Bandín S et al. (2013), Regional expression of Pax7 in the brain of Xen...

XB-ART-48341

Front Neuroanat 2013 Dec 24;7:48. doi: 10.3389/fnana.2013.00048.

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Regional expression of Pax7 in the brain of Xenopus laevis during embryonic and larval development.

Bandín S , Morona R , Moreno N , González A .

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Pax7 is a member of the highly conserved Pax gene family that is expressed in restricted zones of the central nervous system (CNS) during development, being involved in early brain regionalization and the maintenance of the regional identity. Using sensitive immunohistochemical techniques we have analyzed the spatiotemporal pattern of Pax7 expression in the brain of the anuran amphibian Xenopus laevis, during development. Pax7 expression was first detected in early embryos in the basal plate of prosomere 3, roof and alar plates of prosomere 1 and mesencephalon, and the alar plate of rhombomere 1. As development proceeded, Pax7 cells were observed in the hypothalamus close to the catecholaminergic population of the mammillary region. In the diencephalon, Pax7 was intensely expressed in a portion of the basal plate of prosomere 3, in the roof plate and in scattered cells of the thalamus in prosomere 2, throughout the roof of prosomere 1, and in the commissural and juxtacommissural domains of the pretectum. In the mesencephalon, Pax7 cells were localized in the optic tectum and, to a lesser extent, in the torus semicircularis. The rostral portion of the alar part of rhombomere 1, including the ventricular layer of the cerebellum, expressed Pax7 and, gradually, some of these dorsal cells were observed to populate ventrally the interpeduncular nucleus and the isthmus (rhombomere 0). Additionally, Pax7 positive cells were found in the ventricular zone of the ventral part of the alar plate along the rhombencephalon and the spinal cord. The findings show that the strongly conserved features of Pax7 expression through development shared by amniote vertebrates are also present in the anamniote amphibians as a common characteristic of the brain organization of tetrapods.

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Species referenced: Xenopus laevis
Genes referenced: nkx2-1 nos1 nos3 npy otp pax7

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	Figure 1. Schematic drawings of transverse sections through the brain of Xenopus laevis at early embryonic stage 37/38 (A–H) and late embryonic stage 42 (I–P) showing the distribution of Pax7 immunoreactive cells. The levels of the sections are indicated in the schemes of lateral views of the brain where the shaded areas represent the regions expressing Pax7. Scale bars = 100 μm. See list for abbreviations.
	Figure 2. Schematic drawings of transverse sections through the brain of Xenopus laevis at premetamorphic stage 50 (A–E) and prometamorphic stage 56 (F–J) showing the distribution of Pax7 immunoreactive cells. The levels of the sections are indicated in the schemes of lateral views of the brain where the shaded areas represent the regions expressing Pax7. Scale bars = 200 μm. See list for abbreviations.
	Figure 3. Schematic drawings of transverse sections through the brain of Xenopus laevis at the metamorphic climax stage 65 (A–I) showing the distribution of Pax7 immunoreactive cells. The levels of the sections are indicated in the scheme of the lateral view of the brain where the shaded areas represent the regions expressing Pax7. Scale bars = 400 μm. See list for abbreviations.
	Figure 4. Photomicrographs of single-stained transverse (A–D, F–P) and sagittal (E) sections through the brain of Xenopus laevis showing the localization of Pax7 cells. Different stages (indicated in the upper right corner of each photomicrograph) corresponding to early embryos are illustrated. All images are oriented following the same standard: dorsal is upwards in transverse and sagittal sections, and rostral is to the left in sagittal sections. The neuromeric boundaries and main brain subdivisions are indicated to assist in the precise localization of the labeled cells. Scale bars = 50 μm. See list for abbreviations.
	Figure 5. Photomicrographs of single-stained sagittal (A,B) and transverse (C–J) sections through the brain of Xenopus laevis showing the localization of Pax7 cells. Different stages (indicated in the upper right corner of each photomicrograph) corresponding to late embryos are illustrated. All images are oriented following the same standard: dorsal is upwards in transverse and sagittal sections, and rostral is to the left in sagittal sections. The neuromeric boundaries and main brain subdivisions are indicated to assist in the precise localization of the labeled cells. Scale bars = 50 μm. See list for abbreviations.
	Figure 6. Photomicrographs of single-stained sagittal (A,E-G) and transverse (B–D, H-O) sections through the brain of Xenopus laevis showing the localization of Pax7 cells. Different stages (indicated in the upper right corner of each photomicrograph) corresponding to premetamorphic (A–H) and prometamorphic (I–O) tadpoles are illustrated. All images are oriented following the same standard: dorsal is upwards in transverse and sagittal sections, and rostral is to the left in sagittal sections. The neuromeric boundaries and main brain subdivisions are indicated to assist in the precise localization of the labeled cells. Scale bars = 100 μm. See list for abbreviations.
	Figure 7. Photomicrographs of single-stained transverse (A–M) sections through the brain of Xenopus laevis showing the localization of Pax7 cells. Different stages (indicated in the upper right corner of each photomicrograph) corresponding to tadpoles at the climax of the metamorphosis are illustrated. In all transverse images dorsal is upwards. The neuromeric boundaries and main brain subdivisions are indicated to assist in the precise localization of the labeled cells. Scale bars =100 μm. See list for abbreviations.
	Figure 8. Photomicrographs of double-labeled sagittal (A–C) or transverse (D–Q) sections through the brain of Xenopus laevis showing the localization of Pax7 cells (gree fluorescence) in relationship to GABA (red fluorescence) at different embryonic stages (indicated in the upper right corner of each photomicrograph). All images are oriented following the same standard: dorsal is upwards in transverse and sagittal sections, and rostral is to the left in sagittal sections. The neuromeric boundaries and main brain subdivisions are indicated to assist in the precise localization of the labeled cells. Asterisk in (Q) indicates the weak expression found in the ventricular zone of the developing cerebellum. Scale bars = 50 μm. See list for abbreviations.
	Figure 9. Photomicrographs of double-labeled transverse (A–D,H) and sagittal (E–G) sections through the brain of Xenopus laevis showing the localization of Pax7 cells (green fluorescence) in relation to the markers Nkx2.1, Otp, and TH (red fluorescence; indicated in color code in the upper right corner of each photomicrograph). The developmental stages are indicated in the upper left corner of each photomicrograph. All images are oriented following the same standard: dorsal is upwards in transverse and sagittal sections, and rostral is to the left in sagittal sections. The neuromeric boundaries and main brain subdivisions are indicated to assist in the precise localization of the labeled cells. Scale bars = 50 μm. See list for abbreviations.
	Figure 10. Photomicrographs of double-labeled sagittal (A–D) and transverse (E–I) sections through the brain of Xenopus laevis showing the localization of Pax7 cells (green fluorescence) in relation to the markers NPY, TH, CR, Nkx2.1, and NOS (red fluorescence; indicated in color code in the upper right corner of each photomicrograph). The developmental stages are indicated in the upper left corner of each photomicrograph. All images are oriented following the same standard: dorsal is upwards in transverse and sagittal sections, and rostral is to the left in sagittal sections. The neuromeric boundaries and main brain subdivisions are indicated to assist in the precise localization of the labeled cells. Scale bars = 100 μm. See list for abbreviations.

References [+] :

Agoston, Genetic and physical interaction of Meis2, Pax3 and Pax7 during dorsal midbrain development. 2012, Pubmed