Gene Networks Database

Strongylocentrotus purpuratus Genes in Development: Actins

Cytoskeletal actin IIb


CyIIb codes for cytoskeletal actin IIb. 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 IIb

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.
CyIIb message accumulation is transcriptionally regulated (Lee et al., 1992). The accumulation of zygotic origin transcripts of CyIIb is first observed at 12 hr after fertilization (Lee et al., 1992).
Specification of the founder cell populations for the cell type that will express cytoskeletal actin genes begins as early as 3rd cleavage and is compleated by the 64-cell stage (Cameron et al., 1987).
In situ hybridization (Cox et al.,1986) and lineage tracer studies suggest that all cells at the 64-cell stage activate CyIIb. CyIIb is initially globally expressed but ultimately is silenced in aboral ectoderm while continuing to be actively expressed in oral ectoderm and gut.

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 CyIIb gene 245 200 550
Amount of actin mRNA as measured by 1 (transcripts/embryo) 1,1 x 10^4 1,2 x 10^4 5,9 x 10^4
Amount of actin mRNA as measured by 2 (transcripts/embryo) 2,8 x 10^4 2,0 x 10^3 2,8 x 10^4

Spatial localization

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

Stage 20 hr late gastrula pluteus
Tissue All cells The lineages destined to form oral ectoderm and gut Oral ectoderm, stomach, intestine



Regulatory Regions


Regulatory Connections

Upstream Genes


Downstream Genes

Evolutionary Homologues


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