RESUMEN
In this study, the expression of IGF-II and H19 was examined in the liver, skeletal muscle and choroid plexus of the neonatal rat during normal maturation and after the administration of dexamethasone. If the two genes share common regulatory elements as postulated by an enhancer competition system, their patterns of expression should remain similar throughout maturation and after treatment with dexamethasone. In the liver, down-regulation of IGF-II and H19 during maturation and after dexamethasone administration was shown. This is consistent with the hypothesis that IGF-II and H19 are regulated by common enhancers. In the secretory cells of the choroid plexus, where expression of IGF-II is known to be biallelic, IGF-II was expressed in both untreated and dexamethasone-treated animals, regardless of age, whereas H19 expression was not detectable. This is consistent with the postulate that only one gene from each allele can be engaged by the enhancers. In skeletal muscle, H19 continues to be expressed in the adult after IGF-II is switched off suggesting that IGF-II can also be regulated independently of H19.
Asunto(s)
Dexametasona/farmacología , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Factor II del Crecimiento Similar a la Insulina/genética , Proteínas Musculares/genética , ARN Mensajero/genética , ARN no Traducido , Animales , Animales Recién Nacidos , Plexo Coroideo/citología , Plexo Coroideo/metabolismo , Hígado/metabolismo , Músculo Esquelético/metabolismo , ARN Largo no Codificante , Ratas , Ratas Sprague-Dawley , Ratas WistarRESUMEN
Insulin-like growth factor II (IGF-II) is expressed during embryogenesis in rodents and humans, but is not produced in most adult tissues. This pattern of expression is closely shared by the gene H19, which lies 3' to IGF-II. This, together with the fact that the genes are reciprocally imprinted, has led to the proposal that the genes are under common transcriptional control by the H19 enhancers during development. In the present study, embryonic stem (ES) cells have been used to generate teratocarcinomas in mice. These tumours generate a wide range of differentiated tissues which have been subjected to hybridisation histochemistry with RNA probes to H19 and IGF-II. Coexpression of the two genes was found in a range of tissues, a pattern consistent with the idea of common transcriptional control. However, there were some areas in which H19 was expressed strongly in comparison with IGF-II and vice versa suggesting the existence of further control elements other than the H19 enhancers.