Gene Networks Database

LvSM30

Function

Protein

Subcellular location

Expression Pattern

mRNA level

Stage	Hatched blastula	Early mesenchyme blastula	Late mesenchyme blastula	Midgastrula	Late gastrula	Prism	Early pluteus	Late pluteus
Level	8	10	15	19	35	53	70	100

*Values were corrected for relative amounts of hybridizable RNA based on ubiquitin expression levels.

Stage	Early gastrula	Late gastrula	Prism	Early pluteus	Pluteus larva
Tissue	PMCs that are forming in the ventrolateral clusters	PMCs in the ventrolateral clusters (highest level), PMCS in the dorsal chain (intermediate level)	PMCs that are forming in the ventrolateral clusters, especially along anonymous rods (highest level)	PMCs at the tips of postoral arms (highest level), most PMCs except those along ventral transverse rods (increased level)	all PMCs except those along ventral transverse rods (highest level)

Ectopic expression

NiCl₂ ventralizes the ectoderm; as a consequence, the arrangement of PMCs in the blastocoel is altered and the number of spicule rudiments is increased (Hardin et al., 1992; Armstrong et al., 1993).
When embryos were raised continuously from fertilization in 0.05 mM NiCl₂, both the patterning of the PMC ring and the expression of LvSM30 were altered. In most NiCl₂-treated embryos, LvSM30 expression was relatively uniform throughout the PMC ring. In some embryos, multiple, discrete clusters of cells expressing high levels of LvSM30 were visible, with lower transcript levels exhibited by cells connecting these clusters. This pattern of expression was more common in embryos cultured in higher concentrations of nickel (e.g. 0.2 mM).
To determine whether the aberrant LvSM30 expression pattern was due to an effect of nickel on the ectoderm or the PMCs, we examined LvSM30 expression after transplanting nickel-treated PMCs into untreated, PMC-depleted host embryos. In such embryos, nickel-treated PMCs formed a ring and exhibited a pattern of LvSM30 expression similar to that observed in control embryos. In 6/7 cases, the PMCs formed a ring in which two clusters and either the ventral and/or the dorsal chain were distinguishable. PMCs in the two ventrolateral clusters exhibited the highest expression of LvSM30. The dorsal chain, when present, exhibited faint to strong staining, whereas the ventral chain showed consistently low expression. As a control, a sample of nickel-treated donor embryos was allowed to continue development in IO in parallel with the experimental embryos. These donor embryos were ventralized and showed an aberrant pattern of LvSM30 expression. These results indicate that nickel causes a misregulation of LvSM30 expression by altering the ectoderm (Guss et al., 1997).

Transplantation of PMCs into recipient embryos of different developmental stages has been used to provide evidence that aspects of PMC behavior are regulated by extrinsic cues (Ettensohn and McClay, 1986). Here the PMCs from mesenchyme blastulae were transferred into younger embryos (pre-hatching blastulae) and LvSM30 expression was examined after 5- 5,5 hours, when sibling donor embryos had reached the mid-late gastrula stage and were expressing high levels of LvSM30 mRNA. As a control for the transplantation procedure, PMCs were removed from mesenchyme blastulae and microinjected into recipient embryos of the same developmental stage from which all endogenous PMCs had been removed (isochronic controls).
In the combined results of three series of heterochronic transplants, in 23 of 40 experimental embryos, the PMCs showed no significant signal above background The remaining embryos contained 1-2 cells exhibiting signal above background (6/40) or more than two cells above background (11/40).
In contrast to the low levels of LvSM30 expression observed following heterochronic transplantations, 26/27 isochronic control embryos exhibited more than two positive cells, although signal intensity ranged from just above background to very strong. In 17 of those embryos, a ring was distinguishable and the PMCs exhibited some degree of spatial regulation of LvSM30 expression, e.g. the highest degree of signal was localized to cells in at least one cluster. In the remaining cases, the presence of a ring could not be confirmed because of the orientation of the embryos (five cases), or the ring was incompletely formed and/or there were no differences in levels of staining in cells in different regions of the ring (four cases). Thus, the delay in LvSM30 expression following heterochronic PMC transplantation cannot be attributed to the effects of microsurgery alone, since almost all of the isochronic controls showed detectable levels of LvSM30 expression after the same period of time (Guss et al., 1997).

Sequences

• GenBank

Regulatory Regions

• Regions

Regulatory Connections

Evolutionary Homologues

• SM30 Strongylocentrotus purpuratus

Links

• Urchin Web