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2.
Neuron ; 103(5): 865-877.e7, 2019 09 04.
Artigo em Inglês | MEDLINE | ID: mdl-31300277

RESUMO

The ability of neurons to identify correct synaptic partners is fundamental to the proper assembly and function of neural circuits. Relative to other steps in circuit formation such as axon guidance, our knowledge of how synaptic partner selection is regulated is severely limited. Drosophila Dpr and DIP immunoglobulin superfamily (IgSF) cell-surface proteins bind heterophilically and are expressed in a complementary manner between synaptic partners in the visual system. Here, we show that in the lamina, DIP mis-expression is sufficient to promote synapse formation with Dpr-expressing neurons and that disrupting DIP function results in ectopic synapse formation. These findings indicate that DIP proteins promote synapses to form between specific cell types and that in their absence, neurons synapse with alternative partners. We propose that neurons have the capacity to synapse with a broad range of cell types and that synaptic specificity is achieved by establishing a preference for specific partners.


Assuntos
Proteínas de Drosophila/metabolismo , Imunoglobulinas/metabolismo , Proteínas de Membrana/metabolismo , Neurônios/metabolismo , Lobo Óptico de Animais não Mamíferos/metabolismo , Sinapses/metabolismo , Animais , Animais Geneticamente Modificados , Proteínas de Drosophila/genética , Drosophila melanogaster , Imunoglobulinas/genética , Proteínas de Membrana/genética , Neurônios/citologia , Lobo Óptico de Animais não Mamíferos/citologia , Mapas de Interação de Proteínas
3.
Development ; 145(3)2018 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-29361567

RESUMO

The assembly of functional neuronal circuits requires growth cones to extend in defined directions and recognize the correct synaptic partners. Homophilic adhesion between vertebrate Sidekick proteins promotes synapse formation between retinal neurons involved in visual motion detection. We show here that Drosophila Sidekick accumulates in specific synaptic layers of the developing motion detection circuit and is necessary for normal optomotor behavior. Sidekick is required in photoreceptors, but not in their target lamina neurons, to promote the alignment of lamina neurons into columns and subsequent sorting of photoreceptor axons into synaptic modules based on their precise spatial orientation. Sidekick is also localized to the dendrites of the direction-selective T4 and T5 cells, and is expressed in some of their presynaptic partners. In contrast to its vertebrate homologs, Sidekick is not essential for T4 and T5 to direct their dendrites to the appropriate layers or to receive synaptic contacts. These results illustrate a conserved requirement for Sidekick proteins in establishing visual motion detection circuits that is achieved through distinct cellular mechanisms in Drosophila and vertebrates.


Assuntos
Proteínas de Drosophila/fisiologia , Drosophila melanogaster/crescimento & desenvolvimento , Drosophila melanogaster/fisiologia , Proteínas do Olho/fisiologia , Percepção de Movimento/fisiologia , Moléculas de Adesão de Célula Nervosa/fisiologia , Células Fotorreceptoras de Invertebrados/fisiologia , Animais , Animais Geneticamente Modificados , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Proteínas do Olho/genética , Feminino , Genes de Insetos , Masculino , Mutação , Moléculas de Adesão de Célula Nervosa/genética , Células Fotorreceptoras de Invertebrados/citologia , Sinapses/metabolismo , Vias Visuais/citologia , Vias Visuais/crescimento & desenvolvimento , Vias Visuais/fisiologia
4.
J Neurogenet ; 28(3-4): 291-301, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24697410

RESUMO

Each neuropil module, or cartridge, in the fly's lamina has a fixed complement of cells. Of five types of monopolar cell interneurons, only L4 has collaterals that invade neighboring cartridges. In the proximal lamina, these collaterals form reciprocal synapses with both the L2 of their own cartridge and the L4 collateral branches from two other neighboring cartridges. During synaptogenesis, L4 collaterals strongly express the cell adhesion protein Kirre, a member of the irre cell recognition module (IRM) group of proteins ( Fischbach et al., 2009 , J Neurogenet, 23, 48-67). The authors show by mutant analysis and gene knockdown techniques that L4 neurons develop their lamina collaterals in the absence of this cell adhesion protein. Using electron microscopy (EM), the authors demonstrate, however, that without Kirre protein these L4 collaterals selectively form fewer synapses. The collaterals of L4 neurons of various genotypes reconstructed from serial-section EM revealed that the number of postsynaptic sites was dramatically reduced in the absence of Kirre, almost eliminating any synaptic input to L4 neurons. A significant reduction of presynaptic sites was also detected in kirre(0) mutants and gene knockdown flies using RNA interference. L4 neuron reciprocal synapses are thus almost eliminated. A presynaptic marker, Brp-short(GFP) confirmed these data using confocal microscopy. This study reveals that removing Kirre protein specifically disrupts the functional L4 synaptic network in the Drosophila lamina.


Assuntos
Proteínas de Drosophila/metabolismo , Proteínas de Membrana/metabolismo , Proteínas Musculares/metabolismo , Rede Nervosa/metabolismo , Neurônios/metabolismo , Lobo Óptico de Animais não Mamíferos/metabolismo , Sinapses/metabolismo , Animais , Animais Geneticamente Modificados , Drosophila , Proteínas de Drosophila/genética , Proteínas de Membrana/genética , Proteínas Musculares/genética , Rede Nervosa/citologia , Neurônios/citologia , Lobo Óptico de Animais não Mamíferos/citologia
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