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Gene Review

SPARC  -  secreted protein, acidic, cysteine-rich...

Gallus gallus

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Disease relevance of SPARC

  • To estimate the contribution of SPARC down-regulation to the major aspects of the transformed phenotype, we have reexpressed this protein from a self-replicating retrovirus Rcas, designated R-SPARC, in the transformed cultures [1].
  • Significant levels of SPARC transcripts were first observed within the ganglion cell layer (GCL) at E17 prior to accumulation of SPARC within the nerve fiber layer, seen first at E20 [2].

High impact information on SPARC


Biological context of SPARC

  • Chicken SPARC can be defined by four sequence signatures: (a) a conserved spacing of 11 cysteine residues in domain II, (b) the pentapeptide KKGHK in domain II, which is contained within a larger region of 31 identical residues, (c) a 100% conserved region of 10 residues in domain III, and (d) a C-terminal, calcium-binding EF-hand motif [4].
  • Taken together, these data strongly suggest that down-regulation of SPARC contributes to the transformed phenotype triggered by vSrc and vJun in primary avian fibroblasts, by facilitating in vivo tumorigenesis [1].

Anatomical context of SPARC

  • This situation is reminiscent of a situation previously reported with the tata-less, SPARC (secreted protein, acidic, and rich in cysteine) target promoter that regulates the expression of another extracellular matrix component in the same model of cell transformation [5].
  • In the adult retina SPARC was retained in the nerve fiber layer and present in the inner nuclear layer (INL) and outer nuclear layer (ONL), but lost from the IPL and OPL [2].
  • SPARC protein was first detected within the developing retinal pigment epithelium (RPE) at E10 and increased significantly at RPE cells ceased to proliferate and continued differentiating [2].
  • SPARC transcripts were first detected within the proliferating neural ectoderm at embryonic day 4 [2].

Analytical, diagnostic and therapeutic context of SPARC


  1. Down-regulation of the extracellular matrix protein SPARC in vSrc- and vJun-transformed chick embryo fibroblasts contributes to tumor formation in vivo. Vial, E., Castellazzi, M. Oncogene (2000) [Pubmed]
  2. Spatiotemporal distribution of SPARC/osteonectin in developing and mature chicken retina. Kim, S.Y., Ondhia, N., Vidgen, D., Malaval, L., Ringuette, M., Kalnins, V.I. Exp. Eye Res. (1997) [Pubmed]
  3. Expression of SPARC during development of the chicken chorioallantoic membrane: evidence for regulated proteolysis in vivo. Iruela-Arispe, M.L., Lane, T.F., Redmond, D., Reilly, M., Bolender, R.P., Kavanagh, T.J., Sage, E.H. Mol. Biol. Cell (1995) [Pubmed]
  4. Molecular analysis of chicken embryo SPARC (osteonectin). Bassuk, J.A., Iruela-Arispe, M.L., Lane, T.F., Benson, J.M., Berg, R.A., Sage, E.H. Eur. J. Biochem. (1993) [Pubmed]
  5. v-Jun downregulates the alpha 2 (I) collagen target gene indirectly through Sp1/3. Chamboredon, S., Castellazzi, M. Oncogene (2005) [Pubmed]
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