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Abstract - Gene duplication and the evolution of vertebrate skeletal mineralization
The mineralized skeleton is a critical innovation that evolved
early in vertebrate history. The tissues found in dermal skeletons
of ancient vertebrates are similar to the dental tissues
of modern vertebrates; both consist of a highly mineralized
surface hard tissue, enamel or enameloid, more resilient
body dentin, and basal bone. Many proteins regulating mineralization
of these tissues are evolutionarily related and
form the secretory calcium-binding phosphoprotein (SCPP)
family. We hypothesize here the duplication histories
of SCPP genes and their common ancestors, SPARC and
SPARCL1 . At around the same time that Paleozoic jawless vertebrates
first evolved mineralized skeleton, SPARCL1 arose
from SPARC by whole genome duplication. Then both before
and after the split of ray-finned fish and lobe-finned fish,
tandem gene duplication created two types of SCPP genes,
each residing on the opposite side of SPARCL1 . One type was
subsequently used in surface tissue and the other in body
tissue. In tetrapods, these two types of SCPP genes were
separated by intrachromosomal rearrangement. While new
SCPP genes arose by duplication, some old genes were
eliminated from the genome. As a consequence, phenogenetic
drift occurred: while mineralized skeleton is maintained
by natural selection, the underlying genetic basis has
changed.
Keywords:
- Gene duplication
- Genome duplication
- Mineralized tissue
- Skeletal mineralization
- Vertebrate evolution
Sources:
- Molecular Evolution and Genetic Defects of Teeth, Cells Tissues Organs, 2007