Gene Networks Database
Lytechinus variegatus Genes in Development:
alphaSU2 belongs to the family of alpha integrins.
alphaSU2 integrin contributes to epithelial cell-substrate adhesion. It functions in adhesion of epithelia to the
alphaSU2 may serve as a primary receptor binding the blastula-
stage cells to the basal lamina (Hertzler et al., 1999).
alphaSU2 is an alpha integrin.
The first stop codon at nucleotide position 3885-3887 produces
an open reading frame of 1041 amino acids, and the mature protein
of 1018 amino acids is calculated to have a molecular mass
of 110,706 daltons. The protein is approximtely 140 kDa
as blotted with the antibody to an expressed fragment of the protein,
suggesting thet alphaSU2, like other alpha integrins,
A large region corresponding to the
extracellular domain extends to amino acid residue 982,
followed by a stretch of 25 hydrophobic amino acids,
which is an acceptable transmembrane domain.
A short cytoplasmic domain of 31 amino acids constitutes
the remainder of the sequence. A consensus site for
proteolytic cleavage K/RRE/D (Bossy et al., 1991) is present
at amino acid residues 876-878.
Alignment of alphaSU2 with other alpha integrins
reveals a number of conserved protein domains.
Seven repeats characteristic of alpha integrins
are present in the extracellular domain. Domains IV-VII
each contain potential divalent cation-binding domains
corresponding to at least a 11/12 match for the consensus
sequence DX(D/N)X(D/N)-GXXDXXV within EF-hand calcium-
binding domains (Kretsinger, 1980). Sixteen of eighteen
cystein residues are present in conserved positions
throughout the extracellular domain. Eleven sites
of potential N-glycosylation corresponding to the consensus
NX(T/S) are present. The sequence GFFER is located in the cytoplasmic
domain adjacent to the transmembrane region, a 4/5 match to the
consensus GFFKR in other alpha integrins (Sastry and Horwitz, 1993).
A potential tyrosine phosphorylation site is also present
in the intracellular domain. Thus, all the major structural
elements of alpha integrins are conserved in alphaSU2 (Hertzler et al., 1999).
Whole-mount immunofluorescence showed that alphaSU2 protein first appears
on the basal cell surface of epithelia at the midblastula stage and
remains at high levels on the basal surface of ectoderm cells
but is temporary reduced or eliminated from endoderm cells
during their convergent-extension movements (Hertzler et al., 1999).
Nothern blotting of poly [A]+ RNA revealed that a
single band approximately 11,3 kb is present in eggs and mesenchyme
blastula, midgastrula, late gastrula, prism, and pluteus larval stages.
The levels of alphaSU2 integrin RNA remain rather constant
or decrease slightly during development.
Western blot data also show the protein to be present
Whole-mount immunofluorescence revealed no staining in eggs or embryos
up to about 5 h. Beginning in the midblastula stage (6 h), punctate
staining is first observed on the basal side of some blastomeres.
By 9-10 h, in late blastula stages, there is intense staining on the basal
surface of most cells in the blastoderm, especially on the thickened
vegetal plate from which the PMCs and secondary mesenchyme cells (SMCs)
will later ingress. There are no discontinuities in the staining pattern
of the vegetal plate at this stage, so most cells, including most,
if not all, PMC and SMC precursors express the integrin at this stage.
Later at PMC ingression (12 h), the basal staining pattern
becomes discontinuous in the region of ingression and PMCs fail to stain
for the integrin during and following the ingression process.
In early gastrulae (15 h), the basal side of ectodermal cells remains
immunopositive but during archenteron invagination endoderm cells
stain much less intensively for the integrin. In the early prism
stage the archenteron still has reduced integrin staining
relative to the basal side of the ectoderm but the ectoderm/endoderm
levels appear the same in plutei (Hertzler et al., 1999).
Method: Nothern blot analysis
Reference: Hertzler et al., 1999
Protein spatial localization
Method: Whole mount immunofluorescence
Reference: Hertzler et al., 1999
||9 h late blastula
||12 h mesenchyme blastula
||15 h early gastrula
||18 h late gastrula
||21 h prism
||32 h pluteus larva
||Punctate staining on the basal side of some blastomeres
||Intense staining on the basal surface of most cells
in the blastoderm, especially on the thickened
vegetal plate (including most, if not all, PMC and SMC precursors)
||The basal staining pattern becomes discontinuous
in the region of ingression and PMCs fail to stain
for the integrin during and following the ingression process
||The basal side of ectodermal cells remains
||During archenteron invagination endoderm cells
stain much less intensively than ectoderm cells
||Archenteron still has reduced integrin staining
relative to the basal side of the ectoderm
levels appear to be the same
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