Abstract
There is a continuing need for driver strains to enable cell-type-specific manipulation in the nervous system. Each cell type expresses a unique set of genes, and recapitulating expression of marker genes by BAC transgenesis or knock-in has generated useful transgenic mouse lines. However, since genes are often expressed in many cell types, many of these lines have relatively broad expression patterns. We report an alternative transgenic approach capturing distal enhancers for more focused expression. We identified an enhancer trap probe often producing restricted reporter expression and developed efficient enhancer trap screening with the PiggyBac transposon. We established more than 200 lines and found many lines that label small subsets of neurons in brain substructures, including known and novel cell types. Images and other information about each line are available online (enhancertrap.bio.brandeis.edu).
Highlights
The mammalian brain is likely comprised of thousands of distinct neuronal cell types
We found a construct containing the minimal HSP promoter most efficiently generated lines with specific expression patterns in brain (28.8%, see Table 1) and see supplemental note and Figure 1—figure supplement 2 for details of other constructs tried
We have developed a highly efficient method of enhancer trapping in the mouse and have used it to generate a resource of lines that allow targeting of a wide range of known and novel neuronal cell types
Summary
The mammalian brain is likely comprised of thousands of distinct neuronal cell types. Conditional transgenes like fluorescent reporters or alleles that sense or modify neuronal activity can be turned on in cells of interest through the use of ’driver’ strains selectively expressing Cre recombinase or the tet transactivator (Huang and Zeng, 2013; Luo et al, 2008). Selective expression patterns often depend both on elements within the proximal promoter, and on enhancers and other regulatory elements that can be located quite distally (Visel et al, 2009). Recapitulating endogenous expression requires either a knock-in approach (Taniguchi et al, 2011), or making transgenics from very large genomic fragments containing both the promoter and distal control elements (e.g. BAC transgenics (Gong et al, 2003; 2007; Yang et al, 1997)
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