Limits...
FoxA4 favours notochord formation by inhibiting contiguous mesodermal fates and restricts anterior neural development in Xenopus embryos.

Murgan S, Castro Colabianchi AM, Monti RJ, Boyadjián López LE, Aguirre CE, Stivala EG, Carrasco AE, López SL - PLoS ONE (2014)

Bottom Line: In addition, we show that foxA4 is required for the correct regionalisation and maintenance of the central nervous system.FoxA4 participates in constraining the prospective rostral forebrain territory during neural specification and is necessary for the correct segregation of the most anterior ectodermal derivatives, such as the cement gland and the pituitary anlagen.Moreover, the early expression of foxA4 in the BCNE (which contains precursors of the whole forebrain and most of the midbrain and hindbrain) is directly required to restrict anterior neural development.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Embriología Molecular "Prof. Dr. Andrés E. Carrasco," Instituto de Biología Celular y Neurociencia, Facultad de Medicina, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina.

ABSTRACT
In vertebrates, the embryonic dorsal midline is a crucial signalling centre that patterns the surrounding tissues during development. Members of the FoxA subfamily of transcription factors are expressed in the structures that compose this centre. Foxa2 is essential for dorsal midline development in mammals, since knock-out mouse embryos lack a definitive node, notochord and floor plate. The related gene foxA4 is only present in amphibians. Expression begins in the blastula -chordin and -noggin expressing centre (BCNE) and is later restricted to the dorsal midline derivatives of the Spemann's organiser. It was suggested that the early functions of mammalian foxa2 are carried out by foxA4 in frogs, but functional experiments were needed to test this hypothesis. Here, we show that some important dorsal midline functions of mammalian foxa2 are exerted by foxA4 in Xenopus. We provide new evidence that the latter prevents the respecification of dorsal midline precursors towards contiguous fates, inhibiting prechordal and paraxial mesoderm development in favour of the notochord. In addition, we show that foxA4 is required for the correct regionalisation and maintenance of the central nervous system. FoxA4 participates in constraining the prospective rostral forebrain territory during neural specification and is necessary for the correct segregation of the most anterior ectodermal derivatives, such as the cement gland and the pituitary anlagen. Moreover, the early expression of foxA4 in the BCNE (which contains precursors of the whole forebrain and most of the midbrain and hindbrain) is directly required to restrict anterior neural development.

Show MeSH
Model for foxA4 function in Xenopus embryos.(A) Summary of foxA4 functions in A–P regionalisation and in DML development. For simplicity, they are depicted in a diagram of an embryo at neural plate stage, shown in dorsal view, when foxA4 is only expressed in the DML (pink). FoxA4 modulates A–P development by inhibiting anterior fates (red lines) in the axial mesoderm (prechordal mesoderm, PM) and in the neuroectoderm (NE) and ectoderm, while favouring posterior fates (green arrows) in the neural plate and the dorsal midline (notochord, NO; floor plate, FP). In the trunk, foxA4 prevents the respecification of dorsal midline precursors towards contiguous fates, by inhibiting (red lines) the paraxial mesodermal fate (PAM). Yellow, prechordal mesoderm. Grey, paraxial mesoderm. The dotted light blue line demarcates de neural plate. (B) Diagram of a blastula stage embryo in dorsal view, showing the expression of foxA4 in the BCNE centre (pink), which is composed by precursors of the Spemann's organiser and of the whole forebrain and most of the midbrain and hindbrain [37]. An, animal; Veg, vegetal. FoxA4 modulates the initial CNS regionalisation by operating on the BCNE, favouring posterior fates among BCNE derivatives (green arrow), while restricting anterior fates (red line), as revealed by the markers Xanf1 (rostral forebrain), otx2 (caudal forebrain/midbrain), en2 (midbrain/hindbrain boundary).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4208771&req=5

pone-0110559-g014: Model for foxA4 function in Xenopus embryos.(A) Summary of foxA4 functions in A–P regionalisation and in DML development. For simplicity, they are depicted in a diagram of an embryo at neural plate stage, shown in dorsal view, when foxA4 is only expressed in the DML (pink). FoxA4 modulates A–P development by inhibiting anterior fates (red lines) in the axial mesoderm (prechordal mesoderm, PM) and in the neuroectoderm (NE) and ectoderm, while favouring posterior fates (green arrows) in the neural plate and the dorsal midline (notochord, NO; floor plate, FP). In the trunk, foxA4 prevents the respecification of dorsal midline precursors towards contiguous fates, by inhibiting (red lines) the paraxial mesodermal fate (PAM). Yellow, prechordal mesoderm. Grey, paraxial mesoderm. The dotted light blue line demarcates de neural plate. (B) Diagram of a blastula stage embryo in dorsal view, showing the expression of foxA4 in the BCNE centre (pink), which is composed by precursors of the Spemann's organiser and of the whole forebrain and most of the midbrain and hindbrain [37]. An, animal; Veg, vegetal. FoxA4 modulates the initial CNS regionalisation by operating on the BCNE, favouring posterior fates among BCNE derivatives (green arrow), while restricting anterior fates (red line), as revealed by the markers Xanf1 (rostral forebrain), otx2 (caudal forebrain/midbrain), en2 (midbrain/hindbrain boundary).

Mentions: In the present work, we present evidence that foxA4 plays an important role in the formation of the DML and in A–P patterning in Xenopus laevis. FoxA4 is necessary for the specification and correct allocation of the components of the trunk DML and for the correct formation of the rostral forebrain and anterior ectodermal derivatives (Fig. 10). In overall, foxA4 modulates A–P development, restricting anterior axial mesodermal and neural/ectodermal fates (Fig. 14).


FoxA4 favours notochord formation by inhibiting contiguous mesodermal fates and restricts anterior neural development in Xenopus embryos.

Murgan S, Castro Colabianchi AM, Monti RJ, Boyadjián López LE, Aguirre CE, Stivala EG, Carrasco AE, López SL - PLoS ONE (2014)

Model for foxA4 function in Xenopus embryos.(A) Summary of foxA4 functions in A–P regionalisation and in DML development. For simplicity, they are depicted in a diagram of an embryo at neural plate stage, shown in dorsal view, when foxA4 is only expressed in the DML (pink). FoxA4 modulates A–P development by inhibiting anterior fates (red lines) in the axial mesoderm (prechordal mesoderm, PM) and in the neuroectoderm (NE) and ectoderm, while favouring posterior fates (green arrows) in the neural plate and the dorsal midline (notochord, NO; floor plate, FP). In the trunk, foxA4 prevents the respecification of dorsal midline precursors towards contiguous fates, by inhibiting (red lines) the paraxial mesodermal fate (PAM). Yellow, prechordal mesoderm. Grey, paraxial mesoderm. The dotted light blue line demarcates de neural plate. (B) Diagram of a blastula stage embryo in dorsal view, showing the expression of foxA4 in the BCNE centre (pink), which is composed by precursors of the Spemann's organiser and of the whole forebrain and most of the midbrain and hindbrain [37]. An, animal; Veg, vegetal. FoxA4 modulates the initial CNS regionalisation by operating on the BCNE, favouring posterior fates among BCNE derivatives (green arrow), while restricting anterior fates (red line), as revealed by the markers Xanf1 (rostral forebrain), otx2 (caudal forebrain/midbrain), en2 (midbrain/hindbrain boundary).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4208771&req=5

pone-0110559-g014: Model for foxA4 function in Xenopus embryos.(A) Summary of foxA4 functions in A–P regionalisation and in DML development. For simplicity, they are depicted in a diagram of an embryo at neural plate stage, shown in dorsal view, when foxA4 is only expressed in the DML (pink). FoxA4 modulates A–P development by inhibiting anterior fates (red lines) in the axial mesoderm (prechordal mesoderm, PM) and in the neuroectoderm (NE) and ectoderm, while favouring posterior fates (green arrows) in the neural plate and the dorsal midline (notochord, NO; floor plate, FP). In the trunk, foxA4 prevents the respecification of dorsal midline precursors towards contiguous fates, by inhibiting (red lines) the paraxial mesodermal fate (PAM). Yellow, prechordal mesoderm. Grey, paraxial mesoderm. The dotted light blue line demarcates de neural plate. (B) Diagram of a blastula stage embryo in dorsal view, showing the expression of foxA4 in the BCNE centre (pink), which is composed by precursors of the Spemann's organiser and of the whole forebrain and most of the midbrain and hindbrain [37]. An, animal; Veg, vegetal. FoxA4 modulates the initial CNS regionalisation by operating on the BCNE, favouring posterior fates among BCNE derivatives (green arrow), while restricting anterior fates (red line), as revealed by the markers Xanf1 (rostral forebrain), otx2 (caudal forebrain/midbrain), en2 (midbrain/hindbrain boundary).
Mentions: In the present work, we present evidence that foxA4 plays an important role in the formation of the DML and in A–P patterning in Xenopus laevis. FoxA4 is necessary for the specification and correct allocation of the components of the trunk DML and for the correct formation of the rostral forebrain and anterior ectodermal derivatives (Fig. 10). In overall, foxA4 modulates A–P development, restricting anterior axial mesodermal and neural/ectodermal fates (Fig. 14).

Bottom Line: In addition, we show that foxA4 is required for the correct regionalisation and maintenance of the central nervous system.FoxA4 participates in constraining the prospective rostral forebrain territory during neural specification and is necessary for the correct segregation of the most anterior ectodermal derivatives, such as the cement gland and the pituitary anlagen.Moreover, the early expression of foxA4 in the BCNE (which contains precursors of the whole forebrain and most of the midbrain and hindbrain) is directly required to restrict anterior neural development.

View Article: PubMed Central - PubMed

Affiliation: Laboratorio de Embriología Molecular "Prof. Dr. Andrés E. Carrasco," Instituto de Biología Celular y Neurociencia, Facultad de Medicina, Universidad de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina.

ABSTRACT
In vertebrates, the embryonic dorsal midline is a crucial signalling centre that patterns the surrounding tissues during development. Members of the FoxA subfamily of transcription factors are expressed in the structures that compose this centre. Foxa2 is essential for dorsal midline development in mammals, since knock-out mouse embryos lack a definitive node, notochord and floor plate. The related gene foxA4 is only present in amphibians. Expression begins in the blastula -chordin and -noggin expressing centre (BCNE) and is later restricted to the dorsal midline derivatives of the Spemann's organiser. It was suggested that the early functions of mammalian foxa2 are carried out by foxA4 in frogs, but functional experiments were needed to test this hypothesis. Here, we show that some important dorsal midline functions of mammalian foxa2 are exerted by foxA4 in Xenopus. We provide new evidence that the latter prevents the respecification of dorsal midline precursors towards contiguous fates, inhibiting prechordal and paraxial mesoderm development in favour of the notochord. In addition, we show that foxA4 is required for the correct regionalisation and maintenance of the central nervous system. FoxA4 participates in constraining the prospective rostral forebrain territory during neural specification and is necessary for the correct segregation of the most anterior ectodermal derivatives, such as the cement gland and the pituitary anlagen. Moreover, the early expression of foxA4 in the BCNE (which contains precursors of the whole forebrain and most of the midbrain and hindbrain) is directly required to restrict anterior neural development.

Show MeSH