Fig. 2. Renal phenotype of TgALK3^QD and TgALK3^QD/QD mice at E18.5 (A-F) and P10 (G-L) in representative 4 µm tissue sections. Sections in A-J are stained with Haematoxylin and Eosin. (A-F) E18.5. (A) The kidney of control mice is characterized by a well-differentiated cortex (C) and medulla (M). The box highlights the outer cortex. (B) Higher magnification view of the cortex in a control kidney. It is characterized by glomerular progenitors in the outer cortex and a mature glomerulus (G) in the deep cortex. (C) Higher magnification view of the medulla in a control kidney. It consists of a densely packed linear array of tubules. Note the lack of intervening mesenchyme. (D) The kidney of TgALK3^QD/QD mice is characterized by decreased density of immature glomeruli in the outer cortex, cortical cysts, a paucity of medullary collecting ducts in the medulla, a marked increase in mesenchyme in the medulla and medullary cysts. (E) Higher magnification view of the kidney cortex of a TgALK3^QD/QD mouse. Note the decreased density of glomerular progenitors in the outer cortex (compared with B) and the presence of a cyst (Cy). (F) Higher magnification view of the kidney medulla of a TgALK3^QD/QD mouse. Note the cystic dilatation of tubules, the decreased density of tubules and the increase in intervening mesenchyme. (G-L) P10. (G) The kidney of a control mouse is characterized by a well-developed cortex, medulla and papilla (P). (H) The kidney of a TgALK3^QD mouse is smaller in area. It exhibits fewer medullary tubules, has cysts in the cortex and medulla and has a smaller papilla. (I) The kidney of a TgALK3^QD/QD mouse is malformed by large cysts in the cortex and medulla. The outer cortex is compressed. The medulla contains few tubules and shows a large increase in intervening mesenchyme. (J) Higher power view of the renal medulla of a TgALK3^QD/QD mouse. Note the cystic tubules. Some are characterized by a cuboidal epithelium (Cy), whereas others have a squamous epithelium. The intertubular mesenchyme is increased and contains fibroblastic cells. (K,L) A medullary cyst in the kidney of a TgALK3^QD/QD mouse stained with DBA. (L) Positive staining indicates that the cyst epithelium is of ureteric bud origin.