Biomedical subjects

V F Hinman

Publications and source records attributed to V F Hinman.

6 recordsLinked to original sources

PubMed2002

Mox homeobox expression in muscle lineage of the gastropod Haliotis asinina: evidence for a conserved role in bilaterian myogenesis.

Mox homeobox genes are expressed during early vertebrate somitogenesis. Here we describe the expression of Has-Mox, a Mox gene from the gastropod Haliotis asinina. Has-Moxis expressed in the trochophore larva in paraxial mesodermal bands. During larval development, Has-Mox expression remains restricted to mesodermal cells destined to form adult muscle in the foot. This restricted expression of Has-Mox in Haliotis is similar to that observed for vertebrate Mox genes, suggesting a conserved role in myogenesis in deuterostomes and lophotrochozoans. In contrast, Mox is not expressed in muscle lineages in the ecdysozoan representatives Caenorhabditis elegans or Drosophila; the C. elegansgenome has lost Mox altogether. Electronic supplementary material to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00427-002-0223-6.

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PubMed2000

Retinoic acid perturbs Otx gene expression in the ascidian pharynx.

In vertebrate embryos, ectopic application of all-trans retinoic acid (RA) alters the expression of Otx genes in the developing midbrain. In conjunction with RA-induced misexpression of other regulatory genes this leads to a loss of anterior CNS. In the ascidian Herdmania curvata, RA primarily inhibits the development of the juvenile pharynx. An ascidian Otx gene, Hec-Otx, is expressed largely in this tissue, associated stomodeal structures and the anterior endostyle of the juvenile. Treatment with 10-6 M RA reduces Hec-Otx mRNA levels in the juvenile to about 12% of normal and is correlated closely with the loss of pharyngeal structures. During embryogenesis the expression of Hec-Otx becomes restricted to cell lineages fated to give rise to the anterior-most nervous system and the stomodeal component of the primordial pharynx. In hatched larvae Hec-Otx transcripts are detected only in the sensory (brain) vesicle. RA reduces Hec-Otx expression in the tailbud stomodeal pharynx primordium/anterior nervous system cell line but not in the larval sensory vesicle, suggesting that RA regulation of Hec-Otx expression is restricted to pharyngeal tissues throughout embryonic and postlarval development. RA does not affect expression of Hec-Pax2/5/8, which is normally expressed within the developing nervous system immediately posterior to Hec-Otx at the tailbud stage, lending support to the proposition that RA does not impact CNS axial patterning. These data combined with those from other chordates suggest that RA regulation of Otx expression in the anterior nerve cord and pharynx is a primitive chordate feature which has been maintained predominantly in pharyngeal tissues in the ascidian.

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PubMed2000

Neuroectodermal and endodermal expression of the ascidian Cdx gene is separated by metamorphosis.

Ascidians are a group of invertebrate chordates that exhibit a biphasic life history, with chordate-specific structures developing during embryogenesis (dorsal neural tube and notochord) and metamorphosis (pharyngeal gill slits and endostyle). Here we characterize the expression of a caudal/Cdx gene homologue, Hec-Cdx, from the ascidian Herdmania curvata. Vertebrate Cdx genes are expressed at gastrulation and in the posterior of the developing neural tube and endoderm. Hec-Cdx expression is initiated at the earliest stages of gastrulation, with peaks in RNA abundance occurring first during neurulation and tailbud extension and then in 3- to 5-day-old juveniles. Hec-Cdx is expressed in a pair of cells in the anterior lip of the blastopore in the late gastrula which form the most posterior portion of the neural plate. During tailbud formation expression is maintained in and solely restricted to these cells. During metamorphosis expression is localized to the intestine of the juvenile. These data, along with data for the H. curvata Otx gene, suggest that the evolution of the novel ascidian biphasic body plan was not accompanied by a deployment of these genes into new pathways but by a temporal separation of tissue-specific expression.

Amino Acid Sequence↗

PubMed1999

Hemps, a novel EGF-like protein, plays a central role in ascidian metamorphosis.

All chordates share several characteristic features including a dorsal hollow neural tube, a notochord, a pharynx and an endostyle. Unlike other chordate taxa, ascidians have a biphasic life-history with two distinct body plans. During metamorphosis, the larval nerve cord and notochord degenerate and the pharyngeal gill slits and endostyle form. While ascidians, like other marine invertebrates, metamorphose in response to specific environmental cues, it remains unclear how these cues trigger metamorphosis. We have identified a novel gene (Hemps) which encodes a protein with a putative secretion signal sequence and four epidermal growth factor (EGF)-like repeats which is a key regulator of metamorphosis in the ascidian Herdmania curvata. Expression of Hemps increases markedly when the swimming tadpole larva becomes competent to undergo metamorphosis and then during the first 24 hours of metamorphosis. The Hemps protein is localised to the larval papillae and anterior epidermis of the larva in the region known to be required for metamorphosis. When the larva contacts an inductive cue the protein is released, spreading posteriorly and into the tunic as metamorphosis progresses. Metamorphosis is blocked by incubating larvae in anti-Hemps antibodies prior to the addition of the cue. Addition of recombinant Hemps protein to competent larvae induces metamorphosis in a concentration-dependent manner. A subgroup of genes are specifically induced during this process. These results demonstrate that the Hemps protein is a key regulator of ascidian metamorphosis and is distinct from previously described inducers of this process in terrestrial arthropods and aquatic vertebrates.

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PubMed1998

Retinoic acid disrupts anterior ectodermal and endodermal development in ascidian larvae and postlarvae.

In vertebrates, excess all-trans retinoic acid (RA) applied during axis formation leads to the apparent truncation of anterior structures. In this study we sought to determine the type of defects caused by ectopic RA on the development of the ascidian Herdmania curvata. We demonstrate that H. curvata embryos cultured in the presence of RA develop into larvae whose trunks are shortened and superficially resemble those of early metamorphosing postlarvae. Despite RA-treated larvae lacking papillar structures they respond normally to natural cues that induce metamorphosis, indicating that chemosensory functionality previously mapped to the most anterior region of normal larvae is unaffected by RA. Excess RA applied during postlarval development leads to a graded loss of the juvenile pharynx, apparently by respecifying anterior endoderm to a more posterior fate. This structure is considered homologous to the gill slits of amphioxus, which are also lost upon RA treatment. This suggests that RA may have had a role in the development of the pharynx of the ancestral chordate and that this function has been maintained in ascidians and cephalochordates and lost in vertebrates.

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PubMedDate not supplied

Expression of a Scr/Hox5 gene in the larval central nervous system of the gastropod Haliotis, a non-segmented spiralian lophotrochozoan.

Hox genes encode a set of evolutionarily conserved transcription factors that regulate anteroposterior patterning mechanisms in insects and vertebrates and are expressed along this axis in a range of bilaterians. Here we present the developmental expression of a Scr/Hox5 gene in the gastropod mollusc Haliotis. In Haliotis, embryogenesis yields a non-feeding trochophore larva that subsequently develops into the veliger larva, which possesses many of the characteristics of the adult body plan. Quantitative RT-PCR analysis reveals that this gene, which is called Hru-Hox5, is first expressed in the trochophore larva. Hru-Hox5 transcript prevalence increases continually through larval development until metamorphic competence develops in the veliger and then again over the first four days of metamorphosis. In situ hybridization reveals that larval expression of Hru-Hox5 is restricted primarily to the primordial and newly formed branchial ganglia, located between the anterior cerebral-pleuropedal ganglionic complex and the posterior visceral ganglia. The expression of Hru-Hox5 in the central region of the abalone CNS is similar to that observed for its orthologue (Lox20) in the leech, suggesting that Hox5 genes were used, along with other Hox genes, to pattern the CNS of the ancestral spiralian lophotrochozoan.

Amino Acid Sequence↗