SMN deficiency in severe models of spinal muscular atrophy causes widespread intron retention and DNA damage

Jangi, M., Fleet, C., Cullen, P., Gupta, S. V., Mekhoubad, S., Chiao, E., Allaire, N., Bennett, C. F., Rigo, F., Krainer, A. R., Hurt, J. A., Carulli, J. P., Staropoli, J. F. (March 2017) SMN deficiency in severe models of spinal muscular atrophy causes widespread intron retention and DNA damage. Proc Natl Acad Sci U S A, 114 (12). E2347-2356. ISSN 0027-8424

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URL: https://www.ncbi.nlm.nih.gov/pubmed/28270613
DOI: 10.1073/pnas.1613181114

Abstract

Spinal muscular atrophy (SMA), an autosomal recessive neuromuscular disease, is the leading monogenic cause of infant mortality. Homozygous loss of the gene survival of motor neuron 1 (SMN1) causes the selective degeneration of lower motor neurons and subsequent atrophy of proximal skeletal muscles. The SMN1 protein product, survival of motor neuron (SMN), is ubiquitously expressed and is a key factor in the assembly of the core splicing machinery. The molecular mechanisms by which disruption of the broad functions of SMN leads to neurodegeneration remain unclear. We used an antisense oligonucleotide (ASO)-based inducible mouse model of SMA to investigate the SMN-specific transcriptome changes associated with neurodegeneration. We found evidence of widespread intron retention, particularly of minor U12 introns, in the spinal cord of mice 30 d after SMA induction, which was then rescued by a therapeutic ASO. Intron retention was concomitant with a strong induction of the p53 pathway and DNA damage response, manifesting as gamma-H2A.X positivity in neurons of the spinal cord and brain. Widespread intron retention and markers of the DNA damage response were also observed with SMN depletion in human SH-SY5Y neuroblastoma cells and human induced pluripotent stem cell-derived motor neurons. We also found that retained introns, high in GC content, served as substrates for the formation of transcriptional R-loops. We propose that defects in intron removal in SMA promote DNA damage in part through the formation of RNA:DNA hybrid structures, leading to motor neuron death.

Item Type: Paper
Uncontrolled Keywords: DNA damage Sma Smn neurodegeneration splicing
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > introns > intron splicing
diseases & disorders > congenital hereditary genetic diseases > spinal muscular atrophy
CSHL Authors:
Communities: CSHL labs > Krainer lab
Depositing User: Matt Covey
Date: 7 March 2017
Date Deposited: 17 Mar 2017 21:22
Last Modified: 25 May 2018 19:23
PMCID: PMC5373344
Related URLs:
URI: http://repository.cshl.edu/id/eprint/34272

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