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Fgf16 is required for specification of GABAergic neurons and oligodendrocytes in the zebrafish forebrain.

Miyake A, Chitose T, Kamei E, Murakami A, Nakayama Y, Konishi M, Itoh N - PLoS ONE (2014)

Bottom Line: The knockdown of fgf16 decreased cell proliferation in the forebrain and midbrain. fgf16 was also essential for development of the ventral telencephalon and diencephalon, whereas fgf16 was not required for dorsoventral patterning in the midbrain. fgf16 was additionally required for the specification and differentiation of γ-aminobutyric acid (GABA)ergic interneurons and oligodendrocytes, but not for those of glutamatergic neurons in the forebrain.The fgf16 morphant phenotype was similar to that of the fgf19 morphant and embryos blocked Hh signaling.The results of the present study indicate that Fgf16 signaling, which is regulated by the downstream pathways of Hh-Fgf19 in the forebrain, is involved in forebrain development.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetic Biochemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Sakyo, Kyoto, Japan.

ABSTRACT
Fibroblast growth factor (Fgf) signaling plays crucial roles in various developmental processes including those in the brain. We examined the role of Fgf16 in the formation of the zebrafish brain. The knockdown of fgf16 decreased cell proliferation in the forebrain and midbrain. fgf16 was also essential for development of the ventral telencephalon and diencephalon, whereas fgf16 was not required for dorsoventral patterning in the midbrain. fgf16 was additionally required for the specification and differentiation of γ-aminobutyric acid (GABA)ergic interneurons and oligodendrocytes, but not for those of glutamatergic neurons in the forebrain. Cross talk between Fgf and Hedgehog (Hh) signaling was critical for the specification of GABAergic interneurons and oligodendrocytes. The expression of fgf16 in the forebrain was down-regulated by the inhibition of Hh and Fgf19 signaling, but not by that of Fgf3/Fgf8 signaling. The fgf16 morphant phenotype was similar to that of the fgf19 morphant and embryos blocked Hh signaling. The results of the present study indicate that Fgf16 signaling, which is regulated by the downstream pathways of Hh-Fgf19 in the forebrain, is involved in forebrain development.

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Effects of fgf16 on the differentiation of GABAergic interneurons and oligodendrocytes.(A, B) Dorsal views of wild-type embryos (A) and fgf16 morphants (B), labeled to show GABA immunoreactivity at 3 dpf. (C, D) The expression of plp in wild-type embryos (C) and fgf16 morphants (D) at 4.5 dpf. Lateral views with anterior to the left and dorsal to the top.
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pone-0110836-g007: Effects of fgf16 on the differentiation of GABAergic interneurons and oligodendrocytes.(A, B) Dorsal views of wild-type embryos (A) and fgf16 morphants (B), labeled to show GABA immunoreactivity at 3 dpf. (C, D) The expression of plp in wild-type embryos (C) and fgf16 morphants (D) at 4.5 dpf. Lateral views with anterior to the left and dorsal to the top.

Mentions: GABAergic interneurons were previously shown to be generated in the subpallial telencephalon and ventral thalamus of the forebrain [68]–[71]. gad1 encoding glutamic acid decarboxylase was found to be expressed specifically in GABAergic interneurons [42]. To examine whether the knockdown of fgf16 had any effects on GABAergic interneuron differentiation in the forebrain, gad1 expression was analyzed in fgf16 morphants at 28 hpf. gad1 was expressed in the subpallial telencephalon and nucleus of the tract of the postoptic commissure (nTPOC) in the forebrain [42]. In fgf16 morphants, the expression of gad1 was severely reduced in both the ventral telencephalon and the nTPOC (n = 27/28) (Fig. 6E, F). We also investigated whether GABAergic neurons fully differentiated in fgf16 morphants. GABA-immunoreactive cells were not detected in the forebrains of fgf16 morphants at 3 dpf (n = 20/20) (Fig. 7A, B). Oligodendrocytes in the telencephalon also originated from the subpallial domain [70]. To investigate the involvement of fgf16 in oligodendrocyte specification, we examined the expression of olig2, a marker of the oligodendrocyte precursor, in fgf16 morphants at 28 hpf. In addition to the subpallial telencephalon, olig2 was also shown to be expressed in the ventral thalamus and dorsal thalamus [44]. In fgf16 morphants, the expression of olig2 was significantly reduced in the subpallial telencephalon, ventral thalamus, and dorsal thalamus (n = 14/20) (Fig. 6G, H). Furthermore, we determined whether fgf16 was involved in the formation of myelinating oligodendrocytes. PLP (proteolipid protein)/DM20 is a marker of oligodendrocyte differentiation and is expressed in newly formed oligodendrocyte progenitor cells, well before myelination [72]–[74]. The expression of plp was not detected in the forebrains of fgf16 morphants at 4.5 dpf (n = 12/12) (Fig. 7C, D). In addition, the expression of plp in the hindbrain disappeared in fgf16 morphants at 4.5 dpf (n = 10/12) (Fig. 7C, D). The immunoreactivity of CC1/APC, which is normally detected in mature oligodendrocyte cell bodies, was also lost in the hindbrains of fgf16 morphants at 4.5 dpf (n = 11/11) (Fig. S2A, B). These results demonstrated that the specification and differentiation of GABAergic interneurons and oligodendrocytes in the forebrain was suppressed in fgf16 morphants. We investigated whether the knockdown of fgf16 had any effects on the differentiation of glutamatergic neurons generated in the pallial telencephalon [75]. The expression of slc17a6a/vesicular glutamate transporter (vglut) 2.2, the postmitotic marker of glutamatergic neurons, was analyzed in fgf16 morphants at 28 hpf. In fgf16 morphants, the expression of slc17a6a was unaffected in both the pallial telencephalon and diencephalon (n = 14/14) (Fig. 6I, J). This result demonstrated that glutamatergic neurons in both the pallial telencephalon and diencephalon were specified in fgf16 morphants. Thus, fgf16 was required for the specification and differentiation of GABAergic neurons and oligodendrocytes, but not for that of glutamatergic neuron in the forebrain.


Fgf16 is required for specification of GABAergic neurons and oligodendrocytes in the zebrafish forebrain.

Miyake A, Chitose T, Kamei E, Murakami A, Nakayama Y, Konishi M, Itoh N - PLoS ONE (2014)

Effects of fgf16 on the differentiation of GABAergic interneurons and oligodendrocytes.(A, B) Dorsal views of wild-type embryos (A) and fgf16 morphants (B), labeled to show GABA immunoreactivity at 3 dpf. (C, D) The expression of plp in wild-type embryos (C) and fgf16 morphants (D) at 4.5 dpf. Lateral views with anterior to the left and dorsal to the top.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4214708&req=5

pone-0110836-g007: Effects of fgf16 on the differentiation of GABAergic interneurons and oligodendrocytes.(A, B) Dorsal views of wild-type embryos (A) and fgf16 morphants (B), labeled to show GABA immunoreactivity at 3 dpf. (C, D) The expression of plp in wild-type embryos (C) and fgf16 morphants (D) at 4.5 dpf. Lateral views with anterior to the left and dorsal to the top.
Mentions: GABAergic interneurons were previously shown to be generated in the subpallial telencephalon and ventral thalamus of the forebrain [68]–[71]. gad1 encoding glutamic acid decarboxylase was found to be expressed specifically in GABAergic interneurons [42]. To examine whether the knockdown of fgf16 had any effects on GABAergic interneuron differentiation in the forebrain, gad1 expression was analyzed in fgf16 morphants at 28 hpf. gad1 was expressed in the subpallial telencephalon and nucleus of the tract of the postoptic commissure (nTPOC) in the forebrain [42]. In fgf16 morphants, the expression of gad1 was severely reduced in both the ventral telencephalon and the nTPOC (n = 27/28) (Fig. 6E, F). We also investigated whether GABAergic neurons fully differentiated in fgf16 morphants. GABA-immunoreactive cells were not detected in the forebrains of fgf16 morphants at 3 dpf (n = 20/20) (Fig. 7A, B). Oligodendrocytes in the telencephalon also originated from the subpallial domain [70]. To investigate the involvement of fgf16 in oligodendrocyte specification, we examined the expression of olig2, a marker of the oligodendrocyte precursor, in fgf16 morphants at 28 hpf. In addition to the subpallial telencephalon, olig2 was also shown to be expressed in the ventral thalamus and dorsal thalamus [44]. In fgf16 morphants, the expression of olig2 was significantly reduced in the subpallial telencephalon, ventral thalamus, and dorsal thalamus (n = 14/20) (Fig. 6G, H). Furthermore, we determined whether fgf16 was involved in the formation of myelinating oligodendrocytes. PLP (proteolipid protein)/DM20 is a marker of oligodendrocyte differentiation and is expressed in newly formed oligodendrocyte progenitor cells, well before myelination [72]–[74]. The expression of plp was not detected in the forebrains of fgf16 morphants at 4.5 dpf (n = 12/12) (Fig. 7C, D). In addition, the expression of plp in the hindbrain disappeared in fgf16 morphants at 4.5 dpf (n = 10/12) (Fig. 7C, D). The immunoreactivity of CC1/APC, which is normally detected in mature oligodendrocyte cell bodies, was also lost in the hindbrains of fgf16 morphants at 4.5 dpf (n = 11/11) (Fig. S2A, B). These results demonstrated that the specification and differentiation of GABAergic interneurons and oligodendrocytes in the forebrain was suppressed in fgf16 morphants. We investigated whether the knockdown of fgf16 had any effects on the differentiation of glutamatergic neurons generated in the pallial telencephalon [75]. The expression of slc17a6a/vesicular glutamate transporter (vglut) 2.2, the postmitotic marker of glutamatergic neurons, was analyzed in fgf16 morphants at 28 hpf. In fgf16 morphants, the expression of slc17a6a was unaffected in both the pallial telencephalon and diencephalon (n = 14/14) (Fig. 6I, J). This result demonstrated that glutamatergic neurons in both the pallial telencephalon and diencephalon were specified in fgf16 morphants. Thus, fgf16 was required for the specification and differentiation of GABAergic neurons and oligodendrocytes, but not for that of glutamatergic neuron in the forebrain.

Bottom Line: The knockdown of fgf16 decreased cell proliferation in the forebrain and midbrain. fgf16 was also essential for development of the ventral telencephalon and diencephalon, whereas fgf16 was not required for dorsoventral patterning in the midbrain. fgf16 was additionally required for the specification and differentiation of γ-aminobutyric acid (GABA)ergic interneurons and oligodendrocytes, but not for those of glutamatergic neurons in the forebrain.The fgf16 morphant phenotype was similar to that of the fgf19 morphant and embryos blocked Hh signaling.The results of the present study indicate that Fgf16 signaling, which is regulated by the downstream pathways of Hh-Fgf19 in the forebrain, is involved in forebrain development.

View Article: PubMed Central - PubMed

Affiliation: Department of Genetic Biochemistry, Kyoto University Graduate School of Pharmaceutical Sciences, Sakyo, Kyoto, Japan.

ABSTRACT
Fibroblast growth factor (Fgf) signaling plays crucial roles in various developmental processes including those in the brain. We examined the role of Fgf16 in the formation of the zebrafish brain. The knockdown of fgf16 decreased cell proliferation in the forebrain and midbrain. fgf16 was also essential for development of the ventral telencephalon and diencephalon, whereas fgf16 was not required for dorsoventral patterning in the midbrain. fgf16 was additionally required for the specification and differentiation of γ-aminobutyric acid (GABA)ergic interneurons and oligodendrocytes, but not for those of glutamatergic neurons in the forebrain. Cross talk between Fgf and Hedgehog (Hh) signaling was critical for the specification of GABAergic interneurons and oligodendrocytes. The expression of fgf16 in the forebrain was down-regulated by the inhibition of Hh and Fgf19 signaling, but not by that of Fgf3/Fgf8 signaling. The fgf16 morphant phenotype was similar to that of the fgf19 morphant and embryos blocked Hh signaling. The results of the present study indicate that Fgf16 signaling, which is regulated by the downstream pathways of Hh-Fgf19 in the forebrain, is involved in forebrain development.

Show MeSH
Related in: MedlinePlus