spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online November 26, 2007
doi: 10.1242/10.1242/dev.009118

Development 134, 4405-4415 (2007)
Published by The Company of Biologists 2007
This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplementary Material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Raft, S.
Right arrow Articles by Groves, A. K.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Raft, S.
Right arrow Articles by Groves, A. K.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati   Add to Twitter  
What's this?

Cross-regulation of Ngn1 and Math1 coordinates the production of neurons and sensory hair cells during inner ear development

Steven Raft1, Edmund J. Koundakjian2, Herson Quinones3, Chathurani S. Jayasena1, Lisa V. Goodrich2, Jane E. Johnson3, Neil Segil1,4,* and Andrew K. Groves1,4,*

1 Gonda Department of Cell and Molecular Biology, House Ear Institute, 2100 West 3rd Street, Los Angeles CA 90057, USA.
2 Department of Neurobiology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
3 Center for Basic Neuroscience, UT Southwestern Medical Center, Dallas, TX 75390, USA.
4 Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.


Figure 1
View larger version (78K):
[in this window]
[in a new window]

  		Fig. 1. Neurogenesis and hair cell production coincide in the otic epithelium. (A) Temporal-spatial relationships between neurogenesis (cyan) and sensory epithelial differentiation (beige). Activity levels are schematized in color above the time-line. Ut, utricle; Sac, saccule. (B) E11.5 otocyst (rotated from A) with NeuroD domain (cyan) and Math1 expression (beige hatching) highlighted. pUt, presumptive utricle; pSac, presumptive saccule. (C) Part of the early inner ear labyrinth at E13.5, defined by the red box, shown on same scale as B. Orientation and color codes are as in B. Math1 expression in the anterior and lateral cristae is shown in dark gray. (D) NeuroD (cyan) and Math1 (beige) epithelial expression domain areas versus developmental stage. (E) Epithelial NeuroD+ cell number versus developmental stage. (F) Alternating serial sections through the presumptive (E11.5) and definitive (E14.5) utricle, hybridized for NeuroD or Math1. Arrow indicates early Math1 expression. (G-J) Math1-GFP reporter tissue double-labeled with NeuroD antisense RNA (red) and anti-GFP antibody (green). In G, triple arrowheads and arrow indicate lateral and medial stripes of Math1-GFP, respectively, as illustrated in B. In H and I, arrowheads and bracket indicate spatial overlap of the two markers. Arrowheads in J indicate the border of Math1-GFP and NeuroD expression. Axes in F apply to F-J. Scale bars: 50 µm.

 

Figure 2
View larger version (120K):
[in this window]
[in a new window]

  		Fig. 2. Fate mapping identifies Ngn1 derivatives in the VIIIth ganglion and ear epithelium. (A-F) Structures from E16.5 (A) or E14.5 (B-F) Ngn1-CreER;Z/EG embryos, double-stained for transgenic GFP (green, Ngn1 derivatives) and myosin VIIa (red, sensory hair cells). ac, anterior crista; ger, greater epithelial ridge; lc, lateral crista; oC, organ of Corti, pc, posterior crista; poC, presumptive organ of Corti; sac. m., saccular macula; sp. g. spiral ganglion; ut. m. utricular macula; ut. non-sens, utricular non-sensory; vest. g., vestibular ganglion. Arrows in E and inset indicate Ngn1 derivatives in non-sensory tissue between the lateral crista and utricular macula. (G) Summary of Ngn1 derivatives in the ear. Gray areas represent sensory structures lacking Ngn1 derivatives. (H-K) Ngn1 derivative cell phenotypes (green) in sensory maculae. Red label is myosin VIIa in H,I and phalloidin in J. Arrowhead in I indicates a double-positive cell. In K, arrowheads indicate supporting cells; asterisks indicate hair cells.

 

Figure 3
View larger version (32K):
[in this window]
[in a new window]

  		Fig. 3. Ngn1 expression decreases over time in the prospective utricle. (A) E14.5 utricular macula schematized in the same orientation as the scatterplots in B and E-E''. A cross-section of the macula along the dotted line is represented at the bottom. The macula (region of myosin VIIa staining) is in gray. The active neurogenic region (Ng, region of Ngn1-GFP staining) is white. ut m-lc, non-sensory tissue between the utricular macula and lateral crista; ut m-sac m, non-sensory tissue between the utricular macula and saccular macula. (B) Distribution of GFP+ cells (blue crosses, cyan in image) from three E14.5 Ngn1-GFP BAC transgenic utricles, plotted on a normalized scale, defines the region of active neurogenesis. Gray area represents an averaged macular area (myosin VIIa +); the yellow area is non-sensory epithelium between the utricular macula and lateral crista. White arrow marks the lateral extent of the macula. (C) Number of Ngn1 derivatives in the Ngn1-CreER;Z/EG utricle versus time of first tamoxifen feeding for embryos sacrificed at E14.5. Each point is based on four or more ears from two or more litters. (D) Sections through utricular maculae, representing the change in the spatial distribution of Ngn1 derivatives (green) with different tamoxifen regimens. Downturned brackets indicate overlap between Ngn1 derivatives and myosin VIIa + hair cells. Upturned brackets indicate the region of active neurogenesis. White arrows indicate the lateral extent of the macula. Asterisk shows an Ngn1 derivative in non-sensory tissue between the utricular macula and lateral crista. (E-E''') Spatial distributions of Ngn1 derivatives from E14.5 utricles exposed to different tamoxifen administration regimens, as indicated at the top of each plot. (E) n=4 utricles; (E') n=6 utricles; (E'') n=14 utricles. Ngn1 derivative cell types and regions of the plot are coded as shown in E'''.

 

Figure 4
View larger version (103K):
[in this window]
[in a new window]

  		Fig. 4. Complementary phenotypes of Math1 and Ngn1 mutants. (A,B) Ectopic Ngn1 expression in the E13.5 wild-type and Math1-/- utricle. Axes apply to all images. (C) Ectopic Math1 expression in the E13.5 wild-type and Ngn1-/- utricle. (D-M) Expression of Ngn1-GFP transgene (cyan), myosin VIIa protein (red) and Math1 mRNA in wild-type, Math1 and Ngn1 mutant utricles at E14.5. Brackets in E,G indicate abnormal overlap of neural precursors and hair cells in heterozygotes. Arrowheads in K-M indicate macular expansion in Ngn1 mutants. (N) NeuroD+ epithelial cell numbers in utricle and saccule of Math1-/- and wild-type littermates over time. Asterisks denote significance at P<0.05. Points represent the mean and standard deviation of three ears from separate litters. (O) Utricular maculae of wild-type and Ngn1+/- littermates at E14.5, hybridized identically for Math1. Scale bars: 50 µm.

 

Figure 5
View larger version (57K):
[in this window]
[in a new window]

  		Fig. 5. Ngn1 negatively autoregulates and interacts with the Notch pathway. (A-D) Ngn1-GFP BAC transgene expression in a wild-type E10 otocyst (A), wild-type E12.5 utricle (B), Math1-/- E14.5 utricle (C) and Ngn1-/- E12.5 utricle (D). Arrowheads in A indicate delaminating cells with stronger GFP signal than their neighbors. (E,F) Dll1 expression in wild-type and Ngn1-/- otic epithelia at E11.5. pUt, presumptive utricle; pSac, presumptive saccule. (G,H) Ngn1 mRNA expression in wild-type and Pofut-/- embryos at E9. Insets show the invaginating otic epithelium. Arrowheads and arrows (insets) indicate Ngn1 mRNA signal in the otic epithelium, outlined with dotted white line. o, otic epithelium; mb, midbrain; t, trigeminal placode; ep, epibranchial placode; sp, spinal cord.

 

Figure 6
View larger version (84K):
[in this window]
[in a new window]

  		Fig. 6. Positive autoregulation of Math1 in the otic epithelium. (A,B) Math1-GFP BAC transgene expression in wild-type and Math1-/- ears and hindbrain regions (insets). (C,D) 1.4 kb Math1-GFP transgene expression in wild-type and Math1-/- ears and hindbrain regions. lc, lateral crista; ut, utricle; sac, saccule; hb, hindbrain. Scale bars: 100 µm.

 

Figure 7
View larger version (31K):
[in this window]
[in a new window]

  		Fig. 7. A model of the transition from neurogenesis to sensory hair cell formation. (A-A'') Tissue-level changes in Ngn1 expression (cyan), Math1 expression (beige hatching), and regions where Ngn1 expression has been extinguished (dark blue/gray) from E10.5-14.5. Light gray stripe at E11.5 represents Bmp4 expression, which marks the prospective anterior and lateral cristae. pUt, presumptive utricular macula; pSac, presumptive saccular macula; ut m, utricular macula; sac m, saccular macula; ac, anterior crista; lc, lateral crista. (B-B'') Changes in gene expression and behavior (delamination) on a cellular scale and over short periods (denoted by arrows) in the neurogenic region of the otocyst (B), presumptive maculae (B') and definitive maculae (B''). Shades of blue represent various intensities of Ngn1 expression (see key). Beige represents Math1+ cells. White represents cells expressing neither bHLH gene (sensory-restricted progenitors) that can differentiate as either hair or supporting cells. (C,C') Genetic interactions (black lines), gene functions (gray lines) and cell fate transformations (red lines) before (C) and after (C') the onset of Math1 expression. Dll1, delta-like 1; N, Notch receptor. Solid gray and black lines indicate cell-autonomous interactions or functions. Dotted gray and black lines indicate non-cell-autonomous interactions or functions. Solid and dotted lines between Ngn1 and Math1 indicate that either, or both, mechanisms might mediate cross-inhibition.

 

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati   Add to Twitter Twitter    What's this?



© The Company of Biologists Ltd 2007