ZPR1 prevents R-loop accumulation, upregulates SMN2 expression and rescues spinal muscular atrophy.

Abstract

Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by homozygous mutation or deletion of the survival motor neuron 1 (SMN1) gene. A second copy, SMN2, is similar to SMN1 but produces ∼10% SMN protein because of a single-point mutation that causes splicing defects. Chronic low levels of SMN cause accumulation of co-transcriptional R-loops and DNA damage leading to genomic instability and neurodegeneration in SMA. Severity of SMA disease correlates inversely with SMN levels. SMN2 is a promising target to produce higher levels of SMN by enhancing its expression. Mechanisms that regulate expression of SMN genes are largely unknown. We report that zinc finger protein ZPR1 binds to RNA polymerase II, interacts in vivo with SMN locus and upregulates SMN2 expression in SMA mice and patient cells. Modulation of ZPR1 levels directly correlates and influences SMN2 expression levels in SMA patient cells. ZPR1 overexpression in vivo results in a systemic increase of SMN levels and rescues severe to moderate disease in SMA mice. ZPR1-dependent rescue improves growth and motor function and increases the lifespan of male and female SMA mice. ZPR1 reduces neurodegeneration in SMA mice and prevents degeneration of cultured primary spinal cord neurons derived from SMA mice. Further, we show that the low levels of ZPR1 associated with SMA pathogenesis cause accumulation of co-transcriptional RNA-DNA hybrids (R-loops) and DNA damage leading to genomic instability in SMA mice and patient cells. Complementation with ZPR1 elevates senataxin levels, reduces R-loop accumulation and rescues DNA damage in SMA mice, motor neurons and patient cells. In conclusion, ZPR1 is critical for preventing accumulation of co-transcriptional R-loops and DNA damage to avert genomic instability and neurodegeneration in SMA. ZPR1 enhances SMN2 expression and leads to SMN-dependent rescue of SMA. ZPR1 represents a protective modifier and a therapeutic target for developing a new method for the treatment of SMA.

• Authors: Annapoorna Kannan, Xiaoting Jiang, Lan He, Saif Ahmad, Laxman Gangwani
• Journal: Brain : a journal of neurology (Brain) Vol. 143 Issue 1 Pg. 69-93 (01 01 2020) ISSN: 1460-2156 [Electronic] England
• PMID: 31828288 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: © The Author(s) (2019). Published by Oxford University Press on behalf of the Guarantors of Brain.

Chemical References

• Intracellular Signaling Peptides and Proteins
• Membrane Transport Proteins
• Multifunctional Enzymes
• SMN2 protein, mouse
• Smn1 protein, mouse
• Survival of Motor Neuron 1 Protein
• Survival of Motor Neuron 2 Protein
• ZPR1 protein, human
• Zfp259 protein, mouse
• RNA Polymerase II
• SETX protein, human
• SETX protein, mouse
• DNA Helicases
• RNA Helicases

Topics

• Animals
• DNA Damage
• DNA Helicases (metabolism)
• Disease Models, Animal
• Female
• Fibroblasts (metabolism)
• HeLa Cells
• Humans
• Immunohistochemistry
• In Vitro Techniques
• Intracellular Signaling Peptides and Proteins (genetics)
• Male
• Membrane Transport Proteins (genetics)
• Mice
• Mice, Transgenic
• Motor Neurons (metabolism)
• Multifunctional Enzymes (metabolism)
• Muscle, Skeletal (metabolism, pathology)
• Primary Cell Culture
• R-Loop Structures
• RNA Helicases (metabolism)
• RNA Polymerase II (metabolism)
• Severity of Illness Index
• Spinal Cord (metabolism, pathology)
• Spinal Muscular Atrophies of Childhood (genetics, metabolism, pathology, physiopathology)
• Survival of Motor Neuron 1 Protein (genetics)
• Survival of Motor Neuron 2 Protein (genetics, metabolism)
• Up-Regulation