Cytoskeletal actin I

Function

CyI codes for cytoskeletal actin type protein I. 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.

Protein

Cytoskeletal actin I
GenBank: 71622

Subcellular location

Cytoplasmic

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.
CyI message accumulation is transcriptionally regulated (Lee et al., 1992). The accumulation of zygotic origin transcripts of CyI is first observed at 12 hr after fertilization (Lee et al., 1992).
CyI is initially globally expressed but ultimately is silenced in aboral ectoderm while continuing to be actively expressed in oral ectoderm and gut (Cox et al., 1986).
At early stages of development (18 hr) the transcripts of CyI accumulate in all cells of the embryo. In the late pluteus, CyI messages are confined to the oral ectoderm, stomach, and intestine (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 CyI gene 245 200 550

Amount of actin mRNA as measured by 1 (transcripts/embryo) 3,7 x 10^4 4,0 x 10^4 2,1 x 10^5

Amount of actin mRNA as measured by 2 (transcripts/embryo) 3,3 x 10^4 6,0 x 10^3 4,9 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

Sequences

GenBank:

3' untranslated region

Regulatory Regions

Regulatory region

Regulatory Connections

Upstream Genes

CyI

Downstream Genes

Evolutionary Homologues

CyIIa S.purpuratus
CyIIb S.purpuratus
CyIIIa S.purpuratus
CyIIIb S.purpuratus
M actin S.purpuratus
other actins

Links

Urchin Web

Bibliography

UrchiNet

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Developmental time interval (hr)	8-20	20-36	36-65
Average number of cells expressing CyI gene	245	200	550
Amount of actin mRNA as measured by 1 (transcripts/embryo)	3,7 x 10^4	4,0 x 10^4	2,1 x 10^5
Amount of actin mRNA as measured by 2 (transcripts/embryo)	3,3 x 10^4	6,0 x 10^3	4,9 x 10^4

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