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Thorsten B H Reusch

Publications and source records attributed to Thorsten B H Reusch.

5 recordsLinked to original sources
PubMed2004

Recent duplication and inter-locus gene conversion in major histocompatibility class II genes in a teleost, the three-spined stickleback.

Using a bacterial artificial chromosome (BAC) library, we analysed a 99.5 kb genomic segment containing the major histocompatibility class II genes of a teleost, the three-spined stickleback Gasterosteus aculeatus. Experiments with G. aculeatus have provided direct evidence for balancing selection by pathogens and mate choice driving MH class II beta polymorphism. Two sets of paralogous class II alpha genes and beta genes in a tandem arrangement were identified, designated Gaac-DAA/DAB and Gaac-DBA/DBB. Expression analysis of the beta genes using single-strand conformation polymorphism revealed that both gene copies are expressed. Based on an analysis of pairwise nucleotide polymorphisms, we estimate that the duplication into two paralogous class II loci occurred only 1.2-2.4 million years ago, 1-2 orders of magnitude more recently than in other fish, bird or mammalian species. At the 3'-direction of the classical MH loci, we identified another seven genes or gene fragments, two of which (small inducible cytokine, complement regulatory factor) are related to immune function in other vertebrates. None of these genes were associated with MH class II genes in zebrafish, suggesting a markedly different organisation of the MH class II region in sticklebacks, and presumably, across bony fishes. When the nucleotide substitution pattern of the novel class II beta genes was analysed together with a representative sequence sample isolated from fish in northern Germany (n=27), we found that the peptide binding region of the Gaac-DAB and Gaac-DBB loci had undergone an inter-locus gene conversion (P=0.007). In accordance, we found a 10- to 20-fold higher frequency of CpG-islands on the MH class II segment compared to other species, a feature that may be conducive for inter-locus recombination.

Amino Acid Sequence↗
PubMed2004

Major histocompatibility complex diversity influences parasite resistance and innate immunity in sticklebacks.

Proteins of the major histocompatibility complex (MHC) play a central role in the presentation of antigens to the adaptive immune system. The MHC also influences the odour-based choice of mates in humans and several animal taxa. It has recently been shown that female three-spined sticklebacks (Gasterosteus aculeatus) aim at a moderately high MHC diversity in their offspring when choosing a mate. Do they optimize the immune systems of their offspring? Using three-spined sticklebacks that varied in their individual numbers of MHC class IIB molecules, we tested, experimentally, whether allelic diversity at the MHC influences parasite resistance and immune parameters. We found that sticklebacks with low MHC diversity suffered more from parasite infection after experimental exposure to Schistocephalus solidus tapeworms and Glugea anomala microsporidians. They also showed the highest proportion of granulocytes and the strongest respiratory burst reaction, which are correlates of innate immunity. This indicates a strong activity of the innate immune system after challenge by parasites when MHC diversity is suboptimal. Individuals with very high allelic diversity at the MHC seemed inferior to those with moderately high diversity. Such a pattern is consistent with theoretical expectations of an optimal balance between the number of recognizable antigens and self-tolerance.

Alleles↗
PubMed2004

Parasites and individual major histocompatibility complex diversity--an optimal choice?

Overdominant selection or heterozygote advantage can partly explain the extraordinary polymorphism found at classical major histocompatibility complex (MHC) loci. However, several studies employing only single infectious agents often failed to detect it. Here, we review recent studies suggesting that due to the dominant nature of MHC-mediated resistance, a heterozygote advantage is most likely to be detected in multiple pathogen challenges.

Animals↗
PubMed2004

North Atlantic phylogeography and large-scale population differentiation of the seagrass Zostera marina L.

As the most widespread seagrass in temperate waters of the Northern Hemisphere, Zostera marina provides a unique opportunity to investigate the extent to which the historical legacy of the last glacial maximum (LGM18 000-10 000 years bp) is detectable in modern population genetic structure. We used sequences from the nuclear rDNA-internal transcribed spacer (ITS) and chloroplast matK-intron, and nine microsatellite loci to survey 49 populations (> 2000 individuals) from throughout the species' range. Minimal sequence variation between Pacific and Atlantic populations combined with biogeographical groupings derived from the microsatellite data, suggest that the trans-Arctic connection is currently open. The east Pacific and west Atlantic are more connected than either is to the east Atlantic. Allelic richness was almost two-fold higher in the Pacific. Populations from putative Atlantic refugia now represent the southern edges of the distribution and are not genetically diverse. Unexpectedly, the highest allelic diversity was observed in the North Sea-Wadden Sea-southwest Baltic region. Except for the Mediterranean and Black Seas, significant isolation-by-distance was found from ~150 to 5000 km. A transition from weak to strong isolation-by-distance occurred at ~150 km among northern European populations suggesting this scale as the natural limit for dispersal within the metapopulation. Links between historical and contemporary processes are discussed in terms of the projected effects of climate change on coastal marine plants. The identification of a high genetic diversity hotspot in Northern Europe provides a basis for restoration decisions.

Base Sequence↗