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Differential requirements for Gli2 and Gli3 in the regional specification of the mouse hypothalamus.

Haddad-Tóvolli R, Paul FA, Zhang Y, Zhou X, Theil T, Puelles L, Blaess S, Alvarez-Bolado G - Front Neuroanat (2015)

Bottom Line: The hypothalamus, a forebrain region regulating vital functions like homeostasis and hormone secretion, shows dynamic and intricate Shh expression as well as complex regional differentiation.Finally, we have mapped our results on a recent model which considers the hypothalamus as a transverse region with alar and basal portions.Our data confirm the model and are explained by it.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Cell Biology and Neuroanatomy, University of Heidelberg Heidelberg, Germany.

ABSTRACT
Secreted protein Sonic hedgehog (Shh) ventralizes the neural tube by modulating the crucial balance between activating and repressing functions (GliA, GliR) of transcription factors Gli2 and Gli3. This balance-the Shh-Gli code-is species- and context-dependent and has been elucidated for the mouse spinal cord. The hypothalamus, a forebrain region regulating vital functions like homeostasis and hormone secretion, shows dynamic and intricate Shh expression as well as complex regional differentiation. Here we asked if particular combinations of Gli2 and Gli3 and of GliA and GliR functions contribute to the variety of hypothalamic regions, i.e., we wanted to approach the question of a possible hypothalamic version of the Shh-Gli code. Based on mouse mutant analysis, we show that: (1) hypothalamic regional heterogeneity is based in part on differentially stringent requirements for Gli2 or Gli3; (2) another source of diversity are differential requirements for Shh of neural vs. non-neural origin; (3) the medial progenitor domain known to depend on Gli2 for its development generates several essential hypothalamic nuclei plus the pituitary and median eminence; (4) the suppression of Gli3R by neural and non-neural Shh is essential for hypothalamic specification. Finally, we have mapped our results on a recent model which considers the hypothalamus as a transverse region with alar and basal portions. Our data confirm the model and are explained by it.

No MeSH data available.


Related in: MedlinePlus

Abnormal medial domain in the Gli2zfd/zfd mutant. (A–H)In situ detection of gene expression on forebrain sections of E10.5 embryos, genotypes, and markers as indicated. In (E–H), pituitary (E,G) and median eminence (F,H) levels are shown. Scale bar in (G,H), 200 μm. (I,J)In situ detection of Six3 expression on sagittal sections of E12.5 WT (A) and Gli2zfd/zfd(B) mouse embryos. Arrows show thickness of midline. Scale bars, 500 μm.
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Figure 5: Abnormal medial domain in the Gli2zfd/zfd mutant. (A–H)In situ detection of gene expression on forebrain sections of E10.5 embryos, genotypes, and markers as indicated. In (E–H), pituitary (E,G) and median eminence (F,H) levels are shown. Scale bar in (G,H), 200 μm. (I,J)In situ detection of Six3 expression on sagittal sections of E12.5 WT (A) and Gli2zfd/zfd(B) mouse embryos. Arrows show thickness of midline. Scale bars, 500 μm.

Mentions: In order to analyze the Gli2zfd/zfd phenotype in the basal hypothalamus (tuberal and mamillary regions), we examined expression of Shh and Gli genes as well as regional markers at E8.5 and E10.5. At E8.5, expression of Gli1, Gli3 and the regional marker Nkx2-1 was not changed in the Gli2zfd/zfd mutant (Figures 2F,H–J), except of course for the disappearance of the Gli2 domain (Figure 2G). Expression of Shh, however, seemed expanded (Figure 2I). At E10.5, expression of Gli1 and Gli3 was strongly downregulated in the midline around the infundibular area (red arrowheads in Figures 3D,E,P,Q) in the Gli2zfd/zfd mutants. At mamillary levels, however, the two lateral expression domains seem to have fused in a thickened midline [Figures 3F,R; this is also true of the expression of the truncated (inactive) form of Gli2 in the mutant (Figure 3L)]. At this age, Shh expression is normally downregulated in the medial domain of the tuberal region (Manning et al., 2006; arrow in Figure 5A). In the Gli2zfd/zfd mutant this Shh-negative domain was absent (arrow in Figure 5B). Nkx2-1, a transcription factor gene defining regional specification of the basal hypothalamus (Kimura et al., 1996; Puelles et al., 2004, 2012), was expressed in an appropriate but smaller domain, with stronger expression shifted into the medial domain (Figures 5C,D). Six3 is a transcription factor required for initiation of hypothalamic specification (Kobayashi et al., 2002). It is normally expressed strongly along the entire medial domain and flanking hypothalamus, except the mamillary part. Six3 expression was severely reduced at both the infundibular (Figures 5E,F) and median eminence levels (Figures 5G,H). Together with the alterations in gene expression, we observed again a thickening of the medial domain of the tuberal region (arrowheads in Figures 5F,H). Analysis of Six3 expression on sagittal sections at E12.5 (Figures 5I,J) confirmed Six3 downregulation and a thickened medial domain of the Gli2zfd/zfd mutant (arrowheads in Figures 5I,J). Since expression of Six3 (Figures 5E,F) indicated alterations of the infundibulum, which is essential for pituitary development, we then examined the expression of appropriate gene markers for this region (Figure 6). Infundibular expression of Tbx2 (Manning et al., 2006) and Fgf8 (Ericson et al., 1998; Figures 6A–D), as well as expression of pituitary markers Lhx3 (Figures 6E,F), and Pitx2 (Figures 6 G,H) was completely lost in the Gli2zfd/zfd presumptive hypothalamus at E10.5 (see also Park et al., 2000). These results indicated that Gli2 is required for appropriate development of the medial domain in the basal hypothalamus and for the development of the neurohypophysis.


Differential requirements for Gli2 and Gli3 in the regional specification of the mouse hypothalamus.

Haddad-Tóvolli R, Paul FA, Zhang Y, Zhou X, Theil T, Puelles L, Blaess S, Alvarez-Bolado G - Front Neuroanat (2015)

Abnormal medial domain in the Gli2zfd/zfd mutant. (A–H)In situ detection of gene expression on forebrain sections of E10.5 embryos, genotypes, and markers as indicated. In (E–H), pituitary (E,G) and median eminence (F,H) levels are shown. Scale bar in (G,H), 200 μm. (I,J)In situ detection of Six3 expression on sagittal sections of E12.5 WT (A) and Gli2zfd/zfd(B) mouse embryos. Arrows show thickness of midline. Scale bars, 500 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4373379&req=5

Figure 5: Abnormal medial domain in the Gli2zfd/zfd mutant. (A–H)In situ detection of gene expression on forebrain sections of E10.5 embryos, genotypes, and markers as indicated. In (E–H), pituitary (E,G) and median eminence (F,H) levels are shown. Scale bar in (G,H), 200 μm. (I,J)In situ detection of Six3 expression on sagittal sections of E12.5 WT (A) and Gli2zfd/zfd(B) mouse embryos. Arrows show thickness of midline. Scale bars, 500 μm.
Mentions: In order to analyze the Gli2zfd/zfd phenotype in the basal hypothalamus (tuberal and mamillary regions), we examined expression of Shh and Gli genes as well as regional markers at E8.5 and E10.5. At E8.5, expression of Gli1, Gli3 and the regional marker Nkx2-1 was not changed in the Gli2zfd/zfd mutant (Figures 2F,H–J), except of course for the disappearance of the Gli2 domain (Figure 2G). Expression of Shh, however, seemed expanded (Figure 2I). At E10.5, expression of Gli1 and Gli3 was strongly downregulated in the midline around the infundibular area (red arrowheads in Figures 3D,E,P,Q) in the Gli2zfd/zfd mutants. At mamillary levels, however, the two lateral expression domains seem to have fused in a thickened midline [Figures 3F,R; this is also true of the expression of the truncated (inactive) form of Gli2 in the mutant (Figure 3L)]. At this age, Shh expression is normally downregulated in the medial domain of the tuberal region (Manning et al., 2006; arrow in Figure 5A). In the Gli2zfd/zfd mutant this Shh-negative domain was absent (arrow in Figure 5B). Nkx2-1, a transcription factor gene defining regional specification of the basal hypothalamus (Kimura et al., 1996; Puelles et al., 2004, 2012), was expressed in an appropriate but smaller domain, with stronger expression shifted into the medial domain (Figures 5C,D). Six3 is a transcription factor required for initiation of hypothalamic specification (Kobayashi et al., 2002). It is normally expressed strongly along the entire medial domain and flanking hypothalamus, except the mamillary part. Six3 expression was severely reduced at both the infundibular (Figures 5E,F) and median eminence levels (Figures 5G,H). Together with the alterations in gene expression, we observed again a thickening of the medial domain of the tuberal region (arrowheads in Figures 5F,H). Analysis of Six3 expression on sagittal sections at E12.5 (Figures 5I,J) confirmed Six3 downregulation and a thickened medial domain of the Gli2zfd/zfd mutant (arrowheads in Figures 5I,J). Since expression of Six3 (Figures 5E,F) indicated alterations of the infundibulum, which is essential for pituitary development, we then examined the expression of appropriate gene markers for this region (Figure 6). Infundibular expression of Tbx2 (Manning et al., 2006) and Fgf8 (Ericson et al., 1998; Figures 6A–D), as well as expression of pituitary markers Lhx3 (Figures 6E,F), and Pitx2 (Figures 6 G,H) was completely lost in the Gli2zfd/zfd presumptive hypothalamus at E10.5 (see also Park et al., 2000). These results indicated that Gli2 is required for appropriate development of the medial domain in the basal hypothalamus and for the development of the neurohypophysis.

Bottom Line: The hypothalamus, a forebrain region regulating vital functions like homeostasis and hormone secretion, shows dynamic and intricate Shh expression as well as complex regional differentiation.Finally, we have mapped our results on a recent model which considers the hypothalamus as a transverse region with alar and basal portions.Our data confirm the model and are explained by it.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Cell Biology and Neuroanatomy, University of Heidelberg Heidelberg, Germany.

ABSTRACT
Secreted protein Sonic hedgehog (Shh) ventralizes the neural tube by modulating the crucial balance between activating and repressing functions (GliA, GliR) of transcription factors Gli2 and Gli3. This balance-the Shh-Gli code-is species- and context-dependent and has been elucidated for the mouse spinal cord. The hypothalamus, a forebrain region regulating vital functions like homeostasis and hormone secretion, shows dynamic and intricate Shh expression as well as complex regional differentiation. Here we asked if particular combinations of Gli2 and Gli3 and of GliA and GliR functions contribute to the variety of hypothalamic regions, i.e., we wanted to approach the question of a possible hypothalamic version of the Shh-Gli code. Based on mouse mutant analysis, we show that: (1) hypothalamic regional heterogeneity is based in part on differentially stringent requirements for Gli2 or Gli3; (2) another source of diversity are differential requirements for Shh of neural vs. non-neural origin; (3) the medial progenitor domain known to depend on Gli2 for its development generates several essential hypothalamic nuclei plus the pituitary and median eminence; (4) the suppression of Gli3R by neural and non-neural Shh is essential for hypothalamic specification. Finally, we have mapped our results on a recent model which considers the hypothalamus as a transverse region with alar and basal portions. Our data confirm the model and are explained by it.

No MeSH data available.


Related in: MedlinePlus