RESUMEN

Neural circuit assembly requires selection of specific cell fates, axonal trajectories, and synaptic targets. By analyzing the function of a secreted semaphorin, Sema-2b, in Drosophila olfactory receptor neuron (ORN) development, we identified multiple molecular and cellular mechanisms that link these events. Notch signaling limits Sema-2b expression to ventromedial ORN classes, within which Sema-2b cell-autonomously sensitizes ORN axons to external semaphorins. Central-brain-derived Sema-2a and Sema-2b attract Sema-2b-expressing axons to the ventromedial trajectory. In addition, Sema-2b/PlexB-mediated axon-axon interactions consolidate this trajectory choice and promote ventromedial axon-bundle formation. Selecting the correct developmental trajectory is ultimately essential for proper target choice. These findings demonstrate that Sema-2b couples ORN axon guidance to postsynaptic target neuron dendrite patterning well before the final target selection phase, and exemplify how a single guidance molecule can drive consecutive stages of neural circuit assembly with the help of sophisticated spatial and temporal regulation.

Asunto(s)

Axones/fisiología , Proteínas de Drosophila/genética , Neurópilo/citología , Vías Olfatorias/citología , Neuronas Receptoras Olfatorias/crecimiento & desarrollo , Semaforinas/genética , Animales , Animales Modificados Genéticamente , Drosophila , Proteínas de Drosophila/metabolismo , Regulación del Desarrollo de la Expresión Génica , Conos de Crecimiento/fisiología , Neurópilo/metabolismo , Bulbo Olfatorio/citología , Bulbo Olfatorio/metabolismo , Neuronas Receptoras Olfatorias/metabolismo , Señales de Clasificación de Proteína , Semaforinas/metabolismo

RESUMEN

Stem cell behavior is regulated by extrinsic signals from specialized microenvironments, or niches, and intrinsic factors required for execution of context-appropriate responses to niche signals. Here we show that function of the transcriptional regulator longitudinals lacking (lola) is required cell autonomously for germline stem cell and somatic cyst stem cell maintenance in the Drosophila testis. In addition, lola is also required for proper execution of key developmental transitions during male germ cell differentiation, including the switch from transit amplifying progenitor to spermatocyte growth and differentiation, as well as meiotic cell cycle progression and spermiogenesis. Different lola isoforms, each having unique C-termini and zinc finger domains, may control different aspects of proliferation and differentiation in the male germline and somatic cyst stem cell lineages.

Asunto(s)

Diferenciación Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citología , Drosophila melanogaster/genética , Espermatozoides/citología , Células Madre/citología , Testículo/citología , Factores de Transcripción/metabolismo , Animales , Diferenciación Celular/genética , División Celular , Linaje de la Célula/genética , Proteínas de Drosophila/genética , Regulación del Desarrollo de la Expresión Génica , Técnicas de Silenciamiento del Gen , Quinasas Janus/metabolismo , Masculino , Meiosis , Mutación/genética , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Interferencia de ARN , Factores de Transcripción STAT/metabolismo , Transducción de Señal , Espermatogénesis/genética , Espermatogonias/citología , Espermatogonias/metabolismo , Espermatozoides/metabolismo , Células Madre/metabolismo , Factores de Transcripción/genética , Factor de Crecimiento Transformador beta/metabolismo