Fig. 2. Loss of SPARC function results in embryonic lethality and compromised basal lamina stability. (A-H) A-D Wild-type embryos A-D and SPARC-mutant embryos (E-H) immunostained with anti-laminin (red) and anti-neurotactin (green) antibodies to highlight the developing central nervous system (CNS). (A) Lateral view of a late ES11 wild-type embryo shows that laminin accumulates along the mesoderm-neuroepithelium interface (arrowhead). (B) Laminin sheets form around the CNS and internal organs by ES13. (C) Thicker laminin sheets surround the CNS, body-wall muscles and the digestive tract by ES17. (D) A different confocal view of the embryo shown in C. Note that the entire VNC can be seen in a single confocal section. (E) Laminin is loosely associated with the VNC because spaces are observed between the deformed CNS and the discontinuous laminin sheet (arrow) at ES15. (F) The ventral view of an ES16 embryo shows fragmented laminin immunostaining around the VNC. (G) Laminin immunostaining around the CNS and other tissues is discontinuous at ES17 in the SPARC-mutant embryo. (H) A different confocal plane of the embryo in shown in G shows a distorted and uncondensed VNC. (I) Ventral view of an ES17 wild-type embryo immunostained with anti-perlecan antibodies (red) shows continuous perlecan distribution around the condensed VNC. Commissures of the VNC are highlighted by anti-CNS axons antibodies (green). Perlecan immunostaining around the ventral cord is continuous. (J) The ventral view of an ES17 SPARC-mutant embryo also shows continuous perlecan immunostaining around the VNC. (K) Lateral view of an ES16 deficiency embryo that lacks both collagen IV genes immunostained with laminin. Laminin distribution is also discontinuous around the VNC (green). (L) Lateral view of a SPARC-mutant embryo showing a complete absence of ventral and head cuticle. (M) Ventral view of SPARC-mutant embryonic cuticle highlighting cuticle holes along the ventral surface. All images of immunostains are single confocal sections.