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Ola Frang Wetten defended his thesis on November 11th 2011
Ane Gro Siri SkjelfjordMolecular studies of Atlantic cod (Gadus morhua) globin genes – functional effects of hemoglobin polymorphisms and their geographical distributions
Abstract from the thesis - PhD thesis 2011:56
Author: Ola Frang Wetten
The phenotypic variation among Atlantic cod hemoglobins and their physiological properties has been of great interest to researchers for several decades, and many cod stocks have been "genotyped" according to the HbI nomenclature established by Knud Sick in 1961, stating that the HbI-1 and HbI-2 variants are related to warm and cold waters, respectively. Paper I unambiguously connects the HbI phenotypes to the two haplotypic variants Met55-Lys62 and Val55-Ala62 of the polymorphic β1-globin gene. From three dimensional (3D) modeling of tetrametric α1β1α1β1 hemoglobin, we proposed that the polymorphisms at β1-55 and β1-62 are related to variable O2 affinity and variation in temperature sensitivity, respectively. To haplotype these loci efficiently, a High Resolution Melting (HRM) assay was developed (Paper IV). Multiple variants, including recombinations between the β1-55 and β1-62 loci, were identified in trans-Atlantic populations.
The intergenic promoter of the head-to-head organized α1-β1 genes were shown to display an indel polymorphism of 73 bp strongly linked to the β1-55 and β1-62 polymorphisms (Paper III). Comparison of transcriptional activity revealed that the longer β1-Val55-Ala62-linked promoter, mostly found in colder waters, generated twice the activity of the short one at temperatures of 15 and 20°C. The increased activity at elevated temperatures is suggested to be a compensatory mechanism to counterbalance the low O2 affinity at high temperatures of the β1-Val55-Ala62 haplotype by increasing the Hb-β1 concentration in erythrocytes.
Studies of the draft genome sequence of Atlantic cod showed that it harbors two unlinked globin clusters which host β5-α1-β1-α4 and β3-β4-α2-α3-β2, respectively (Paper II). Expression analyses confirmed that several of the genes are mainly expressed during embryo development, putatively serving immunological functions, whilst α1, α2, β1 and β2 contributed polypeptides constituting the adult hemoglobins. The clusters are flanked by genes conserved in other genome-sequenced teleosts, and some flanking genes are also found in extant urochordate and cephalochordate species, linked or not to globins, leading to speculations about the origin of the ancestral vertebrate globin cluster.
Oppdatert: 11.11.11
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