Zebrafish IGF genes: gene duplication, conservation and divergence, and novel roles in midline and notochord development.
Insulin-like growth factors (IGFs) are key regulators of development, growth, and longevity.In most vertebrate species including humans, there is one IGF-1 gene and one IGF-2 gene.Here we report the identification and functional characterization of 4 distinct IGF genes (termed as igf-1a, -1b, -2a, and -2b) in zebrafish.These genes encode 4 structur