Dynamic neurotransmitter specific transcription factor expression profiles during Drosophila development

Abstract

The remarkable diversity of neurons in the nervous system is generated during development, when properties such as cell morphology, receptor profiles and neurotransmitter identities are specified. In order to gain a greater understanding of neurotransmitter specification we profiled the transcription state of cholinergic, GABAergic and glutamatergic neurons in vivo at three developmental time points. We identified 86 differentially expressed transcription factors that are uniquely enriched, or uniquely depleted, in a specific neurotransmitter type. Some transcription factors show a similar profile across development, others only show enrichment or depletion at specific developmental stages. Profiling of Acj6 (cholinergic enriched) and Ets65A (cholinergic depleted) binding sites in vivo reveals that they both directly bind the ChAT locus, in addition to a wide spectrum of other key neuronal differentiation genes. We also show that cholinergic enriched transcription factors are expressed in mostly non-overlapping populations in the adult brain, implying the absence of combinatorial regulation of neurotransmitter fate in this context. Furthermore, our data underlines that, similar to Caenorhabditis elegans, there are no simple transcription factor codes for neurotransmitter type specification. This article has an associated First Person interview with the first author of the paper.

Decoding gene regulation in the fly brain

“…There are hundreds of cell types in the fly brain, impeding the use of bulk datasets for accurately deciphering diversity. Even more, compared to the embryo 58,[83][84][85][86][87] or imaginal discs 59,[88][89][90][91][92][93][94] , the number of ChIP-seq or other epigenomic datasets is very limited in the brain 24,[95][96][97] . In contrast, in this study we constructed 40 eGRNs at once, covering 88 transcription factors with 7833 enhancers that are linked to 3776 target genes.…”

“…One difference we observe is in neurotransmitter usage, where cell types from branch 4 and 5 tend to be non-cholinergic. One of the eGRNs that overlaps with these branches is Ets65A, a factor previously hypothesized to be involved in noncholinergic fate 24 . We further note a correlation with neuropils, with most Tm neurons of the medulla and the T-neurons of the lobula plate belonging to separate branches 73 .…”

“…This patterning of neural progenitors is presumed to give rise to the diverse cell types found in the adult brain. The combinatorial expression of transcription factors also governs key neuronal features by guiding dendritic targeting and neurotransmitter determination 2,[24][25][26][27] and changing expression of a single TF can lead to a change in neuronal fate 28,29 . Whereas transcriptomic studies in Drosophila have led to the inference of TFs and their putative target genes, they suffer from high false positive rates.…”

Patient-associated mutations inDrosophilaAlk perturb neuronal differentiation and promote survival

“…Fig. 2D), and we identified several other unique marker genes for each subtype (Ariss et al , 2020; Brunet Avalos et al , 2019; Cattenoz et al , 2016; Estacio-Gomez et al , 2020; Michki et al , 2021)(Suppl. Fig.…”

Constructing and Tuning Excitatory Cholinergic Synapses: The Multifaceted Functions of Nicotinic Acetylcholine Receptors in Drosophila Neural Development and Physiology

“…Although the temporal regulation of nAchR subunits is demonstrated for multiple subunits, the upstream transcription factors remain unclear. Nonetheless, certain regulators have been uncovered through various screens and phenotypic analyses, including Ttk88 and Eve, two transcriptional repressors, and Acj6, a transcription factor which binds to the Dα4 and ChAT promoters ( Estacio-Gomez et al, 2020 ). The Ttk88 consensus binding site AGGG C / T GG was identified in the Dβ2 gene, as well as several other neural-specific genes, including para and synapsin ( Dallman et al, 2004 ).…”