Current Biology . . . Lockley group and others used single-cell sequencing to reveal the development mechanism of olfactory neurons in fruit flies.

The function of neurons is determined by their physiological characteristics and neural connections, but the mechanism of transcriptional regulation to coordinate the two is still unclear.there are 50 kinds of olfactory receptor neurons (ORN) in Drosophila olfactory system.each ORN expresses one or a group of olfactory receptors, which determines the response to different olfactory stimuli.ORN sends olfactory signals to the olfactory bulb located in the brain through axons.in mice, olfactory receptors partially regulate neural connectivity specificity.however, Drosophila olfactory receptors do not regulate axonal localization, so how does the receptor expression coordinate with the specificity of neural connections? In recent years, single cell RNA sequencing (scrna SEQ) has been used to classify and identify different types and markers of neurons in the brain.in addition, single cell transcriptome can also promote the understanding of olfactory receptor expression and neural connection coordination mechanism.in 2017, Luo Liqun's team and Stephen R. quake's team (together as Li Hongjie and Felix horns) published an article on cell classifying drophila olfactory project neuron subtypes by single cell RNA It is the first time to apply this technology to the olfactory neurons of Drosophila.on February 13, 2020, Luo Liqun and Li Hongjie team continued to work with Stephen R. quake team (together as Li Hongjie and Li Tongchao) to publish an article in Current Biology Magazine single cell transcripts reveal different regulatory strategies for olfactory receptor expression and axon Targeting, using single cell sequencing, revealed that neurons coordinate receptor expression and neural connectivity through transcription factors in Drosophila olfactory receptor neurons.first, the researchers sequenced the olfactory receptor neurons (ORN) of Drosophila melanogaster, identified 33 different transcriptome clusters, and matched 20 of them to the corresponding olfactory bulb.this result also enriches our understanding of the cell in 2017. Only six types of olfactory projection neurons were decoded in the cell, while 20 olfactory receptor neuron types (more than 3 times) were decoded this time.secondly, researchers have solved a basic problem in neurobiology by using single cell transcriptome and genetic analysis: how neurons coordinate their physiological and neural connectivity characteristics, which are the two basic characteristics that determine the final function of neurons.Drosophila olfactory neurons are a good system to study this problem, because each ORN type must make two decisions: the olfactory receptor to express (to determine the physiological response characteristics) and axon targeting (to determine the neural connection).the mammalian olfactory system partly solves this problem by using olfactory receptors to regulate neural connectivity specificity, but in Drosophila, neural connectivity specificity is not dependent on olfactory receptors.through transcriptome sequencing, researchers have focused on some transcription factors (TF), and identified a variety of transcription strategies to coordinate Drosophila olfactory neurons: (1) the widely expressed TF only regulates the receptor expression of one type of ORN, and only regulates the neural connection specificity of another ORN type; (2) the specially expressed TF only regulates the receptor expression; (3) all the ORN expressing it The other type of TF regulates both receptor expression and neural junction specificity.this is the first time that a transcription factor has been found to regulate two basic characteristics of neurons simultaneously in olfactory system.in conclusion, this study used single cell transcriptome sequencing to analyze the physiological characteristics and neural connection characteristics of Drosophila olfactory neurons, and answered how Drosophila olfactory neurons coordinate receptor expression and neural connection, that is, transcription factors play a key regulatory role.this research provides a wealth of resources for the field of olfaction, and will expand our understanding of the development and function of brain neurons.Image Source: Eric Keller link: