Fig. 1.

SLC13A4 expression in the brain. (a) Slc13a4 is expressed in the placenta and brain. (b) Slc13a4 expression within all the four choroid plexuses (ChP) and the pia mater by ISH, choroid plexus of the lateral (i) and 4th ventricle (ii) shown in higher magnification. Sense probe negative control can be seen in Supplemental fig. S4d. (c) SLC13A4 protein expression in the basolateral membrane of ChP epithelium (i), but not in other cell types within the lateral ventricle (ii). (d) Isolated ChPs transfected with EGFP-SLC13A4 plasmid in vitro. Immunofluorescence for GFP (green), fused to SLC13A4, is complementary to ATP1A1 (red), a known marker for the apical membrane of ChP epithelium. (e) Five minutes following injection of 400 μCi ³⁵SO₄²⁻ into the tail vein, isolated Slc13a4^+/− brains contained significantly lower radioactive counts than Slc13a4^+/+ brains (each genotype n = 6, two-tailed t-test, Welch's correction, **P = .0022). Black scale bar = 100 μm, white scale bar = 20 μm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)