Abstract
We have examined the process by which cell diversity is generated in neuroblast (NB) lineages in the central nervous system of Drosophila melanogaster. Thoracic NB6-4 (NB6-4t) generates both neurons and glial cells, whereas NB6-4a generates only glial cells in abdominal segments. This is attributed to an asymmetric first division of NB6-4t, localizing prospero (pros) and glial cell missing (gcm) only to the glial precursor cell, and a symmetric division of NB6-4a, where both daughter cells express pros and gcm. Here we show that the NB6-4t lineage represents the ground state, which does not require the input of any homeotic gene, whereas the NB6-4a lineage is specified by the homeotic genes abd-A and Abd-B. They specify the NB6-4a lineage by down-regulating levels of the G1 cyclin, DmCycE (CycE). CycE, which is asymmetrically expressed after the first division of NB6-4t, functions upstream of pros and gcm to specify the neuronal sublineage. Loss of CycE function causes homeotic transformation of NB6-4t to NB6-4a, whereas ectopic CycE induces reverse transformations. However, other components of the cell cycle seem to have a minor role in this process, suggesting a critical role for CycE in regulating cell fate in segment-specific neural lineages.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Cell Differentiation / genetics*
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Cell Lineage / genetics*
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Central Nervous System / cytology
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Central Nervous System / embryology*
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Central Nervous System / metabolism
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Cyclin E / genetics
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Cyclin E / metabolism*
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DNA-Binding Proteins
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Down-Regulation / physiology
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Drosophila Proteins / genetics
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Drosophila Proteins / metabolism
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Drosophila melanogaster / embryology*
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Drosophila melanogaster / genetics
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Drosophila melanogaster / metabolism
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Ganglia, Invertebrate / cytology
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Ganglia, Invertebrate / metabolism
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Gene Expression Regulation, Developmental / physiology
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Genes, Homeobox / physiology
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Homeodomain Proteins / genetics
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Homeodomain Proteins / metabolism
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Nerve Tissue Proteins / genetics
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Nerve Tissue Proteins / metabolism
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Neuroglia / cytology
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Neuroglia / metabolism
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Neurons / cytology
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Neurons / metabolism
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Neuropeptides / genetics
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Neuropeptides / metabolism
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism
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Stem Cells / cytology
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Stem Cells / metabolism*
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Trans-Activators / genetics
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Trans-Activators / metabolism
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Transcription Factors / genetics
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Transcription Factors / metabolism
Substances
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Abd-B proteins, Drosophila
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Cyclin E
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DNA-Binding Proteins
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Drosophila Proteins
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GCM protein, Drosophila
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Homeodomain Proteins
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Nerve Tissue Proteins
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Neuropeptides
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Nuclear Proteins
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Trans-Activators
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Transcription Factors
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pros protein, Drosophila
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abd-A protein, Drosophila