Gene Networks Database

Strongylocentrotus purpuratus Genes in Development: Actins

Cytoskeletal actin IIa


CyIIa codes for cytoskeletal actin IIa (Davidson, 1989). Actin represents one of the most abundunt and best characterized structural components in eucaryotic cells, involved in a wide variety of cytoskeletal, locomotive, and tension-generating functions. Five functional cytoskeletal actin genes are organized in two linkage groups within the genome: CyI-CyIIa-CyIIb and CyIIIa-CyIIIb.


Cytoskeletal actin IIa

Subcellular location


Expression Pattern

Developmental studies of actin mRNA prevalence have been caried out using several sensitive methods including in situ hybridization (Cox et al., 1986), molecular titration with single-strand RNA probes (Lee et al., 1986), RNA gel blot hybridization, and cDNA analysis (Shott et al., 1984; Crain et al., 1981; Garcia et al., 1984).
All of the S. purpuratus cytoskeletal actin genes are activated at 8-9 hr of development, a time when 64-128 cell embryos are predominant in large cultures.
CyIIa message accumulation is transcriptionally regulated (Lee et al., 1992). The first evidence of CyIIa transcriptional activity was obtained at 20 - 22 hr postfertilization (Lee et al., 1992). No measurements have been made for this gene between 9 and 20 hr. The accumulation of zygotic origin transcripts of CyIIa is first observed at 20 hr after fertilization.
CyIIa mRNA is initially observed in primary mesenchyme cells within the blastocoel and in presumptive mesenchyme cells still embedded in the vegetal plate of the hatched blastula (Cox et al., 1986). However, by late gastrula, expression is limited to secondary mesenchyme; in the pluteus CyIIa is expressed in the stomach and intestine as well (Lee et al., 1992).

mRNA level

Temporal accumulation

Method 1: in vivo labeling
Reference: Lee et al., 1992
Method 2: molecular titration
Reference: Lee et al., 1986

Developmental time interval (hr) 8-20 20-36 36-65
Average number of cells expressing CyIIa gene 15 54 155
Amount of actin mRNA as measured by 1 (transcripts/embryo) 1,5 x 10^3 8,8 x 10^3 4,7 x 10^4
Amount of actin mRNA as measured by 2 (transcripts/embryo) 1,4 x 10^3 8,0 x 10^3 4,6 x 10^3

Spatial localization

Method: in situ hybridization
Reference: Cox et al., 1986

Stage 20 hr late gastrula pluteus
Tissue Primary mesenchyme cells within the blastocoel. Presumptive mesenchyme cells embedded in the vegetal plate. Secondary mesenchyme Stomach and intestine



Regulatory Regions


Regulatory Connections

Upstream Genes


Downstream Genes

Evolutionary Homologues


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