Assuntos
Evolução Biológica , Cordados/fisiologia , Fósseis , Animais , Cordados/anatomia & histologia , Cordados/classificação , Extremidades/anatomia & histologia , Extremidades/fisiologia , Peixes/anatomia & histologia , Peixes/fisiologia , Marcha/fisiologia , História Antiga , Modelos Biológicos , Filogenia , PolôniaRESUMO
A role for Wnt/beta-catenin signaling in axial patterning has been demonstrated in animals as basal as cnidarians, while roles in axial patterning for retinoic acid (RA) probably evolved in the deuterostomes and may be chordate-specific. In vertebrates, these two pathways interact both directly and indirectly. To investigate the evolutionary origins of interactions between these two pathways, we manipulated Wnt/beta-catenin and RA signaling in the basal chordate amphioxus during the gastrula stage, which is the RA-sensitive period for anterior/posterior (A/P) patterning. The results show that Wnt/beta-catenin and RA signaling have distinctly different roles in patterning the A/P axis of the amphioxus gastrula. Wnt/beta-catenin specifies the identity of the ends of the embryo (high Wnt = posterior; low Wnt = anterior) but not intervening positions. Thus, upregulation of Wnt/beta-catenin signaling induces ectopic expression of posterior markers at the anterior tip of the embryo. In contrast, RA specifies position along the A/P axis, but not the identity of the ends of the embryo-increased RA signaling strongly affects the domains of Hox expression along the A/P axis but has little or no effect on the expression of either anterior or posterior markers. Although the two pathways may both influence such things as specification of neuronal identity, interactions between them in A/P patterning appear to be minimal.
Assuntos
Padronização Corporal/fisiologia , Cordados/embriologia , Cordados/metabolismo , Transdução de Sinais/fisiologia , Tretinoína/metabolismo , Proteínas Wnt/metabolismo , beta Catenina/metabolismo , Animais , Evolução Biológica , Biomarcadores/metabolismo , Cordados/classificação , Proteínas Fetais/genética , Proteínas Fetais/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Filogenia , Proteínas com Domínio T/genética , Proteínas com Domínio T/metabolismo , Fatores de Transcrição TCF/genética , Fatores de Transcrição TCF/metabolismo , Proteínas Wnt/genética , beta Catenina/genéticaRESUMO
An amphioxus cDNA, encoding phosphatidylcholine transfer protein (AmphiPCTP), was identified for the first time from the gut cDNA library of Branchiostoma belcheri. It contains a 660-bp open reading frame corresponding to a deduced protein of 219 amino acids. Phylogenetic tree analysis showed that AmphiPCTP clustered with PCTP subgroup of PCTP subfamily containing steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) domains. AmphiPCTP had an exon-intron organization similar to that of human and rat PCTP genes in terms of both exon number and sequence homology of each exon, suggesting that PCTP has probably maintained a similar function in both amphioxus and mammalian species. Both in situ hybridization histochemistry and whole-mount in situ hybridization revealed a tissue-specific expression pattern of AmphiPCTP with the high levels in the hepatic caecum and primitive gut, including the region where the hepatic caecum will form later during development. This apparently agrees with the hypothesis that amphioxus hepatic caecum is equivalent to vertebrate liver. These results suggest a conserved role of PCTPs in amphioxus as well as mammalian species.