An evolutionarily ancient mechanism for regulation of hemoglobin expression in vertebrate red cells.

The oxygen transport function of hemoglobin (HB) is thought to have arisen ∼500 million years ago, roughly coinciding with the divergence between jawless (Agnatha) and jawed (Gnathostomata) vertebrates. Intriguingly, extant HBs of jawless and jawed vertebrates were shown to have evolved twice, and independently, from different ancestral globin proteins. This raises the question of whether erythroid-specific expression of HB also evolved twice independently. In all jawed vertebrates studied to date, one of the HB gene clusters is linked to the widely expressed NPRL3 gene. Here we show that the nprl3-linked hb locus of a jawless vertebrate, the river lamprey (Lampetra fluviatilis), shares a range of structural and functional properties with the equivalent jawed vertebrate HB locus. Functional analysis demonstrates that an erythroid-specific enhancer is located in intron 7 of lamprey nprl3, which corresponds to the NPRL3 intron 7 MCS-R1 enhancer of jawed vertebrates. Collectively, our findings signify the presence of an nprl3-linked multiglobin gene locus, which contains a remote enhancer that drives globin expression in erythroid cells, before the divergence of jawless and jawed vertebrates. Different globin genes from this ancestral cluster evolved in the current NPRL3-linked HB genes in jawless and jawed vertebrates. This provides an explanation of the enigma of how, in different species, globin genes linked to the same adjacent gene could undergo convergent evolution.

Genetic effects of supportive stockings on native pikeperch populations in boreal lakes--cases, three different outcomes.

The genetic consequences and gene flow of pikeperch (Sander lucioperca) stocking were assessed in three boreal lakes based on admixture model analysis and comparison of the pre- and post-release patterns of genetic variability at 9 DNA microsatellite loci in the recipient populations. In two out of the three cases, the releases of fish from foreign populations caused significant changes in the genetic structure of the recipient population. The largest changes were observed in Lake Oulujärvi, where the post-release sample was almost identical to the released Lake Vanajanselkä population, and about 90% of the catch was composed of the released population. The genetic composition of Lake Lohjanjärvi pikeperch also shifted markedly towards that of the released Lake Vanajanselkä population, and about half of the later catch was of released Vanajanselkä origin. In Lake Vanajanselkä, in contrast, releases of pikeperch from lakes Painio and Averia had only a small impact on the genetic structure of the pikeperch population. These results indicate that the current stocking practices create an effective artificial gene flow that may strongly shape and reduce the genetic differentiation among the remaining native pikeperch populations. A common feature of all three cases was the lack of prior appraisal of the potential genetic and ecological risks in relation to the expected benefits of the release programmes.

Coastal and freshwater pikeperch (Sander lucioperca) populations differ genetically in the Baltic Sea basin.

Microsatellite DNA based analysis of the pattern of genetic diversity among three coastal and five freshwater populations of pikeperch Sander lucioperca in the northern part of the Baltic Sea drainage basin indicated marked genetic differentiation between the coastal and lake populations. The F(st) between these population groups was as high as 0.25 and R(st) =0.32. In general, the lake populations showed higher genetic diversity than the coastal ones. In terms of genetic distance, the three coastal populations (Vanhankaupunginlahti, Västanfjärd and Taivassalo) grouped tightly together. The freshwater samples formed a looser group, in which the northern Lake Kemijärvi showed greater distance from the southern lakes than these did from each other. The two lake populations originally established through stockings (Lakes Painio and Averia) grouped near to their source population of Lake Lohjanjärvi and their diversity level was nearly the same. Safeguarding the unique Baltic coastal populations of S. lucioperca against gene flow from increasing hatchery releases using freshwater S. lucioperca should be a high management priority.