Using human iPSC-derived microglia to study the function of the human-specific nicotinic receptor subunit, CHRFAM7A, in vitro and in vivo

The CHRNA7 gene codes for the alpha 7 nicotine acetylcholine receptor (alpha7-nAChR) subunit, which plays an anti-inflammatory role in microglia. The alpha7-nAChR is also involved in the phagocytosis of amyloid beta (ABeta) oligomers, an early marker of Alzheimer’s Disease (AD). A human specific duplication of CHRNA7 led to the formation of a new gene; CHRFAM7A. The gene product of CHRFAM7A, dup-alpha7, codes for a truncated subunit and is thought to negatively modulate the functions of alpha7-nAChR. The aim of the project is to comprehend how dup-alpha7 expression modulates alpha7-nAChR mediated functions in human microglia. A CHRFAM7A-TdT lentivirus is used to overexpress CHRFAM7A in human induced pluripotent stem cells (hiPSC), which are subsequently differentiated via hematopoietic progenitor cells (HPC) into microglia-like (MGL) cells. In vitro, the effect of CHRFAM7A expression on the inflammatory response is assessed by exposing the MGL cells to liposaccharide (LPS) and ABeta oligomers. To translate these effects to in-vivo conditions, the hiPSC-derived HPC are transplanted into the mouse prefrontal cortex (PFC) in-utero (E17.5), and matured in-vivo into microglia. 1 month post transplantation (1MPT), we will inject an adeno-associated virus that carries a mutated amyloid precursor protein (APP), to trigger the pathological production of ABeta oligomers. This will allow us to study the effect of CHRFAM7A expression on the interaction of xenografted human microglia with ABeta oligomers in-vivo. This could give insights into the human specific response of microglia to pathological insults, and the understanding of the pathogenesis of AD.