Fig 2: The Ostf1 LacZ/LacZ mouse is a knockout with β-galactosidase activity reflecting levels of Ostf1 expression. a Gene knockout strategy: out of 10 exons (blue boxes), exons 3 and 4 are replaced by a LacZ Neo cassette (red). b Western blotting to detect endogenous OSTF1 in different tissues. OSTF1 protein expression is observed in wild-type kidney, liver, cortex and spine, but absent in Ostf1 LacZ/LacZ tissues. β-galactosidase (LacZ) protein expression is only detected in Ostf1 LacZ/LacZ tissues. β-actin was used as a loading control. c Expression of OSTF1 in lysates from MEFs derived from wild type (WT), Ostf1 +/LacZ and Ostf1 LacZ/LacZ mice. β-actin was used as a loading control

Fig 3: OSTF1 is expressed throughout the embryonic placenta and the umbilical cord. a Low magnification view of the placenta of an Ostf1 LacZ/LacZ embryo implanted in the uterine wall of its Ostf1 +/LacZ mother. b All tissues of embryonic origin express high levels of OSTF1, specially the spongiotrophoblast layer (Sp) and the labyrinth layer (Lab). The glycogen cells also express high levels of OSTF1 while less is found in the maternal decidua (Md) and none in the myometrium (Myo). There is high level of expression in the mesodermal cells of the yolk sac (Mes). c In the umbilical cord, there is high level of expression in the blood vessels (bv) but none in the gut. Scale bar a = 500 µm, scale bars in b, c = 100 µm

Fig 4: OSTF1 is highly expressed in the kidney. a Transverse section through adult kidney demonstrates that OSTF1 is expressed in the cortex (Ctx), Medulla (Med), blood vessels (Bv), calyx (Cx) and Ureter but not in the underlying adipose tissue. b In the cortical region, OSTF1 is found in the glomeruli (Gl) and the proximal convoluted tubules. c OSTF1 is expressed at varying levels in all tubules of the medulla. d Renal arteries express OSTF1 in the endothelium and underlying smooth muscle. e The ureter wall expresses OSTF1 in a mosaic of high expression patches surrounded by low expression. f Whole mount expression in the P0 kidney shows wide expression in the kidneys and ureter (arrowhead) but not the adrenal glands (*). g In the embryonic kidney, OSTF1 is exclusively confined to the developing capillary network. Scale bars = 100 µm

Fig 5: OSTF1 is expressed in the eye. a–d LacZ stained flat mounted retina indicate OSTF1 is scattered on the retina surface. b, c Isolectin-B4 staining (white in panel b, c) does not colocalise with OSTF1, suggesting that the retinal blood vessels (BV) do not express OSTF1. c, d OSTF1 is found concentrated, in the ganglia cell layer, around cells with large nuclei (stained with DAPI) and cytoplasm (arrow), presumably G1 cells. e In transverse section of the retina of an OSTF1LacZ/LacZ albino mouse, OSTF1 is found in the ganglia cell layer (GCL), the outer plexiform layer (OPL) and the retinal pigmented epithelium (RPE) but not the inner plexiform layer (IPL), inner nuclear layer (INL), outer nuclear layer (ONL), inner (IS) and outer segments (OS) of the photoreceptors, choroid and sclera. f Muller glial cells (arrow) express OSTF1. g The outer cells of the cornea express OSTF1. h, i In the embryo and P6 pup, OSTF1 is found in the capillary network (arrows) and can be counterstained with isolectin B4 (white in panel i). All scale bars = 50 µm