Aggregation of maternal pigment granules is induced by the cytosolic discoidin domain of the Xenopus Del1 protein.
Xenopus oocytes generate pigment granules (melanosomes) that predominantly localize to the animal hemisphere cortex. During embryonic development, these granules are located near the membranes of outer layer ectoderm cells. We report a novel phenotype found during an expression cloning screen in Xenopus laevis embryos. The phenotype is characterized by dissociation of pigment granules from the cell membrane to form large central aggregates. This phenomenon was induced by a truncated form of the Xenopus Del1 (XDel1) protein that contains only the C-terminal discoidin (D2) domain. This truncated form of XDel1 localized to membranes as shown by a chimeric enhanced green fluorescent protein construct. Although a similar localization occurred in immature oocytes, dissociation of pigment granules was limited to the oocyte vegetal hemisphere. The full-length XDel1 cDNA was cloned, and XDel1 mRNA expression was found to be ubiquitous and continuous from early oocyte to tail bud stages, with a transient enrichment in the cement gland. Ectopic expression of various deletion or full-length constructs or antisense morpholino oligonucleotides did not induce any significant developmental phenotypes.
Tsabar
Nir
N
Department of Biochemistry, The Rappaport Family Institute for Research in the Medical Sciences, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel.
Gefen
Aharon
A
Elias
Sarah
S
Frank
Dale
D
D000595:Amino Acid Sequence; D000818:Animals; D003600:Cytosol / Q000502:physiology*; D018076:DNA, Complementary; D000070821:Discoidins; D006801:Humans; D037102:Lectins / Q000502:physiology; D020460:Melanosomes / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000502:physiology; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D029867:Xenopus Proteins / Q000235:genetics / Q000502:physiology*; D014982:Xenopus laevis
D018076:DNA, Complementary; D000070821:Discoidins; C503184:EDIL3 protein, Xenopus; D037102:Lectins; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D015800:Protozoan Proteins; D029867:Xenopus Proteins