Developmental anomalies of Xenopus embryos following microinjection of SPARC antibodies.

The function of SPARC (Secreted Protein, Acidic, Rich in Cysteine) in early embryonic development was assayed by microinjecting affinity-purified antibodies directed against SPARC into the blastocoel cavity of Xenopus embryos. Microinjection of SPARC antibodies did not appear to interfere with development until late neurulation. By hatching, a broad spectrum of external developmental anomalies were observable, including bent embryonic axes, accentuated ventral masses, shortened embryonic axes, and lack of visible eye pigment. Histological sections of injected embryos demonstrated that lack of visible eye pigmentation was often associated with deformities in eye development. Bending and shortening of the embryonic axis was associated with highly disorganized myotome patterns and loss of segmental boundaries. The results indicate a requirement for SPARC in the early morphological development of several tissues in Xenopus.