60
Xenopus
work so far centers on AP patterning of the neural tissues,
with only limited studies on AP specifcation of mesodermal and endodermal tissues (Deimling and Drysdale, 2009,
2011; McLin et al., 2007; Rankin et al., 2018). AP patterning not only involves cell fates but also morphogenesis,
with posterior tissues undergoing elongation. How caudalizing signals modulate expression or activity of regulators
of cell behaviors is largely unclear (Janesick et al., 2014).
These issues await further examination. With microsurgery,
molecular biology, and genomic tools at hand, we expect to
obtain a more detailed picture and deeper understanding of
AP embryonic patterning in the future.
ACKNOWLEDGMENTS
This work is supported by NIH grants R01GM127371 and
R01HD102015. I apologize to the investigators whose works
are not cited here due to the space limitation.
REFERENCES
Amaya, E., T.J. Musci, and M.W. Kirschner. 1991. Expression of a
dominant negative mutant of the FGF receptor disrupts mesoderm formation in Xenopus embryos. Cell. 66:257–270.
Bayramov, A.V., F.M. Eroshkin, N.Y. Martynova, G.V. Ermakova,
E.A. Solovieva, and A.G. Zaraisky. 2011. Novel functions of
Noggin proteins: Inhibition of Activin/Nodal and Wnt signaling. Development. 138:5345–5356.
Belyaeva, O.V., S.A. Lee, M.K. Adams, C. Chang, and N.Y.
Kedishvili. 2012. Short chain dehydrogenase/reductase rdhe2
is a novel retinol dehydrogenase essential for frog embryonic
development. J Biol Chem. 287:9061–9071.
Blitz, I.L., and K.W. Cho. 1995. Anterior neurectoderm is progressively induced during gastrulation: The role of the Xenopus
homeobox gene orthodenticle. Development. 121:993–1004.
Blumberg, B., J. Bolado, Jr., T.A. Moreno, C. Kintner, R.M. Evans,
and N. Papalopulu. 1997. An essential role for retinoid signaling in anteroposterior neural patterning. Development.
124:373–379.
Bouwmeester, T., S. Kim, Y. Sasai, B. Lu, and E.M. De Robertis.
1996. Cerberus is a head-inducing secreted factor expressed
in the anterior endoderm of Spemann’s organizer. Nature.
382:595–601.
Bradley, L.C., A. Snape, S. Bhatt, and D.G. Wilkinson. 1993. The
structure and expression of the Xenopus Krox-20 gene:
Conserved and divergent patterns of expression in rhombomeres and neural crest. Mech Dev. 40:73–84.
Brivanlou, A.H., and R.M. Harland. 1989. Expression of an
engrailed-related protein is induced in the anterior neural ectoderm of early Xenopus embryos. Development.
106:611–617.
Chang, L.S., M. Kim, A. Glinka, C. Reinhard, and C. Niehrs. 2020.
The tumor suppressor PTPRK promotes ZNRF3 internalization and is required for Wnt inhibition in the Spemann organizer. Elife. 9.
Chen, M., N. Amado, J. Tan, A. Reis, M. Ge, J.G. Abreu, and X. He.
2020. TMEM79/MATTRIN defnes a pathway for Frizzled
regulation and is required for Xenopus embryogenesis. Elife. 9.
Chen, Y., L. Huang, and M. Solursh. 1994. A concentration gradient of retinoids in the early Xenopus laevis embryo. Dev Biol.
161:70–76.
Chen, Y., N. Pollet, C. Niehrs, and T. Pieler. 2001. Increased
XRALDH2 activity has a posteriorizing effect on the central
nervous system of Xenopus embryos. Mech Dev . 101:91–103.
Christen, B., and J.M. Slack. 1997. FGF-8 is associated with
anteroposterior patterning and limb regeneration in Xenopus.
Dev Biol. 192:455–466.
Christian, J.L., J.A. McMahon, A.P. McMahon, and R.T. Moon.
1991. Xwnt-8, a Xenopus Wnt-1/int-1-related gene responsive to mesoderm-inducing growth factors, may play a role
in ventral mesodermal patterning during embryogenesis.
Development. 111:1045–1055.
Christian, J.L., and R.T. Moon. 1993. Interactions between Xwnt-8
and Spemann organizer signaling pathways generate dorsoventral pattern in the embryonic mesoderm of Xenopus.
Genes Dev. 7:13–28.
Conlon, R.A. 1995. Retinoic acid and pattern formation in vertebrates. Trends Genet. 11:314–319.
Cox, W.G., and A. Hemmati-Brivanlou. 1995. Caudalization of
neural fate by tissue recombination and bFGF. Development.
121:4349–4358.
Curran, K.L., and R.M. Grainger. 2000. Expression of activated
MAP kinase in Xenopus laevis embryos: Evaluating the roles
of FGF and other signaling pathways in early induction and
patterning. Dev Biol. 228:41–56.
Darken, R.S., and P.A. Wilson. 2001. Axis induction by Wnt signaling: Target promoter responsiveness regulates competence.
Dev Biol. 234:42–54.
Davidson, G., B. Mao, I. del Barco Barrantes, and C. Niehrs. 2002.
Kremen proteins interact with Dickkopf1 to regulate anteroposterior CNS patterning. Development. 129:5587–5596.
Deimling, S.J., and T.A. Drysdale. 2009. Retinoic acid regulates
anterior-posterior patterning within the lateral plate mesoderm of Xenopus. Mech Dev. 126:913–923.
Deimling, S.J., and T.A. Drysdale. 2011. FGF is required to regulate anterior-posterior patterning in the Xenopus lateral plate
mesoderm. Mech Dev. 128:327–341.
Dekker, E.J., M. Pannese, E. Houtzager, A. Timmermans, E.
Boncinelli, and A. Durston. 1992. Xenopus Hox-2 genes
are expressed sequentially after the onset of gastrulation and are differentially inducible by retinoic acid. Dev
Suppl:195–202.
Dekker, E.J., M.J. Vaessen, C. van den Berg, A. Timmermans, S.
Godsave, T. Holling, P. Nieuwkoop, A. Geurts van Kessel,
and A. Durston. 1994. Overexpression of a cellular retinoic acid binding protein (xCRABP) causes anteroposterior defects in developing Xenopus embryos. Development.
120:973–985.
Dibner, C., S. Elias, and D. Frank. 2001. XMeis3 protein activity
is required for proper hindbrain patterning in Xenopus laevis
embryos. Development. 128:3415–3426.
Dibner, C., S. Elias, R. Ofr, J. Souopgui, P.J. Kolm, H. Sive, T.
Pieler, and D. Frank. 2004. The Meis3 protein and retinoid
signaling interact to pattern the Xenopus hindbrain. Dev Biol.
271:75–86.
Ding, Y., G. Colozza, E.A. Sosa, Y. Moriyama, S. Rundle, L.
Salwinski, and E.M. De Robertis. 2018. Bighead is a Wnt
antagonist secreted by the Xenopus Spemann organizer
that promotes Lrp6 endocytosis. Proc Natl Acad Sci U S A.
115:E9135–E9144.
Domingos, P.M., N. Itasaki, C.M. Jones, S. Mercurio, M.G. Sargent,
J.C. Smith, and R. Krumlauf. 2001. The Wnt/beta-catenin
pathway posteriorizes neural tissue in Xenopus by an indirect mechanism requiring FGF signalling. Dev Biol. 239:
148–160.
Xenopus
work so far centers on AP patterning of the neural tissues,
with only limited studies on AP specifcation of mesodermal and endodermal tissues (Deimling and Drysdale, 2009,
2011; McLin et al., 2007; Rankin et al., 2018). AP patterning not only involves cell fates but also morphogenesis,
with posterior tissues undergoing elongation. How caudalizing signals modulate expression or activity of regulators
of cell behaviors is largely unclear (Janesick et al., 2014).
These issues await further examination. With microsurgery,
molecular biology, and genomic tools at hand, we expect to
obtain a more detailed picture and deeper understanding of
AP embryonic patterning in the future.
ACKNOWLEDGMENTS
This work is supported by NIH grants R01GM127371 and
R01HD102015. I apologize to the investigators whose works
are not cited here due to the space limitation.
REFERENCES
Amaya, E., T.J. Musci, and M.W. Kirschner. 1991. Expression of a
dominant negative mutant of the FGF receptor disrupts mesoderm formation in Xenopus embryos. Cell. 66:257–270.
Bayramov, A.V., F.M. Eroshkin, N.Y. Martynova, G.V. Ermakova,
E.A. Solovieva, and A.G. Zaraisky. 2011. Novel functions of
Noggin proteins: Inhibition of Activin/Nodal and Wnt signaling. Development. 138:5345–5356.
Belyaeva, O.V., S.A. Lee, M.K. Adams, C. Chang, and N.Y.
Kedishvili. 2012. Short chain dehydrogenase/reductase rdhe2
is a novel retinol dehydrogenase essential for frog embryonic
development. J Biol Chem. 287:9061–9071.
Blitz, I.L., and K.W. Cho. 1995. Anterior neurectoderm is progressively induced during gastrulation: The role of the Xenopus
homeobox gene orthodenticle. Development. 121:993–1004.
Blumberg, B., J. Bolado, Jr., T.A. Moreno, C. Kintner, R.M. Evans,
and N. Papalopulu. 1997. An essential role for retinoid signaling in anteroposterior neural patterning. Development.
124:373–379.
Bouwmeester, T., S. Kim, Y. Sasai, B. Lu, and E.M. De Robertis.
1996. Cerberus is a head-inducing secreted factor expressed
in the anterior endoderm of Spemann’s organizer. Nature.
382:595–601.
Bradley, L.C., A. Snape, S. Bhatt, and D.G. Wilkinson. 1993. The
structure and expression of the Xenopus Krox-20 gene:
Conserved and divergent patterns of expression in rhombomeres and neural crest. Mech Dev. 40:73–84.
Brivanlou, A.H., and R.M. Harland. 1989. Expression of an
engrailed-related protein is induced in the anterior neural ectoderm of early Xenopus embryos. Development.
106:611–617.
Chang, L.S., M. Kim, A. Glinka, C. Reinhard, and C. Niehrs. 2020.
The tumor suppressor PTPRK promotes ZNRF3 internalization and is required for Wnt inhibition in the Spemann organizer. Elife. 9.
Chen, M., N. Amado, J. Tan, A. Reis, M. Ge, J.G. Abreu, and X. He.
2020. TMEM79/MATTRIN defnes a pathway for Frizzled
regulation and is required for Xenopus embryogenesis. Elife. 9.
Chen, Y., L. Huang, and M. Solursh. 1994. A concentration gradient of retinoids in the early Xenopus laevis embryo. Dev Biol.
161:70–76.
Chen, Y., N. Pollet, C. Niehrs, and T. Pieler. 2001. Increased
XRALDH2 activity has a posteriorizing effect on the central
nervous system of Xenopus embryos. Mech Dev . 101:91–103.
Christen, B., and J.M. Slack. 1997. FGF-8 is associated with
anteroposterior patterning and limb regeneration in Xenopus.
Dev Biol. 192:455–466.
Christian, J.L., J.A. McMahon, A.P. McMahon, and R.T. Moon.
1991. Xwnt-8, a Xenopus Wnt-1/int-1-related gene responsive to mesoderm-inducing growth factors, may play a role
in ventral mesodermal patterning during embryogenesis.
Development. 111:1045–1055.
Christian, J.L., and R.T. Moon. 1993. Interactions between Xwnt-8
and Spemann organizer signaling pathways generate dorsoventral pattern in the embryonic mesoderm of Xenopus.
Genes Dev. 7:13–28.
Conlon, R.A. 1995. Retinoic acid and pattern formation in vertebrates. Trends Genet. 11:314–319.
Cox, W.G., and A. Hemmati-Brivanlou. 1995. Caudalization of
neural fate by tissue recombination and bFGF. Development.
121:4349–4358.
Curran, K.L., and R.M. Grainger. 2000. Expression of activated
MAP kinase in Xenopus laevis embryos: Evaluating the roles
of FGF and other signaling pathways in early induction and
patterning. Dev Biol. 228:41–56.
Darken, R.S., and P.A. Wilson. 2001. Axis induction by Wnt signaling: Target promoter responsiveness regulates competence.
Dev Biol. 234:42–54.
Davidson, G., B. Mao, I. del Barco Barrantes, and C. Niehrs. 2002.
Kremen proteins interact with Dickkopf1 to regulate anteroposterior CNS patterning. Development. 129:5587–5596.
Deimling, S.J., and T.A. Drysdale. 2009. Retinoic acid regulates
anterior-posterior patterning within the lateral plate mesoderm of Xenopus. Mech Dev. 126:913–923.
Deimling, S.J., and T.A. Drysdale. 2011. FGF is required to regulate anterior-posterior patterning in the Xenopus lateral plate
mesoderm. Mech Dev. 128:327–341.
Dekker, E.J., M. Pannese, E. Houtzager, A. Timmermans, E.
Boncinelli, and A. Durston. 1992. Xenopus Hox-2 genes
are expressed sequentially after the onset of gastrulation and are differentially inducible by retinoic acid. Dev
Suppl:195–202.
Dekker, E.J., M.J. Vaessen, C. van den Berg, A. Timmermans, S.
Godsave, T. Holling, P. Nieuwkoop, A. Geurts van Kessel,
and A. Durston. 1994. Overexpression of a cellular retinoic acid binding protein (xCRABP) causes anteroposterior defects in developing Xenopus embryos. Development.
120:973–985.
Dibner, C., S. Elias, and D. Frank. 2001. XMeis3 protein activity
is required for proper hindbrain patterning in Xenopus laevis
embryos. Development. 128:3415–3426.
Dibner, C., S. Elias, R. Ofr, J. Souopgui, P.J. Kolm, H. Sive, T.
Pieler, and D. Frank. 2004. The Meis3 protein and retinoid
signaling interact to pattern the Xenopus hindbrain. Dev Biol.
271:75–86.
Ding, Y., G. Colozza, E.A. Sosa, Y. Moriyama, S. Rundle, L.
Salwinski, and E.M. De Robertis. 2018. Bighead is a Wnt
antagonist secreted by the Xenopus Spemann organizer
that promotes Lrp6 endocytosis. Proc Natl Acad Sci U S A.
115:E9135–E9144.
Domingos, P.M., N. Itasaki, C.M. Jones, S. Mercurio, M.G. Sargent,
J.C. Smith, and R. Krumlauf. 2001. The Wnt/beta-catenin
pathway posteriorizes neural tissue in Xenopus by an indirect mechanism requiring FGF signalling. Dev Biol. 239:
148–160.