Gene Networks Database

Strongylocentrotus purpuratus Genes in Development: Primary mesenchyme-specific genes

SM30

Function

The SM30 gene participates in the process of biomineralization and construction of the embryonic spicules.
It codes for a 30,6 kDa spicule matrix protein (George et al., 1991).
There are at least two SM30 genes per haploid genome (Akasaka et al., 1994).

Protein

The SM30 protein is acidic and very similar to the C-type lectin proteins.
It has a low concentration of basic residues (Lyz and Arg make up 6.2% of the total protein and 3.9% of the acidic region).
While the overall protein is acidic, its carboxyl end is very basic. The carbohyl one-sixth of the peptide, beginning at residue 225, contains approximately one-half of the total basic residues. This region also comprises the most hydrophilic portion of the protein. The SM30 basic region may be involved in interacting with acidic domains of itself and/or with other spicule matrix proteins.
Another feature of the SM30 protein is its proline-rich character. Proline, at 11% of the total residues, is the most abundant amino acid. A short stretch of residues beginning at amino acid 205 is extremely proline-rich. This sequence lies between the acidic and the basic portions of the protein and may thus serve as a hinge region interconnecting the two domains.
The SM30 protein contains a putative hydrophobic signal sequence at its amino end, indicating that the mature peptide may be secreted.
The size of the SM30 protein after cleavage of the putative signal sequence is approximately 30,6 kDa. Benson et al.(1986), Vekatesan et al.(1986), Killian et al.(1996) have shown that a group of matrix proteins exists around this size. However, due to a presence of the potential N-linked glycosilation site, the 30,6 kDa SM30 protein may actually turn out to be modified so that it migrates during electrophoresis as one of the largest spicule matrix proteins (George et al., 1991).
SWISS_PROT: P28163

Subcellular location

Expression Pattern

The SM30 gene is expressed at the time of spicule formation in the embryo.
The RNA blot analysis shows that the SM30 mRNA accumulates exclusively in mineralized tissues.
Within the embryo SM30 transcript accumulation is restricted exclusively to the primary mesenchyme cells.
Few or no transcripts are detectable from fertilization through the mesenchyme blastula stage. The first appearance of SM30 transcripts corresponds to the time when PMCs are migrating through the blastocoel.
There is a sharp increase in the levels of the SM30 1.8-kb mRNA at middle to late mesenchyme blastula stage (26 to 28 hr).
By the prism stage there are about 29,000 SM30 transcripts present per embryo, which averages to approximately 480 transcripts per primary mesenchyme cell. The transcript levels remain high through the 3-day pluteus stage (George et al., 1991).

mRNA level

Temporal accumulation
Method 1: Nothern blot analysis
Reference: George et al., 1991
Method 2: RNase protection assay
Reference: Akasaka et al., 1994

Stage Egg 12h 24h 39h 48h 72h 96h

Level - - - + + + + +