Transcription factors encoded by Antennapedia-class homeobox genes play crucial roles in controlling development of animals, and are often found clustered in animal genomes. The Hox and ParaHox gene clusters have been...Transcription factors encoded by Antennapedia-class homeobox genes play crucial roles in controlling development of animals, and are often found clustered in animal genomes. The Hox and ParaHox gene clusters have been regarded as evolutionary sisters and evolved from a putative common ancestral gene complex, the ProtoHox cluster, prior to the divergence of the Cnidaria and Bilateria （bilaterally symmetrical animals）. The Deuterostomia is a monophyletic group of animals that belongs to the Bilateria, and a sister group to the Protostomia. The deuterostomes include the vertebrates （to which we belong）, invertebrate chordates, hemichordates, echinoderms and possibly xenoturbellids, as well as acoelomorphs. The studies of Hox and ParaHox genes provide insights into the origin and subsequent evolution of the bilaterian animals. Recently, it becomes apparent that among the Hox and ParaHox genes, there are significant variations in organization on the chromosome, expression pattern, and function. In this review, focusing on invertebrate deuterostomes, I first summarize recent findings about Hox and ParaHox genes. Next, citing unsolved issues, I try to provide clues that might allow us to reconstruct the common ancestor of deuterostomes, as well as understand the roles of Hox and ParaHox genes in the development and evolution of deuterostomes.展开更多
Hox and ParaHox genes constitute two families of developmental regulators that pattern the Anterior-Posterior body axis in all bilaterians. The members of these two groups of genes are usually arranged in genomic clus...Hox and ParaHox genes constitute two families of developmental regulators that pattern the Anterior-Posterior body axis in all bilaterians. The members of these two groups of genes are usually arranged in genomic clusters and work in a coordinated fashion, both in space and in time. While the mechanistic aspects of their action are relatively well known, it is still unclear how these systems evolved. For instance, we still need a proper model of how the Hox and ParaHox clusters were assembled over time. This problem is due to the shortage of information on gene complements for many taxa （mainly basal metazoans） and the lack of a consensus phylogenetic model of animal relationships to which we can relate our new findings. Recently, several studies have shown that the Acoelomorpha most probably represent the first offshoot of the Bilateria. This finding has prompted us, and others, to study the Hox and ParaHox complements in these animals, as well as their activity during development. In this review, we analyze how the current knowledge of Hox and ParaHox genes in the Acoelomorpha is shaping our view of bilaterian evolution.展开更多
The discovery of the homeobox motif and its presence in each gene of the Hox clusters revolutionized the fields of developmental biology and evolutionary developmental biology （1, 2）, providing a rapid entrance into...The discovery of the homeobox motif and its presence in each gene of the Hox clusters revolutionized the fields of developmental biology and evolutionary developmental biology （1, 2）, providing a rapid entrance into investigating the mechanisms of development of almost any animal taxon as well as dramatically altering conceptions on the extent of genetic conservation across the animal kingdom.展开更多
文摘Transcription factors encoded by Antennapedia-class homeobox genes play crucial roles in controlling development of animals, and are often found clustered in animal genomes. The Hox and ParaHox gene clusters have been regarded as evolutionary sisters and evolved from a putative common ancestral gene complex, the ProtoHox cluster, prior to the divergence of the Cnidaria and Bilateria （bilaterally symmetrical animals）. The Deuterostomia is a monophyletic group of animals that belongs to the Bilateria, and a sister group to the Protostomia. The deuterostomes include the vertebrates （to which we belong）, invertebrate chordates, hemichordates, echinoderms and possibly xenoturbellids, as well as acoelomorphs. The studies of Hox and ParaHox genes provide insights into the origin and subsequent evolution of the bilaterian animals. Recently, it becomes apparent that among the Hox and ParaHox genes, there are significant variations in organization on the chromosome, expression pattern, and function. In this review, focusing on invertebrate deuterostomes, I first summarize recent findings about Hox and ParaHox genes. Next, citing unsolved issues, I try to provide clues that might allow us to reconstruct the common ancestor of deuterostomes, as well as understand the roles of Hox and ParaHox genes in the development and evolution of deuterostomes.
文摘Hox and ParaHox genes constitute two families of developmental regulators that pattern the Anterior-Posterior body axis in all bilaterians. The members of these two groups of genes are usually arranged in genomic clusters and work in a coordinated fashion, both in space and in time. While the mechanistic aspects of their action are relatively well known, it is still unclear how these systems evolved. For instance, we still need a proper model of how the Hox and ParaHox clusters were assembled over time. This problem is due to the shortage of information on gene complements for many taxa （mainly basal metazoans） and the lack of a consensus phylogenetic model of animal relationships to which we can relate our new findings. Recently, several studies have shown that the Acoelomorpha most probably represent the first offshoot of the Bilateria. This finding has prompted us, and others, to study the Hox and ParaHox complements in these animals, as well as their activity during development. In this review, we analyze how the current knowledge of Hox and ParaHox genes in the Acoelomorpha is shaping our view of bilaterian evolution.
文摘The discovery of the homeobox motif and its presence in each gene of the Hox clusters revolutionized the fields of developmental biology and evolutionary developmental biology （1, 2）, providing a rapid entrance into investigating the mechanisms of development of almost any animal taxon as well as dramatically altering conceptions on the extent of genetic conservation across the animal kingdom.
