Article

In vivo neuronal subtype-specific targets of Atoh1 (Math1) in dorsal spinal cord.

Department of Neuroscience, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA.
Journal of Neuroscience (Impact Factor: 6.75). 07/2011; 31(30):10859-71. DOI: 10.1523/JNEUROSCI.0445-11.2011
Source: PubMed

ABSTRACT Neural basic helix-loop-helix (bHLH) transcription factors are crucial in regulating the differentiation and neuronal subtype specification of neurons. Precisely how these transcription factors direct such processes is largely unknown due to the lack of bona fide targets in vivo. Genetic evidence suggests that bHLH factors have shared targets in their common differentiation role, but unique targets with respect to their distinct roles in neuronal subtype specification. However, whether neuronal subtype-specific targets exist remains an unsolved question. To address this question, we focused on Atoh1 (Math1), a bHLH transcription factor that specifies distinct neuronal subtypes of the proprioceptive pathway in mammals including the dI1 (dorsal interneuron 1) population of the developing spinal cord. We identified transcripts unique to the Atoh1-derived lineage using microarray analyses of specific bHLH-sorted populations from mouse. Chromatin immunoprecipitation-sequencing experiments followed by enhancer reporter analyses identified five direct neuronal subtype-specific targets of Atoh1 in vivo along with their Atoh1-responsive enhancers. These targets, Klf7, Rab15, Rassf4, Selm, and Smad7, have diverse functions that range from transcription factors to regulators of endocytosis and signaling pathways. Only Rab15 and Selm are expressed across several different Atoh1-specified neuronal subtypes including external granule cells (external granule cell layer) in the developing cerebellum, hair cells of the inner ear, and Merkel cells. Our work establishes on a molecular level that neuronal differentiation bHLH transcription factors have distinct lineage-specific targets.

0 Bookmarks
 · 
134 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The proper balance of excitatory and inhibitory neurons is crucial for normal processing of somatosensory information in the dorsal spinal cord. Two neural basic helix-loop-helix transcription factors (TFs), Ascl1 and Ptf1a, have contrasting functions in specifying these neurons. To understand how Ascl1 and Ptf1a function in this process, we identified their direct transcriptional targets genome-wide in the embryonic mouse neural tube using ChIP-Seq and RNA-Seq. We show that Ascl1 and Ptf1a directly regulate distinct homeodomain TFs that specify excitatory or inhibitory neuronal fates. In addition, Ascl1 directly regulates genes with roles in several steps of the neurogenic program, including Notch signaling, neuronal differentiation, axon guidance and synapse formation. By contrast, Ptf1a directly regulates genes encoding components of the neurotransmitter machinery in inhibitory neurons, and other later aspects of neural development distinct from those regulated by Ascl1. Moreover, Ptf1a represses the excitatory neuronal fate by directly repressing several targets of Ascl1. Ascl1 and Ptf1a bind sequences primarily enriched for a specific E-Box motif (CAGCTG) and for secondary motifs used by Sox, Rfx, Pou and homeodomain factors. Ptf1a also binds sequences uniquely enriched in the CAGATG E-box and in the binding motif for its co-factor Rbpj, providing two factors that influence the specificity of Ptf1a binding. The direct transcriptional targets identified for Ascl1 and Ptf1a provide a molecular understanding of how these DNA-binding proteins function in neuronal development, particularly as key regulators of homeodomain TFs required for neuronal subtype specification.
    Development 06/2014; · 6.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Atoh1 is a transcription factor that regulates neural development in multiple tissues and is conserved among species. Prior mouse models of Atoh1, though effective and important in the evolution of our understanding of the gene, have been limited by perinatal lethality. Here we describe a novel point mutation of Atoh1 (designated Atoh1(trhl) ) underlying a phenotype of trembling gait and hearing loss. Histology revealed inner ear hair cell loss and cerebellar atrophy. Auditory Brainstem Response (ABR) and Distortion Product Otoacoustic Emission (DPOAE) showed functional abnormalities in the ear. Normal lifespan and fecundity of Atoh1(trhl) mice provide a complementary model to facilitate elucidation of ATOH1 function in hearing,central nervous system and cancer biology.
    PLoS ONE 11/2013; 8(11):e79791. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Signaling networks controlled by Sonic hedgehog (SHH) and the transcription factor Atoh1 regulate the proliferation and differentiation of cerebellar granule neuron progenitors (GNPs). Deregulations in those developmental processes lead to medulloblastoma formation, the most common malignant brain tumor in childhood. Although the protein Atoh1 is a key factor during both cerebellar development and medulloblastoma formation, up-to-date detailed mechanisms underlying its function and regulation have remained poorly understood. Here, we report that SHH regulates Atoh1 stability by preventing its phosphodependent degradation by the E3 ubiquitin ligase Huwe1. Our results reveal that SHH and Atoh1 contribute to a positive autoregulatory loop promoting neuronal precursor expansion. Consequently, Huwe1 loss in mouse SHH medulloblastoma illustrates the disruption of this developmental mechanism in cancer. Hence, the crosstalk between SHH signaling and Atoh1 during cerebellar development highlights a collaborative network that could be further targeted in medulloblastoma.
    Developmental cell. 06/2014; 29(6):649-661.

Preview

Download
0 Downloads
Available from