Hi #fly folks! Are you looking for cell-type-specific drivers for your favorite cells in your research? Are you hunting for developmental driver lines to label your neurons across throughout development? Check out our latest work in Despaln lab - Thread
https://twitter.com/biorxivpreprint/status/1621864025217794052?s=20&t=WQHmAlQt2aGG2hy3wgGx3A
1/ Neuronal diversity is the hallmark of the nervous system. Neuronal types can be classified in various ways (morphology, electrical properties, transcriptomes). Ex: a recent study identified 28 cortical GABAergic interneuron types in the mouse visual cortex! PMID: 33186530 
2/ While we all know many cell types that exist, there is still a lack of systematic genetic tools to access and manipulate them in a cell-type-specific way.
3/ #Drosophila has served as a genetic model system for a century with lots of sophisticated genetic tools. Ex: thousands of enhancers (cis-regulatory modules) derived GAL4 drivers allow ectopic expression of transgenes in a tissue-specific way.
4/ The expression patterns of the enhancer-GAL4 lines (both GMR-GAL4 and VT-GAL4) have been documented so we can screen through the images to find tools labeling your cell type of interest. It's good but not good enough to achieve high cell-type-specificity.
5/ To improve labeling specificity, split-GAL4 system comes to the rescue! With the expression of GAL4DBD and GAL4AD domains under the control of different enhancers, only the overlapping cell population can express functional GAL4.
6/ Many enhancer-baesed GAL4 lines have been converting to split-GAL4 lines. However, it still requires significant time and resources to screen through various combinations of split-GAL4 to find the ideal one.
7/ Here, we combined some old tricks to create an exciting opportunity to make highly cell-type-specific split-GAL4 lines. To demonstrate our approach, we use fly visual system as a model, where we know neuronal morphology and transcriptomes of different cell types quite well!
8/ Here is how we make it in a nutshell. Find two genes that specifically label your cell type in scRNAseq dataset. Make gene-specific split-GAL4 lines instead of enhancer-based split-GAL4 lines to better recapitulate the expression of selected gene pair.
9/ Want to know how we find gene pairs? We present a user-friendly pipeline to help you find the gene pair for your cell type of interest using a scRNAseq dataset.
10/ What's the predictive power of gene-specific split-GAL4 lines in labeling targeted cell types? 100% so far. We always see predicted neurons labeled, although occasionally, there are additional cell types that might be labeled as well.
11/ Reveal the identity of unannotated clusters in scRNAseq dataset. No problem!
12/ Find novel cell types that have never been described before. You got it!
13/ Getting developmental drivers when the selected gene pairs are both expressed during development based on scRNAseq data? Yes, you can! Such highly cell-type-specific developmental drivers are gold treasures for every developmental neurobiologist!!
14/ Cost-efficient way to convert existing lines into gene-specific split-GAL4 lines? Yes, we are piggybacking a large collection of coding intronic MiMIC/CRIMIC lines for gene-specific split-GAL4 conversion.
15/ Limited funding to make the lines via embryo injection? We also made donor flies for in vivo swapping by genetic crosses. Good for Course-Based Undergraduate Research Experience (CURE)! Good for everyone since these lines are adaptable to every fly research by design!
16/ Check the paper out. It will change the way you find a cell-type-specific tool. Thanks to my excellent co-authors @ycchen_tw @raghuvanshi_98 @tederclik @lacinhaluk @ClaudeDesplan and my two amazing NYU undergrad mentees (Nathalie and Maisha). Get in touch for any feedback🙂
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