CSF1R protein is expressed exclusively in macrophages and their progenitors. The CSF1R-Fusion Red transgenic line has a reporter gene inserted into the 3-end of the mouse locus, in frame with the N-terminus of CSF1R and separated by a self-cleaving peptide. The upper images show a whole mount image of testis (left) and a section of lung (right). The lower panel is taken from the published report (Grabert et al) and is a series of whole mount images of freshly-isolated tissues. The analysis of this transgenic reporter as shown in these images demonstrated that CSF1R protein is indeed expressed only in macrophages and is absent from neurons and various epithelial cells (gut and kidney) where previous studies have claimed it may be expressed. This conclusion is important for understanding the phenotypic impact of Csf1r mutations in humans and experimental animals.
J Immunol. 2020 Dec 1;205(11):3154-3166. doi: 10.4049/jimmunol.2000835. Epub 2020 Nov 2