RESUMEN
Myelination of the peripheral nervous system requires Schwann cells (SC) differentiation into the myelinating phenotype. The peripheral myelin protein-22 (PMP22) is an integral membrane glycoprotein, expressed in SC. It was initially described as a growth arrest-specific (gas3) gene product, up-regulated by serum starvation. PMP22 mutations were pathognomonic for human hereditary peripheral neuropathies, including the Charcot-Marie-Tooth disease (CMT). Trembler-J (TrJ) is a heterozygous mouse model carrying the same pmp22 point mutation as a CMT1E variant. Mutations in lamina genes have been related to a type of peripheral (CMT2B1) or central (autosomal dominant leukodystrophy) neuropathy. We explore the presence of PMP22 and Lamin B1 in Wt and TrJ SC nuclei of sciatic nerves and the colocalization of PMP22 concerning the silent heterochromatin (HC: DAPI-dark counterstaining), the transcriptionally active euchromatin (EC), and the nuclear lamina (H3K4m3 and Lamin B1 immunostaining, respectively). The results revealed that the number of TrJ SC nuclei in sciatic nerves was greater, and the SC volumes were smaller than those of Wt. The myelin protein PMP22 and Lamin B1 were detected in Wt and TrJ SC nuclei and predominantly in peripheral nuclear regions. The level of PMP22 was higher, and those of Lamin B1 lower in TrJ than in Wt mice. The level of PMP22 was higher, and those of Lamin B1 lower in TrJ than in Wt mice. PMP22 colocalized more with Lamin B1 and with the transcriptionally competent EC, than the silent HC with differences between Wt and TrJ genotypes. The results are discussed regarding the probable nuclear role of PMP22 and the relationship with TrJ neuropathy.
Asunto(s)
Enfermedad de Charcot-Marie-Tooth , Proteínas de la Mielina , Células de Schwann , Animales , Enfermedad de Charcot-Marie-Tooth/genética , Enfermedad de Charcot-Marie-Tooth/metabolismo , Lamina Tipo B/genética , Lamina Tipo B/metabolismo , Ratones , Proteínas de la Mielina/genética , Proteínas de la Mielina/metabolismo , Células de Schwann/metabolismoRESUMEN
The increase in senescent cells in tissues, including the brain, is a general feature of normal aging and age-related pathologies. Senescent cells exhibit a specific phenotype, which includes an altered nuclear morphology and transcriptomic changes. Astrocytes undergo senescence in vitro and in age-associated neurodegenerative diseases, but little is known about whether this process also occurs in physiological aging, as well as its functional implication. Here, we investigated astrocyte senescence in vitro, in old mouse brains, and in post-mortem human brain tissue of elderly. We identified a significant loss of lamin-B1, a major component of the nuclear lamina, as a hallmark of senescent astrocytes. We showed a severe reduction of lamin-B1 in the dentate gyrus of aged mice, including in hippocampal astrocytes, and in the granular cell layer of the hippocampus of post-mortem human tissue from non-demented elderly. The lamin-B1 reduction was associated with nuclear deformations, represented by an increased incidence of invaginated nuclei and loss of nuclear circularity in senescent astrocytes in vitro and in the aging human hippocampus. We also found differences in lamin-B1 levels and astrocyte nuclear morphology between the granular cell layer and polymorphic layer in the elderly human hippocampus, suggesting an intra-regional-dependent aging response of human astrocytes. Moreover, we described senescence-associated impaired neuritogenic and synaptogenic capacity of mouse astrocytes. Our findings show that reduction of lamin-B1 is a conserved feature of hippocampal cells aging, including astrocytes, and shed light on significant defects in nuclear lamina structure which may contribute to astrocyte dysfunctions during aging.
Asunto(s)
Astrocitos/metabolismo , Hipocampo/fisiopatología , Lamina Tipo B/metabolismo , Animales , Senescencia Celular , Humanos , RatonesRESUMEN
Nuclear ß-dystroglycan (ß-DG) is involved in the maintenance of nuclear architecture and function. Nonetheless, its relevance in defined nuclear processes remains to be determined. In this study we generated a C2C12 cell-based DG-null model using CRISPR-Cas9 technology to provide insights into the role of ß-DG on nuclear processes. Since DG-null cells exhibited decreased levels of lamin B1, we aimed to elucidate the contribution of DG to senescence, owing to the central role of lamin B1 in this pathway. Remarkably, the lack of DG enables C2C12 cells to acquire senescent features, including cell-cycle arrest, increased senescence-associated-ß-galactosidase activity, heterochromatin loss, aberrant nuclear morphology and nucleolar disruption. We demonstrated that genomic instability is one driving cause of the senescent phenotype in DG-null cells via the activation of a DNA-damage response associated with mitotic failure, as shown by the presence of multipolar mitotic spindles, which in turn induced the formation of micronuclei and γH2AX foci (DNA-damage marker), telomere shortening and p53/p21 upregulation. Altogether, these events might ultimately lead to premature senescence, impeding the replication of the damaged genome. In summary, we present evidence supporting a role for DG in protecting against senescence, through the maintenance of proper lamin B1 expression/localization and proper mitotic spindle organization.
Asunto(s)
Senescencia Celular/genética , Distroglicanos/genética , Inestabilidad Genómica/genética , Mitosis/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Puntos de Control del Ciclo Celular/genética , Línea Celular , Núcleo Celular/genética , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/genética , Daño del ADN/genética , Histonas/genética , Lamina Tipo B/genética , Ratones , Ratones Noqueados , Huso Acromático/genética , Telómero/genética , Proteína p53 Supresora de Tumor/genética , Regulación hacia Arriba/genética , beta-Galactosidasa/genéticaRESUMEN
The study of Hutchinson-Gilford progeria syndrome (HGPS) has provided important clues to decipher mechanisms underlying aging. Progerin, a mutant lamin A, disrupts nuclear envelope structure/function, with further impairment of multiple processes that culminate in senescence. Here, we demonstrate that the nuclear protein export pathway is exacerbated in HGPS, due to progerin-driven overexpression of CRM1, thereby disturbing nucleocytoplasmic partitioning of CRM1-target proteins. Enhanced nuclear export is central in HGPS, since pharmacological inhibition of CRM1 alleviates all aging hallmarks analyzed, including senescent cellular morphology, lamin B1 downregulation, loss of heterochromatin, nuclear morphology defects, and expanded nucleoli. Exogenous overexpression of CRM1 on the other hand recapitulates the HGPS cellular phenotype in normal fibroblasts. CRM1 levels/activity increases with age in fibroblasts from healthy donors, indicating that altered nuclear export is a common hallmark of pathological and physiological aging. Collectively, our findings provide novel insights into HGPS pathophysiology, identifying CRM1 as potential therapeutic target in HGPS.
Asunto(s)
Envejecimiento Prematuro/metabolismo , Núcleo Celular/metabolismo , Senescencia Celular , Carioferinas/metabolismo , Proteínas Nucleares/metabolismo , Progeria/metabolismo , Receptores Citoplasmáticos y Nucleares/metabolismo , Transporte Activo de Núcleo Celular , Envejecimiento Prematuro/patología , Células Cultivadas , Humanos , Fenotipo , Progeria/patología , Proteína Exportina 1RESUMEN
Telomeric Repeat Binding Factors (TRFs) are architectural nuclear proteins with critical roles in telomere-length regulation, chromosome end protection and, fusion prevention, DNA damage detection, and senescence regulation. Entamoeba histolytica, the parasite responsible of human amoebiasis, harbors three homologs of human TRFs, based on sequence similarities to their Myb DNA binding domain. These proteins were dubbed EhTRF-like I, II and III. In this work, we revealed that EhTRF-like I and II share similarity with human TRF1, while EhTRF-like III shares similarity with human TRF2 by in silico approach. The analysis of ehtrf-like genes showed they are expressed differentially under basal culture conditions. We also studied the cellular localization of EhTRF-like I and III proteins using subcellular fractionation and western blot assays. EhTRF-like I and III proteins were enriched in the nuclear fraction, but they were also present in the cytoplasm. Indirect immunofluorescence showed that these proteins were located at the nuclear periphery co-localizing with Lamin B1 and trimethylated H4K20, which is a characteristic mark of heterochromatic regions and telomeres. We found by transmission electron microscopy that EhTRF-like III was located in regions of more condensed chromatin. Finally, EMSA assays showed that EhTRF-like III forms specific DNA-protein complexes with telomeric related sequences. Our data suggested that EhTRF-like proteins play a role in the maintenance of the chromosome ends in this parasite.
Asunto(s)
Entamoeba histolytica/metabolismo , Proteínas Protozoarias/metabolismo , Proteínas de Unión a Telómeros/metabolismo , Telómero/metabolismo , Western Blotting , Núcleo Celular/química , Biología Computacional , Citoplasma/química , Ensayo de Cambio de Movilidad Electroforética , Entamoeba histolytica/química , Entamoeba histolytica/genética , Técnica del Anticuerpo Fluorescente Indirecta , Perfilación de la Expresión Génica , Humanos , Microscopía Electrónica de Transmisión , Unión Proteica , Proteínas Protozoarias/genética , Homología de Secuencia de Aminoácido , Proteínas de Unión a Telómeros/genéticaRESUMEN
PROPOSE: Endometriosis is a benign disease characterized by implantation and the growth of endometrial tissue outside the uterine cavity and it shares similarities with cancer. Lamin B1, p16 and p21 play a role on cell cycle regulation, development, cell repair and its activities are related to cancers. Considering the similarities between endometriosis and cancer, the aim of the present cross-sectional study is to detect p16, p21 and Lamin B1 in the ectopic endometrium of patients with endometriosis (n = 8) with eutopic (n = 8) and control endometrium (n = 8) and relate them to the maintenance and development of endometriosis. METHODS: Biopsies were obtained from both eutopic and ectopic, from deep infiltrating lesions, endometrium frozen and used for immunofluorescent (p16) or immunohistochemistry procedures (p16, p21, lamin B1). RESULTS: Detected higher lamin B1 in the eutopic endometrium when compared with ectopic endometrium, with no differences between endometriosis tissue with control endometrium. Similar presence of p16 in all groups of patients and no p21 detection was observed. CONCLUSION: We observed reduced detection of lamin B1 in the ectopic endometrium raising the possibility that the presence of senescent cells might be contributing to the maintenance and progression of endometriosis by apoptosis resistance and peritoneal stress inherent of the disease.
Asunto(s)
Biopsia , Endometriosis/metabolismo , Endometrio/metabolismo , Lamina Tipo B/metabolismo , Enfermedades Uterinas/metabolismo , Adulto , Apoptosis , Biomarcadores/metabolismo , Estudios de Casos y Controles , Estudios Transversales , Endometriosis/sangre , Endometriosis/patología , Endometrio/patología , Femenino , Técnica del Anticuerpo Fluorescente , Genes p16 , Humanos , Inmunohistoquímica , Lamina Tipo B/genética , Enfermedades Uterinas/sangre , Enfermedades Uterinas/patología , Útero/patologíaRESUMEN
Autosomal dominant leukodystrophy is a neurodegenerative disorder caused by either point mutations or duplication of the lamin B1 gene on chromosome 5q23. The typical clinical picture consists of autonomic symptoms as well as cerebellar and pyramidal signs. Here we present the case of a 57-year-old female referred to our clinic due to cognitive decline. Neurological examination was significant for cognitive impairment as well as pyramidal and cerebellar signs. Brain MRI displayed diffuse hyperintense lesions in the subcortical white matter, pontine nuclei, brachium pontis and restiform body. The diagnosis was confirmed via genetic testing. Autosomal dominant leukodystrophy should be included in the differential diagnosis of patients presenting with cognitive impairment, motor signs, and leukodystrophy-like images.