TABLE 7.5 (Continued)
Core Components of the Notch Pathway in the Development of Germ Layers and the Dorsal Midline in Xenopus
Expression
Gain-of-Function
Loss-of-Function
Role/Details
(Dominant-Negative/Morpholino)
dlc
dll1
Gene
Onset in the IMZ at early gastrula (NF10.5, ISH), with a gap
of lower expression in the GO, with scattered dll1+ cells
( López et al., 2005 ). Expression in the pre-involuted IMZ
does not persist in involuted cells ( Wittenberger et al.,
1999 ; López et al., 2005 ).
Germ layers:
Dll1 signaling from pre-involuted IMZ activates Notch
signaling in the NIMZ, promoting neural-ectodermal and
inhibiting endomesodermal fates ( Revinski et al., 2010 ).
DML:
Within the GO, Dll1 promotes FP development at the
expense of notochordal fate.
DML:
dll1, dorsal overexpression; analysis at gastrula stage : ↑FP
precursors (hes4), ↓notochordal precursors (chrd) in the GO
( López et al., 2005 ).
Germ layers:
dll1 STU (dorsal injection), analysis at gastrula stage: ↓tbxt in its
normal domain, displaced by expanded supra-blastoporal
endoderm (sox17) that took its place; ↓neural ectoderm (sox2)
because of the animal shift and expansion of the presumptive
mesoderm (tbxt) ( Revinski et al., 2010 ).
dll1 MO (lateral injection), analysis at gastrula stage: impaired
blastopore closure, ↓circumblastoporal tbxt expression (only a
vegetal view was shown). Both effects were rescued by
co-injection of NICD1 mRNA ( Kinoshita et al., 2011 ).
DML:
dll1 STU, dorsal injection; analysis at gastrula stage :
↑
precursors (
notochordal
chrd), ↓FP precursors (hes4 ) in
the GO ( López et al., 2005 ).
Onset in the IMZ at early gastrula (NF10.5, ISH) in a
complete circumblastoporal ring; a lower expression
gap appears at NF11 at the GO (Peres et al., 2006).
Necessary for hox genes expression in the IMZ. There are
restrictions, at least for hox genes, to respond to Dlc
signaling outside the IMZ (see Table 7.12 for additional
information).
dlc overexpression: did not affect hoxc6 and hoxd1 in the IMZ and
could not expand them outside their normal region (ISH,
gastrula stage) (Peres et al., 2006).
dlc MO: ↓hoxb4, hoxc6, hoxb9, and bmp4 in the IMZ (ISH,
gastrula stage); tbxt expression unaffected in the IMZ (ISH,
late gastrula) ( Peres et al., 2006 ).
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Xenopus
Core Components of the Notch Pathway in the Development of Germ Layers and the Dorsal Midline in Xenopus
Expression
Gain-of-Function
Loss-of-Function
Role/Details
(Dominant-Negative/Morpholino)
dlc
dll1
Gene
Onset in the IMZ at early gastrula (NF10.5, ISH), with a gap
of lower expression in the GO, with scattered dll1+ cells
( López et al., 2005 ). Expression in the pre-involuted IMZ
does not persist in involuted cells ( Wittenberger et al.,
1999 ; López et al., 2005 ).
Germ layers:
Dll1 signaling from pre-involuted IMZ activates Notch
signaling in the NIMZ, promoting neural-ectodermal and
inhibiting endomesodermal fates ( Revinski et al., 2010 ).
DML:
Within the GO, Dll1 promotes FP development at the
expense of notochordal fate.
DML:
dll1, dorsal overexpression; analysis at gastrula stage : ↑FP
precursors (hes4), ↓notochordal precursors (chrd) in the GO
( López et al., 2005 ).
Germ layers:
dll1 STU (dorsal injection), analysis at gastrula stage: ↓tbxt in its
normal domain, displaced by expanded supra-blastoporal
endoderm (sox17) that took its place; ↓neural ectoderm (sox2)
because of the animal shift and expansion of the presumptive
mesoderm (tbxt) ( Revinski et al., 2010 ).
dll1 MO (lateral injection), analysis at gastrula stage: impaired
blastopore closure, ↓circumblastoporal tbxt expression (only a
vegetal view was shown). Both effects were rescued by
co-injection of NICD1 mRNA ( Kinoshita et al., 2011 ).
DML:
dll1 STU, dorsal injection; analysis at gastrula stage :
↑
precursors (
notochordal
chrd), ↓FP precursors (hes4 ) in
the GO ( López et al., 2005 ).
Onset in the IMZ at early gastrula (NF10.5, ISH) in a
complete circumblastoporal ring; a lower expression
gap appears at NF11 at the GO (Peres et al., 2006).
Necessary for hox genes expression in the IMZ. There are
restrictions, at least for hox genes, to respond to Dlc
signaling outside the IMZ (see Table 7.12 for additional
information).
dlc overexpression: did not affect hoxc6 and hoxd1 in the IMZ and
could not expand them outside their normal region (ISH,
gastrula stage) (Peres et al., 2006).
dlc MO: ↓hoxb4, hoxc6, hoxb9, and bmp4 in the IMZ (ISH,
gastrula stage); tbxt expression unaffected in the IMZ (ISH,
late gastrula) ( Peres et al., 2006 ).
94
Xenopus