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An amphioxus LIM-homeobox gene, AmphiLim1/5, expressed early in the invaginating organizer region and later in differentiating cells of the kidney and central nervous system.

ABSTRACT: A LIM-homeobox gene, AmphiLim1/5, from the Florida amphioxus (Branchiostoma floridae) encodes a protein that phylogenetic analysis positions at the base of a clade comprising vertebrate Lim1 and Lim5. Amphioxus AmphiLim1/5 is expressed in domains that are a composite of those of vertebrate Lim1 and Lim5, which evidently underwent subfunctionalization after duplication of an ancestral protochordate Lim1/5. During amphioxus development, transcription is first detected in the ectoderm of the blastula. Then, in the gastrula, a second expression domain appears in the mesendoderm just within the dorsal lip of the blastopore, a region known to have organizer properties in amphioxus. This mesendodermal expression corresponds to Lim1 expression in the Spemann organizer of vertebrates. At least one of the functions of vertebrate Lim1 in the organizer is to control the transcription of genes involved in cell and tissue movements during gastrulation, and a comparable early function seems likely for AmphiLim1/5 during gastrular invagination of amphioxus. Later embryos and larvae of amphioxus express AmphiLim1/5 in clusters of cells, probably motoneurons, in the anterior part of the central nervous system, in the hindgut, in Hatschek's right diverticulum (a rudiment of the rostral coelom), and in the wall of the first somite on the left side (a precursor of Hatschek's nephridium). In the early larva, expression continues in neural cells, in Hatschek's nephridium, in the wall of the rostral coelom, in the epidermis of the upper lip, and in mesoderm cells near the opening of the second gill slit. The developmental expression in Hatschek's nephridium is especially interesting because it helps support the homology between this amphioxus organ and the vertebrate pronephros.

SUBMITTER: Langeland JA

PROVIDER: S-EPMC1458433 | biostudies-literature | 2006

REPOSITORIES: biostudies-literature

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An amphioxus LIM-homeobox gene, AmphiLim1/5, expressed early in the invaginating organizer region and later in differentiating cells of the kidney and central nervous system.

Langeland James A JA Holland Linda Z LZ Chastain Roger A RA Holland Nicholas D ND

International journal of biological sciences 20060505 3

A LIM-homeobox gene, AmphiLim1/5, from the Florida amphioxus (Branchiostoma floridae) encodes a protein that phylogenetic analysis positions at the base of a clade comprising vertebrate Lim1 and Lim5. Amphioxus AmphiLim1/5 is expressed in domains that are a composite of those of vertebrate Lim1 and Lim5, which evidently underwent subfunctionalization after duplication of an ancestral protochordate Lim1/5. During amphioxus development, transcription is first detected in the ectoderm of the blastu ...[more]

PMID: 16763670

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Project description:BackgroundLIM homeobox (Lhx) transcription factors are unique to the animal lineage and have patterning roles during embryonic development in flies, nematodes and vertebrates, with a conserved role in specifying neuronal identity. Though genes of this family have been reported in a sponge and a cnidarian, the expression patterns and functions of the Lhx family during development in non-bilaterian phyla are not known.ResultsWe identified Lhx genes in two cnidarians and a placozoan and report the expression of Lhx genes during embryonic development in Nematostella and the demosponge Amphimedon. Members of the six major LIM homeobox subfamilies are represented in the genomes of the starlet sea anemone, Nematostella vectensis, and the placozoan Trichoplax adhaerens. The hydrozoan cnidarian, Hydra magnipapillata, has retained four of the six Lhx subfamilies, but apparently lost two others. Only three subfamilies are represented in the haplosclerid demosponge Amphimedon queenslandica. A tandem cluster of three Lhx genes of different subfamilies and a gene containing two LIM domains in the genome of T. adhaerens (an animal without any neurons) indicates that Lhx subfamilies were generated by tandem duplication. This tandem cluster in Trichoplax is likely a remnant of the original chromosomal context in which Lhx subfamilies first appeared. Three of the six Trichoplax Lhx genes are expressed in animals in laboratory culture, as are all Lhx genes in Hydra. Expression patterns of Nematostella Lhx genes correlate with neural territories in larval and juvenile polyp stages. In the aneural demosponge, A. queenslandica, the three Lhx genes are expressed widely during development, including in cells that are associated with the larval photosensory ring.ConclusionsThe Lhx family expanded and diversified early in animal evolution, with all six subfamilies already diverged prior to the cnidarian-placozoan-bilaterian last common ancestor. In Nematostella, Lhx gene expression is correlated with neural territories in larval and juvenile polyp stages. This pattern is consistent with a possible role in patterning the Nematostella nervous system. We propose a scenario in which Lhx genes play a homologous role in neural patterning across eumetazoans.

Dataset Information

An amphioxus LIM-homeobox gene, AmphiLim1/5, expressed early in the invaginating organizer region and later in differentiating cells of the kidney and central nervous system.

Publications

An amphioxus LIM-homeobox gene, AmphiLim1/5, expressed early in the invaginating organizer region and later in differentiating cells of the kidney and central nervous system.

Similar Datasets

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