In utero electroporation alters microglia expression signatures throughout the embryonic brain. a E15.5 wild-type Iba1 and Cd45 expression show even distribution of Iba1+ cells throughout the brain parenchyma and Cd45high cells lining the periphery of the brain. Higher magnification images of E15.5 wild-type Iba1 and Cd45 expression in the embryonic hypothalamus (a’, a”) and cortex (a”’). b E15.5 pCIG2 IUE (E14.5) Iba1 and Cd45 expression show even distribution of Iba1+ cells throughout the brain parenchyma, while Cd45high cells are present both lining the ventricles in the brain parenchyma and surrounding the periphery of the brain. Higher magnification images of E15.5 pCIG2 IUE (E14.5) Iba1 and Cd45 expression in the embryonic hypothalamus (b’, b”) and cortex (b”’). c E15.5 wild-type Iba1 and P2ry12 expression shows even distribution of both Iba1+ and P2ry12+ cells throughout the brain parenchyma. Higher magnification images of E15.5 wild-type Iba1 and P2ry12 expression in the embryonic hypothalamus (c’, c”) and cortex (c”’). d E15.5 pCIG2 IUE (E14.5) brains highlight Iba1 and P2ry12 expression. Iba1+ cells are evenly distributed throughout the brain parenchyma, while P2ry12 expression is downregulated or absent. Higher magnification images of E15.5 pCIG2 IUE (E14.5) Iba1 and P2ry12 expression in the embryonic hypothalamus (d’, d”) and cortex (d”’). LV, lateral ventricle; 3V, third ventricle. Dashed lines outline the ventricles and mark the division between the thalamus and hypothalamus. White arrows mark Iba1+ single-positive (a”–a”’), Iba1+/Cd45high double-positive (b”–b”’), or Iba1+/P2ry12+ double-positive (c”, c”’, d”, d”’) cells, while white arrowheads mark Cd45high single-positive (b”–b”’), or Iba1+ single-positive (c”, d”, d”’) cells. Scale bar represents 250 μm (a–d”’)