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The amphioxus genome and the evolution of the chordate karyotype
Whole-genome comparisons illuminate the murky relationships among the three chordate groups (tunicates, lancelets and vertebrates), and allow not only reconstruction of the gene complement of the last common chordate ancestor but also partial reconstruction of its genomic organization.
The amphioxus genome illuminates vertebrate origins and cephalochordate biology.
The results indicate that the amphioxus genome is elemental to an understanding of the biology and evolution of nonchordate deuterostomes, invertebrate chordates, and vertebrates.
Axial patterning in cephalochordates and the evolution of the organizer
The gastrula of the cephalochordate amphioxus expresses dorsal/ventral (D/V) patterning genes in patterns reminiscent of those of their vertebrate orthlogues, and it is proposed that separate signalling centres for patterning the D/V and A/P axes may be an ancestral chordate character.
AmphiPax3/7, an amphioxus paired box gene: insights into chordate myogenesis, neurogenesis, and the possible evolutionary precursor of definitive vertebrate neural crest
The early neural expression patterns of AmphiPax3/7 and other neural crest markers of amphioxus and tunicates suggest that cell populations that eventually gave rise to definitive vertebrate neural crest may have been present in ancestral invertebrate chordates.
Sequence and embryonic expression of the amphioxus engrailed gene (AmphiEn): the metameric pattern of transcription resembles that of its segment-polarity homolog in Drosophila.
The segmental expression of AmphiEn in forming somites suggests that the functions of engrailed homologs in establishing and maintaining a metameric body plan may have arisen only once during animal evolution.
An amphioxus Pax gene, AmphiPax-1, expressed in embryonic endoderm, but not in mesoderm: implications for the evolution of class I paired box genes.
It is likely that, during animal evolution, class I paired box genes originally functioned in endoderm development and were only later co-opted for other roles in mesodermdevelopment; however, other scenarios cannot be ruled out until homologues of these genes are studied in more invertebrate phyla and in the lower vertebrates.
Conservation of Brachyury (T) genes in amphioxus and vertebrates: developmental and evolutionary implications.
It is proposed that roles of Brachyury in notochord differentiation are more ancient than roles in mesoderm formation, and that the latter are shared by cephalochordates and all vertebrates.
The retinoic acid signaling pathway regulates anterior/posterior patterning in the nerve cord and pharynx of amphioxus, a chordate lacking neural crest.
The results suggest a model for anteroposterior patterning of the amphioxus nerve cord and pharynx, which is probably applicable to vertebrates as well, in which a low anterior level of AmphiRAR (caused, at least in part, by competitive inhibition by AmphiTR2/4) is necessary for patterning the forebrain and formation of gill slits.
Phylogenetic relationships of the Fox (Forkhead) gene family in the Bilateria.
Sequence and developmental expression of AmphiDll, an amphioxus Distal-less gene transcribed in the ectoderm, epidermis and nervous system: insights into evolution of craniate forebrain and neural…
The results suggest that craniates evolved from an amphioxus-like creature that had the beginnings of a forebrain and possibly a precursor of neural crest - namely, the cell population leading the epidermal overgrowth of the neural plate during early neurulation.