Major Genomic Events and Their Consequences for Vertebrate Evolution and Endocrinology

Abstract

Comparative studies of proteins often face the problem of distinguishing a true orthologue (species homologue) from a paralogue (a gene duplicate). This identification task is particularly challenging for endocrine peptides and neuropeptides because they are short and usually have several invariant positions. For some peptide families, this has led to a terminology with peptide names relating to the first species where a specific peptide sequence was determined, such as chicken or salmon gonadotropin-releasing hormone, or names that highlight amino acid differences, e.g., Lys-vasopressin. With accumulating information from multiple species, such a terminology becomes almost impenetrable for nonexperts and difficult even for aficionados. The sequenced genomes offer a new way to distinguish orthologues and paralogues, namely by location of the genes relative to neighboring genes on the chromosomes. In addition, the genome databases can ideally provide a complete listing of the family members in each species. Many vertebrate gene families have expanded in the two basal tetraploidizations (2R) and the teleost fish third tetraploidization (3R), after which some vertebrate lineages have lost some of the duplicates. We review here some peptide families (neuropeptide Y, oxytocin-vasopressin, and somatostatin) where genomic information helps simplify nomenclature. This approach is useful also for other gene families, such as peptide receptors.

Neurohormones: oxytocin, vasopressin and related peptides – structure, genes, receptors, and evolution

“…A number of gene families in vertebrates have expanded in the two basal tetraploidizations (2R) and teleost fish third tetraploidization (3R), after which some vertebrate lineages lost some of the duplicates. The exact time points for the two tetraploidizations, relative to the divergence of the cyclostome lineages comprised by hagfishes and lampreys, will become more evident after obtaining more extensive sequence data from species representing these two lineages (Larhammar et al, 2009). The current results and evidence show that one tetraploidization took place before the cyclostome-gnathostome divergence and one tetraploidization happened after this in the gnathosome ancestor (Escriva et al, 2002;Stadler et al, 2004).…”

“…In recent studies, the sequenced genomes have made it possible to precisely indicate the orthologue and paralogue by location of the genes relative to neighbouring genes on the chromosomes (Larhammar et al, 2009). The obtained genome databases are able to provide a complete list of the individual family members in particular species.…”

“…It is relatively well established that all euteleosts share a common ancestor that underwent a third tetraploidization (3R). Sturgeons branched off before the teleost tetraploidization but seem to have undergone an independent third tetraploidization, followed by diploidization (Fontana et al, 2008;Larhammar et al, 2009). …”

“…Mesotocin and isotocin have one or two different amino acid residues different from oxytocin, respectively. New sequence data and sequences of the prepropeptides, make it possible to classify vasotocin as orthologous to vasopressin, while isotocin and vasotocin, as orthologous to oxytocin (Larhammar et al, 2009).…”

“…Many unknown sequences and evolutionary pathways have been resolved by the very important research results of the comparative study of the genes in the coelacanth Latimeria manadoensis and several tetrapods and teleost fishes by the outstanding research team of Vankatesh (Gwee et al, 2008(Gwee et al, , 2009Larhammar et al, 2009).…”