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Dcc regulates asymmetric outgrowth of forebrain neurons in zebrafish.

Gao J, Zhang C, Yang B, Sun L, Zhang C, Westerfield M, Peng G - PLoS ONE (2012)

Bottom Line: We found that ADt axons normally project ventrally.We found that individual ADt neurons projected axons dorsally or formed multiple processes after morpholino knock down of Dcc function.We further found that knock down of the Dcc ligand, Netrin1, also caused ADt neurons to project axons dorsally.

View Article: PubMed Central - PubMed

Affiliation: Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China.

ABSTRACT
The guidance receptor DCC (deleted in colorectal cancer) ortholog UNC-40 regulates neuronal asymmetry development in Caenorhabditis elegans, but it is not known whether DCC plays a role in the specification of neuronal polarity in vertebrates. To examine the roles of DCC in neuronal asymmetry regulation in vertebrates, we studied zebrafish anterior dorsal telencephalon (ADt) neuronal axons. We generated transgenic zebrafish animals expressing the photo-convertible fluorescent protein Kaede in ADt neurons and then photo-converted Kaede to label specifically the ADt neuron axons. We found that ADt axons normally project ventrally. Knock down of Dcc function by injecting antisense morpholino oligonucleotides caused the ADt neurons to project axons dorsally. To examine the axon projection pattern of individual ADt neurons, we labeled single ADt neurons using a forebrain-specific promoter to drive fluorescent protein expression. We found that individual ADt neurons projected axons dorsally or formed multiple processes after morpholino knock down of Dcc function. We further found that knock down of the Dcc ligand, Netrin1, also caused ADt neurons to project axons dorsally. Knockdown of Neogenin1, a guidance receptor closely related to Dcc, enhanced the formation of aberrant dorsal axons in embryos injected with Dcc morpholino. These experiments provide the first evidence that Dcc regulates polarized axon initiation and asymmetric outgrowth of forebrain neurons in vertebrates.

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Expression patterns of dcc and netrin.(A) dcc is expressed in the dorsal telencephalic region at 24 hpf and 36 hpf. (B) dcc and lhx5 are co-expressed in the dorsal telencephalon at 20 hpf. ADt neurons are migrating from their medial positions in the neural tube to lateral positions at 20 hpf. Scale bar: 100 µm for lateral view; 60 µm for frontal view.
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pone-0036516-g002: Expression patterns of dcc and netrin.(A) dcc is expressed in the dorsal telencephalic region at 24 hpf and 36 hpf. (B) dcc and lhx5 are co-expressed in the dorsal telencephalon at 20 hpf. ADt neurons are migrating from their medial positions in the neural tube to lateral positions at 20 hpf. Scale bar: 100 µm for lateral view; 60 µm for frontal view.

Mentions: The guidance receptor Dcc and its ligand Netrin1 are expressed in the central nervous system during zebrafish embryonic development [25]–[28]. During the pharyngula period (at 24 hpf and 36 hpf), dcc is expressed in dorsal telencephalic regions (Fig. 2A). Double labeling by fluorescent in situ hybridization demonstrated that dcc is co-expressed with lhx5 in the ADt neurons at 20 hpf, a stage when the lhx5:Kaede labeled ADt neurons are still migrating and lack axonal processes (Fig. 2B). During these periods of development, netrin1a and netrin1b, the duplicated genes orthologous to the mammalian Netrin1 gene, are expressed in the ventral midline region of the forebrain and ventral regions along the SOT ([27], [28], and data not shown). These expression patterns indicate that the guidance receptor Dcc is expressed in the right place at the right time to direct the asymmetric growth of the ADt neurons.


Dcc regulates asymmetric outgrowth of forebrain neurons in zebrafish.

Gao J, Zhang C, Yang B, Sun L, Zhang C, Westerfield M, Peng G - PLoS ONE (2012)

Expression patterns of dcc and netrin.(A) dcc is expressed in the dorsal telencephalic region at 24 hpf and 36 hpf. (B) dcc and lhx5 are co-expressed in the dorsal telencephalon at 20 hpf. ADt neurons are migrating from their medial positions in the neural tube to lateral positions at 20 hpf. Scale bar: 100 µm for lateral view; 60 µm for frontal view.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3351449&req=5

pone-0036516-g002: Expression patterns of dcc and netrin.(A) dcc is expressed in the dorsal telencephalic region at 24 hpf and 36 hpf. (B) dcc and lhx5 are co-expressed in the dorsal telencephalon at 20 hpf. ADt neurons are migrating from their medial positions in the neural tube to lateral positions at 20 hpf. Scale bar: 100 µm for lateral view; 60 µm for frontal view.
Mentions: The guidance receptor Dcc and its ligand Netrin1 are expressed in the central nervous system during zebrafish embryonic development [25]–[28]. During the pharyngula period (at 24 hpf and 36 hpf), dcc is expressed in dorsal telencephalic regions (Fig. 2A). Double labeling by fluorescent in situ hybridization demonstrated that dcc is co-expressed with lhx5 in the ADt neurons at 20 hpf, a stage when the lhx5:Kaede labeled ADt neurons are still migrating and lack axonal processes (Fig. 2B). During these periods of development, netrin1a and netrin1b, the duplicated genes orthologous to the mammalian Netrin1 gene, are expressed in the ventral midline region of the forebrain and ventral regions along the SOT ([27], [28], and data not shown). These expression patterns indicate that the guidance receptor Dcc is expressed in the right place at the right time to direct the asymmetric growth of the ADt neurons.

Bottom Line: We found that ADt axons normally project ventrally.We found that individual ADt neurons projected axons dorsally or formed multiple processes after morpholino knock down of Dcc function.We further found that knock down of the Dcc ligand, Netrin1, also caused ADt neurons to project axons dorsally.

View Article: PubMed Central - PubMed

Affiliation: Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China.

ABSTRACT
The guidance receptor DCC (deleted in colorectal cancer) ortholog UNC-40 regulates neuronal asymmetry development in Caenorhabditis elegans, but it is not known whether DCC plays a role in the specification of neuronal polarity in vertebrates. To examine the roles of DCC in neuronal asymmetry regulation in vertebrates, we studied zebrafish anterior dorsal telencephalon (ADt) neuronal axons. We generated transgenic zebrafish animals expressing the photo-convertible fluorescent protein Kaede in ADt neurons and then photo-converted Kaede to label specifically the ADt neuron axons. We found that ADt axons normally project ventrally. Knock down of Dcc function by injecting antisense morpholino oligonucleotides caused the ADt neurons to project axons dorsally. To examine the axon projection pattern of individual ADt neurons, we labeled single ADt neurons using a forebrain-specific promoter to drive fluorescent protein expression. We found that individual ADt neurons projected axons dorsally or formed multiple processes after morpholino knock down of Dcc function. We further found that knock down of the Dcc ligand, Netrin1, also caused ADt neurons to project axons dorsally. Knockdown of Neogenin1, a guidance receptor closely related to Dcc, enhanced the formation of aberrant dorsal axons in embryos injected with Dcc morpholino. These experiments provide the first evidence that Dcc regulates polarized axon initiation and asymmetric outgrowth of forebrain neurons in vertebrates.

Show MeSH
Related in: MedlinePlus