Gene Networks Database
purpuratus Genes in Development: Primary
The SM50 gene serves as a marker of the earliest known
sceletogenic lineage-specific gene expression.
This gene occurs once per haploid genome (Davidson et al.,1989).
SM50 encodes a protein of the matrix within which
the mineral elements of the sceletal structures are
embedded (Makabe et al., 1995).
SM50 is the 50-kDa spicule matrix glycoprotein (Davidson et al.,1989).
This protein includes a typical N-terminal signal
peptide and an N-linked glycosylation site near
the C terminus. About 45% of the length of the protein
is included in a domain composed of consecutive
approximate repetitions of a 13-amino-acid
element, the consensus sequence of which is
The protein also contains an internal domain unusually
rich in proline residues and a very basic C-terminal
region (Sucov et al.,1987).
The SM50 gene is expressed in the skeletogenic
mesenchyme by the cells located at the original
vegetal pole of the egg.
SM50 is silent early in cleavage, it appears to be
transcriptionally activated shortly after the 6th or
7th cleavage divisions (Davidson et al.,1989).
The SM50 2,2-kb mRNA attains a maximum level of 8000 to
10,000 transcripts per embryo by the gastrula stage,
representing 120 to 200 SM50 mRNAs per primary mesenchyme cell.
Method: solution hybridization (Lee et al., 1986)
Reference: Killian et al., 1989, Davidson, 1986.
||16-cell||200-cell (12 hr)
||Early mesenchyme blastula (18 hr)
||Mesenchyme blastula (24 hr)
||Gastrula (39 hr)||Prism
||3-Day pluteus (72 hr)||4-Day pluteus (96 hr)
|Average No. transcripts/per embryo||N.D.
|No. of expressing cells||-
|Average No. transcripts/per cell||-
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