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Is there a common ancestor to the highly specialized ECM (extracellular matrix) protein genes
It has been reported that many of these highly
specialized ECM protein genes have evolved from a
common ancestor and they constitute the secretory calcium-
binding phosphoprotein (SCPP) gene family [Kawasaki
and Weiss, 2003]. Before their origin, the last
common ancestor of this gene family, SPARCL1 (secreted
protein, acidic, cysteine-rich like 1) arose from SPARC
(also called osteonectin) that also codes a major ECM
protein for both dentin and bone [Kawasaki et al., 2004;
Sanetra et al., 2005]. Many SCPP genes, involved in tissue
mineralization, have been identified in tetrapods and
teleost fish. However, in these two lineages, SCPP genes
arose independently by parallel gene duplication [Kawasaki
et al., 2005]. Later in tetrapods, SCPPs were co-opted
for milk caseins and salivary proteins in mammals, and
an eggshell matrix protein in birds. All these descendants
are also involved in some sort of mineralization: milk caseins
help infants to grow teeth and bone, salivary SCPPs
maintain enamel integrity, and the eggshell SCPP organizes
calcification of the shell [Kawasaki and Weiss,
2006]. Here we describe the duplication histories of the
SPARC , SPARCL1 , and SCPP genes, and discuss possible
scenarios linking these genes and skeletal mineralization.
Sources:
- Molecular Evolution and Genetic Defects of Teeth, Cells Tissues Organs, 2007