnosed with DNM1-related disorder with variants affecting alternative tenth exons. We performed RNA sequencing in pediatric brain tissue samples obtained from 39 unaffected individuals and quantified DNM1 transcript expression. We used a pCAS2 splice reporter minigene assay to determine the transcriptional consequence of the recurrent intronic variant, and structurally modeled the predicted resulting monomer and oligomer. We performed neuropathological analysis of samples obtained from one deceased individual with the recurrent variant.
Results: Ten individuals had variants affecting exon 10a, eight with the intronic variant c.1197-8G >A, and two with missense variants: p.Arg399Trp and p.Gly401Asp. All had severe clinical features similar to the established DNM1-related DEE. In contrast, one individual with p.Pro405Leu in exon 10b had a much milder presentation. We found that transcripts containing exon 10a constitute the primary isoform expressed in the pediatric cortex. We determined that the intronic variant leads to an upstream splice acceptor and a two-amino acid insertion, thought to impair oligomerization-dependent dynamin-1 vesicle fission activity. Correspondingly, neuropathological samples demonstrated an accumulation of synaptic vesicles abutting the plasma membrane; these findings suggest this DNM1 variant impairs vesicular fission.
Conclusions: Our study highlights a recurrent variant in DNM1, showing how this intronic variant can lead to a dominant-negative mechanism of disease indistinguishable from previously reported DNM1-related disorders. We also establish transcripts containing exon 10a as the disease-related isoform of DNM1, emphasizing the importance of considering clinically relevant isoforms in identifying disease-causing variants.
Funding: Children’s Hospital of Philadelphia, NINDS, Fundação de Amparo à Pesquisa de Minas Gerais, and National Health and Medical Research Council of Australia
Basic Mechanisms