spLBP/p40

Function

spLBP/p40 gene encodes a protein very similar to mammalian LBP/p40 nonintegrin, laminin binding protein.
But the results of experiments argue against a laminin binding function for this the spLBP/p40 protein; instead they place the spLBP/p40 gene in a class of sea urchin genes involved in growth and proliferation (Hung et al., 1995).

Protein

spLBP/p40 is the S. purpuratus homologue to the 67-kDa LBP/p40 protein in mammals.
The protein displays features found in all isoforms of the LBP/p40. There is a four-amino-acid consensus site for cdc 2 kinase phosphorylation and sites for phosphorylation by protein kinase C and casein kinase II. The carboxyl end of the protein contains a region rich in alanine and proline, a feature shared with the LBP/p40 protein from U. caupo, but not with proteins identified from other sourses (Hung et al., 1995).
SWISS_PROT: P46771

Subcellular location

Whole mount immunocytochemistry showed that at four- to eight cell and mesenchyme blastula stage embryos spLBP/p40 protein is distributed throughout the cytoplasm of all cells. In all stages, staining is not localized on the cell surface as might be expected for cell surface extracellular matrix receptor (Hung et al., 1995).

Expression Pattern

Nothern blot analysis detected a single 2.6-kb mRNA in unfertilized eggs. The level of this transcript remains essentially unchanged through the the hatching blastula stage (20 hr). The concentration of spLBP/p40 mRNA begins to increase at mesenchyme blastula stage and continues to increase through the pluteus stage.
Nuclear run-on experiments showed that persistence of maternal transcripts is responsible for spLBP/p40 mRNA levels until the blastula stage when active transcription of the gene begins.
Whole mount in situ hybridization was used to determine the spatial accumulation of the spLBP/p40 mRNA in pre- and postgastrula embryos. The results indicate that most if not all cells in the mesenchyme blastula have the spLBP/p40 mRNA.
By the prism stage, however, hybridization is concentrated over the gut and oral epithelium. Aboral ectoderm do not hybridize to detectable levels of the anti-sense probe. Although the hybridization signal was periodically detected in the primary mesenchyme of pluteus larvae.
Immunoblot analysis showed that spLBP/p40 protein is present in the egg and remains at relatively constant concentration through the prism larvae stage.
Whole mount immunocytochemistry indicated that the distribution of the protein is relatively uniform at four- to eight cell and mesenchyme blastula stage embryos throughout all cells, except for newly ingressed primary mesenchyme cells which stain less intensely than cells of the epithelium. In late prism stages the significant staining is observed in cells of the gut, primary mesenchyme, and oral epithelium. Staining of aboral ectoderm cells is detectable but is significantly reduced compared to the aforementioned tissues (Hung et al., 1995).

mRNA level

Temporal accumulation
Method: Nothern blot analysis
Reference: Hung et al., 1995

Stage	Egg	4 cells (4h)	Morula (9h)	Hatched blastula	Mesenchyme blastula	Late gastrula	Pluteus larva (75 h)
Level	+	+	+	+	+ +	+ +	+ +

mRNA spatial localization
Method: Whole mount in situ hybridization
Reference: Hung et al., 1995

Stage	Mesenchyme blastula	Prism
Tissue	Relatively uniformly distributed in the embryo	Hybridization is concentrated over the gut and oral epithelium

Protein level

Temporal accumulation
Method: Immunoblot analysis
Reference: Hung et al., 1995

Stage	Egg	Morula (12 h)	Mesenchyme blastula (22 h)	Late gastrula (50 h)	Late prism (75 h)
Level	+	+	+	+	+

Protein spatial localization
Method: Whole mount immunocytochemistry
Reference: Hung et al., 1995

Stage	Four- to eight cells	Mesenchyme blastula	Late prism
Tissue	Uniform distribution	Uniform distribution, newly ingressed primary mesenchyme cells stain less intensely	Significant staining in cells of the gut, primary mesenchyme, and oral epithelium. Staining of aboral ectoderm cells is significantly reduced

Sequences

partial cds

Regulatory Regions

Regions

Regulatory Connections

Upstream Genes

spLBP/p40

Downstream Genes

Evolutionary Homologues

LBP/p40 T.gratilla
LBP/p40 mammals

Links

Urchin Web

Bibliography

UrchiNet

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