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P J Roy

Publications and source records attributed to P J Roy.

At least 19 recordsLinked to original sources
PubMed2000

The forkhead transcription factor UNC-130 is required for the graded spatial expression of the UNC-129 TGF-beta guidance factor in C. elegans.

Secreted proteins required for cellular movements along the circumference of the body wall in Caenorhabditis elegans include UNC-6/netrin and the novel TGF-beta UNC-129. Expression of these proteins is graded along the dorsoventral (D/V) axis, providing polarity information to guide migrations. Here we show that the graded expression of UNC-129 in dorsal but not ventral body muscles depends on unc-130, which encodes a Forkhead transcription factor. The phenotype of unc-130 mutants closely mimics the reported effects of ectopically expressing unc-129 in both dorsal and ventral body muscles (). This fits our present finding that unc-130 cell autonomously represses unc-129 expression in the ventral body muscles. Thus the cell-specific effects of unc-130 on ventral, but not dorsal, body muscle expression of unc-129 accounts for the D/V polarity information required for UNC-129-mediated guidance. Genetic interactions between unc-130 and other guidance genes show that several molecular pathways function in parallel to guide the ventral to dorsal migration of distal tip cells (DTCs) and axonal growth cones in C. elegans. Genetic interactions confirm that UNC-129 does not require the only known type II TGF-beta receptor in C. elegans (DAF-4) for its guidance functions. Also, unc-130 is partially required for male tail morphogenesis and for embryogenesis.

Amino Acid Sequence↗
PubMed2000

mab-20 encodes Semaphorin-2a and is required to prevent ectopic cell contacts during epidermal morphogenesis in Caenorhabditis elegans.

The Semaphorins are a family of secreted and transmembrane proteins known to elicit growth cone repulsion and collapse. We made and characterized a putative null mutant of the C. elegans gene semaphorin-2a (Ce-sema-2a). This mutant failed to complement mutants of mab-20 (Baird, S. E., Fitch, D. H., Kassem, I. A. A. and Emmons, S. W. (1991) Development 113, 515-526). In addition to low-frequency axon guidance errors, mab-20 mutants have unexpected defects in epidermal morphogenesis. Errant epidermal cell migrations affect epidermal enclosure of the embryo, body shape and sensory rays of the male tail. These phenotypic traits are explained by the formation of inappropriate contacts between cells of similar type and suggest that Ce-Sema-2a may normally prevent formation or stabilization of ectopic adhesive contacts between these cells.

Amino Acid Sequence↗
PubMed1999

Multiple ephrins control cell organization in C. elegans using kinase-dependent and -independent functions of the VAB-1 Eph receptor.

Eph receptor (EphR) tyrosine kinases and their ephrin ligands mediate direct cell-to-cell signaling. The C. elegans genome encodes four potential GPI-modified ephrins (EFN-1 to -4) and one EphR (VAB-1). Single and multiple ephrin mutants reveal functions for EFN-1, EFN-2, and EFN-3 in epidermal cell organization that, in aggregate, mirror those of VAB-1. Ephrin mutants have defects in head morphology and enclosure of the embryo by the epidermis and identify ephrin-EphR signaling functions involved in aligning and fusing tail and head epidermal cells, respectively. Biochemical analyses indicate that EFN-1, EFN-2, and EFN-3 jointly activate the VAB-1 tyrosine kinase in vivo. Mutant phenotypes and expression pattern analysis suggest that multiple ephrins are involved in distinct aspects of kinase-dependent and kinase-independent VAB-1 signaling required for proper cell organization during development in C. elegans.

Amino Acid Sequence↗
PubMed1999

A BMP homolog acts as a dose-dependent regulator of body size and male tail patterning in Caenorhabditis elegans.

We cloned the dbl-1 gene, a C. elegans homolog of Drosophila decapentaplegic and vertebrate BMP genes. Loss-of-function mutations in dbl-1 cause markedly reduced body size and defective male copulatory structures. Conversely, dbl-1 overexpression causes markedly increased body size and partly complementary male tail phenotypes, indicating that DBL-1 acts as a dose-dependent regulator of these processes. Evidence from genetic interactions indicates that these effects are mediated by a Smad signaling pathway, for which DBL-1 is a previously unidentified ligand. Our study of the dbl-1 expression pattern suggests a role for neuronal cells in global size regulation as well as male tail patterning.

Amino Acid Sequence↗
PubMed1998

Cloning and sequencing of an alpha-tubulin cDNA from Artemia franciscana: evidence for translational regulation of alpha-tubulin synthesis.

The brine shrimp, Artemia franciscana, exhibits a limited number of tubulin isotypes which change little during early postgastrula growth. In order to better understand the synthesis of alpha-tubulins during Artemia development, a cDNA termed alphaAT1 was cloned and sequenced. Alignment analyses revealed that the polypeptide encoded by alphaAT1 is similar to alpha-tubulins from other species. Hybridization of alphaAT1 to restriction-digested DNA on Southern blots produced a simple banding pattern, indicating that Artemia have a small number of alpha-tubulin genes. Probing of Northern blots demonstrated an abundant supply of alpha-tubulin mRNA in dormant cysts, emerging nauplii and instar I larvae. However, it was not until instar I larvae were produced that the amount of polysomal alpha-tubulin mRNA increased, suggesting that synthesis of the tubulin corresponding to alphaAT1 is translationally controlled. This work provides one of the few examples where tubulin synthesis is thought to be translationally regulated. Moreover, when considered in the light of previous analyses, the findings imply that cell differentiation in postgastrula Artemia and the diversification of microtubule function certain to accompany this process occur with little or no change in alpha-tubulin composition.

Amino Acid Sequence↗