Topoisomerase 1 facilitates nucleosome reassembly at stress genes during recovery.

Chromatin remodeling is essential to allow full development of alternative gene expression programs in response to environmental changes. In fission yeast, oxidative stress triggers massive transcriptional changes including the activation of hundreds of genes, with the participation of histone modifying complexes and chromatin remodelers. DNA transcription is associated to alterations in DNA topology, and DNA topoisomerases facilitate elongation along gene bodies. Here, we test whether the DNA topoisomerase Top1 participates in the RNA polymerase II-dependent activation of the cellular response to oxidative stress. Cells lacking Top1 are resistant to H2O2 stress. The transcriptome of Δtop1 strain was not greatly affected in the absence of stress, but activation of the anti-stress gene expression program was more sustained than in wild-type cells. Top1 associated to stress open reading frames. While the nucleosomes of stress genes are partially and transiently evicted during stress, the chromatin configuration remains open for longer times in cells lacking Top1, facilitating RNA polymerase II progression. We propose that, by removing DNA tension arising from transcription, Top1 facilitates nucleosome reassembly and works in synergy with the chromatin remodeler Hrp1 as opposing forces to transcription and to Snf22 / Hrp3 opening remodelers.

Lysosomal glycogen accumulation in Pompe disease results in disturbed cytoplasmic glycogen metabolism.

Pompe disease is an inherited metabolic myopathy caused by deficiency of acid alpha-glucosidase (GAA), resulting in lysosomal glycogen accumulation. Residual GAA enzyme activity affects disease onset and severity, although other factors, including dysregulation of cytoplasmic glycogen metabolism, are suspected to modulate the disease course. In this study, performed in mice and patient biopsies, we found elevated protein levels of enzymes involved in glucose uptake and cytoplasmic glycogen synthesis in skeletal muscle from mice with Pompe disease, including glycogenin (GYG1), glycogen synthase (GYS1), glucose transporter 4 (GLUT4), glycogen branching enzyme 1 (GBE1), and UDP-glucose pyrophosphorylase (UGP2). Expression levels were elevated before the loss of muscle mass and function. For first time, quantitative mass spectrometry in skeletal muscle biopsies from five adult patients with Pompe disease showed increased expression of GBE1 protein relative to healthy controls at the group level. Paired analysis of individual patients who responded well to treatment with enzyme replacement therapy (ERT) showed reduction of GYS1, GYG1, and GBE1 in all patients after start of ERT compared to baseline. These results indicate that metabolic changes precede muscle wasting in Pompe disease, and imply a positive feedforward loop in Pompe disease, in which lysosomal glycogen accumulation promotes cytoplasmic glycogen synthesis and glucose uptake, resulting in aggravation of the disease phenotype.

A stress-blinded Atf1 can fully assemble heterochromatin in a RNAi-independent minimal mat locus but impairs directionality of mat2/3 switching.

The MAP kinase Sty1 phosphorylates and activates the transcription factor Atf1 in response to several stress conditions, which then shifts from a transcriptional repressor to an activator. Atf1 also participates in heterochromatin assembly at the mat locus, in combination with the RNA interference (RNAi) machinery. Here, we study the role of signal-dependent phosphorylation of Atf1 in heterochromatin establishment at mat, using different Atf1 phospho mutants. Although a hypo-phosphorylation Atf1 mutant, Atf1.10M, mediates heterochromatin assembly, the phosphomimic Atf1.10D is unable to maintain silencing. In a minimal mat locus, lacking the RNAi-recruiting cis elements and displaying intermediate silencing, Atf1.10M restores full heterochromatin and silencing. However, evolution experiments with this stress-blinded Atf1.10M show that it is unable to facilitate switching between the donor site mat3 and mat1. We propose that the unphosphorylated, inactive Atf1 contributes to proper heterochromatin assembly by recruiting repressive complexes, but its stress-dependent phosphorylation is required for recombination/switching to occur.

An in vitro assay to quantify satellite cell activation using isolated mouse myofibers.

Isolated myofibers offer the possibility of in vitro study of satellite cells in their niche. We describe a mouse myofiber isolation assay to assess satellite cell activation by quantifying myofiber-derived satellite cell progeny. The assay allows isolation of myofibers from a mouse using standard equipment and reagents. It can be used to compare satellite cells across different mouse models or to evaluate their response to treatments, offering a valuable complementary tool for in vitro experimentation.

Phosphorylation of the Transcription Factor Atf1 at Multiple Sites by the MAP Kinase Sty1 Controls Homologous Recombination and Transcription.

Transcription factors are often the downstream effectors of signaling cascades. In fission yeast, the transcription factor Atf1 is phosphorylated by the MAP kinase Sty1 under several environmental stressors to promote transcription initiation of stress genes. However, Sty1 and Atf1 have also been involved in other cellular processes such as homologous recombination at hotspots, ste11 gene expression during mating and meiosis, or regulation of fbp1 gene transcription under glucose starvation conditions. Using different phospho-mutants of Atf1, we have investigated the role of Atf1 phosphorylation by Sty1 in those biological processes. An Atf1 mutant lacking the canonical MAP kinase phosphorylation sites cannot activate fbp1 transcription when glucose is depleted, but it is still able to induce recombination at ade6.M26 and to induce ste11 after nitrogen depletion; in these last cases, Sty1 is still required, suggesting that additional non-canonical sites are activating the transcription factor. In all cases, an Atf1 phosphomimetic mutant bypasses the requirement of the Sty1 kinase in these diverse biological processes, highlighting the essential role of the DNA binding factor Atf1 on chromatin remodeling and cell adaptation to nutritional changes. We propose that post-translational modifications of Atf1 by Sty1, either at canonical or non-canonical sites, are sufficient to activate some of the functions of Atf1, those involving chromatin remodeling and transcription initiation. However, in the case of fbp1 where Atf1 acts synergistically with other transcription factors, elimination of the canonical sites is sufficient to hamper some of the interactions required in this complex scenario and to impair transcription initiation.

Contributions to the study of spinocerebellar ataxia type 38 (SCA38).

OBJECTIVE: To report clinical and ancillary findings in a kindred with spinocerebellar ataxia 38 (SCA38). PATIENTS AND METHODS: Five family members spanning two generations developed gait ataxia and intermittent diplopia. On examination, a cerebellar syndrome accompanied by downbeat nystagmus and a saccadic head impulse test (HIT) were found. RESULTS: Whole-exome sequencing demonstrated a heterozygous variant in ELOVL5, c.779A > G (p.Tyr260Cys), in four tested patients. Intermittent concomitant esotropia and hypertropia caused transient diplopia in one individual each. Saccadic HIT responses were found in four subjects. Sensorineural hypoacusis was present in every case. Electrophysiological studies demonstrated a sensory neuronopathy in patients from the first generation, with prolonged disease duration. Baseline serum docosahexaenoic acid (DHA) percent was diminished in four individuals. Oral 26-week dietary DHA supplementation, 650 mg/day, raised serum DHA percent and induced a statistically significant reduction in Scale for the Assessment and Rating of Ataxia (SARA) total scores, and in stance and heel-shin slide item scores. CONCLUSION: The mentioned ELOVL5 variant segregated with disease in this kindred. Downbeat nystagmus, intermittent heterotropia causing transient diplopia, vestibular impairment demonstrated by abnormal HIT, and sensory neuronopathy were part of the clinical picture in this series. DHA supplementation raised serum DHA percent in cases with diminished levels, and induced a clinical amelioration and a statistically significant reduction in SARA scores in the study group. Further studies are needed to investigate the role of these findings in SCA38, and to determine the response to prolonged DHA supplementation.

A new adaptation strategy to glucose starvation: modulation of the gluconate shunt and pentose phosphate pathway by the transcriptional repressor Rsv1.

Survival upon glucose starvation requires a delicate balance between different metabolic pathways. A recent work by the Roe laboratory provides a mechanistic link between glucose deprivation and the regulation of the pentose phosphate pathway, with the transcriptional repressor Rsv1 playing a key role in the process. Rsv1 regulates the flow of glucose into its possible metabolic fates and promotes long-term survival under low glucose.

Restoring the regenerative balance in neuromuscular disorders: satellite cell activation as therapeutic target in Pompe disease.

Skeletal muscle is capable of efficiently regenerating after damage in a process mediated by tissue-resident stem cells called satellite cells. This regenerative potential is often compromised under muscle-degenerative conditions. Consequently, the damage produced during degeneration is not efficiently repaired and the balance between repair and damage is lost. Here we review recent progress on the role of satellite cell-mediated repair in neuromuscular disorders with a focus on Pompe disease, an inherited metabolic myopathy caused by deficiency of the lysosomal enzyme acid alpha glucosidase (GAA). Studies performed in patient biopsies as well as in Pompe disease mouse models demonstrate that muscle regeneration activity is compromised despite progressing muscle damage. We describe disease-specific mechanisms of satellite cell dysfunction to highlight the differences between Pompe disease and muscle dystrophies. The mechanisms involved provide possible targets for therapy, such as modulation of autophagy, muscle exercise, and pharmacological modulation of satellite cell activation. Most of these approaches are still experimental, although promising in animal models, still warrant caution with respect to their safety and efficiency profile.

Regulation of Fn14 Receptor and NF-κB Underlies Inflammation in Meniere's Disease.

Meniere's disease (MD) is a rare disorder characterized by episodic vertigo, sensorineural hearing loss, tinnitus, and aural fullness. It is associated with a fluid imbalance between the secretion of endolymph in the cochlear duct and its reabsorption into the subarachnoid space, leading to an accumulation of endolymph in the inner ear. Epidemiological evidence, including familial aggregation, indicates a genetic contribution and a consistent association with autoimmune diseases (AD). We conducted a case-control study in two phases using an immune genotyping array in a total of 420 patients with bilateral MD and 1,630 controls. We have identified the first locus, at 6p21.33, suggesting an association with bilateral MD [meta-analysis leading signal rs4947296, OR = 2.089 (1.661-2.627); p = 1.39 × 10-09]. Gene expression profiles of homozygous genotype-selected peripheral blood mononuclear cells (PBMCs) demonstrated that this region is a trans-expression quantitative trait locus (eQTL) in PBMCs. Signaling analysis predicted several tumor necrosis factor-related pathways, the TWEAK/Fn14 pathway being the top candidate (p = 2.42 × 10-11). This pathway is involved in the modulation of inflammation in several human AD, including multiple sclerosis, systemic lupus erythematosus, or rheumatoid arthritis. In vitro studies with genotype-selected lymphoblastoid cells from patients with MD suggest that this trans-eQTL may regulate cellular proliferation in lymphoid cells through the TWEAK/Fn14 pathway by increasing the translation of NF-κB. Taken together; these findings suggest that the carriers of the risk genotype may develop an NF-κB-mediated inflammatory response in MD.

Explicación ontogénica para la asociación entre dehiscencia del tegmen tympani y dehiscencia del canal semicircular superior / Ontogenetic explanation for tegmen tympani dehiscence and superior semicircular canal dehiscence association

Objetivos: Analizar la ontogenia del canal semicircular superior y del tegmen tympani y determinar si hay factores embriológicos comunes que expliquen la dehiscencia asociada de ambos. Métodos: Se han analizado 77 series embriológicas humanas de edades comprendidas entre las 6 semanas y recién nacidos. Las preparaciones estaban cortadas en serie y teñidas con la técnica de tricrómico de Martins. Resultados: La prolongación tegmentaria del tegmen tympani y el canal semicircular superior se originan de la misma estructura, la cápsula ótica, y poseen el mismo tipo de osificación endocondral; mientras que la prolongación escamosa del tegmen tympani se desarrolla desde la escama del temporal y su osificación es de tipo directa o intramembranosa. En la osificación de la prolongación tegmentaria colaboran los núcleos de osificación de los canales semicirculares superior, externo y accesorio del tegmen, los cuales por crecimiento se extienden hasta la prolongación tegmentaria, este hecho sumado a que ambas estructuras comparten una capa común de periostio externo podría explicar la coexistencia de falta de cobertura ósea en el tegmen y en el canal. Conclusión: El desarrollo del canal semicircular y tegmen tympani podrían explicar las causas de la asociación de ambas dehiscencias (AU)

Objectives: To analyze the ontogeny of the superior semicircular canal and tegmen tympani and determine if there are common embryological factors explaining both associated dehiscence. Methods: We analyzed 77 human embryological series aged between 6 weeks and newborn. Preparations were serially cut and stained with Masson's trichrome technique. Results: The tegmental prolongation of tegmen tympani and superior semicircular canal originate from the same structure, the otic capsule, and have the same type of endochondral ossification; while the extension of the squamous prolongation of tegmen tympani runs from the temporal squama and ossification is directly of intramembranous type. The nuclei of ossification of the superior and external semicircular canals and accessory of tegmen collaborate in the ossification of the tegmental extension and by growth extend to the tegmental prolongation. This fact plus the fact that both structures share a common layer of external periosteum could explain the coexistence of lack of bone coverage in tegmen and superior semicircular canal. Conclusion: The development of the semicircular canal and tegmen tympani could explain the causes of the association of both dehiscences (AU)

Ontogenetic explanation for tegmen tympani dehiscence and superior semicircular canal dehiscence association. / Explicación ontogénica para la asociación entre dehiscencia del tegmen tympani y dehiscencia del canal semicircular superior.

OBJECTIVES: To analyze the ontogeny of the superior semicircular canal and tegmen tympani and determine if there are common embryological factors explaining both associated dehiscence. METHODS: We analyzed 77 human embryological series aged between 6 weeks and newborn. Preparations were serially cut and stained with Masson's trichrome technique. RESULTS: The tegmental prolongation of tegmen tympani and superior semicircular canal originate from the same structure, the otic capsule, and have the same type of endochondral ossification; while the extension of the squamous prolongation of tegmen tympani runs from the temporal squama and ossification is directly of intramembranous type. The nuclei of ossification of the superior and external semicircular canals and accessory of tegmen collaborate in the ossification of the tegmental extension and by growth extend to the tegmental prolongation. This fact plus the fact that both structures share a common layer of external periosteum could explain the coexistence of lack of bone coverage in tegmen and superior semicircular canal. CONCLUSION: The development of the semicircular canal and tegmen tympani could explain the causes of the association of both dehiscences.

Síndrome de ataxia cerebelosa, arreflexia vestibular y neuropatía: diagnóstico mediante estimulación vestibular calórica / Syndrome of cerebellar ataxia, neuropathy and vestibular areflexia: diagnosis by caloric vestibular stimulation

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Mitochondrial ribosome and Ménière's disease: a pilot study.

Ménière's disease patients experience vestibular disability. When most of medical treatments fail, a chemical labyrinthectomy using aminoglycosides is indicated. However, this process frequently causes hearing damage. Aminoglycosides, interacting with mitochondrial rRNAs, alter mitochondrial protein synthesis and the oxidative phosphorylation system, which provide most of the energy in sensory hair cells. For this reason, we hypothesized that genetic variation in mitochondrial rRNA genes and in two nuclear genes coding for proteins that also modify the susceptibility to aminoglycosides might affect the risk of hearing loss in Ménière's disease patients suffering chemical labyrinthectomy. However, there were no differences in mitochondrial rRNA, TFB1M or MRPS12 genetic variation between those patients that experienced or did not experience hearing loss. This is only a pilot study and larger studies are required to use this therapeutic approach in a rational way and decrease the risk of hearing damage.

[Ontogenic development of the incudostapedial joint]. / Desarrollo ontogénico de la articulación incudoestapedial.

OBJECTIVE: To study the development of the incudostapedial joint in human embryos and foetuses. MATERIAL AND METHOD: 46 temporal bones with specimens between 9 mm and newborns were studied. The preparations were sliced serially and dyed using the Martins trichrome technique. RESULTS: The incudostapedial joint takes on the characteristics of a spheroidal joint at 16 weeks of development. The cartilage covering the articular surfaces is formed by different strata that develop in succession: the superficial stratum at 19 weeks, the transitional between 20 and 23 weeks, and the radial from 24 weeks on. The subchondral bone develops after 29 weeks by the mechanisms of apposition and extension of the periosteal and endosteal bones, but it is not until week 34 that it completely covers the articular surfaces, following constitution of the bone fascicles transmitting the lines of force. The articular capsule is formed from the inter-zone, the surface zone develops the capsular ligament, and the internal surface develops the synovial membrane. CONCLUSIONS: At the time of birth, the incudostapedial joint is completely developed.

Desarrollo ontogénico de la articulación incudoestapedial / Ontogenic development of the incudostapedial joint

Objetivo: Estudiar el desarrollo de la articulación incudoestapedial en embriones y fetos humanos. Material y método: Se han estudiado 46 huesos temporale scon ejemplares comprendidos entre 9 mm y recién nacidos. Las preparaciones estaban cortadas en serie y teñidas con la técnica de tricrómico de Martins. Resultados: La articulación incudoestapedial adquiere las características de una articulación sinovial de tipo enartrosisa las 16 semanas de desarrollo. El cartílago que recubre las superficies articulares está formado por diferentes estratos que se desarrollan sucesivamente: el superficial, a las 19 semanas; el de transición, entre las 20 y las 23 semanas, y el radial, a partir de las 24 semanas. El hueso subcondral se desarrolla a partir de las 29 semanas por los mecanismos de aposición y extensión del periostal y el endostal, pero no es hasta la semana 34 cuando recubre por completo las superficies articulares, constituidos los fascículos óseos por los que se transmitirán las líneas de fuerza. La cápsula articularse forma a partir de la interzona, la zona superficial desarrolla el ligamento capsular y la interna, la sinovial. Conclusiones: En el momento del nacimiento la articulación incudoestapedial está completamente desarrollada (AU)

Objective: To study the development of the incudostapedial joint in human embryos and foetuses. Material and method: 46 temporal bones with specimens between 9 mm and new-borns were studied. The preparations were sliced serially and dyed using the Martins trichrome technique. Results: The incudostapedial joint takes on the characteristics of a spheroidal joint at 16 weeks of development. The cartilage covering the articular surfaces is formed by different strata that develop in succession: the superficial stratum at 19 weeks, the transitional between 20 and 23 weeks, and the radial from 24 weeks on. The subchondral bone develops after 29 weeks by the mechanisms of apposition and extension of the periosteal and endosteal bones, but it is not until week 34 that it completely covers the articular surfaces, following constitution of the bone fascicles transmitting the lines of force. The articular capsule is formed from the inter-zone, the surface zone develops the capsular ligament, and the internal surface develops the synovial membrane. Conclusions: At the time of birth, the incudostapedial joint is completely developed (AU)

Carcinoma neuroendocrino de fosa nasal ¿una entidad independiente? / Neuroendocrine carcinoma of nasal fossa. An independant entity?

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[The role of video-nystagmography in the diagnosis of acoustic neuroma]. / El papel de la videonistagmografía en el diagnóstico del neurinoma del acústico.

AIM: Schwannoma of the vestibular nerve represents 75% of all expansive processes affecting the pontocerebellosum angle. Hearing loss is the most frequent symptom at diagnosis (86%) with or without tinnitus, in the intracanalicular tumors. Vestibular symptoms are described in 60% of patients. MATERIAL AND METHOD: We study twenty cases of acoustic neuromas diagnosed between years 2000 and 2002 in both Otolaryngology and Neurosurgery Departments in our hospital. Videonystagmography (VNG) was performed in all of them. Videonystagmographic findings were analyzed statistically together with the tumoral size and hypoacusia level. DISCUSSION AND CONCLUSION: According to the medical literature reviewed for this paper, we conclude that caloric tests are the most frequently altered ones (77%), showing vestibular hyporreflexia or arreflexia.