Project description:Several transcription factors are known to be expressed in discrete regions of the otic vesicle and Dlx5 is one of those that is expressed highly in the presumptive dorsal vestibular region. Mice lacking Dlx5 have vestibular defects. Specifically, they fail to form the endolymphatic duct (a defect visible as early as E10) as well as the anterior and posterior semi-circular canals. The lateral canal does form but is smaller, whereas the saccule, the utricle and the cochlea appear relatively normal. The goal of this study was to use microarrays to identify differentially expressed genes between wild-type and Dlx5-null otic vesicles microdissected from E10 and 10.5 and identify downstream targets of Dlx5 by searching the immediate 3kb promoter regions of the differentially expressed genes for homeodomain binding sites followed by chromatin immunoprecipitation in an otic vesicle-derived cell line over-expressing Dlx5. Normal vestibular morphogenesis is compromised in mice lacking Dlx5, a member of the Distal-less family of homeobox transcription factors. We identified its direct downstream targets in the developing mouse inner ear by gene expression profiling wild-type and Dlx5 null otic vesicles from embryonic stages E10 and E10.5. Four hundred genes were differentially expressed in mutants when compared to wild-type in at least one of the two stages. To further constrain the list of likely direct targets of Dlx5, we examined the genomic DNA sequences in the 3kb promoter regions immediately proximal to the transcriptional start sites of these genes. We searched for (i) one or more previously described binding site for Dlx5, (ii) one or more novel 12bp-long motifs with a canonical homeodomain response element (HDRE) shared by promoters of two or more genes, and (iii) 100% conservation of the 12bp-long HDRE-containing motifs in promoter regions of human orthologs. Forty genes passed one or more of these filters, 12 of which are known to be expressed in the developing otic vesicle in domains that at least partially overlap with that of Dlx5 in one or both stages that we examined. Chromatin immunoprecipitation using a Dlx5 antibody confirmed direct binding of Dlx5 to promoter regions of seven of these genes (Atbf1, Bmper, Large, Lrrtm1, and Msx1, all of which were down-regulated in mutants, and Ebf1 and Lhx1, both of which were up-regulated in mutants) in an otic vesicle-derived cell line over-expressing Dlx5. Gene expression profiling of this cell line showed that Bmper and Lrrtm1 transcripts were up-regulated, further supporting their identification as direct targets of Dlx5 activity. Otic vesicles from wild-type and Dlx5-null embryos were microdissected from mouse developmental stages E10 and E10.5 and expression profiled in duplicate for each stage and genotype. Dlx5-transfected and empty vector-transfected 2B1 cell line samples were also profiled in duplicate (independent cell cultures).
Project description:Several transcription factors are known to be expressed in discrete regions of the otic vesicle and Dlx5 is one of those that is expressed highly in the presumptive dorsal vestibular region. Mice lacking Dlx5 have vestibular defects. Specifically, they fail to form the endolymphatic duct (a defect visible as early as E10) as well as the anterior and posterior semi-circular canals. The lateral canal does form but is smaller, whereas the saccule, the utricle and the cochlea appear relatively normal. The goal of this study was to use microarrays to identify differentially expressed genes between wild-type and Dlx5-null otic vesicles microdissected from E10 and 10.5 and identify downstream targets of Dlx5 by searching the immediate 3kb promoter regions of the differentially expressed genes for homeodomain binding sites followed by chromatin immunoprecipitation in an otic vesicle-derived cell line over-expressing Dlx5. Normal vestibular morphogenesis is compromised in mice lacking Dlx5, a member of the Distal-less family of homeobox transcription factors. We identified its direct downstream targets in the developing mouse inner ear by gene expression profiling wild-type and Dlx5 null otic vesicles from embryonic stages E10 and E10.5. Four hundred genes were differentially expressed in mutants when compared to wild-type in at least one of the two stages. To further constrain the list of likely direct targets of Dlx5, we examined the genomic DNA sequences in the 3kb promoter regions immediately proximal to the transcriptional start sites of these genes. We searched for (i) one or more previously described binding site for Dlx5, (ii) one or more novel 12bp-long motifs with a canonical homeodomain response element (HDRE) shared by promoters of two or more genes, and (iii) 100% conservation of the 12bp-long HDRE-containing motifs in promoter regions of human orthologs. Forty genes passed one or more of these filters, 12 of which are known to be expressed in the developing otic vesicle in domains that at least partially overlap with that of Dlx5 in one or both stages that we examined. Chromatin immunoprecipitation using a Dlx5 antibody confirmed direct binding of Dlx5 to promoter regions of seven of these genes (Atbf1, Bmper, Large, Lrrtm1, and Msx1, all of which were down-regulated in mutants, and Ebf1 and Lhx1, both of which were up-regulated in mutants) in an otic vesicle-derived cell line over-expressing Dlx5. Gene expression profiling of this cell line showed that Bmper and Lrrtm1 transcripts were up-regulated, further supporting their identification as direct targets of Dlx5 activity.
Project description:The otic placode, from which the inner ear develops, initially forms as a thickened ectodermal patch adjacent to the dorsolateral hindbrain. Induction of otic placodal cells from human pluripotent stem cells (hPSCs) provides a robust approach to investigation of otic development. However, attempts to recapitulate otic lineage specification from hPSCs by stepwise differentiation methods have had limited success. One possible reason is that the role of signaling pathways in otic cell differentiation is not fully understood. Here, we developed a novel differentiation system involving use of suspension culture (3D floating culture) in combination with signaling factors for generating otic placodal cells via stepwise differentiation of hPSCs. We demonstrate that hPSC-derived pre-placodal cells acquired the potential to differentiate into posterior placodal cells after fibroblast growth factor 2 (FGF2) and retinoic acid (RA) treatment. Subsequent activation of WNT signaling following posterior placode specification induced differentiation of SIX1+/PAX8+/SOX2+ otic placodal cells. qPCR analysis showed that WNT activation increased expression of otocyst markers, including PAX8, PAX2, DLX5 and FBXO2. Moreover, induced otic cells exhibited similar gene expression patterns to the ventral and medial portions of the otocyst that give rise to the sensory epithelium of the inner ear. Collectively, our results indicate a critical role for FGF2, RA, and WNT signaling for the in vitro differentiation of the otic cell lineage from hPSCs. Our new culture system paves the way for improved modeling of early human inner ear development and will be of value to studies on the further differentiation of sensory epithelial cells.
Project description:The T-box transcription factor Tbx1 is expressed in the otic vesicle and surrounding periotic mesenchyme during inner ear development. Mesenchymal Tbx1 is essential for inner ear development, with conditional mutants displaying defects in both auditory and vestibular systems. We have previously identified reduced expression of retinoic acid metabolic genes in the periotic mesenchyme of mesoderm conditional Tbx1 mutants, using the T-Cre mouse line, implicating retinoic acid in mesenchymal-epithelial signaling downstream of Tbx1 in the periotic mesenchyme. In order to identify downstream effectors of mesenchymal-epithelial signaling downstream of mesenchymal Tbx1, we have utilized a gene profiling approach comparing embryonic day 11.5 otic vesicle tissue from T-Cre-mediated conditional Tbx1 mutants (Mest-KO) and conditional heterozygous control litter mates (control). E11.5 T-Cre-mediated conditional Tbx1 mutants (Mest-KO) and control (T-Cre conditional Tbx1 heterozygotes) embryos were microdissected to isolate the otic vesicle. Left and right ears from 3 embryos of the same genotype were pooled for each chip.
Project description:The inner ear arises from multipotent placodal precursors that are gradually committed to the otic fate and further differentiate into all inner ear cell types, with the exception of a few neural crest-derived cells. The otocyst has a pivotal role during inner ear development: otic progenitor cells sub-compartmentalize into non-sensory regions and regions giving rise to prosensory domains where subsequently also hair cells differentiate. The genes and pathways underlying this progressive subdivision and differentiation process are not entirely known. The goal of this study was to identify a comprehensive set of genes expressed in the chicken otocyst using the serial analysis of gene expression (SAGE) method. Our analysis revealed several hundred transcriptional regulators, potential signaling proteins, and receptors. We identified a substantial collection of genes that were previously known in the context of inner ear development, but we also found many new candidate genes, such as Sox4, Sox5, Sox7, Sox8, Sox11, and Sox18, which previously were not known to be expressed in the developing inner ear. Despite its obvious limitation of not being all-inclusive, the generated otocyst SAGE library is a practical bioinformatics tool to study otocyst gene expression and to identify candidate genes for developmental studies.
Project description:The T-box transcription factor Tbx1 is expressed in the otic vesicle and surrounding periotic mesenchyme during inner ear development. Mesenchymal Tbx1 is essential for inner ear development, with conditional mutants displaying defects in both auditory and vestibular systems. We have previously identified reduced expression of retinoic acid metabolic genes in the periotic mesenchyme of mesoderm conditional Tbx1 mutants, using the T-Cre mouse line, implicating retinoic acid in mesenchymal-epithelial signaling downstream of Tbx1 in the periotic mesenchyme. In order to identify downstream effectors of mesenchymal-epithelial signaling downstream of mesenchymal Tbx1, we have utilized a gene profiling approach comparing embryonic day 11.5 otic vesicle and surrounding periotic mesenchyme from T-Cre-mediated conditional Tbx1 mutants (Mest-KO) and conditional heterozygous control litter mates (control). This data was used in conjunction with OV-only data (GSE34064) to identify expression changes within the periotic mesenchyme. E11.5 T-Cre-mediated conditional Tbx1 mutants (Mest-KO) and control (T-Cre conditional Tbx1 heterozygotes) embryos were microdissected to isolate the otic vesicle and surrounding periotic mesenchyme. Left and right ears from 3 embryos of the same genotype were pooled for each chip, and 3 biological replicates of each chip were performed.
Project description:The inner ear arises from multipotent placodal precursors that are gradually committed to the otic fate and further differentiate into all inner ear cell types, with the exception of a few neural crest-derived cells. The otocyst has a pivotal role during inner ear development: otic progenitor cells sub-compartmentalize into non-sensory regions and regions giving rise to prosensory domains where subsequently also hair cells differentiate. The genes and pathways underlying this progressive subdivision and differentiation process are not entirely known. The goal of this study was to identify a comprehensive set of genes expressed in the chicken otocyst using the serial analysis of gene expression (SAGE) method. Our analysis revealed several hundred transcriptional regulators, potential signaling proteins, and receptors. We identified a substantial collection of genes that were previously known in the context of inner ear development, but we also found many new candidate genes, such as Sox4, Sox5, Sox7, Sox8, Sox11, and Sox18, which previously were not known to be expressed in the developing inner ear. Despite its obvious limitation of not being all-inclusive, the generated otocyst SAGE library is a practical bioinformatics tool to study otocyst gene expression and to identify candidate genes for developmental studies. Otocysts were dissected from HH stage 18-19 chicken embryos, total RNA was extracted, and subjected to a commercial long-SAGE protocol, resulting in a library of concatemerized tags. 3,512 individual clones of SAGE concatemers were sequenced resulting in 39,326 17-bp tags with tag counts up to 718 for the most abundant tag; 3,292 tags that were represented between two and five times, whereas the majority of tags (11,717) were only found once. Overall, we identified 16,008 unique sequence tags.
Project description:The T-box transcription factor Tbx1 is expressed in the otic vesicle and surrounding periotic mesenchyme during inner ear development. Mesenchymal Tbx1 is essential for inner ear development, with conditional mutants displaying defects in both auditory and vestibular systems. We have previously identified reduced expression of retinoic acid metabolic genes in the periotic mesenchyme of mesoderm conditional Tbx1 mutants, using the T-Cre mouse line, implicating retinoic acid in mesenchymal-epithelial signaling downstream of Tbx1 in the periotic mesenchyme. In order to identify downstream effectors of mesenchymal-epithelial signaling downstream of mesenchymal Tbx1, we have utilized a gene profiling approach comparing embryonic day 11.5 otic vesicle tissue from T-Cre-mediated conditional Tbx1 mutants (Mest-KO) and conditional heterozygous control litter mates (control).
Project description:The T-box transcription factor Tbx1 is expressed in the otic vesicle and surrounding periotic mesenchyme during inner ear development. Mesenchymal Tbx1 is essential for inner ear development, with conditional mutants displaying defects in both auditory and vestibular systems. We have previously identified reduced expression of retinoic acid metabolic genes in the periotic mesenchyme of mesoderm conditional Tbx1 mutants, using the T-Cre mouse line, implicating retinoic acid in mesenchymal-epithelial signaling downstream of Tbx1 in the periotic mesenchyme. In order to identify downstream effectors of mesenchymal-epithelial signaling downstream of mesenchymal Tbx1, we have utilized a gene profiling approach comparing embryonic day 12.5 periotic tissue from T-Cre-mediated conditional Tbx1 mutants (Mest-KO) and conditional heterozygous control litter mates (control). E12.5 T-Cre-mediated conditional Tbx1 mutants (Mest-KO) and control (T-Cre conditional Tbx1 heterozygotes) embryos were microdissected to isolate the otic vesicle and surrounding periotic mesenchyme. Left and right tissue from each individual embryo was pooled, and 5 control and 5 mutant embryos were analyzed on individual microarrays using Affymetrix Mouse Gene ST 1.0 chips.
Project description:The molecular characterization of early stages of human inner ear development is limited by the difficulty in accessing samples at early gestational stages. Some aspects of inner ear morphogenesis can be recapitulated using pluripotent stem cell directed differentiation in inner ear organoids (IEOs). Once validated and benchmarked, these models could provide a unique tool to complement and refine our understanding of human otic differentiation and could be used to model developmental defects.Here we provide a first characterization of early human embryonic otocyst development and compare the primary tissue to the iPSC-derived inner ear cell types. Multiplex immunostaining and single cell RNA sequencing were used to characterize human iPSC-derived IEOs at 3 key developmental steps, providing a new and unique signature of in vitro derived otic- placode, epithelium, neuroblasts and sensory epithelia. The expression and localization of key markers were further evaluated in human embryos. We show that the otic placode derived in vitro (day 8-12) matches marker expression of Carnegie Stage (CS) 11 embryos, and subsequently (day 20-40) gives rise to otic epithelia and neuroblasts comparable to the CS13 embryonic stage. Differentiation of sensory epithelia, including supporting cells and hair cells, starts in vitro at day 50-60 of culture. The maturity of these cells is equivalent to vestibular sensory epithelia at week 10 or cochlear tissue at week 12 of development, prior to functional onset. Taken together these data indicates that the current state of the art protocol enables the specification of bona fide otic tissue, supporting further application of IEOs to model inner ear biology and disease