RESUMEN
Heterozygous, missense mutations in α- or ß-tubulin genes are associated with a wide range of human brain malformations, known as tubulinopathies. We seek to understand whether a mutation's impact at the molecular and cellular levels scale with the severity of brain malformation. Here, we focus on two mutations at the valine 409 residue of TUBA1A, V409I, and V409A, identified in patients with pachygyria or lissencephaly, respectively. We find that ectopic expression of TUBA1A-V409I/A mutants disrupt neuronal migration in mice and promote excessive neurite branching and a decrease in the number of neurite retraction events in primary rat neuronal cultures. These neuronal phenotypes are accompanied by increased microtubule acetylation and polymerization rates. To determine the molecular mechanisms, we modeled the V409I/A mutants in budding yeast and found that they promote intrinsically faster microtubule polymerization rates in cells and in reconstitution experiments with purified tubulin. In addition, V409I/A mutants decrease the recruitment of XMAP215/Stu2 to plus ends in budding yeast and ablate tubulin binding to TOG (tumor overexpressed gene) domains. In each assay tested, the TUBA1A-V409I mutant exhibits an intermediate phenotype between wild type and the more severe TUBA1A-V409A, reflecting the severity observed in brain malformations. Together, our data support a model in which the V409I/A mutations disrupt microtubule regulation typically conferred by XMAP215 proteins during neuronal morphogenesis and migration, and this impact on tubulin activity at the molecular level scales with the impact at the cellular and tissue levels.
Proteins are molecules made up of long chains of building blocks called amino acids. When a mutation changes one of these amino acids, it can lead to the protein malfunctioning, which can have many effects at the cell and tissue level. Given that human proteins are made up of 20 different amino acids, each building block in a protein could mutate to any of the other 19 amino acids, and each mutations could have different effects. Tubulins are proteins that form microtubules, thin tubes that help give cells their shape and allow them to migrate. These proteins are added or removed to microtubules depending on the cell's needs, meaning that microtubules can grow or shrink depending on the situation. Mutations in the tubulin proteins have been linked to malformations of varying severities involving the formation of ridges and folds on the surface of the brain, including lissencephaly, pachygyria or polymicrogyria. Hoff et al. wanted to establish links between tubulin mutations and the effects observed at both cell and tissue level in the brain. They focused on two mutations in the tubulin protein TUBA1A that affect the amino acid in position 409 in the protein, which is normally a valine. One of the mutations turns this valine into an amino acid called isoleucine. This mutation is associated with pachygyria, which leads to the brain developing few ridges that are broad and flat. The second mutation turns the valine into an alanine, and is linked to lissencephaly, a more severe condition in which the brain develops no ridges, appearing smooth. Hoff et al. found that both mutations interfere with the development of the brain by stopping neurons from migrating properly, which prevents them from forming the folds in the brain correctly. At the cellular level, the mutations lead to tubulins becoming harder to remove from microtubules, making microtubules more stable than usual. This results in longer microtubules that are harder for the cell to shorten or destroy as needed. Additionally, Hoff et al. showed that the mutant versions of TUBA1A have weaker interactions with a protein called XMAP215, which controls the addition of tubulin to microtubules. This causes the microtubules to grow uncontrollably. Hoff et al. also established that the magnitude of the effects of each mutation on microtubule growth scale with the severity of the disorder they cause. Specifically, cells in which TUBA1A is not mutated have microtubules that grow at a normal rate, and lead to typical brain development. Meanwhile, cells carrying the mutation that turns a valine into an alanine, which is linked to the more severe condition lissencephaly, have microtubules that grow very fast. Finally, cells in which the valine is mutated to an isoleucine the mutation associated with the less severe malformation pachygyria have microtubules that grow at an intermediate rate. These findings provide a link between mutations in tubulin proteins and larger effects on cell movement that lead to brain malformations. Additionally, they also link the severity of the malformation to the severity of the microtubule defect caused by each mutation. Further work could examine whether microtubule stabilization is also seen in other similar diseases, which, in the long term, could reveal ways to detect and treat these illnesses.
Asunto(s)
Lisencefalia , Tubulina (Proteína) , Animales , Humanos , Lisencefalia/genética , Ratones , Proteínas Asociadas a Microtúbulos , Microtúbulos/metabolismo , Neurogénesis , Neuronas/metabolismo , Ratas , Saccharomyces cerevisiae , Proteínas de Saccharomyces cerevisiae , Tubulina (Proteína)/metabolismoRESUMEN
PURPOSE: To develop two item content-matched, precise, score-level targeted inpatient physical function (PF) short form (SF) measures: one clinician-reported, one patient-reported. Items were derived from PROMIS PF bank content; scores are reported on the PROMIS PF T-score metric. METHODS: The PROMIS PF item bank was reviewed for content measuring lower-level PF status (T-scores 10-50) with high item set score-level reliability (≥ 0.90). Selected patient-reported (PR) items were also edited to function as clinician-reported (CR) items. Items were reviewed by clinicians and field tested; responses were assessed for meeting PROMIS measure development standards. New CR and PR items were calibrated using patient responses to the original PROMIS PF items as anchoring data. SFs were constructed, based on content and precision. RESULTS: Nine PROMIS PF items were candidates for CR and PR inpatient PF assessment; three new items were written to extend content coverage. An inpatient sample (N = 515; 55.1% female; mean age = 66.2 years) completed 12 PR items and was assessed by physical therapists (using 12 CR items). Analyses indicated item sets met expected measure development standards. Twelve new CR and three new PR items were linked to the PROMIS PF metric (raw score r = 0.73 and 0.90, respectively). A 5-item CR SF measure was constructed; score-level reliabilities were ≥ 0.90 for T-scores 13-45. A 5-item PR SF measure was assembled, mirroring CR SF content. CONCLUSIONS: Two item content-matched SFs have been developed for clinician and patient reporting and are an effective, efficient means of assessing inpatient PF and offer complementary perspectives.
Asunto(s)
Pacientes Internos , Calidad de Vida , Adulto , Anciano , Recolección de Datos , Femenino , Humanos , Masculino , Medición de Resultados Informados por el Paciente , Calidad de Vida/psicología , Estándares de Referencia , Reproducibilidad de los Resultados , Encuestas y CuestionariosRESUMEN
Mutations and copy number variants of the CUB and Sushi multiple domains 2 (CSMD2) gene are associated with neuropsychiatric disease. CSMD2 encodes a single-pass transmembrane protein with a large extracellular domain comprising repeats of CUB and Sushi domains. High expression of CSMD2 in the developing and mature brain suggests possible roles in neuron development or function, but the cellular functions of CSMD2 are not known. In this study, we show that mouse Csmd2 is expressed in excitatory and inhibitory neurons in the forebrain. Csmd2 protein exhibits a somatodendritic localization in the neocortex and hippocampus, with smaller puncta localizing to the neuropil. Using immunohistochemical and biochemical methods, we demonstrate that Csmd2 localizes to dendritic spines and is enriched in the postsynaptic density (PSD). Accordingly, we show that the cytoplasmic tail domain of Csmd2 interacts with synaptic scaffolding proteins of the membrane-associated guanylate kinase (MAGUK) family. The association between Csmd2 and MAGUK member PSD-95 is dependent on a PDZ-binding domain on the Csmd2 tail, which is also required for synaptic targeting of Csmd2. Finally, we show that knock-down of Csmd2 expression in hippocampal neuron cultures results in reduced complexity of dendritic arbors and deficits in dendritic spine density. Knock-down of Csmd2 in immature developing neurons results in reduced filopodia density, whereas Csmd2 knock-down in mature neurons causes significant reductions in dendritic spine density and dendrite complexity. Together, these results point toward a function for Csmd2 in development and maintenance of dendrites and synapses, which may account for its association with certain psychiatric disorders.
Asunto(s)
Espinas Dendríticas/metabolismo , Homólogo 4 de la Proteína Discs Large/metabolismo , Hipocampo/metabolismo , Proteínas de la Membrana/metabolismo , Neocórtex/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Neuronas/fisiología , Densidad Postsináptica/metabolismo , Animales , Células Cultivadas , Femenino , Hipocampo/citología , Masculino , Proteínas de la Membrana/deficiencia , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Proteínas del Tejido Nervioso/deficiencia , Neuronas/metabolismo , Seudópodos/metabolismoRESUMEN
Various retinal degenerative diseases including dry and neovascular age-related macular degeneration (AMD), retinitis pigmentosa, and diabetic retinopathy are associated with the degeneration of the retinal pigmented epithelial (RPE) layer of the retina. This consequently results in the death of rod and cone photoreceptors that they support, structurally and functionally leading to legal or complete blindness. Therefore, developing therapeutic strategies to preserve cellular homeostasis in the RPE would be a favorable asset in the clinic. The aryl hydrocarbon receptor (AhR) is a conserved, environmental ligand-dependent, per ARNT-sim (PAS) domain containing bHLH transcription factor that mediates adaptive response to stress via its downstream transcriptional targets. Using in silico, in vitro and in vivo assays, we identified 2,2'-aminophenyl indole (2AI) as a potent synthetic ligand of AhR that protects RPE cells in vitro from lipid peroxidation cytotoxicity mediated by 4-hydroxynonenal (4HNE) as well as the retina in vivo from light-damage. Additionally, metabolic characterization of this molecule by LC-MS suggests that 2AI alters the lipid metabolism of RPE cells, enhancing the intracellular levels of palmitoleic acid. Finally, we show that, as a downstream effector of 2AI-mediated AhR activation, palmitoleic acid protects RPE cells from 4HNE-mediated stress, and light mediated retinal degeneration in mice.