M actin gene

Function

M actin gene codes for the muscle-specific type actin. 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. (Lee et al., 1992).

Protein

M gene protein is the muscle-specific actin (Lee et al., 1992).
SWISS_PROT: P12431

Subcellular location

Cytoplasmic

Expression Pattern

M actin gene transcription was not detected in the assays of Lee et al. (1992) or Hickey et al.(1987) until the 65 hr prism/pluteus stage. However the molecular titration experiments of Lee et al.(1986) detected the zygotic M transcripts at 36 hr postfertilization (early gastrula), when about 2-4 cells express the gene (Cox et al.,1986).
The M gene mRNA accumulates only in two small clusters of cells in the vicinity of the esophagus of the archenteron wall in the late gastrulae. The cells which express the M gene are a part of the first differentiated muscle structures of the embryo. They are few in number, accounting for only 40-65 of the approximately 1200 cells in the 65-hr pluteus.
At the 65-67 hr embryo M actin gene is transcribed at the rate of about 12 molecules per embryo /min. This rate is the maximal observed for any actin gene (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 M gene 0 0 40

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

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

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

Stage 20 hr late gastrula pluteus

Tissue - - Muscle cells surrounding the esophagus

Sequences

GenBank:

Regulatory Regions

Regions

Regulatory Connections

Upstream Genes

M gene

Downstream Genes

Evolutionary homologues

CyI S.purpuratus
CyIIa S.purpuratus
CyIIb S.purpuratus
CyIIIa S.purpuratus
CyIIIb 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 M gene	0	0	40
Amount of actin mRNA as measured by 1 (transcripts/embryo)	0	0	2,1 x 10^4
Amount of actin mRNA as measured by 2 (transcripts/embryo)	0	1,7 x 10^2	2,5 x 10^4

Stage	20 hr	late gastrula	pluteus
Tissue	-	-	Muscle cells surrounding the esophagus