Abstract
Purpose:
Retinal microglia comprise a heterogeneous population of cells, believed to be of hemangioblastic mesodermal origin. Apart from being specialized immunocompetent cells, they are also implicated in vasculogenesis, angiogenesis and vascular remodelling. However their exact role in the retina remains ill-defined. In order to examine this further, we have constructed a genetic tool that allows genetic targeting of resident central nervous system microglia in mice.
Methods:
We have chosen the Aif1 gene (producing a protein known as Iba1), which is strongly expressed by resident, retinal macrophages (confirmed by immunohistochemistry). A bacterial artificial chromosomes (BAC), containing the Aif1 gene was obtained and a construct coding for a tamoxifen inducible form of Cre (CreERT2) was recombined into the open reading frame of the Aif1 gene. The modified BAC was then used for transgenesis by pronuclear injections and resulting offspring was screened for founders by PCR. In vivo recombination efficiency was tested in a ROSA-EGFP reporter strain (Gt(ROSA)26Sortm4(ACTB-tdTomato,-EGFP)Luo/J).
Results:
Two founders were obtained and a transgenic line was established from one of them (Aif1-CreER). ROSA-EGFP reporter mice showed that in perinatal retinas, recombination could be achieved in most resident microglia expressing Iba1. The brain, thymus and spleen also showed some positive cells with macrophage morphology
Conclusions:
Aif1-CreER is a valuable research tool to manipulate genes in resident microglia of postnatal mice at specific time-points.
Keywords: 595 microglia •
740 transgenics/knock-outs •
688 retina