Proposed somatostatin receptor evolutionary scheme

Published in: Ocampo Daza D, Sundström G, Bergqvist CA, Larhammar D. The evolution of vertebrate somatostatin receptors and their gene regions involves extensive chromosomal rearrangements. BMC Evolutionary Biology 2012, 12:231 doi:10.1186/1471-2148-12-231. Please refer to this article if using this figure.

Figure 2 Proposed somatostatin receptor evolutionary scheme. Numbers denote
chromosome or linkage group assignments of SSTR genes in mapped genomes. Some of the
SSTR genes have not been mapped to chromosomes or linkage groups, which is indicated by
asterisks. Evolutionary scheme: Two ancestral vertebrate SSTR genes located on two
different chromosomes duplicated in 2R, generating the vertebrate SSTR gene repertoire of
SSTR1, -4 and -6, and SSTR2, -3 and -5 respectively. SSTR6 was lost from the lobe-finned
fish lineage some time after the divergence of the coelacanth, and SSTR4 was lost from the
ray-finned fish lineage some time before the divergence of the spotted gar. Following
chromosome fusions, the ancestral teleost SSTR2, -3 and -5 genes duplicated in 3R, while
only one gene for each of SSTR1 or -6 genes were conserved in some teleost lineages.
Subsequent chromosome rearrangements in teleost evolution moved SSTR genes to different
chromosomes. Data from neighboring genes families are consistent with these chromosome
rearrangements. Not all SSTR subtype genes could be identified in some teleost genomes
(Table 1). This could be either due to genuine gene losses, or perhaps due to the incomplete
nature of these genome databases.