Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
Cells in the prospective somite of Xenopus laevis embryos rotate in an orchestrated manner to form a segregated somite. The prospective somite boundaries are prepatterned by gene expressions in the unsegmented presomitic mesoderm (PSM). However, the roles of polarized gene expression in this boundary formation are not well elucidated. Here we identified a novel gene, bowline, which localizes to the anterior halves of S-II, III in the PSM of X. laevis. Bowline associated with corepressor XGrg-4, a Xenopus homolog of Groucho/TLE protein. A WRPW tetrapeptide motif in Bowline was prerequisite for coprecipitation with XGrg-4 and for downregulation of X-Delta-2 by bowline RNA injection. This study indicates that Bowline is a novel protein interacting with Groucho/TLE and may play a role in somitogenesis in X. laevis.
Fig. 1. Structural features of Bowline.
The complete peptide sequence of Bowline
deduced from its nucleotide sequence
is aligned with human �similar to DSCR6�
(s-DSCR6; NP001009994), chick hypothetical
protein (XP419859) and X. laevis
Ledgerline (BAB90857). Asterisks under
the sequences indicate the position of
conserved amino acids. A yellow box indicates
the position of the conserved WRPW
sequence and a red box indicates the
BDLC-region. Sequences were aligned
using GENETYX software. The Genbank
accession number for the bowline nucleotide
sequence is AB105905.
Fig. 2. Localization and transcriptional
regulation of bowline
transcripts. (A-C) Xenopus
embryos from different
stages were stained for expression
of bowline mRNA by
whole-mount in situ hybridization
at (A) stage 13, (B) stage
18 and (C) stage 30. Embryos
are oriented in dorsal view with
anterior to the top except for
(C), for which the anterior is to
the left. (D-I) Longitudinal section
through stage 20 embryos
stained for expression of XDelta-
2 (D), bowline (E,G,I) and
Thy1 (F,H). Embryos are oriented
with anterior to the left.
Arrowheads on the lower side
of the embryos indicate the
anterior end of X-Delta-2-and
Thy1-expressing regions. The
probes used are shown in the
upper right corner. In (H and I),
the width of the expression region
for Thy1 and bowline are
indicated as red and black lines,
respectively. (J) Diagram showing
the position of bowline expression
relative to that of other
genes known to be expressed
segmentally in X. laevis embryos (Jen et al., 1997, Kim et al., 2000, Sparrow et al., 1998). (KM)
Embryos were unilaterally injected with β-gal RNA (K), XotchδE RNA (L), or XSu(H)DBM
RNA (M) and analyzed for the expression of bowline (K,L,M) by whole-mount in situ
hybridization at stage 20. RNA encoding the lineage tracer β-gal was co-injected to identify
the injected side (red staining). Dorsal views with anterior towards the top are shown.
Injected sides are indicated as �inj.� Somitomeres were demarcated as S0, S-I, S-II, S-III
based on the annotation of Pourqui� and Tam (Pourqui� and Tam, 2001). Bars, 100 μm.
BowlineδWRPWFig.
3. The WRPW motif is required for Bowline interaction with
XGrg-4. (A) Extracts prepared from embryos injected with bowline-
EGFP alone (lane 1), Myc-XGrg4 and bowline-EGFP (lane 2), or Myc-
XGrg4 and bowlineδWRPW-EGFP (lane 3) were subjected to immunoprecipitation
(IP) with an anti-myc antibody followed by Western blotting
(WB) with either anti-GFP or anti-myc antibody. (B) Extract prepared from
embryos injected with Myc-XGrg4 alone (lane 1), Myc-XGrg-4 and bowline-
EGFP (lane 2), or Myc-XGrg-4 and bowlineδWRPW-EGFP (lane 3)
were subjected to IP with an anti-GFP antibody, followed by WB with the
anti-myc antibody. Lane 4 was an uninjected negative control. (A,B) 5%
of embryo extracts were loaded as input to indicate the expression (A,B;
lanes 5-8). (C,D) Subcellular localization of Bowline-EGFP protein. EGFP
RNA (1 ng) (C) or bowline-EGFP RNA (1 ng) (D) was injected into two
animal blastomeres of two-cell stage embryos. Animal caps were excised
at stage 9-10 and examined for GFP fluorescence. Bars, 50 μm. (EG)
Embryos injected unilaterally at the 4-cell stage with β-gal RNA (E),
bowline RNA (F) or bowlineδWRPW (G) and analyzed for the expression
of X-Delta-2 (E,F,G) by whole-mount in situ hybridization at stage 20. RNA
encoding the lineage tracer β-gal was co-injected to identify the injected
side (red staining). Dorsal views with anterior towards the top are shown.
Injected sides are indicated as �inj.�
ripply2.2 (ripply2 homolog, gene 2) gene expression in Xenopus laevis embryo, NF stage 13, as assayed by in situ hybridization. Dorsal view: anterior up.
ripply2.2 (ripply2 homolog, gene 2) gene expression in Xenopus laevis embryo, NF stage 30, as assayed by in situ hybridization. lateral view: anteriorleft, dorsal up.
