RESUMEN
The Arctic APP mutation (E693G) within the amyloid ß (Aß) domain of amyloid precursor protein (APP) leads to dementia with clinical features similar to Alzheimer's disease (AD), which is believed to be mediated via increased formation of protofibrils. We have generated a transgenic mouse model, TgAPParc, with neuron-specific expression of human amyloid precursor protein with the Arctic mutation (hAPParc), showing mild amyloid pathology with a relatively late onset. Here we performed a detailed analysis of the spatiotemporal progression of neuropathology in homozygous TgAPParc, focusing on intracellular Aß and diffuse Aß aggregates rather than amyloid plaques. We show that the neuropathology in homozygous TgAPParc mice starts with intracellular Aß aggregates, which is followed by diffuse extracellular Aß deposits in subiculum that later expands to brain regions receiving neuronal projections from regions already affected. Together this suggests that the pathology in TgAPParc mice affects interconnected brain regions and may represent a valuable tool to study the spread and progression of neuropathology in Alzheimer's disease.
Asunto(s)
Enfermedad de Alzheimer , Péptidos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Hipocampo/metabolismo , Mutación/genética , Fragmentos de Péptidos/metabolismo , Factores de Edad , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Precursor de Proteína beta-Amiloide/metabolismo , Análisis de Varianza , Animales , Modelos Animales de Enfermedad , Ensayo de Inmunoadsorción Enzimática/métodos , Femenino , Hipocampo/patología , Hipocampo/ultraestructura , Humanos , Masculino , Ratones , Ratones Transgénicos , Microscopía InmunoelectrónicaRESUMEN
Most cases of the segmental progeroid syndrome, Hutchinson-Gilford progeria syndrome (HGPS), are caused by a de novo dominant mutation within a single codon of the LMNA gene. This mutation leads to the increased usage of an internal splice site that generates an alternative lamin A transcript with an internal deletion of 150 nucleotides, called lamin A Delta 150. The LMNA gene encodes two major proteins of the inner nuclear lamina, lamins A and C, but not much is known about their expression levels. Determination of the overall expression levels of the LMNA gene transcripts is an important step to further the understanding of the HGPS. In this study, we have performed absolute quantification of the lamins A, C and A Delta 150 transcripts in primary dermal fibroblasts from HGPS patients and unaffected age-matched and parent controls. We show that the lamin A Delta 150 transcript is present in unaffected controls but its expression is >160-fold lower than that in samples from HGPS patients. Analysis of transcript expression during in vitro aging shows that although the levels of lamin A and lamin C transcripts remain unchanged, the lamin A Delta 150 transcript increases in late passage cells from HGPS patients and parental controls. This study provides a new method for LMNA transcript analysis and insights into the expression of the LMNA gene in HGPS and normal cells.
Asunto(s)
Senescencia Celular/genética , Lamina Tipo A/biosíntesis , Progeria , Empalme Alternativo , Western Blotting , Línea Celular , Expresión Génica , Humanos , Lamina Tipo A/genética , Progeria/genética , Progeria/metabolismo , Isoformas de Proteínas/biosíntesis , Isoformas de Proteínas/genética , ARN/análisis , ARN/genética , Regulación hacia ArribaRESUMEN
Multiple genetic disorders caused by mutations that affect the proteins lamin A and C show strong skin phenotypes. These disorders include the premature aging disorders Hutchinson-Gilford progeria syndrome and mandibuloacral dysplasia, as well as restrictive dermopathy. Prior studies have shown that the lamin A/C and B proteins are expressed in skin, but little is known about their normal expression in the different skin cell-types and during the hair cycle. Our immunohistochemical staining for lamins A/C and B in wild-type mice revealed strong expression in the basal cell layer of the epidermis, the outer root sheath, and the dermal papilla during all stages of the hair cycle. Lower expression of both lamins A/C and B was seen in suprabasal cells of the epidermis, in the hypodermis, and in the bulb of catagen follicles. In addition, we have utilized a previously described mouse model of Hutchinson-Gilford progeria syndrome and show here that the expression of progerin does not result in pronounced effects on hair cycling or the expression of lamin B.
Asunto(s)
Folículo Piloso/metabolismo , Laminas/metabolismo , Animales , Fenómenos Biológicos , Epidermis/metabolismo , Expresión Génica , Laminas/genética , Ratones , Progeria/genética , Progeria/metabolismo , Proteínas/genética , Proteínas/metabolismoRESUMEN
Hutchinson-Gilford progeria syndrome (HGPS) is a rare human genetic disorder characterized by striking progeroid features. Clinical findings in the skin include scleroderma, alopecia and loss of subcutaneous fat. HGPS is usually caused by a dominant-negative mutation in LMNA, a gene that encodes two major proteins of the inner nuclear lamina: lamin A and lamin C. We have generated tetracycline-inducible transgenic lines that carry a minigene of human LMNA under the control of a tet-operon. Two mouse lines were created: one carrying the wild-type sequence of LMNA and the other carrying the most common HGPS mutation. Targeted expression of the HGPS mutation in keratin-5-expressing tissues led to abnormalities in the skin and teeth, including fibrosis, loss of hypodermal adipocytes, structural defects in the hair follicles and sebaceous glands, and abnormal incisors. The severity of the defects was related to the level of expression of the transgene in different mouse lines. These transgenic mice appear to be good models for studies of the molecular mechanisms of skin abnormalities in HGPS and other related disorders.