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Deltex1 is inhibited by the Notch-Hairy/E(Spl) signaling pathway and induces neuronal and glial differentiation.

Cheng YC, Huang YC, Yeh TH, Shih HY, Lin CY, Lin SJ, Chiu CC, Huang CW, Jiang YJ - Neural Dev (2015)

Bottom Line: Examination of the expression of her2 and her8a in embryos with altered Dtx1 expression showed that Dxt1-induced neuronal differentiation did not require a regulatory effect on the Notch-Hairy/E(Spl) pathway.Our results demonstrated that Dtx1 is regulated by Notch-Hairy/E(Spl) signaling and is a major factor specifically regulating neural differentiation.Thus, our results provide new insights into the mediation of neural development by the Notch signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, 259 Wen-Hwa 1 Road, Taoyuan, 33383, Taiwan. yccheng@mail.cgu.edu.tw.

ABSTRACT

Background: Notch signaling has been conserved throughout evolution and plays a fundamental role in various neural developmental processes and the pathogenesis of several human cancers and genetic disorders. However, how Notch signaling regulates various cellular processes remains unclear. Although Deltex proteins have been identified as cytoplasmic downstream elements of the Notch signaling pathway, few studies have been reported on their physiological role.

Results: We isolated zebrafish deltex1 (dtx1) and showed that this gene is primarily transcribed in the developing nervous system, and its spatiotemporal expression pattern suggests a role in neural differentiation. The transcription of dtx1 was suppressed by the direct binding of the Notch downstream transcription factors Her2 and Her8a. Overexpressing the complete coding sequence of Dtx1 was necessary for inducing neuronal and glial differentiation. By contrast, disrupting Dtx1 expression by using a Dtx1 construct without the RING finger domain reduced neuronal and glial differentiation. This effect was phenocopied by the knockdown of endogenous Dtx1 expression by using morpholinos, demonstrating the essential function of the RING finger domain and confirming the knockdown specificity. Cell proliferation and apoptosis were unaltered in Dtx1-overexpressed and -deficient zebrafish embryos. Examination of the expression of her2 and her8a in embryos with altered Dtx1 expression showed that Dxt1-induced neuronal differentiation did not require a regulatory effect on the Notch-Hairy/E(Spl) pathway. However, both Dtx1 and Notch activation induced glial differentiation, and Dtx1 and Notch activation negatively inhibited each other in a reciprocal manner, which achieves a proper balance for the expression of Dtx1 and Notch to facilitate glial differentiation. We further confirmed that the Dtx1-Notch-Hairy/E(Spl) cascade was sufficient to induce neuronal and glial differentiation by concomitant injection of an active form of Notch with dtx1, which rescued the neuronogenic and gliogenic defects caused by the activation of Notch signaling.

Conclusions: Our results demonstrated that Dtx1 is regulated by Notch-Hairy/E(Spl) signaling and is a major factor specifically regulating neural differentiation. Thus, our results provide new insights into the mediation of neural development by the Notch signaling pathway.

No MeSH data available.


Related in: MedlinePlus

dtx1 expression in developing zebrafish. dtx1 expression was detected using in situ hybridization in the developing nervous system during zebrafish embryogenesis. The embryo stages are shown in the bottom right corner of each panel. a Lateral view with anterior to the right. b–e Dorsal view with anterior to the top. b–fdtx1 expression occurred first in the developing nervous system during the bud stage (b) and remained until the final stage that was analyzed (e) Arrows in c and d indicate dtx1 expressing cells flanking the midline. E, eye; FB, forebrain; HB, hindbrain; MB, midbrain; MHB, midbrain-hindbrain boundary; SC, spinal cord
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Fig1: dtx1 expression in developing zebrafish. dtx1 expression was detected using in situ hybridization in the developing nervous system during zebrafish embryogenesis. The embryo stages are shown in the bottom right corner of each panel. a Lateral view with anterior to the right. b–e Dorsal view with anterior to the top. b–fdtx1 expression occurred first in the developing nervous system during the bud stage (b) and remained until the final stage that was analyzed (e) Arrows in c and d indicate dtx1 expressing cells flanking the midline. E, eye; FB, forebrain; HB, hindbrain; MB, midbrain; MHB, midbrain-hindbrain boundary; SC, spinal cord

Mentions: The expression of dtx1 was analyzed using whole-mount in situ hybridization. Transcripts first appeared in the developing nervous system at the bud stage in the primordium of the brain and spinal cord (Fig. 1b). From the midsegmentation stages, cells with different dtx1 expression levels spanned the entire central nervous system, with strong expression in cells flanking the midline (arrows in Fig. 1c,d). This expression remained until the late pharyngula stages (48 hpf; Fig. 1e). Abundant dtx1 expression was also detected in the entire brain but not in the mid-hindbrain boundary at 48 hpf (Fig. 1e). In general, the expression pattern of zebrafish dtx1 was similar to that of mouse Dtx1, which is also expressed in the developing central nervous system [9, 17].Fig. 1


Deltex1 is inhibited by the Notch-Hairy/E(Spl) signaling pathway and induces neuronal and glial differentiation.

Cheng YC, Huang YC, Yeh TH, Shih HY, Lin CY, Lin SJ, Chiu CC, Huang CW, Jiang YJ - Neural Dev (2015)

dtx1 expression in developing zebrafish. dtx1 expression was detected using in situ hybridization in the developing nervous system during zebrafish embryogenesis. The embryo stages are shown in the bottom right corner of each panel. a Lateral view with anterior to the right. b–e Dorsal view with anterior to the top. b–fdtx1 expression occurred first in the developing nervous system during the bud stage (b) and remained until the final stage that was analyzed (e) Arrows in c and d indicate dtx1 expressing cells flanking the midline. E, eye; FB, forebrain; HB, hindbrain; MB, midbrain; MHB, midbrain-hindbrain boundary; SC, spinal cord
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4696291&req=5

Fig1: dtx1 expression in developing zebrafish. dtx1 expression was detected using in situ hybridization in the developing nervous system during zebrafish embryogenesis. The embryo stages are shown in the bottom right corner of each panel. a Lateral view with anterior to the right. b–e Dorsal view with anterior to the top. b–fdtx1 expression occurred first in the developing nervous system during the bud stage (b) and remained until the final stage that was analyzed (e) Arrows in c and d indicate dtx1 expressing cells flanking the midline. E, eye; FB, forebrain; HB, hindbrain; MB, midbrain; MHB, midbrain-hindbrain boundary; SC, spinal cord
Mentions: The expression of dtx1 was analyzed using whole-mount in situ hybridization. Transcripts first appeared in the developing nervous system at the bud stage in the primordium of the brain and spinal cord (Fig. 1b). From the midsegmentation stages, cells with different dtx1 expression levels spanned the entire central nervous system, with strong expression in cells flanking the midline (arrows in Fig. 1c,d). This expression remained until the late pharyngula stages (48 hpf; Fig. 1e). Abundant dtx1 expression was also detected in the entire brain but not in the mid-hindbrain boundary at 48 hpf (Fig. 1e). In general, the expression pattern of zebrafish dtx1 was similar to that of mouse Dtx1, which is also expressed in the developing central nervous system [9, 17].Fig. 1

Bottom Line: Examination of the expression of her2 and her8a in embryos with altered Dtx1 expression showed that Dxt1-induced neuronal differentiation did not require a regulatory effect on the Notch-Hairy/E(Spl) pathway.Our results demonstrated that Dtx1 is regulated by Notch-Hairy/E(Spl) signaling and is a major factor specifically regulating neural differentiation.Thus, our results provide new insights into the mediation of neural development by the Notch signaling pathway.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, 259 Wen-Hwa 1 Road, Taoyuan, 33383, Taiwan. yccheng@mail.cgu.edu.tw.

ABSTRACT

Background: Notch signaling has been conserved throughout evolution and plays a fundamental role in various neural developmental processes and the pathogenesis of several human cancers and genetic disorders. However, how Notch signaling regulates various cellular processes remains unclear. Although Deltex proteins have been identified as cytoplasmic downstream elements of the Notch signaling pathway, few studies have been reported on their physiological role.

Results: We isolated zebrafish deltex1 (dtx1) and showed that this gene is primarily transcribed in the developing nervous system, and its spatiotemporal expression pattern suggests a role in neural differentiation. The transcription of dtx1 was suppressed by the direct binding of the Notch downstream transcription factors Her2 and Her8a. Overexpressing the complete coding sequence of Dtx1 was necessary for inducing neuronal and glial differentiation. By contrast, disrupting Dtx1 expression by using a Dtx1 construct without the RING finger domain reduced neuronal and glial differentiation. This effect was phenocopied by the knockdown of endogenous Dtx1 expression by using morpholinos, demonstrating the essential function of the RING finger domain and confirming the knockdown specificity. Cell proliferation and apoptosis were unaltered in Dtx1-overexpressed and -deficient zebrafish embryos. Examination of the expression of her2 and her8a in embryos with altered Dtx1 expression showed that Dxt1-induced neuronal differentiation did not require a regulatory effect on the Notch-Hairy/E(Spl) pathway. However, both Dtx1 and Notch activation induced glial differentiation, and Dtx1 and Notch activation negatively inhibited each other in a reciprocal manner, which achieves a proper balance for the expression of Dtx1 and Notch to facilitate glial differentiation. We further confirmed that the Dtx1-Notch-Hairy/E(Spl) cascade was sufficient to induce neuronal and glial differentiation by concomitant injection of an active form of Notch with dtx1, which rescued the neuronogenic and gliogenic defects caused by the activation of Notch signaling.

Conclusions: Our results demonstrated that Dtx1 is regulated by Notch-Hairy/E(Spl) signaling and is a major factor specifically regulating neural differentiation. Thus, our results provide new insights into the mediation of neural development by the Notch signaling pathway.

No MeSH data available.


Related in: MedlinePlus