FB2026_03 , released September 17, 2026
CV Term Report
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General Information
Term transmedullary neuron Tm20 ID (Ontology) FBbt:00003808 (Fly Anatomy)
Definition Transmedullary neuron that has dendritic arborization in medulla layers M1-M3, as well as presynaptic sites in M8 (Fischbach and Dittrich, 1989; Gao et al., 2008). In the medulla, it spans just one column (Kind et al., 2021), and receives input from lamina monopolar neuron L3 (Takemura et al., 2013) and an R8 photoreceptor (Kind et al., 2021). Its axon follows the anterior edge of its cognate medulla column (Ting et al., 2014), then crosses the second optic chiasma and projects to lobula layer 5 (Fischbach and Dittrich, 1989; Gao et al., 2008). It provides input to the lobula intrinsic neuron Li4 via many synapses (Lin et al., 2016). It is a cholinergic neuron (Gao et al., 2008). There is usually one of these cells per optic column (Nern et al., 2025).[ FlyBase:FBrf0049410 FlyBase:FBrf0206213 FlyBase:FBrf0222324 FlyBase:FBrf0224196 FlyBase:FBrf0230403 FlyBase:FBrf0252485 FlyBase:FBrf0262545 ]
Also Known As"Tm20"
CommentConnectivity in the medulla based on EM (Takemura et al., 2013; Kind et al., 2021). Connectivity in the lobula was assessed by GRASP and double-labeling EM (Lin et al., 2016). Neurotransmitter was assessed using a cha-GAL4DBD driver (Gao et al., 2008).
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VFB:FBbt_00003808
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Data ClassFieldDirect annotations
Alleles (FBal)PHENOTYPE_MANIFEST_IN
Insertions (FBti)EXPRESSION_STAGE_TISSUE_POSITION
Insertions (FBti)PHENOTYPE_MANIFEST_IN
Constructs (FBtp)PHENOTYPE_MANIFEST_IN
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 transmedullary neuron Tm20 (all annotations which use CV term, excluding "NOT" statements)
     transmedullary neuron Tm20 | somatic clone
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transmedullary neuron
 |__narrow field transmedullary neuron_____
cholinergic neuron                         |
 |__adult cholinergic neuron_______________|
adult neuron                               |
 |__adult cholinergic neuron_______________|
secondary neuron                           |
 |__Notch ON hemilineage secondary neuron__|
Notch ON hemilineage neuron                |
 |__Notch ON hemilineage secondary neuron__|
optic lobe narrow field columnar neuron    |
 |__narrow field transmedullary neuron_____|
                                           transmedullary neuron Tm20  45 rec.
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Is a narrow field transmedullary neuron
Notch ON hemilineage secondary neuron
adult cholinergic neuron
Develops from immature transmedullary neuron Tm20
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FlyBrain_NDB:10145
VFB:FBbt_00003808