A Liquid-to-Solid Phase Transition of the ALS Protein FUS Accelerated by Disease Mutation

https://www.cell.com/cell/pdf/S0092-8674(15)01176-9.pdf

Phase Separation by Low Complexity Domains Promotes Stress Granule Assembly and Drives Pathological Fibrillization

https://people.mbi.ucla.edu/david/Reprints/McKnight.Kato.Fus.2012.pdf

Cell-free Formation of RNA Granules: Low Complexity Sequence Domains Form Dynamic Fibers within Hydrogels

http://dosequis.colorado.edu/Courses/BrainWeb/papers/ALS1.pdf

Converging mechanisms in ALS and FTD: disrupted RNA and protein homeostasis.

Amyotrophic lateral sclerosis (ALS) is a fatal human neurodegenerative disease affecting primarily motor neurons. Two RNA-binding proteins, TDP-43 and FUS, aggregate in the degenerating motor neurons of ALS patients, and mutations in the genes encoding these proteins cause some forms of ALS. TDP-43 and FUS and several related RNA-binding proteins harbor aggregation-promoting prion-like domains that allow them to rapidly self-associate. This property is critical for the formation and dynamics of cellular ribonucleoprotein granules, the crucibles of RNA metabolism and homeostasis. Recent work connecting TDP-43 and FUS to stress granules has suggested how this cellular pathway, which involves protein aggregation as part of its normal function, might be coopted during disease pathogenesis.

/pdf/stress-granules-as-crucibles-of-als-pathogenesis-1w2mqece98.pdf

Stress granules as crucibles of ALS pathogenesis

Mutations in the RNA-binding protein FUS (fused in sarcoma) are linked to amyotrophic lateral sclerosis (ALS), but the mechanism by which these mutants cause motor neuron degeneration is not known. We report a novel ALS truncation mutant (R495X) that leads to a relatively severe ALS clinical phenotype compared with FUS missense mutations. Expression of R495X FUS, which abrogates a putative nuclear localization signal at the C-terminus of FUS, in HEK-293 cells and in the zebrafish spinal cord caused a striking cytoplasmic accumulation of the protein to a greater extent than that observed for recessive (H517Q) and dominant (R521G) missense mutants. Furthermore, in response to oxidative stress or heat shock conditions in cultures and in vivo, the ALS-linked FUS mutants, but not wild-type FUS, assembled into perinuclear stress granules in proportion to their cytoplasmic expression levels. These findings demonstrate a potential link between FUS mutations and cellular pathways involved in stress responses that may be relevant to altered motor neuron homeostasis in ALS.

/pdf/mutant-fus-proteins-that-cause-amyotrophic-lateral-sclerosis-4c9shnh26s.pdf

Mutant FUS proteins that cause amyotrophic lateral sclerosis incorporate into stress granules.

Hyperkalemic periodic paralysis (HyperKPP) produces myotonia and attacks of muscle weakness triggered by rest after exercise or by K+ ingestion. We introduced a missense substitution corresponding to a human familial HyperKPP mutation (Met1592Val) into the mouse gene encoding the skeletal muscle voltage-gated Na+ channel NaV1.4. Mice heterozygous for this mutation exhibited prominent myotonia at rest and muscle fiber-type switching to a more oxidative phenotype compared with controls. Isolated mutant extensor digitorum longus muscles were abnormally sensitive to the Na+/K+ pump inhibitor ouabain and exhibited age-dependent changes, including delayed relaxation and altered generation of tetanic force. Moreover, rapid and sustained weakness of isolated mutant muscles was induced when the extracellular K+ concentration was increased from 4 mM to 10 mM, a level observed in the muscle interstitium of humans during exercise. Mutant muscle recovered from stimulation-induced fatigue more slowly than did control muscle, and the extent of recovery was decreased in the presence of high extracellular K+ levels. These findings demonstrate that expression of the Met1592Val Na+ channel in mouse muscle is sufficient to produce important features of HyperKPP, including myotonia, K+-sensitive paralysis, and susceptibility to delayed weakness during recovery from fatigue.

/pdf/targeted-mutation-of-mouse-skeletal-muscle-sodium-channel-et7038iqpc.pdf

Targeted mutation of mouse skeletal muscle sodium channel produces myotonia and potassium-sensitive weakness

Mutations in the RNA-binding protein FUS/TLS (FUS) have been linked to the neurodegenerative disease amyotrophic lateral sclerosis (ALS). Although predominantly nuclear, this heterogenous nuclear ribonuclear protein (hnRNP) has multiple functions in RNA processing including intracellular trafficking. In ALS, mutant or wild-type (WT) FUS can form neuronal cytoplasmic inclusions. Asymmetric arginine methylation of FUS by the class 1 arginine methyltransferase, protein arginine methyltransferase 1 (PRMT1), regulates nucleocytoplasmic shuttling of FUS. In motor neurons of primary spinal cord cultures, redistribution of endogenous mouse and that of ectopically expressed WT or mutant human FUS to the cytoplasm led to nuclear depletion of PRMT1, abrogating methylation of its nuclear substrates. Specifically, hypomethylation of arginine 3 of histone 4 resulted in decreased acetylation of lysine 9/14 of histone 3 and transcriptional repression. Distribution of neuronal PRMT1 coincident with FUS also was detected in vivo in the spinal cord of FUSR495X transgenic mice. However, nuclear PRMT1 was not stable postmortem obviating meaningful evaluation of ALS autopsy cases. This study provides evidence for loss of PRMT1 function as a consequence of cytoplasmic accumulation of FUS in the pathogenesis of ALS, including changes in the histone code regulating gene transcription.

/pdf/cytoplasmic-sequestration-of-fus-tls-associated-with-als-2jmapadtj0.pdf

Cytoplasmic sequestration of FUS/TLS associated with ALS alters histone marks through loss of nuclear protein arginine methyltransferase 1

Bronchogenic cysts are congenital malformations caused by aberrant foregut budding. They major occur in the thorax, with subdiaphragmatic cases being uncommon. Here, we present a series of 19 patients diagnosed with subdiaphragmatic bronchogenic cysts histopathologically at a single institution in China from 2012 to 2021. A literature review was also conducted by searching the PubMed database using keywords related to “bronchogenic cysts” and “subdiaphragmatic,” yielding 107 cases. Taken together, the 126 cases had a median age of 41.0 years (interquartile range, 30.0–51.0 years) and 62 of them were male (49.2%). The cysts were most commonly detected in the left adrenal region (36.2%), followed by the pancreatic region (11.5%) and gastric cardia/lesser curvature of the stomach (9.2%). All patients except two underwent surgery for a definite diagnosis, symptom alleviation, and (or) malignancy prevention. Most patients recovered fast and were discharged from the hospital within 1 week after surgery, and the surgical complications were infrequent. The prognosis was generally favorable, as no recurrence was reported during the follow-up as long as 77 months.

/pdf/subdiaphragmatic-bronchogenic-cysts-case-series-and-1hkf6qoc.pdf

Hongru Zhou

Papers

Mutant FUS proteins that cause amyotrophic lateral sclerosis incorporate into stress granules.

Targeted mutation of mouse skeletal muscle sodium channel produces myotonia and potassium-sensitive weakness

Cytoplasmic sequestration of FUS/TLS associated with ALS alters histone marks through loss of nuclear protein arginine methyltransferase 1

Subdiaphragmatic bronchogenic cysts: Case series and literature review