hey1
hes6.1
hes5.10
hes5.6
hes5.5
Gene
TABLE 7.8 (Continued)
Role of hes/hey Genes in Xenopus Neurogenesis and Epidermal Differentiation
Role/Details
Gain-of-Function
Loss-of-Function
(Dominant-Negative/Morpholino)
Inhibition of PN.
GR-hes5.5 (Dex NF12 or NF18): ↓PN (ISH neurula stage)
Does not interact in vitro with Hey1 ( Taelman
( Taelman et al., 2004 ; Taelman
et al., 2004 ).
et al., 2006 ).
Inhibition of PN.
Does not form homodimers in vivo nor heterodimerizes with
other bHLH-O proteins (Hes1, Hes4, Hes5.6, Hey1).
Heterodimerizes in vivo with bHLH proteins that promote
neurogenesis (Neurog2, Neurod1, Neurod4) (IP assay from
Xenopus embryo extracts) ( Taelman et al., 2004 ).
GR-hes5.6 (Dex NF12 or NF18): ↓PN (ISH neurula stage)
( Taelman et al., 2004 ; Taelman
et al., 2006 ).
Inhibits differentiation of epidermal multiciliate cells in the
inner layer of the non-neural ectoderm through a Dll1/
Notch-dependent lateral inhibition mechanism. Possibly
participates in the inhibition of neurogenesis in the outer
layer of the ectoderm through a different mechanism.
hes5.10 overexpression : ↓density of multiciliate cells in the
epidermis (tailbud stage); ↓dll1 in animal caps (midgastrula) ( Deblandre et al., 1999 ); ↓neurod1 and PN
without affecting neurog2 or neural specif cation; acts
downstream of neurod1, because it prevented ectopic
neurogenesis but not ectopic neurod1 induced by neurog2
( Chalmers et al., 2002 ).
hes5.10 DBM: ↑density of multiciliate cells in the epidermis
(tailbud stage), ↑dll1 in animal caps (mid-gastrula)
(Deblandre et al., 1999).
hes5.10 MO: unable to induce ectopic PN in the deep layer
(Chalmers et al., 2002).
hes6.1 promotes PN by antagonizing other Hes proteins that
suppress neuronal differentiation. It does so in a posttranscriptional, TLE/Groucho-independent, and DNA
binding-independent way ( Koyano-Nakagawa et al., 2000 ;
Murai et al., 2011 ). However, the full promotion of PN
requires TLE/Groucho binding ( Murai et al., 2011 ).
See Table 7.4 for the regulation of hes1 and hes4 by hes6.1.
hes6.1 overexpression : ↑neurog2 domains ( Koyano-Nakagawa
et al., 2000 ) and primary neuron differentiation ( Cossins et
al., 2002 ) throughout the posterior neural plate; ↑dll1, hes5.1,
and hes5.7 domains, indicating that the increase in neuronal
differentiation does not involve transcriptional repression of
genes of the lateral inhibition program ( Koyano-Nakagawa et
al., 2000 ).
Hes6.1 did not affect the binding of Neurog2 to its E12
coactivator during in vitro binding to E-box. Hes6.1 did not
directly interact with Neurog2 (immunoprecipitation
assay). Hes6.1 directly binds and impairs the ability of
Hes1 to repress PN through a TLE/Groucho-independent
mechanism ( Murai et al., 2011 ) .
hes6.1 MO: ↓tubb2b, neurog2, and neurod1 (neural plate stage);
prevented the induction of ectopic neurons by neurog2 or
neurod1 ( Murai et al., 2011 ).
hes6.1 ΔWRPW: did not rescue the inhibition of PN produced
by hes6.1 MO ( Murai et al., 2011 ).
hes6.1 DBM : promoted PN like hes6.1 overexpression,
indicating that DNA binding is not required for this activity
( Cossins et al., 2002 ).
Possible role in suppressing neurogenesis in the FP by
antagonizing proneural genes, contributing to promote or
maintain FP identity. Additional inhibitors might be
required to maintain neurogenesis inhibited in FP.
Hey1 does not bind the co-repressor TLE/Groucho, as it lacks the
typical WRPW motif of bHLH-O repressors ( Pichon et al.,
2004 ). For inhibition of PN, Hey1 acts as a DNA binding
repressor, requiring the Orange domain and the C-terminal
region for dimerization. Hey1 heterodimerizes in vivo with
Hes1 and Hes4 and weakly with Hes2, but it does not bind
Hes5.5 or Hes5.6. It weakly binds bHLH proteins that promote
neuronal differentiation (Neurod1 and Neurod4) but does not
bind the proneural protein Neurog2 ( Taelman et al., 2004 ).
hey1 or GR-hey1 (Dex NF12 or NF18): ↓PN ( Taelman et al.,
2004 ; Taelman et al., 2006 ). hey1 blocked neurog2 ’s ability
to induce ectopic neurogenesis ( Taelman et al., 2004 ).
hey1 DBM : did not inhibit PN and could not block neurog2’s
ability to induce ectopic neurogenesis ( Taelman et al.,
2004 ).
hey1 MO +/- hes4.L MO : did not induce ectopic neurogenesis in
the FP. ( Taelman et al., 2004 ). Note: MO sequences were not
reported in this study.
hey1.L+S MO: tubb2b unaffected (ISH in tailbuds) ( Taelman
et al., 2006 ).
104
Xenopus
hes6.1
hes5.10
hes5.6
hes5.5
Gene
TABLE 7.8 (Continued)
Role of hes/hey Genes in Xenopus Neurogenesis and Epidermal Differentiation
Role/Details
Gain-of-Function
Loss-of-Function
(Dominant-Negative/Morpholino)
Inhibition of PN.
GR-hes5.5 (Dex NF12 or NF18): ↓PN (ISH neurula stage)
Does not interact in vitro with Hey1 ( Taelman
( Taelman et al., 2004 ; Taelman
et al., 2004 ).
et al., 2006 ).
Inhibition of PN.
Does not form homodimers in vivo nor heterodimerizes with
other bHLH-O proteins (Hes1, Hes4, Hes5.6, Hey1).
Heterodimerizes in vivo with bHLH proteins that promote
neurogenesis (Neurog2, Neurod1, Neurod4) (IP assay from
Xenopus embryo extracts) ( Taelman et al., 2004 ).
GR-hes5.6 (Dex NF12 or NF18): ↓PN (ISH neurula stage)
( Taelman et al., 2004 ; Taelman
et al., 2006 ).
Inhibits differentiation of epidermal multiciliate cells in the
inner layer of the non-neural ectoderm through a Dll1/
Notch-dependent lateral inhibition mechanism. Possibly
participates in the inhibition of neurogenesis in the outer
layer of the ectoderm through a different mechanism.
hes5.10 overexpression : ↓density of multiciliate cells in the
epidermis (tailbud stage); ↓dll1 in animal caps (midgastrula) ( Deblandre et al., 1999 ); ↓neurod1 and PN
without affecting neurog2 or neural specif cation; acts
downstream of neurod1, because it prevented ectopic
neurogenesis but not ectopic neurod1 induced by neurog2
( Chalmers et al., 2002 ).
hes5.10 DBM: ↑density of multiciliate cells in the epidermis
(tailbud stage), ↑dll1 in animal caps (mid-gastrula)
(Deblandre et al., 1999).
hes5.10 MO: unable to induce ectopic PN in the deep layer
(Chalmers et al., 2002).
hes6.1 promotes PN by antagonizing other Hes proteins that
suppress neuronal differentiation. It does so in a posttranscriptional, TLE/Groucho-independent, and DNA
binding-independent way ( Koyano-Nakagawa et al., 2000 ;
Murai et al., 2011 ). However, the full promotion of PN
requires TLE/Groucho binding ( Murai et al., 2011 ).
See Table 7.4 for the regulation of hes1 and hes4 by hes6.1.
hes6.1 overexpression : ↑neurog2 domains ( Koyano-Nakagawa
et al., 2000 ) and primary neuron differentiation ( Cossins et
al., 2002 ) throughout the posterior neural plate; ↑dll1, hes5.1,
and hes5.7 domains, indicating that the increase in neuronal
differentiation does not involve transcriptional repression of
genes of the lateral inhibition program ( Koyano-Nakagawa et
al., 2000 ).
Hes6.1 did not affect the binding of Neurog2 to its E12
coactivator during in vitro binding to E-box. Hes6.1 did not
directly interact with Neurog2 (immunoprecipitation
assay). Hes6.1 directly binds and impairs the ability of
Hes1 to repress PN through a TLE/Groucho-independent
mechanism ( Murai et al., 2011 ) .
hes6.1 MO: ↓tubb2b, neurog2, and neurod1 (neural plate stage);
prevented the induction of ectopic neurons by neurog2 or
neurod1 ( Murai et al., 2011 ).
hes6.1 ΔWRPW: did not rescue the inhibition of PN produced
by hes6.1 MO ( Murai et al., 2011 ).
hes6.1 DBM : promoted PN like hes6.1 overexpression,
indicating that DNA binding is not required for this activity
( Cossins et al., 2002 ).
Possible role in suppressing neurogenesis in the FP by
antagonizing proneural genes, contributing to promote or
maintain FP identity. Additional inhibitors might be
required to maintain neurogenesis inhibited in FP.
Hey1 does not bind the co-repressor TLE/Groucho, as it lacks the
typical WRPW motif of bHLH-O repressors ( Pichon et al.,
2004 ). For inhibition of PN, Hey1 acts as a DNA binding
repressor, requiring the Orange domain and the C-terminal
region for dimerization. Hey1 heterodimerizes in vivo with
Hes1 and Hes4 and weakly with Hes2, but it does not bind
Hes5.5 or Hes5.6. It weakly binds bHLH proteins that promote
neuronal differentiation (Neurod1 and Neurod4) but does not
bind the proneural protein Neurog2 ( Taelman et al., 2004 ).
hey1 or GR-hey1 (Dex NF12 or NF18): ↓PN ( Taelman et al.,
2004 ; Taelman et al., 2006 ). hey1 blocked neurog2 ’s ability
to induce ectopic neurogenesis ( Taelman et al., 2004 ).
hey1 DBM : did not inhibit PN and could not block neurog2’s
ability to induce ectopic neurogenesis ( Taelman et al.,
2004 ).
hey1 MO +/- hes4.L MO : did not induce ectopic neurogenesis in
the FP. ( Taelman et al., 2004 ). Note: MO sequences were not
reported in this study.
hey1.L+S MO: tubb2b unaffected (ISH in tailbuds) ( Taelman
et al., 2006 ).
104
Xenopus