Notch signaling regulates the pattern of auditory hair cell differentiation in mammals

The development of the mammalian cochlea is an example of patterning in the peripheral nervous system. Sensory hair cells and supporting cells in the cochlea differentiate via regional and cell fate specification. The Notch signaling components shows both distinct and overlapping expression patterns of Notch1 receptor and its ligands Jagged1 (Jag1) and Jagged2 (Jag2) in the developing auditory epithelium of the rat. On embryonic day 16 (E16), many precursor cells within the Kolliker's organ immunostained for the presence of both Notch1 and Jag1, while the area of hair cell precursors did not express either Notch1 and Jag1. During initial events of hair cell differentiation between E18 and birth, Notch1 and Jag1 expression predominated in supporting cells and Jag2 in nascent hair cells. Early after birth, Jag2 expression decreased in hair cells while the pattern of Notch1 expression now included both supporting cells and hair cells. We show that the normal pattern of hair cell differentiation is disrupted by alteration of Notch signaling. A decrease of either Notch1 or Jag1 expression by antisense oligonucleotides in cultures of the developing sensory epithelium resulted in an increase in the number of hair cells. Our data suggest that the Notch1 signaling pathway is involved in a complex interplay between the consequences of different ligand-Notch1 combinations during cochlear morphogenesis and the phases of hair cell differentiation.

Download Full-text

Hes1 is a negative regulator of inner ear hair cell differentiation

Development ◽

10.1242/dev.127.21.4551 ◽

2000 ◽

Vol 127 (21) ◽

pp. 4551-4560 ◽

Cited By ~ 5

Author(s):

J.L. Zheng ◽

J. Shou ◽

F. Guillemot ◽

R. Kageyama ◽

W.Q. Gao

Keyword(s):

Cell Differentiation ◽

Hair Cell ◽

Inner Ear ◽

Cell Fate ◽

Hair Cells ◽

Outer Hair Cells ◽

Negative Regulator ◽

Pcr Analysis ◽

Loss Of Function ◽

Hair Cell Differentiation

Hair cell fate determination in the inner ear has been shown to be controlled by specific genes. Recent loss-of-function and gain-of-function experiments have demonstrated that Math1, a mouse homolog of the Drosophila gene atonal, is essential for the production of hair cells. To identify genes that may interact with Math1 and inhibit hair cell differentiation, we have focused on Hes1, a mammalian hairy and enhancer of split homolog, which is a negative regulator of neurogenesis. We report here that targeted deletion of Hes1 leads to formation of supernumerary hair cells in the cochlea and utricle of the inner ear. RT-PCR analysis shows that Hes1 is expressed in inner ear during hair cell differentiation and its expression is maintained in adulthood. In situ hybridization with late embryonic inner ear tissue reveals that Hes1 is expressed in supporting cells, but not hair cells, of the vestibular sensory epithelium. In the cochlea, Hes1 is selectively expressed in the greater epithelial ridge and lesser epithelial ridge regions which are adjacent to inner and outer hair cells. Co-transfection experiments in postnatal rat explant cultures show that overexpression of Hes1 prevents hair cell differentiation induced by Math1. Therefore Hes1 can negatively regulate hair cell differentiation by antagonizing Math1. These results suggest that a balance between Math1 and negative regulators such as Hes1 is crucial for the production of an appropriate number of inner ear hair cells.

Download Full-text

A counter gradient of Activin A and follistatin instructs the timing of hair cell differentiation in the murine cochlea

eLife ◽

10.7554/elife.47613 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 3

Author(s):

Meenakshi Prajapati-DiNubila ◽

Ana Benito-Gonzalez ◽

Erin Jennifer Golden ◽

Shuran Zhang ◽

Angelika Doetzlhofer

Keyword(s):

Cell Differentiation ◽

Hair Cell ◽

Hair Cells ◽

Activin A ◽

Sensory Epithelium ◽

Outer Hair Cells ◽

Longitudinal Gradient ◽

Hair Cell Differentiation ◽

Local Gradient ◽

Molecular Signals

The mammalian auditory sensory epithelium has one of the most stereotyped cellular patterns known in vertebrates. Mechano-sensory hair cells are arranged in precise rows, with one row of inner and three rows of outer hair cells spanning the length of the spiral-shaped sensory epithelium. Aiding such precise cellular patterning, differentiation of the auditory sensory epithelium is precisely timed and follows a steep longitudinal gradient. The molecular signals that promote auditory sensory differentiation and instruct its graded pattern are largely unknown. Here, we identify Activin A and its antagonist follistatin as key regulators of hair cell differentiation and show, using mouse genetic approaches, that a local gradient of Activin A signaling within the auditory sensory epithelium times the longitudinal gradient of hair cell differentiation. Furthermore, we provide evidence that Activin-type signaling regulates a radial gradient of terminal mitosis within the auditory sensory epithelium, which constitutes a novel mechanism for limiting the number of inner hair cells being produced.

Download Full-text

The deltaA gene of zebrafish mediates lateral inhibition of hair cells in the inner ear and is regulated by pax2.1

Development ◽

10.1242/dev.126.24.5669 ◽

1999 ◽

Vol 126 (24) ◽

pp. 5669-5678 ◽

Cited By ~ 6

Author(s):

B.B. Riley ◽

M. Chiang ◽

L. Farmer ◽

R. Heck

Keyword(s):

Cell Differentiation ◽

Hair Cell ◽

Inner Ear ◽

Cell Fate ◽

Lateral Inhibition ◽

Hair Cells ◽

Fold Increase ◽

Dominant Negative ◽

Dominant Negative Mutant ◽

Hair Cell Differentiation

Recent studies of inner ear development suggest that hair cells and support cells arise within a common equivalence group by cell-cell interactions mediated by Delta and Notch proteins. We have extended these studies by analyzing the effects of a mutant allele of the zebrafish deltaA gene, deltaA(dx2), which encodes a dominant-negative protein. deltaA(dx2/dx2)homozygous mutants develop with a 5- to 6-fold excess of hair cells and a severe deficiency of support cells. In addition, deltaA(dx2/dx2) mutants show an increased number of cells expressing pax2.1 in regions where hair cells are normally produced. Immunohistological analysis of wild-type and deltaA(dx2/dx2) mutant embryos confirmed that pax2.1 is expressed during the initial stages of hair cell differentiation and is later maintained at high levels in mature hair cells. In contrast, pax2.1 is not expressed in support cells. To address the function of pax2.1, we analyzed hair cell differentiation in no isthmus mutant embryos, which are deficient for pax2.1 function. no isthmus mutant embryos develop with approximately twice the normal number of hair cells. This neurogenic defect correlates with reduced levels of expression of deltaA and deltaD in the hair cells in no isthmus mutants. Analysis of deltaA(dx2/dx2); no isthmus double mutants showed that no isthmus suppresses the deltaA(dx2) phenotype, probably by reducing levels of the dominant-negative mutant protein. This interpretation was supported by analysis of T(msxB)(b220), a deletion that removes the deltaA locus. Reducing the dose of deltaA(dx2) by generating deltaA(dx2)/T(msxB)(b220)trans-heterozygotes weakens the neurogenic effects of deltaA(dx2), whereas T(msxB)(b220) enhances the neurogenic defects of no isthmus. mind bomb, another strong neurogenic mutation that may disrupt reception of Delta signals, causes a 10-fold increase in hair cell production and is epistatic to both no isthmus and deltaA(dx2). These data indicate that deltaA expressed by hair cells normally prevents adjacent cells from adopting the same cell fate, and that pax2.1 is required for normal levels of Delta-mediated lateral inhibition.

Download Full-text

The role of Math1 in inner ear development: Uncoupling the establishment of the sensory primordium from hair cell fate determination

Development ◽

10.1242/dev.129.10.2495 ◽

2002 ◽

Vol 129 (10) ◽

pp. 2495-2505 ◽

Cited By ~ 4

Author(s):

Ping Chen ◽

Jane E. Johnson ◽

Huda Y. Zoghbi ◽

Neil Segil

Keyword(s):

Hair Cell ◽

Inner Ear ◽

Cell Fate ◽

Hair Cells ◽

Organ Of Corti ◽

Sensory Epithelium ◽

Proliferating Cells ◽

Sensory Hair ◽

Sensory Hair Cells ◽

Hair Cell Differentiation

During embryonic development of the inner ear, the sensory primordium that gives rise to the organ of Corti from within the cochlear epithelium is patterned into a stereotyped array of inner and outer sensory hair cells separated from each other by non-sensory supporting cells. Math1, a close homolog of the Drosophila proneural gene atonal, has been found to be both necessary and sufficient for the production of hair cells in the mouse inner ear. Our results indicate that Math1 is not required to establish the postmitotic sensory primordium from which the cells of the organ of Corti arise, but instead is limited to a role in the selection and/or differentiation of sensory hair cells from within the established primordium. This is based on the observation that Math1 is only expressed after the appearance of a zone of non-proliferating cells that delineates the sensory primordium within the cochlear anlage. The expression of Math1 is limited to a subpopulation of cells within the sensory primordium that appear to differentiate exclusively into hair cells as the sensory epithelium matures and elongates through a process that probably involves radial intercalation of cells. Furthermore, mutation of Math1 does not affect the establishment of this postmitotic sensory primordium, even though the subsequent generation of hair cells is blocked in these mutants. Finally, in Math1 mutant embryos, a subpopulation of the cells within the sensory epithelium undergo apoptosis in a temporal gradient similar to the basal-to-apical gradient of hair cell differentiation that occurs in the cochlea of wild-type animals.

Download Full-text

Hair necessities: Hair cell differentiation and regeneration

The Biochemist ◽

10.1042/bio02406009 ◽

2002 ◽

Vol 24 (6) ◽

pp. 9-11

Author(s):

Matthew Holley

Keyword(s):

Cell Differentiation ◽

Hair Cell ◽

Hair Cells ◽

Organ Of Corti ◽

Structural Diversity ◽

Sensory Epithelium ◽

Animal Kingdom ◽

Hair Cell Differentiation ◽

Human Hearing ◽

Mechanosensory Hair Cells

Human hearing is governed by approximately 15 500 mechanosensory hair cells in each ear. These cells are located within the organ of Corti, the elongated auditory sensory epithelium that is stretched inside the coiled cochleae of the inner ear. Despite the structural diversity between the organs of hearing throughout the animal kingdom, hair cells are instantly recognizable. Their shapes and sizes vary considerably, but their apices carry a characteristic bundle of actin-filled stereocilia, or hairs, whose tips are connected by stretch-sensitive ‘tip-links’1. However, unlike most other animals, mammals do not regenerate lost hair cells2, consequently most forms of deafness are irreversible.

Download Full-text

Activin signaling informs the graded pattern of terminal mitosis and hair cell differentiation in the mammalian cochlea

10.1101/380055 ◽

2018 ◽

Author(s):

Meenakshi Prajapati-DiNubila ◽

Ana Benito-Gonzalez ◽

Erin J. Golden ◽

Shuran Zhang ◽

Angelika Doetzlhofer

Keyword(s):

Cell Differentiation ◽

Hair Cell ◽

Hair Cells ◽

Activin A ◽

Sensory Epithelium ◽

Outer Hair Cells ◽

Longitudinal Gradient ◽

Hair Cell Differentiation ◽

Local Gradient ◽

Molecular Signals

ABSTRACTThe mammalian auditory sensory epithelium has one of the most stereotyped cellular patterns known in vertebrates. Mechano-sensory hair cells are arranged in precise rows, with one row of inner and three rows of outer hair cells spanning the length of the spiral-shaped sensory epithelium. Aiding such precise cellular patterning, differentiation of the auditory sensory epithelium is precisely timed and follows a steep longitudinal gradient. The molecular signals that promote auditory sensory differentiation and instruct its graded pattern are largely unknown. Here, we identify Activin A as an activator of hair cell differentiation and show, using mouse genetic approaches, that a local gradient of Activin A signaling within the auditory sensory epithelium times the longitudinal gradient of hair cell differentiation. Furthermore, we provide evidence that Activin-type signaling regulates a radial gradient of terminal mitosis within the auditory sensory epithelium, which constitutes a novel mechanism for limiting the number of inner hair cells being produced.

Download Full-text

A Critical E-box in Barhl1 3′ Enhancer Is Essential for Auditory Hair Cell Differentiation

Cells ◽

10.3390/cells8050458 ◽

2019 ◽

Vol 8 (5) ◽

pp. 458 ◽

Cited By ~ 2

Author(s):

Kun Hou ◽

Hui Jiang ◽

Md. Rezaul Karim ◽

Chao Zhong ◽

Zhouwen Xu ◽

...

Keyword(s):

Cell Differentiation ◽

Hair Cell ◽

Hair Cells ◽

Embryonic Stem ◽

Cell Development ◽

Homologous Gene ◽

Auditory Hair Cells ◽

E Box ◽

Hair Cell Differentiation

Barhl1, a mouse homologous gene of Drosophila BarH class homeobox genes, is highly expressed within the inner ear and crucial for the long-term maintenance of auditory hair cells that mediate hearing and balance, yet little is known about the molecular events underlying Barhl1 regulation and function in hair cells. In this study, through data mining and in vitro report assay, we firstly identified Barhl1 as a direct target gene of Atoh1 and one E-box (E3) in Barhl1 3’ enhancer is crucial for Atoh1-mediated Barhl1 activation. Then we generated a mouse embryonic stem cell (mESC) line carrying disruptions on this E3 site E-box (CAGCTG) using CRISPR/Cas9 technology and this E3 mutated mESC line is further subjected to an efficient stepwise hair cell differentiation strategy in vitro. Disruptions on this E3 site caused dramatic loss of Barhl1 expression and significantly reduced the number of induced hair cell-like cells, while no affections on the differentiation toward early primitive ectoderm-like cells and otic progenitors. Finally, through RNA-seq profiling and gene ontology (GO) enrichment analysis, we found that this E3 box was indispensable for Barhl1 expression to maintain hair cell development and normal functions. We also compared the transcriptional profiles of induced cells from CDS mutated and E3 mutated mESCs, respectively, and got very consistent results except the Barhl1 transcript itself. These observations indicated that Atoh1-mediated Barhl1 expression could have important roles during auditory hair cell development. In brief, our findings delineate the detail molecular mechanism of Barhl1 expression regulation in auditory hair cell differentiation.

Download Full-text

Faculty Opinions recommendation of Notch signaling regulates the pattern of auditory hair cell differentiation in mammals.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1001082.17059 ◽

2001 ◽

Author(s):

Alain Ghysen

Keyword(s):

Cell Differentiation ◽

Hair Cell ◽

Notch Signaling ◽

Hair Cell Differentiation

Download Full-text

Hear, Hear for Notch: Control of Cell Fates in the Inner Ear by Notch Signaling

Biomolecules ◽

10.3390/biom10030370 ◽

2020 ◽

Vol 10 (3) ◽

pp. 370 ◽

Cited By ~ 8

Author(s):

Rogers Brown ◽

Andrew K. Groves

Keyword(s):

Hair Cell ◽

Notch Signaling ◽

Inner Ear ◽

Hair Cells ◽

Notch Pathway ◽

Notch Signaling Pathway ◽

Cell Regeneration ◽

Hair Cell Regeneration ◽

Supporting Cells ◽

Fine Grained

The vertebrate inner ear is responsible for detecting sound, gravity, and head motion. These mechanical forces are detected by mechanosensitive hair cells, arranged in a series of sensory patches in the vestibular and cochlear regions of the ear. Hair cells form synapses with neurons of the VIIIth cranial ganglion, which convey sound and balance information to the brain. They are surrounded by supporting cells, which nourish and protect the hair cells, and which can serve as a source of stem cells to regenerate hair cells after damage in non-mammalian vertebrates. The Notch signaling pathway plays many roles in the development of the inner ear, from the earliest formation of future inner ear ectoderm on the side of the embryonic head, to regulating the production of supporting cells, hair cells, and the neurons that innervate them. Notch signaling is re-deployed in non-mammalian vertebrates during hair cell regeneration, and attempts have been made to manipulate the Notch pathway to promote hair cell regeneration in mammals. In this review, we summarize the different modes of Notch signaling in inner ear development and regeneration, and describe how they interact with other signaling pathways to orchestrate the fine-grained cellular patterns of the ear.

Download Full-text