Limits...
Neurod1 suppresses hair cell differentiation in ear ganglia and regulates hair cell subtype development in the cochlea.

Jahan I, Pan N, Kersigo J, Fritzsch B - PLoS ONE (2010)

Bottom Line: Our data suggest that the long noted cross-regulation of Atoh1 expression by Neurog1 might actually be mediated in large part by Neurod1.We suggest that Neurod1 is regulated by both Neurog1 and Atoh1 and provides a negative feedback for either gene.Through this and other feedback, Neurod1 suppresses alternate fates of neurons to differentiate as hair cells and regulates hair cell subtypes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, United States of America.

ABSTRACT

Background: At least five bHLH genes regulate cell fate determination and differentiation of sensory neurons, hair cells and supporting cells in the mammalian inner ear. Cross-regulation of Atoh1 and Neurog1 results in hair cell changes in Neurog1 mice although the nature and mechanism of the cross-regulation has not yet been determined. Neurod1, regulated by both Neurog1 and Atoh1, could be the mediator of this cross-regulation.

Methodology/principal findings: We used Tg(Pax2-Cre) to conditionally delete Neurod1 in the inner ear. Our data demonstrate for the first time that the absence of Neurod1 results in formation of hair cells within the inner ear sensory ganglia. Three cell types, neural crest derived Schwann cells and mesenchyme derived fibroblasts (neither expresses Neurod1) and inner ear derived neurons (which express Neurod1) constitute inner ear ganglia. The most parsimonious explanation is that Neurod1 suppresses the alternative fate of sensory neurons to develop as hair cells. In the absence of Neurod1, Atoh1 is expressed and differentiates cells within the ganglion into hair cells. We followed up on this effect in ganglia by demonstrating that Neurod1 also regulates differentiation of subtypes of hair cells in the organ of Corti. We show that in Neurod1 conditional mice there is a premature expression of several genes in the apex of the developing cochlea and outer hair cells are transformed into inner hair cells.

Conclusions/significance: Our data suggest that the long noted cross-regulation of Atoh1 expression by Neurog1 might actually be mediated in large part by Neurod1. We suggest that Neurod1 is regulated by both Neurog1 and Atoh1 and provides a negative feedback for either gene. Through this and other feedback, Neurod1 suppresses alternate fates of neurons to differentiate as hair cells and regulates hair cell subtypes.

Show MeSH

Related in: MedlinePlus

Persistent Atoh1 expression in remaining ganglia relates to transformation of ganglionic cells into hair cells in Neurod1 mutant.In situ hybridization of Atoh1 shows a faint and transient expression at E11.5 in some vestibular ganglion cells in wild-type mice (A, A’). This expression is more profound and continues in the ganglia of Neurod1 CKO mice (D, D’). In later stages, Atoh1 in situ signal appears in a cluster of cells in CKO mutants near the utricle and saccule (E–E’, F, G–G’). Some of the Atoh1 positive cells are aligned along the vesicular lumen similar to the Myo VIIa positive cells shown in Fig. 1 (G). To investigate co-localization, we labeled Atoh1 in situ reacted ears with anti-Myo VIIa antibody, embedded in plastic and sectioned. The sections reveal co-localization of Myo VIIa with Atoh1 in these cells (H,H’) thereby providing strong evidence that these cells are hair cells. S, saccule; U, utricle; G, ganglia; V, intraganglionic vesicle. Bar indicates 100 µm except E, E’ and 10 µm in E, E’.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2908541&req=5

pone-0011661-g002: Persistent Atoh1 expression in remaining ganglia relates to transformation of ganglionic cells into hair cells in Neurod1 mutant.In situ hybridization of Atoh1 shows a faint and transient expression at E11.5 in some vestibular ganglion cells in wild-type mice (A, A’). This expression is more profound and continues in the ganglia of Neurod1 CKO mice (D, D’). In later stages, Atoh1 in situ signal appears in a cluster of cells in CKO mutants near the utricle and saccule (E–E’, F, G–G’). Some of the Atoh1 positive cells are aligned along the vesicular lumen similar to the Myo VIIa positive cells shown in Fig. 1 (G). To investigate co-localization, we labeled Atoh1 in situ reacted ears with anti-Myo VIIa antibody, embedded in plastic and sectioned. The sections reveal co-localization of Myo VIIa with Atoh1 in these cells (H,H’) thereby providing strong evidence that these cells are hair cells. S, saccule; U, utricle; G, ganglia; V, intraganglionic vesicle. Bar indicates 100 µm except E, E’ and 10 µm in E, E’.

Mentions: Atoh1 is a hair cell differentiation marker with a well established role in the ear only in the differentiation of hair cells [1], [31], [32]. Only limited expression of Atoh1 has been reported with sophisticated techniques in sensory neurons [17] and none in the neural crest derived Schwann cells or mesenchyme derived perneurial fibrocytes. Using in situ hybridization we observed only a transient Atoh1 expression in the vestibular ganglia of wild-type mice at E11.5 (Fig. 2A, A’). However, in the Neurod1 CKO mice, Atoh1 expression continued in these ganglia past the transient expression found in control animals (Fig. 2D, D’). Atoh1 expression was more profound in later stages and was found in a cluster of cells in the remaining ganglia next to the utricle and saccule, mostly around the ectopic vesicles (Fig. 2E–G’). Immunofluorescence labeling with Myo VIIa antibody revealed that each of the Atoh1 positive cells was also immunopositive for Myo VIIa (Fig. 2 H,H’).


Neurod1 suppresses hair cell differentiation in ear ganglia and regulates hair cell subtype development in the cochlea.

Jahan I, Pan N, Kersigo J, Fritzsch B - PLoS ONE (2010)

Persistent Atoh1 expression in remaining ganglia relates to transformation of ganglionic cells into hair cells in Neurod1 mutant.In situ hybridization of Atoh1 shows a faint and transient expression at E11.5 in some vestibular ganglion cells in wild-type mice (A, A’). This expression is more profound and continues in the ganglia of Neurod1 CKO mice (D, D’). In later stages, Atoh1 in situ signal appears in a cluster of cells in CKO mutants near the utricle and saccule (E–E’, F, G–G’). Some of the Atoh1 positive cells are aligned along the vesicular lumen similar to the Myo VIIa positive cells shown in Fig. 1 (G). To investigate co-localization, we labeled Atoh1 in situ reacted ears with anti-Myo VIIa antibody, embedded in plastic and sectioned. The sections reveal co-localization of Myo VIIa with Atoh1 in these cells (H,H’) thereby providing strong evidence that these cells are hair cells. S, saccule; U, utricle; G, ganglia; V, intraganglionic vesicle. Bar indicates 100 µm except E, E’ and 10 µm in E, E’.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2908541&req=5

pone-0011661-g002: Persistent Atoh1 expression in remaining ganglia relates to transformation of ganglionic cells into hair cells in Neurod1 mutant.In situ hybridization of Atoh1 shows a faint and transient expression at E11.5 in some vestibular ganglion cells in wild-type mice (A, A’). This expression is more profound and continues in the ganglia of Neurod1 CKO mice (D, D’). In later stages, Atoh1 in situ signal appears in a cluster of cells in CKO mutants near the utricle and saccule (E–E’, F, G–G’). Some of the Atoh1 positive cells are aligned along the vesicular lumen similar to the Myo VIIa positive cells shown in Fig. 1 (G). To investigate co-localization, we labeled Atoh1 in situ reacted ears with anti-Myo VIIa antibody, embedded in plastic and sectioned. The sections reveal co-localization of Myo VIIa with Atoh1 in these cells (H,H’) thereby providing strong evidence that these cells are hair cells. S, saccule; U, utricle; G, ganglia; V, intraganglionic vesicle. Bar indicates 100 µm except E, E’ and 10 µm in E, E’.
Mentions: Atoh1 is a hair cell differentiation marker with a well established role in the ear only in the differentiation of hair cells [1], [31], [32]. Only limited expression of Atoh1 has been reported with sophisticated techniques in sensory neurons [17] and none in the neural crest derived Schwann cells or mesenchyme derived perneurial fibrocytes. Using in situ hybridization we observed only a transient Atoh1 expression in the vestibular ganglia of wild-type mice at E11.5 (Fig. 2A, A’). However, in the Neurod1 CKO mice, Atoh1 expression continued in these ganglia past the transient expression found in control animals (Fig. 2D, D’). Atoh1 expression was more profound in later stages and was found in a cluster of cells in the remaining ganglia next to the utricle and saccule, mostly around the ectopic vesicles (Fig. 2E–G’). Immunofluorescence labeling with Myo VIIa antibody revealed that each of the Atoh1 positive cells was also immunopositive for Myo VIIa (Fig. 2 H,H’).

Bottom Line: Our data suggest that the long noted cross-regulation of Atoh1 expression by Neurog1 might actually be mediated in large part by Neurod1.We suggest that Neurod1 is regulated by both Neurog1 and Atoh1 and provides a negative feedback for either gene.Through this and other feedback, Neurod1 suppresses alternate fates of neurons to differentiate as hair cells and regulates hair cell subtypes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Iowa, Iowa City, Iowa, United States of America.

ABSTRACT

Background: At least five bHLH genes regulate cell fate determination and differentiation of sensory neurons, hair cells and supporting cells in the mammalian inner ear. Cross-regulation of Atoh1 and Neurog1 results in hair cell changes in Neurog1 mice although the nature and mechanism of the cross-regulation has not yet been determined. Neurod1, regulated by both Neurog1 and Atoh1, could be the mediator of this cross-regulation.

Methodology/principal findings: We used Tg(Pax2-Cre) to conditionally delete Neurod1 in the inner ear. Our data demonstrate for the first time that the absence of Neurod1 results in formation of hair cells within the inner ear sensory ganglia. Three cell types, neural crest derived Schwann cells and mesenchyme derived fibroblasts (neither expresses Neurod1) and inner ear derived neurons (which express Neurod1) constitute inner ear ganglia. The most parsimonious explanation is that Neurod1 suppresses the alternative fate of sensory neurons to develop as hair cells. In the absence of Neurod1, Atoh1 is expressed and differentiates cells within the ganglion into hair cells. We followed up on this effect in ganglia by demonstrating that Neurod1 also regulates differentiation of subtypes of hair cells in the organ of Corti. We show that in Neurod1 conditional mice there is a premature expression of several genes in the apex of the developing cochlea and outer hair cells are transformed into inner hair cells.

Conclusions/significance: Our data suggest that the long noted cross-regulation of Atoh1 expression by Neurog1 might actually be mediated in large part by Neurod1. We suggest that Neurod1 is regulated by both Neurog1 and Atoh1 and provides a negative feedback for either gene. Through this and other feedback, Neurod1 suppresses alternate fates of neurons to differentiate as hair cells and regulates hair cell subtypes.

Show MeSH
Related in: MedlinePlus