SpARS

Function

SpARS codes for arylsulphatase.
Arylsulfatases are the group of enzymes that remove sulfate moieties from a diverse set of substrates including glycoproteins, steroids, and cerebrosides.
Southern blots revealed that SpARS is a single copy gene in the S. purpuratus genome (Yang et al., 1989).

Protein

The open reading frame of the SpARS cDNA clones is 1701 nt long and encodes a deduced protein with a predicted molecular mass of 61 kDa.
Consistent with the fact that arylsulfatase enzyme activity is extracellular, this polypeptide has a hydrophobic leader sequence and three potential glycosylation sites (Yang et al., 1989).
SWISS_PROT: P50473

Subcellular location

Hybridization in situ shows that in both mesenchyme blastulae and early gastrulae arylsulfatase message is preferentially concentrated around nuclei at the basal sides of cells. Similar subcellular localization is not observed for other aboral-ectoderm-specific mRNAs that encode intracellular proteins, and this mRNA distribution is undoubtedly related to the fact that the SpARS protein is secreted into, and accumulates at high concentration within the blastocoel from blastula through pluteus stages (Yang et al., 1989).

Expression Pattern

RNA blot analysis shows that the SpARS probe detects a single transcript, approximately 2.8 kb in length. This message is undetectable in RNA from eggs and early blastulae (15 hr). Low levels are found at mesenchyme blastula stage (24 hr) and the abundance increases greatly by late gastrula and is maintained at pluteus stage.
To establish the time of onset of accumulation of the SpARS mRNA more precisely, the RNase protection assay was performed. The results showed that the SpARS message does not begin to accumulate until around 15 hr, shortly before hatching which occurs at approximately 18 hr.
Relative intensities of signals compared to those obtained with probes for mRNA of known prevalence indicate that SpARS mRNA is one of the most abundant messages so far identifired in the pluteus larva and is present at a level similar to that of actin CyIIIa mRNA, several hundred copies per cell.
In situ hybridization with a probe for SpARS shows that the sea urchin message accumulates in the embryo only in the single cell type of aboral ectoderm and its precursors (Yang et al., 1989).

mRNA level

Temporal accumulation
Method 1: RNA blot hybridization
Reference: Yang et al., 1989
Method 2: RNase protection assay
Reference: Yang et al., 1989

Stage	Egg	2 cells	32 cells	9 hr	12 hr	15 hr	24 hr	48 hr	72 hr
Level	-	-	-	-	-	+ -	+	+ +	+ +

Spatial localization
Method: In situ hybridization
Reference: Yang et al., 1989

Stage	Unfertilized egg	16-cell stage	Early blastula (about 180 cells at 12 hr)	Early mesenchyme blastula (20 hr)	Mesenchyme blastula (23 hr)	Gastrula (43 hr)	Pluteus larva (73 hr)
Tissue	-	-	-	Two regions corresponding to the future left and right sides of aboral ectoderm (in sections which pass through the A/V axis perpendicular to the O/A axis)	Two regions corresponding to the future left and right sides of aboral ectoderm (in sections which pass through the A/V axis perpendicular to the O/A axis)	All aboral ectoderm cells	All aboral ectoderm cells