Cellular and Molecular Life Sciences

, Volume 67, Issue 18, pp 3089–3099

The role of bHLH genes in ear development and evolution: revisiting a 10-year-old hypothesis

  • Bernd Fritzsch
  • Daniel F. Eberl
  • Kirk W. Beisel
Review

Abstract

In mouse ear development, two bHLH genes, Atoh1 and Neurog1, are essential for hair cell and sensory neuron differentiation. Evolution converted the original simple atonal-dependent neurosensory cell formation program of diploblasts into the derived developmental program of vertebrates that generates two neurosensory cell types, the sensory neuron and the sensory hair cell. This transformation was achieved through gene multiplication in ancestral triploblasts resulting in the expansion of the atonalbHLH gene family. Novel genes of the Neurogenin and NeuroD families are upregulated prior to the expression of Atoh1. Recent data suggest that NeuroD and Neurogenin were lost or their function in neuronal specification reduced in flies, thus changing our perception of the evolution of these genes. This sequence of expression changes was accompanied by modification of the E-box binding sites of these genes to regulate different downstream genes and to form inhibitory loops among each other, thus fine-tuning expression transitions.

Keywords

bHLH genes Neurosensory development Neurosensory evolution Ear development Hair cells 

Copyright information

© Springer Basel AG 2010

Authors and Affiliations

  • Bernd Fritzsch
    • 1
  • Daniel F. Eberl
    • 1
  • Kirk W. Beisel
    • 2
  1. 1.Department of Biology, College of Liberal Arts and SciencesUniversity of IowaIowa CityUSA
  2. 2.Department of Biomedical SciencesCreighton UniversityOmahaUSA

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