The heterogeneous nuclear ribonucleoprotein-R is necessary for axonal β-actin mRNA translocation in spinal motor neurons

Glinka, Michael; Herrmann, Thomas; Funk, Natalja; Havlicek, Steven; Rossoll, Wilfried; Winkler, Christoph; Sendtner, Michael

doi:10.1093/hmg/ddq073

Cited by 88 publications

(102 citation statements)

References 59 publications

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“…Intriguingly, CG17838 is the Drosophila homolog of two closely related vertebrate RNA-binding proteins, HNRNPR and SYNCRIP, both of which bind to SMN in a yeast two-hybrid assay (31) and localize to mRNAcontaining granules that are transported in cultured neurons (27,31,42). Because both SMN and HNRNPR affect localization of mRNA in axons (43,44), this could have profound consequences on local translation in neurons (44).…”

Section: Discussionmentioning

confidence: 99%

Genetic circuitry of Survival motor neuron , the gene underlying spinal muscular atrophy

Sen

Dimlich

Guruharsha

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The clinical severity of the neurodegenerative disorder spinal muscular atrophy (SMA) is dependent on the levels of functional Survival Motor Neuron (SMN) protein. Consequently, current strategies for developing treatments for SMA generally focus on augmenting SMN levels. To identify additional potential therapeutic avenues and achieve a greater understanding of SMN, we applied in vivo, in vitro, and in silico approaches to identify genetic and biochemical interactors of the Drosophila SMN homolog. We identified more than 300 candidate genes that alter an Smn-dependent phenotype in vivo. Integrating the results from our genetic screens, large-scale protein interaction studies, and bioinformatic analysis, we define a unique interactome for SMN that provides a knowledge base for a better understanding of SMA.pinal muscular atrophy (SMA), the leading genetic cause of infant mortality, results from the partial loss of Survival Motor Neuron (SMN) gene activity (1). Numerous studies indicate that SMN functions as a central component of a complex that is responsible for the assembly of spliceosomal small nuclear ribonucleoproteins (snRNPs) (reviewed in ref.2). SMN is also reported to play additional roles, including mRNA trafficking in the axon (3). In humans, SMN is encoded by two nearly identical genes, SMN1 and SMN2, which are located on chromosome 5 (4). SMN2 differs from SMN1 in that only 10% of SMN2 transcripts produce functional SMN due to a single-nucleotide polymorphism that results in inefficient splicing of exon 7 and translation of a truncated, unstable SMN protein (1,5,6). The clinical severity of SMA correlates with the SMN2 copy number, which varies between individuals (7). As the small amount of functional SMN2 protein produced by each copy of the gene is capable of partially compensating for the loss of the SMN1 gene function, higher copy numbers of SMN2 typically result in milder forms of SMA. Therefore, genetic modifiers capable of increasing the abundance and/or specific activity of SMN hold promise as therapeutic targets.The Drosophila genome harbors a single, highly conserved ortholog of SMN1/2, the Smn gene. SMN is essential for cell viability in vertebrates and Drosophila (8, 9). In Drosophila, zygotic loss of Smn function results in recessive larval lethality (not embryonic as might be expected) due to the rescue of early development by maternal contribution of Smn. The larval phenotype includes neuromuscular junction (NMJ) abnormalities that are reminiscent of those associated with the human disease, rendering this invertebrate organism an excellent system to model SMN biology (9-11). We previously described a genetic screen for modifiers of the lethal phenotype resulting from a complete lossof-function Smn allele (12). This screen, although it probed half of the Drosophila genome, identified only a relatively small number of genes that affected the NMJ phenotype associated with Smn loss of function (12). In particular, it did not identify genes involved in snRNP biogenesis, the molecular func...

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Section: Discussionmentioning

confidence: 99%

Genetic circuitry of Survival motor neuron , the gene underlying spinal muscular atrophy

Sen

Dimlich

Guruharsha

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…SMN2 genomic DNA contains a few nucleotide mutations compared with SMN1 (21,22). Full-length SMN protein functions in the U snRNP assembly/disassembly, as well as in the β-actin mRNA transport in neurons (23,24). However, the mutations in SMN2 pre-mRNA cause predominantly skipping of exon 7, which produces SMNΔ7, a truncated and less stable protein with reduced self-oligomerization activity.…”

mentioning

confidence: 99%

Splicing inhibition of U2AF ⁶⁵ leads to alternative exon skipping

Cho

Moon

Loh

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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U2 snRNP auxiliary factor 65 kDa (U2AF 65 ) is a general splicing factor that contacts polypyrimidine (Py) tract and promotes prespliceosome assembly. In this report, we show that U2AF 65 stimulates alternative exon skipping in spinal muscular atrophy (SMA)-related survival motor neuron (SMN) pre-mRNA. A stronger 5′ splice-site mutation of alternative exon abolishes the stimulatory effects of U2AF 65 . U2AF 65 overexpression promotes its own binding only on the weaker, not the stronger, Py tract. We further demonstrate that U2AF 65 inhibits splicing of flanking introns of alternative exon in both three-exon and two-exon contexts. Similar U2AF 65 effects were observed in Fas (Apo-1/CD95) pre-mRNA. Strikingly, we demonstrate that U2AF 65 even inhibits general splicing of adenovirus major late (Ad ML) or β-globin pre-mRNA. Thus, we conclude that U2AF 65 possesses a splicing Inhibitory function that leads to alternative exon skipping.U2AF 65 | pre-mRNA splicing | splicing inhibition | exon exclusion | SMN P re-mRNA splicing is a process in which noncoding intron sequences are removed and exon sequences are then ligated together (1, 2). Pre-mRNA splicing is carried out by spliceosome, a large RNA-protein complex that contains five small nuclear ribonucleoproteins (U snRNPs) and more than 100 additional proteins (3). Pre-mRNA splicing occurs in the consensus sequences at the 5′ splice-site, 3′ splice-site, and branch point that are necessary for splicing. The sequence between 3′ AG dinucleotide and branch point is the polypyrimidine (Py) tract that directs spliceosome assembly on the 3′ splice-site. Alternative splicing provides an important regulatory mechanism in higher eukaryotes for multiple proteins produced from a single gene (4, 5).The U2 snRNP auxiliary factor 65 kDa (U2AF 65 ) exists as a heterodimer with U2AF 35 (6). U2AF 65 contains three C-terminal RNA recognition motifs (RRMs) and an N-terminal arginine/ serine-rich (RS) domain (7,8). Using U2AF 65 depletion/adding back technology with in vitro HeLa nuclear extract, it was demonstrated that U2AF 65 is an essential splicing factor (9). Whereas U2AF 65 binds to Py tract to promote prespliceosome assembly and branchpoint/U2 snRNA base pairing, U2AF 35 plays a role in the 3′ splice-site (10, 11). As U2AF 65 prefers high C/U-rich sequences in the Py tract, a stronger interaction between U2AF 65 and Py tract promotes prespliceosome assembly (12). U2AF 65 is also essential in vertebrate development (13,14). Its expression level is related to myotonic dystrophy, cystic fibrosis, and cancers (15, 16).Proximal spinal muscular atrophy (SMA) is an autosomal recessive genetic disease (17) and a leading cause of infant mortality. The motor neurons in the anterior horn of spinal cord are severely damaged in patients with type 1 SMA, usually leading to death before age 2 y as a result of a lack of respiratory support (18,19). In patients with SMA, the SMN1 gene is deleted or mutated, whereas the SMN2 gene, a duplicate of the SMN1 gene, is included (20). SMN2 genomic DNA...

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“…However, issues such as which transcripts are most sensitive to SMN deficiency and whether their splicing defects lead to SMA pathogenesis remain to be investigated. In addition, it has been shown that SMN forms RNA granules with other RNA-binding proteins such as hnRNP R to deliver -actin mRNA in motor axons (Glinka, et al, 2010;Rossoll, et al, 2003). A recent report showed that clustering of Cav2.2 calcium channels is impaired in axonal growth cones of SMA animals, and such a defect can be restored by rescue of SMN expression (Jablonka, et al, 2007).…”

Section: How Does Smn Deficiency Cause Sma Pathogenesismentioning

confidence: 99%

Recent Advances in Understanding of Alternative Splicing in Neuronal Pathogenesis

Chen¹,

Lin²,

Tarn³

2011

RNA Processing

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The heterogeneous nuclear ribonucleoprotein-R is necessary for axonal β-actin mRNA translocation in spinal motor neurons

Cited by 88 publications

References 59 publications

Genetic circuitry of Survival motor neuron , the gene underlying spinal muscular atrophy

Genetic circuitry of Survival motor neuron , the gene underlying spinal muscular atrophy

Splicing inhibition of U2AF ⁶⁵ leads to alternative exon skipping

Recent Advances in Understanding of Alternative Splicing in Neuronal Pathogenesis

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The heterogeneous nuclear ribonucleoprotein-R is necessary for axonal β-actin mRNA translocation in spinal motor neurons

Cited by 88 publications

References 59 publications

Genetic circuitry of Survival motor neuron , the gene underlying spinal muscular atrophy

Genetic circuitry of Survival motor neuron , the gene underlying spinal muscular atrophy

Splicing inhibition of U2AF 65 leads to alternative exon skipping

Recent Advances in Understanding of Alternative Splicing in Neuronal Pathogenesis

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Product

Resources

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Splicing inhibition of U2AF ⁶⁵ leads to alternative exon skipping