Project description:Mice lacking the POU-domain transcription factor Brn3a exhibit marked defects in sensory axon growth and abnormal sensory apoptosis. We have determined the regulatory targets of Brn3a in the developing trigeminal ganglion using microarray analysis of Brn3a mutant mice. These results show that Brn3 mediates the coordinated expression of neurotransmitter systems, ion channels, structural components of axons and inter- and intracellular signaling systems. Loss of Brn3a also results in the ectopic expression of transcription factors normally detected in earlier developmental stages and in other areas of the nervous system. Target gene expression is normal in heterozygous mice, consistent with prior work showing that autoregulation by Brn3a results in gene dosage compensation. Detailed examination of the expression of several of these downstream genes reveals that the regulatory role of Brn3a in the trigeminal ganglion appears to be conserved in more posterior sensory ganglia but not in the CNS neurons that express this factor. Experiment Overall Design: Microarrays used to compare the patterns of gene expression in the trigeminal ganglia of Brn3a knockout and wild-type mice. Embryonic day 13.5 (E13.5) was chosen because at this point in development mutant mice exhibit major defects in sensory axon growth, but have yet to undergo the period of extensive sensory neuron death associated with later stages.
Project description:Mice lacking the POU-domain transcription factor Brn3a exhibit marked defects in sensory axon growth and abnormal sensory apoptosis. We have determined the regulatory targets of Brn3a in the developing trigeminal ganglion using microarray analysis of Brn3a mutant mice. These results show that Brn3 mediates the coordinated expression of neurotransmitter systems, ion channels, structural components of axons and inter- and intracellular signaling systems. Loss of Brn3a also results in the ectopic expression of transcription factors normally detected in earlier developmental stages and in other areas of the nervous system. Target gene expression is normal in heterozygous mice, consistent with prior work showing that autoregulation by Brn3a results in gene dosage compensation. Detailed examination of the expression of several of these downstream genes reveals that the regulatory role of Brn3a in the trigeminal ganglion appears to be conserved in more posterior sensory ganglia but not in the CNS neurons that express this factor. Keywords: Gene expression in the developing nervous system
Project description:General somatic sensation is conveyed to the central nervous system at cranial levels by the trigeminal ganglion (TG), and at spinal levels by the dorsal root ganglia (DRG). Although these ganglia have similar functions, they have distinct embryological origins, in that both contain neurons originating from the neural crest, while only the TG includes cells derived from the placodal ectoderm. Here we use microarray analysis of E13.5 embryos to demonstrate that the developing DRG and TG have very similar overall patterns of gene expression. In mice lacking the POU-domain transcription factor Brn3a the DRG and TG exhibit many common changes in downstream gene expression, but a subset of genes show increased expression only at cranial levels. Although silent in wild-type ganglia, the promoter regions of genes which are activated in the absence of Brn3a also exhibit increased histone H3-acetylation at levels similar to constitutively transcribed gene loci, and this H3-acetylation is tissue-specific for genes which are increased only in the TG. These results demonstrate that one developmental role of Brn3a is to repress potential differences in gene expression between sensory neurons generated at different axial levels, and to regulate a convergent program of developmental gene expression, in which functionally similar populations of neurons are generated from different embryological substrates. Experiment Overall Design: Microarrays used to compare the patterns of gene expression in the dorsal root ganglia and trigeminal ganglia of Brn3a knockout and wild-type mice. Embryonic day 13.5 (E13.5) was chosen because at this point in development mutant mice exhibit major defects in sensory axon growth, but have yet to undergo the period of extensive sensory neuron death associated with later stages.
Project description:General somatic sensation is conveyed to the central nervous system at cranial levels by the trigeminal ganglion (TG), and at spinal levels by the dorsal root ganglia (DRG). Although these ganglia have similar functions, they have distinct embryological origins, in that both contain neurons originating from the neural crest, while only the TG includes cells derived from the placodal ectoderm. Here we use microarray analysis of E13.5 embryos to demonstrate that the developing DRG and TG have very similar overall patterns of gene expression. In mice lacking the POU-domain transcription factor Brn3a the DRG and TG exhibit many common changes in downstream gene expression, but a subset of genes show increased expression only at cranial levels. Although silent in wild-type ganglia, the promoter regions of genes which are activated in the absence of Brn3a also exhibit increased histone H3-acetylation at levels similar to constitutively transcribed gene loci, and this H3-acetylation is tissue-specific for genes which are increased only in the TG. These results demonstrate that one developmental role of Brn3a is to repress potential differences in gene expression between sensory neurons generated at different axial levels, and to regulate a convergent program of developmental gene expression, in which functionally similar populations of neurons are generated from different embryological substrates. Keywords: Gene expression in the developing nervous system
Project description:In vitro generation of human peripheral sensory neurons may provide a framework for novel drug screening platforms and disease models of touch and pain. However, derivation of a functionally pure sensory neuron population remains a major unmet challenge. We discovered that, by expressing the transcription factors NGN2 and BRN3A, human pluripotent stem cells can be induced to differentiate into a surprisingly homogenous culture of cold- and mechano-sensing neurons. Although such a neuronal subtype has not been reported in mice, we found molecular evidence of its existence in adult human sensory ganglia. Combining NGN2 and BRN3A programming with neural crest patterning, we produced two additional populations of sensory neurons, including a more specialized mechanosensory neuron subtype. Finally, we applied this system to model a rare inherited sensory disorder, characterized by profound impairment of touch sensation and proprioception, caused by inactivating mutations in PIEZO2. Together these findings establish an approach to specify distinct sensory neuron subtypes in vitro, underscoring the utility of stem cell technology to capture human-specific features of physiology and disease.
Project description:In vitro generation of human peripheral sensory neurons may provide a framework for novel drug screening platforms and disease models of touch and pain. However, derivation of a functionally pure sensory neuron population remains a major unmet challenge. We discovered that, by expressing the transcription factors NGN2 and BRN3A, human pluripotent stem cells can be induced to differentiate into a surprisingly homogenous culture of cold- and mechano-sensing neurons. Although such a neuronal subtype has not been reported in mice, we found molecular evidence of its existence in adult human sensory ganglia. Combining NGN2 and BRN3A programming with neural crest patterning, we produced two additional populations of sensory neurons, including a more specialized mechanosensory neuron subtype. Finally, we applied this system to model a rare inherited sensory disorder, characterized by profound impairment of touch sensation and proprioception, caused by inactivating mutations in PIEZO2. Together these findings establish an approach to specify distinct sensory neuron subtypes in vitro, underscoring the utility of stem cell technology to capture human-specific features of physiology and disease.
Project description:Cervical cancer is the fourth most common cancer worldwide in females. This occurs primarily due to the infection of high-risk human papillomavirus (HPV) although in advanced stages it requires support from host cellular factors. BRN3A is one such host cellular factor that upregulates tumorigenic high-risk HPV expression. The expression of BRN3A in cervical cancer remains high where it enhances tumorigenicity. The effect of BRN3A on HPV-mediated cervical cancer and the underlying mechanism remains obscure. Thus, we have investigated the overall effect of BRN3A on genes associated with cancer-related different biological processes. In approach, we have altered the expression of BRN3A through overexpression and knockdown in cervical cancer cells following transcriptome profiling through next-generation RNA-sequencing. This study revealed a substantial change in the expression of several genes associated with cancer-promoting biological processes including viral processes, immune response, cell-death, cell-proliferation, and different signaling pathways, etc. Additionally, promoter analysis through in silico mode revealed that a total of 32.7% of genes possess BRN3A binding sites at their promoters. Physical interaction of BRN3A with IFITM1, OAS3, ISG15, BCL2L1, and HSP90AB1 genes was also confirmed. Thus, the present study identified molecular targets of BRN3A and provided new insight into the pathogenesis of cervical cancer. According to our knowledge, this is the first report on the effect on eukaryotic transcriptomes after over-expression and knocking down BRN3A.
Project description:The sense of taste starts with activation of receptor cells in taste buds by chemical stimuli which then communicate this signal via innervating oral sensory neurons to the CNS. The cell bodies of oral sensory neurons reside in the geniculate ganglion (GG) and nodose/petrosal/jugular ganglion. The geniculate ganglion contains two main neuronal populations, BRN3A+ somatosensory neurons that innervate the pinna, and PHOX2B+ sensory neurons that innervate the oral cavity. While much is known about the different taste bud cell subtypes, much less is known about the molecular identities of PHOX2B+ sensory subpopulations. In the GG as many as 12 different subpopulations have been predicted from electrophysiological studies, while transcriptional identities exist for only 3-6. Importantly, the cell fate pathways that diversify PHOX2B+ oral sensory neurons into these subpopulations are unknown. The transcription factor EGR4 was identified as being highly expressed in GG neurons. EGR4 deletion causes GG oral sensory neurons to lose their expression of PHOX2B and other oral sensory genes, and upregulate BRN3A. This is followed by a severe loss of chemosensory innervation of taste buds, a loss of Type II taste cells responsive to bitter, sweet, and umami stimuli, and a concomitant increase in Type I glial-like taste bud cells. These deficits culminate in a loss of nerve responses to sweet and umami taste qualities. Taken together, we identify a critical role of EGR4 in cell fate specification and maintenance of subpopulations of GG neurons, which in turn maintain the appropriate sweet and umami taste receptor cells.
Project description:Sensory neuron diversity is required for organisms to decipher complex environmental cues. In Drosophila, olfactory environment is detected by 50 different olfactory receptor neuron (ORN) classes that are clustered in combinations within distinct sensilla subtypes. Each sensilla subtype houses stereotypically clustered 1-4 ORN identities that arise through asymmetric divisions from a single multipotent sensory organ precursor (SOP). How each class of SOPs acquires a unique differentiation potential that accounts for ORN diversity is unknown. Previously, we reported a critical component of SOP diversification program, Rotund (Rn), which functions to increase ORN diversity by generating novel developmental trajectories from existing precursors within each independent sensilla type lineages. Here, we show that Rn, along with BarH1/H2, Bric-Ã -brac (Bab), Apterous (Ap) and Dachshund (Dac), constitute a functionally conserved transcription factor (TF) network, previously shown to pattern the segmentation of the leg, that patterns the developing olfactory tissue. Precursors with diverse ORN differentiation potentials are selected from concentric rings defined by unique combinations of these TFs along the proximodistal axis of the developing antennal disc. The combinatorial code that demarcates each precursor field is set up by cross-regulatory interactions among different factors within the network. Modifications of this network lead to predictable changes in the diversity of sensilla subtypes and ORN pools. In light of our data, we propose a molecular map that defines Time-course RNAseq across 4 developmental stages, inlcuding flies mutant for rotund gene (rn), heterozygotes and wildtype