RESUMEN
Gbx2 homeobox genes are important for formation and function of the midbrain/hindbrain boundary, namely the isthmic organizer. Two Gbx2 genes were identified in Xenopus laevis, differing in 13 amino acids, including a change in the homeodomain. Xgbx2a is activated earlier during gastrulation and reaches higher levels of expression while Xgbx2b is expressed later, at lower levels and has an additional domain in the ventral blood islands. Their overexpression results in microcephalic embryos with shortened axes and defects in brain and notochord formation. Both genes encode functionally homologous proteins, which differ primarily in their temporal and spatial expression patterns.
Asunto(s)
Expresión Génica , Cabeza/embriología , Proteínas de Homeodominio/genética , Secuencia de Aminoácidos , Animales , Clonación Molecular , Perfilación de la Expresión Génica , Proteínas de Homeodominio/fisiología , Datos de Secuencia Molecular , Morfogénesis , Isoformas de Proteínas/genética , Isoformas de Proteínas/fisiología , Proteínas de Xenopus , Xenopus laevis/embriología , Xenopus laevis/genéticaRESUMEN
Patterning of the marginal zone in the Xenopus embryo has been attributed to interactions between dorsal genes expressed in the organizer and ventral-specific genes. In this antagonistic interplay of activities, BMP-4, a gene that is not expressed in the organizer, provides a strong ventralizing signal. The Xenopus caudal type homeobox gene, Xcad-2, which is expressed around the blastopore with a gap over the dorsal lip, was analyzed as part of the ventral signal. Xcad-2 was shown to efficiently repress during early gastrula stages the dorsal genes gsc, Xnot-2, Otx-2, XFKH1 and Xlim-1, while it positively regulates the ventral genes, Xvent-1 and Xvent-2, with Xpo exhibiting a strong positive response to Xcad-2 overexpression. Xcad-2 was also capable of inducing BMP-4 expression in the organizer region. Support for a ventralizing role for Xcad-2 was obtained from co-injection experiments with the dominant negative BMP receptor which was used to block BMP-4 signaling. Under lack-of-BMP-signaling conditions Xcad-2 could still regulate dorsal and ventral gene expression and restore normal development, suggesting that it can act downstream of BMP-4 signaling or independently of it. Xcad-2 could also inhibit secondary axis formation and dorsalization induced by the dominant negative BMP receptor. Xcad-2 was also shown to efficiently reverse the dorsalizing effects of LiCl. These results place Xcad-2 as part of the ventralizing gene program which acts during early gastrula stages and can execute its ventralizing function in the absence of BMP signaling.
Asunto(s)
Proteínas Aviares , Tipificación del Cuerpo/genética , Proteínas Morfogenéticas Óseas/fisiología , Gástrula/metabolismo , Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio/fisiología , Proteínas Represoras , Factores de Transcripción , Proteínas de Xenopus/fisiología , Xenopus laevis/embriología , Animales , Proteína Morfogenética Ósea 4 , Proteínas Portadoras/biosíntesis , Proteínas Portadoras/genética , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/genética , Factores de Transcripción Forkhead , Gástrula/fisiología , Genes Homeobox , Proteína Goosecoide , Proteínas de Homeodominio/biosíntesis , Proteínas de Homeodominio/genética , Péptidos y Proteínas de Señalización Intracelular , Proteínas con Homeodominio LIM , Microinyecciones , Proteínas del Tejido Nervioso/biosíntesis , Proteínas del Tejido Nervioso/genética , Organizadores Embrionarios , Factores de Transcripción Otx , Transducción de Señal , Transactivadores/biosíntesis , Transactivadores/genética , Proteínas de Xenopus/biosíntesis , Proteínas de Xenopus/genética , Xenopus laevis/genéticaRESUMEN
Expression of the Xenopus Xcad-1 and Xcad-2 genes initiates during early gastrulation exhibiting a dorsoventral asymmetry in their domains of transcription. At mid-gastrulation the ventral preference becomes stronger and the caudal genes take up a posterior localization in their expression, which they will maintain until their downregulation along the dorsal midline. Comparison of the three Xenopus caudal genes revealed a temporal and spatial nested set of expression patterns. The transcription of the caudal genes is sequentially downregulated with the one expressed most caudally (Xcad-2) being shut down first, this sequence is most evident along the dorsal midline. This pattern of expression suggests a role for the caudal genes as posterior determinants along the anteroposterior axis. In chicken, mouse, man and Xenopus three members of the caudal family have been identified in the genome. Even though in Xenopus the Xcad-3 gene has been previously described, in order to obtain a better insight on the role of the caudal genes a comparative study of all three frog genes was performed.
Asunto(s)
Proteínas Aviares , Vértebra Cervical Axis/embriología , Regulación hacia Abajo/genética , Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio/genética , Proteínas de Xenopus , Xenopus/embriología , Xenopus/genética , Animales , Tipificación del Cuerpo/genética , Proteínas de Drosophila , Proteínas Fetales/biosíntesis , Proteínas Fetales/genética , Proteínas de Homeodominio/biosíntesis , Proteínas de Homeodominio/fisiología , Factores de TranscripciónRESUMEN
Patterning along the anterior-posterior axis takes place during gastrulation and early neurulation. Homeobox genes like Otx-2 and members of the Hox family have been implicated in this process. The caudal genes in Drosophila and C. elegans have been shown to determine posterior fates. In vertebrates, the caudal genes begin their expression during gastrulation and they take up a posterior position. By injecting sense and antisense RNA of the Xenopus caudal gene Xcad-2, we have studied a number of regulatory interactions among homeobox genes along the anterior-posterior axis. Initially, the Xcad-2 and Otx-2 genes are mutually repressed and, by late gastrulation, they mark the posterior- or anterior-most domains of the embryo, respectively. During late gastrulation and neurulation, Xcad-2 plays an additional regulatory function in relation to the Hox genes. Hox genes normally expressed anteriorly are repressed by Xcad-2 overexpression while those normally expressed posteriorly exhibit more anterior expression. The results show that the caudal genes are part of a posterior determining network which during early gastrulation functions in the subdivision of the embryo into anterior head and trunk domains. Later in gastrulation and neurulation these genes play a role in the patterning of the trunk region.
Asunto(s)
Tipificación del Cuerpo/fisiología , Embrión no Mamífero/fisiología , Gástrula/fisiología , Genes Homeobox , Proteínas de Homeodominio/biosíntesis , Rombencéfalo/embriología , Xenopus laevis/embriología , Animales , Caenorhabditis elegans/embriología , Drosophila/embriología , Proteínas de Drosophila , Embrión no Mamífero/citología , Regulación del Desarrollo de la Expresión Génica , Cabeza , Proteínas de Homeodominio/fisiología , Fenotipo , Factores de TranscripciónRESUMEN
Specific signaling molecules play a pivotal role in the induction and specification of tissues during early vertebrate embryogenesis. BMP-4 specifies ventral mesoderm differentiation and inhibits neural induction in Xenopus, whereas three molecules secreted from the organizer, noggin, follistatin and chordin dorsalize mesoderm and promote neural induction. Here we report that follistatin antagonizes the activities of BMP-4 in frog embryos and mouse teratocarcinoma cells. In Xenopus embryos follistatin blocks the ventralizing effect of BMP-4. In mouse P19 cells follistatin promotes neural differentiation. BMP-4 antagonizes the action of follistatin and prevents neural differentiation. In addition we show that the follistatin and BMP-4 proteins can interact directly in vitro. These data provide evidence that follistatin might play a role in modulating BMP-4 activity in vivo.
Asunto(s)
Proteínas Morfogenéticas Óseas/fisiología , Embrión no Mamífero/fisiología , Glicoproteínas/fisiología , Sistema Nervioso/embriología , Animales , Proteína Morfogenética Ósea 4 , Proteínas Morfogenéticas Óseas/antagonistas & inhibidores , Agregación Celular , Diferenciación Celular , Embrión no Mamífero/anatomía & histología , Inducción Embrionaria , Folistatina , Regulación del Desarrollo de la Expresión Génica , Glicoproteínas/biosíntesis , Glicoproteínas/genética , Mesodermo/citología , Mesodermo/fisiología , Ratones , Sistema Nervioso/citología , Reacción en Cadena de la Polimerasa , Prolactina/farmacología , ARN sin Sentido/farmacología , ARN Mensajero/metabolismo , Teratocarcinoma , Tretinoina/farmacología , Células Tumorales Cultivadas , Xenopus/embriología , Xenopus/genética , Proteínas de XenopusRESUMEN
CdxA is a homeobox gene of the caudal type that was previously shown to be expressed in the endoderm-derived gut epithelium during early embryogenesis. Expression of the CDXA protein was studied during intestine morphogenesis from stage 11 (13 somites) to adulthood in the chicken. The CDXA protein can be detected during all stages of gut closure, from stage 11 to 5 days of incubation, and is mainly localized to the intestinal portals, the region where the splanchnopleure is undergoing closure. In this region, which represents the transition between the open and closed gut, the CDXA protein is restricted to the endoderm-derived epithelium. At about day 5 of incubation, the process of formation of the previllous ridges begins, which marks the beginning of the morphogenesis of the villi. From this stage to day 11 expression of CDXA is localized to the epithelial lining of the intestine. In parallel, a gradual increase in CDXA protein expression begins in the mesenchyme that is close in proximity to the CDXA-positive endoderm. Maximal CDXA levels in the mesenchyme are observed at day 9 of incubation. During days 10 and 11 CDXA levels in the mesenchyme remain constant, and by day 12 CDXA becomes undetectable in these cells and the epithelium again becomes the main site of expression. From day 12 of incubation until adulthood the CDXA protein is present in the intestinal epithelium. Until day 18 of incubation expression can be detected along the whole length of the villus with a stronger signal at the tip. With hatching the distribution along the villi changes so that the main site of CDXA protein expression is at the base of the villi and in the crypts. The transient expression of CDXA in the mesenchyme between days 5 and 11 may be related to the interactions taking place between the mesenchyme and the epithelium that ultimately result in the axial specification of the alimentary canal and the differentiation of its various epithelia. The main CDXA spatial distribution during morphogenesis suggests a tight linkage to the formation and differentiation of the intestinal epithelium itself. CDXA appears to play a role in the morphogenetic events leading to closure of the alimentary canal. During previllous ridge formation the CDXA protein is transiently expressed in the mesenchymal cells thought to provide instructive interactions for the regionalization and differentiation of the gut epithelium.(ABSTRACT TRUNCATED AT 400 WORDS)
Asunto(s)
Endodermo/fisiología , Genes Homeobox/fisiología , Intestinos/embriología , Animales , Diferenciación Celular/genética , Embrión de Pollo , Células Epiteliales , Epitelio/embriología , Inmunohistoquímica , Intestinos/fisiología , Morfogénesis/genéticaRESUMEN
Physiological concentrations of insulin support the in vitro growth of LB T-cell lymphoma. We could not detect similar insulin dependence in other tumor cell lines. This study reports that insulin also enhances the growth of LB cells in vivo. Mice treated with Streptozotocin (SZ) developed partial resistance to LB lymphoma growth and they survived longer (p < 0.0025) than non-diabetic mice after LB-cell inoculation. A few diabetic mice developed complete tumor resistance, manifested by total regression of the lymphoma. SZ-treated diabetic mice reconstituted with external insulin died as fast as non-diabetic mice when both were inoculated with the same number of LB cells. The SZ-treated diabetic mice did not develop resistance to the growth of BCLI B-cell leukemia, which demonstrated only a marginal proliferative response to insulin in vitro. Mice fed a low-energy diet exhibited low insulin levels and also developed resistance to lymphoma growth (50% survival 21 days vs. 15 days; p < 0.0005), supporting the concept that insulin enhances LB T-cell tumor development in mice.
Asunto(s)
Diabetes Mellitus Experimental/sangre , Insulina/farmacología , Linfoma de Células T/patología , Animales , Glucemia/análisis , División Celular/efectos de los fármacos , Diabetes Mellitus Experimental/mortalidad , Ingestión de Energía , Femenino , Insulina/deficiencia , Linfoma de Células T/sangre , Linfoma de Células T/mortalidad , Masculino , Ratones , Ratones Endogámicos BALB C , Células Tumorales CultivadasRESUMEN
In the present study, we wished to demonstrate the ability of surface gametocyte antigens to induce protective immunity against Eimeria maxima infections in chickens. In order to accomplish this goal, we employed maternal immunization as a means of providing large amounts of specific antibodies to offspring chicks. Upon challenge with sporulated E. maxima oocysts, chicks from hens immunized with affinity-purified gametocyte antigens showed greatly reduced oocyst production compared with chicks from sham-immunized hens. These results suggest that maternal immunization with gametocyte antigens can be used as a means to provide transmission-blocking immunity against E. maxima infections.
Asunto(s)
Antígenos de Protozoos/inmunología , Animales , Anticuerpos Antiprotozoarios/análisis , Pollos , Coccidiosis/inmunología , Eimeria/crecimiento & desarrollo , Femenino , Inmunización , EmbarazoRESUMEN
The in vitro proliferation of the spontaneous lymphoid T-cell leukemia designated LB was enhanced by physiological, intermediate and supraphysiological concentrations of insulin. The enhancing effect was observed in both serum-free medium (SFM) and medium containing low concentrations of serum. Guinea-pig anti-insulin serum, but not guinea-pig normal serum, inhibited the proliferation of LB cells incubated either in medium containing serum alone or in medium containing serum and supplemented with insulin. This finding suggests that LB cells use serum insulin as a growth factor. Insulin-like growth factors I (IGF-I) and II (IGF-II) failed to stimulate an appreciable proliferation in LB cells, whereas in the same experiment insulin markedly enhanced the proliferation of this lymphoid leukemia. Furthermore, the concentration of unlabelled insulin required to displace 50% of 125I-insulin bound to LB cells was 3 orders of magnitude lower than the concentration of IGF-I required to achieve the same displacement. Our findings indicate that interaction of insulin with its own receptor, and not with IGF-I receptor, triggers the proliferation of LB cells. Radio-receptor assays revealed that LB cells express approximately 3,200 molecules of high affinity (Kd = 10(-9) M) insulin receptor per cell. None of 7 other tumor cell lines tested responded to insulin. The proliferation of insulin-stimulated LB cells was also inhibited with tyrphostin, a tyrosine kinase blocker analogous to tyrosine, which perhaps blocks the tyrosine kinase activity of the insulin receptor beta-chain.
Asunto(s)
Insulina/fisiología , Leucemia de Células T/fisiopatología , Receptor de Insulina/fisiología , Animales , División Celular , Femenino , Factor I del Crecimiento Similar a la Insulina/farmacología , Factor II del Crecimiento Similar a la Insulina/farmacología , Leucemia Experimental/patología , Leucemia Experimental/fisiopatología , Leucemia de Células T/patología , Ratones , Ratones Endogámicos BALB C , Células Tumorales CultivadasRESUMEN
Eimeria maxima gametocytes contain two major antigens with molecular masses of 56 and 82 kilodaltons (kDa) which are recognized by convalescent sera from immune chickens. Preparations enriched in these two antigens were used to immunize mice, and several monoclonal antibodies which specifically reacted with the 56-kDa antigen were produced. One of these monoclonal antibodies of the immunoglobulin M subclass, along with immune chicken sera raised against affinity-purified 56- and 82-kDa antigens, was used to passively immunize chicks. On the basis of the parameter of total oocyst output, it was found that these antibodies provided partial protection (40 to 50% inhibition) against E. maxima challenge infections.
Asunto(s)
Anticuerpos Monoclonales/inmunología , Antígenos de Protozoos/inmunología , Eimeria/inmunología , Inmunización Pasiva , Animales , Antígenos de Protozoos/genética , Pollos , Coccidiosis/prevención & controlRESUMEN
The antigenicity of Eimeria maxima gametocyte proteins during the course of an infection and when injected into mice and rabbits was demonstrated using the Western blotting technique. Serum taken from chickens at various times postinfection reacted to a few gametocyte proteins, with the strongest reactivity seen with serum taken 14-days postinfection. Two major antigens having molecular weights of 56,000 and 82,000 were consistently detected by these sera. Using immune rabbit or mouse sera to whole gametocyte detergent extracts, the 56,000 and 82,000 molecular weight proteins were again the immunodominant antigens, despite their representing only a small proportion of the extract which was used to immunize the animals. These results, together with those obtained by Rose (1971) using recovered chicken serum to passively immunize chickens, indicate that these two gametocyte antigens may play a role in protective immunity to E. maxima.