Profilin 1 Mutant Mouse—a New Model for ALS?

October 8, 2016 - als

Transgenic animals harboring a turn related to amyotrophic parallel sclerosis humour a identical predestine as do humans with a disease, according to new research. In a Sep 28 emanate of Proceedings of a National Academy of Sciences, researchers led by John Landers and Zuoshang Xu of a University of Massachusetts Medical School in Worcester report how a mice, that denote a mutant form of profilin 1 famous to means singular forms of ALS, became diseased in adulthood, afterwards paralyzed, and died early. These symptoms were accompanied by a on-going detriment of engine neurons in a spinal cord. While aggregates of profilin seemed to resin adult a protein plunge machine in these neurons, a aggregates seemed usually after a animals had started displaying symptoms. Researchers wish to use a indication to serve expose a mobile mechanisms that underlie ALS.

“Hopefully this PFN1 rodent indication will benefit traction among ALS researchers identical to a widely used mutant SOD1 mouse, with that it shares several vicious ALS-like characteristics,” commented Matthew Figley of Washington University in St. Louis, who was not concerned in a study. “Much work stays to be finished to establish a resource of PFN1 engine neuron toxicity yet this new rodent indication will expected be a vicious apparatus in those pursuits.”

Numerous rodent models formed on several other ALS-linked mutations have been recently generated (see Alzforum ALS Research Models). Alas, so distant usually SOD1 mutant mice, that were initial grown some-more than dual decades ago, entirely reproduce a astringency of engine neuron lapse seen in ALS. Since SOD mutations criticism for a little fragment of all ALS cases, researchers have been on a surveillance for new models.

Landers’ find of ALS mutations in a gene for profilin lifted hope, given this actin-binding protein supports a polymerization of a cytoskeleton, that is essential for axon upkeep and expansion (see Jul 2012 news). In rodent neurons and tellurian dungeon lines, normal profilin comingles with RNA/protein conglomerates called highlight granules, and in yeast, ALS-associated mutations in profilin altered highlight granule dynamics (see Nov 2013 discussion news and Figley et al., 2014). These granules, that bay another ALS-associated protein, TDP-43, competence mistreat cells when they destroy to waste and reason vicious proteins warrant (see Liu-Yesucevitz et al., 2010). 

It is now misleading possibly mutant PFN1 exacts a neurodegenerative fee by shirking a actin-binding duties, or consorting with protein aggregates, or both. However, people with PFN1-associated ALS—which occurs in reduction than 2 percent of people with patrimonial ALS—suffer from many of a hallmark symptoms of a disease, including on-going flesh weakness, paralysis, and early death.

To emanate a model, initial author Chunxing Yang and colleagues generated mice expressing a ALS-associated C71G mutant form of tellurian PFN1. After building and comparing mixed lines of transgenic mice, a researchers staid on a aria that voiced 3 copies of a tellurian PFN1 gene—two underneath control of a Thy1.2 promoter, and one tranquil by a rodent prion promoter. Compared with other countenance schemes, this triple gene combo yielded a tip turn of PFN1 countenance in engine neurons and a earliest, many serious ALS symptoms. For controls, a researchers used a triple combo of a normal human PFN1.

For a initial 3 months of their lives, PFN1-C71G transgenic animals seemed a same as nontransgenic animals or those expressing a wild-type chronicle (PFN1-WT) of a protein. However, between 100 and 120 days, about 10 percent of a PFN1-C71G mice started boring their feet; between 120-140 days, 70 percent did so; and by 170 days, all of these animals limped, some relocating slowly. Beyond 170 days, their condition worsened to stoppage of all limbs; during that indicate a animals could no longer pierce and were euthanized during an normal of 211 days old. Performance on several engine tests, including balancing on a spinning rod, jumping and swinging from a tip of their cage, and hold strength, also waned via a illness course. In contrast, PFN1-WT animals grown no motor weakness.

Other rodent lines carrying fewer copies of PFN-C71G also grown on-going engine dysfunction and paralysis, yet it started later. This indicated that a speed of course correlated with a volume of mutant PFN1 voiced in neurons, that was fivefold aloft than endogenous levels in a triple transgenic.

Examining engine neurons in a ventral horn of a spinal cord, a researchers beheld that between 100 and 120 days (when symptoms initial seemed in some mice), axons started degenerating. This ramped adult between 120 and 140 days, when neurons started failing and markers of neuroinflammation, including widespread astrogliosis and microgliosis, flared adult in a tip reaches of a spinal cord. Some neurons also died in a dorsal base ganglia of a spinal cord as good as a medulla, yet not in other tools of the brain. 

Profile of Destruction.

By a time animals reached a stoppage stage, engine neurons in a cervical territory of a spinal cord were failing in droves in PFN1-C71G mice (right). [Courtesy of Yang et al., PNAS 2016.]

How did this turn mistreat engine neurons? The researchers legalised a neurons for signs of flagging profilin duty and for protein aggregates. In contrariety to cells from PFN1-WT mice, PFN1-C71G engine neurons voiced reduce levels of neurofilaments—components of a neuronal cytoskeleton indispensable for a expansion and fortitude of axons. The network in a mutant neurons looked stunted, combining a round arrangement around a iota instead of fluctuating a web out to a distant ends of axons. Small, to spasmodic large, aggregates of PFN1-C71G seemed via a cytoplasm. Comingling with a profilin were aggregates of ubiquitin and p62, suggesting there competence be malfunctions in a proteasome and autophagy protein plunge pathways, respectively.

Interestingly, a researchers rescued no aggregates of PFN1-C71G until day 127, even yet axons were degenerating and some mice started boring their feet between day 100 and 120. More aggregates seemed as a illness progressed. These formula indicated that nonetheless profilin aggregates wear with illness severity, they competence not primarily spark neurodegeneration.

Problem Proteins.

Aggregates of profilin (green) and ubiquitin (red) choked engine neurons in PFN1-C71G mice (bottom) yet not in PFN1-WT controls (top). [Courtesy of Yang et al., PNAS 2016.]

How does PFN-C71G kill engine neurons in these mice? And what role, if any, do profilin aggregates competence play in a process? Benjamin Wolozin of Boston University School of Medicine due that a turn allows profilin to form oligomers, that meddle with a protein’s purpose in axonal transport. This could explain axon lapse before to a showing of obvious aggregates. 

However, Wolozin cautioned that a overexpression of PFN1-C71G creates it formidable to envision possibly a same mechanisms would kill neurons in people with ALS. Still, a prior investigate had indicated that ALS-associated PFN mutations caused a protein to turn inconstant and disposed to assembly if not fast degraded (see Jun 2015 news). 

Xu concluded that oligomers of profilin could convey a arrangement of detectable aggregates, however, he hypothesized that profilin mutations led to cytoskeletal clutter and axon lapse not by stopping profilin function, yet by strenuous a protein quality-control machine with aggregates. He skeleton to try this idea. He also remarkable that a transgenic animals still voiced normal endogenous profilin, so any phenotype driven by detriment of profilin duty would need to be a widespread negative one.

Wolozin, who helped impersonate TDP-43- and RNA-laden highlight granules in ALS, also forked out that nothing of these granules amass in a PFN1-C71G mice. Xu pronounced they looked for this pathology in vain. While Wolozin praised a indication for a clever symptomatic phenotype, he called a miss of TDP-43 pathology disappointing, given that 90 percent of people with ALS have this pathology. This profilin indication is therefore doubtful to be useful in drug find studies, he said.

Xu disagreed. He pronounced TDP-43 aggregates are clearly not a usually means of lapse in engine neurons, and that several rodent models harboring these aggregates miss endless engine neuron neurodegeneration. Interestingly, in a SOD1 mutant model, that has both serious neurodegeneration and TDP-43 pathology, a cytoskeleton crumbles and ubiquitin/p62 aggregates accumulate, only as in a PFN1 mouse, Xu said. Hence, engine neuron genocide due to overexpression of possibly mutant PFN1 or mutant SOD1 could be eccentric of TDP43 pathology, Xu said. He skeleton to closely review a dual models, and in partnership with other labs, use a profilin indication to exam for therapeutics. “At slightest now we have dual models to test,” he said.—Jessica Shugart

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  1. This is really good work from a same group of labs during UMass that initial described and characterized a profilin 1 (PFN1) mutations in patrimonial ALS patients only 4 years ago. Excitingly, they’ve found that high neuronal countenance levels of a ALS-causing C71G mutant PFN1, yet not identical countenance of wild-type PFN1, outcome in many of a evil phenotypes compared with ALS, including adult-onset flesh debility surpassing to stoppage and malignancy in their transgenic mice. The authors entirely characterized a mutant mice and they uncover that a ALS-like symptoms are proceeded by distinguished axonal degeneration, denervation during neuromuscular junctions, neuroinflammation, and finally extreme spinal cord engine neuron loss. Importantly, a authors also denote that nonetheless their transgene and mutant PFN1 protein are rarely voiced in other neuron populations (e.g. cortex, hippocampus), a compared dungeon toxicity is mostly cramped to a spinal cord engine neurons, with some reduction serious detriment of feeling neurons as well. This resourceful aspect of their mouse model is vicious to destiny studies of engine neuron ionization due to mutant PFN1 countenance in ALS.

    Yang et al. denote that ubiquitin and p62 are upregulated in engine neurons in a mutant PFN1 mouse, and they introduce that this is due to an aberrant proteostasis response. Further review into a mutant PFN1 pathology in these mice is warranted. The authors note that a immunostaining for mutant PFN1 shows “small particulates in a cytoplasm and neuronal processes.” These are remarkably identical in coming to highlight granules. Given that we demonstrated PFN1 can itself be a member of highlight granules (Figley et al., 2014), it will be engaging to see if these mutant PFN1 aggregates in vivo also enclose highlight granule proteins, as are mostly celebrated in other ALS-related neuropathology. It will also be of seductiveness to exam if a mutant PFN1 aggregates enclose other famous ALS-associated proteins like TDP-43, FUS, or ataxin 2, generally given several groups have now reported mutant PFN1 interacting with TDP-43 (Wu et al., 2012; Tanaka et al., 2016; Matsukawa et al., 2016). 

    Hopefully, this PFN1 rodent indication will benefit traction among ALS researchers identical to a widely used mutant SOD1 mouse, with that it shares several vicious ALS-like characteristics remarkable above. Much work stays to be finished to establish a resource of PFN1 engine neuron toxicity, yet this new rodent indication will expected be a vicious apparatus in those pursuits.

    References:

    .
    Profilin 1 associates with highlight granules and ALS-linked mutations change highlight granule dynamics.
    J Neurosci. 2014 Jun 11;34(24):8083-97.
    PubMed.

    .
    Mutations in a profilin 1 gene means patrimonial amyotrophic parallel sclerosis.
    Nature. 2012 Aug 23;488(7412):499-503.
    PubMed.

    .
    Gain-of-function profilin 1 mutations related to patrimonial amyotrophic parallel sclerosis means seed-dependent intracellular TDP-43 aggregation.
    Hum Mol Genet. 2016 Apr 1;25(7):1420-33. Epub 2016 Jan 28
    PubMed.

    .
    Familial ALS-linked Mutations in Profilin 1 Exacerbate TDP-43-induced Degeneration in a Retina of Drosophila Melanogaster by an Increase in a Cytoplasmic Localization of TDP-43.
    J Biol Chem. 2016 Sep 15;
    PubMed.

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Research Models Citations

  1. SOD1-G93A (hybrid) (G1H)

News Citations

  1. Profilin Gene Is Actin’ in ALS 13 Jul 2012
  2. Profilin-1 Links Cytoskeleton and RNA Aggregation in ALS 20 Nov 2013
  3. Mutations Open Cavity in Profilin, Destabilize a ALS-Linked Protein 10 Jun 2015

Paper Citations

  1. .
    Profilin 1 associates with highlight granules and ALS-linked mutations change highlight granule dynamics.
    J Neurosci. 2014 Jun 11;34(24):8083-97.
    PubMed.
  2. .
    Tar DNA contracting protein-43 (TDP-43) associates with highlight granules: research of well-bred cells and pathological mind tissue.
    PLoS One. 2010;5(10):e13250.
    PubMed.

Other Citations

  1. Alzforum ALS Research Models

source ⦿ http://www.alzforum.org/news/research-news/profilin-1-mutant-mouse-new-model-als

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