Limits...
Characterisation of a novel paralog of scavenger receptor class B member I (SCARB1) in Atlantic salmon (Salmo salar).

Sundvold H, Helgeland H, Baranski M, Omholt SW, Våge DI - BMC Genet. (2011)

Bottom Line: Red flesh colour is a unique trait found in some salmonid genera.A better understanding of the molecular mechanisms underlying the cellular uptake and deposition of carotenoids could potentially be used to improve the low muscle deposition rate that is typically found in farmed Atlantic salmon.A total of seven different SCARB1-2 alleles comprising repetitive enhancer of zeste motifs (EZH2) were identified in the founding parents of a resource Atlantic salmon population.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Integrative Genetics, Dept. of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, 1432 Aas, Norway. Hilde.Sundvold@oslo-universitetssykehus.no

ABSTRACT

Background: Red flesh colour is a unique trait found in some salmonid genera. Carotenoid pigments are not synthesized de novo in the fish, but are provided by dietary uptake. A better understanding of the molecular mechanisms underlying the cellular uptake and deposition of carotenoids could potentially be used to improve the low muscle deposition rate that is typically found in farmed Atlantic salmon. In addition, from an evolutionary point of view, the establishment and maintenance of this trait is still poorly understood. It has been demonstrated in several species that scavenger receptor class B, member 1 (SCARB1) is involved in intestinal absorption of carotenoids, which makes this gene a possible source of genetic variation in salmonid flesh pigmentation.

Results: In this study, a novel paralog of SCARB1 (SCARB1-2) was detected through screening for genetic variation in Atlantic salmon SCARB1. Full length SCARB1-2 encodes a protein with 89% identity to Atlantic salmon SCARB1, except for the C-terminal cytoplasmic tail that shows only 12% identity. The most prominent site of SCARB1 mRNA expression was in the mid gut, while a five-fold lower level was detected in Atlantic salmon skeletal muscle and liver. The SCARB1-2 mRNA was equally expressed in liver, muscle and mid gut, and at a lower level than SCARB1 mRNA. A total of seven different SCARB1-2 alleles comprising repetitive enhancer of zeste motifs (EZH2) were identified in the founding parents of a resource Atlantic salmon population. We mapped the SCARB1-2 paralog to a region on Atlantic salmon chromosome 1, containing a putative QTL for flesh colour. Addition of the SCARB1-2 marker increased the significance of this QTL, however the large confidence interval surrounding the QTL precludes confirmation of SCARB1-2 as a causative gene underlying variation in this trait.

Conclusion: We have characterised a novel paralog of SCARB1 (SCARB1-2), have mapped it to Atlantic salmon chromosome 1 and have described its expression in various tissues. Mapping with SCARB1-2 alleles added further evidence for a QTL affecting flesh colour on this chromosome, however further studies are needed to confirm a functional role for this gene in flesh colour pigmentation.

Show MeSH
Position of SCARB1-2 on the male and female chromosome 1 linkage maps. The relative position of SCARB1-2 on the male(M) and female(F) chromosome 1 linkage maps used in this study. Chr1-F1 and Chr1-F2 represent two unlinked segments in the female map.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3118963&req=5

Figure 2: Position of SCARB1-2 on the male and female chromosome 1 linkage maps. The relative position of SCARB1-2 on the male(M) and female(F) chromosome 1 linkage maps used in this study. Chr1-F1 and Chr1-F2 represent two unlinked segments in the female map.

Mentions: Genotyping of the six founding parents in the SALBANK population and the F2 progeny resulted in four amplifying alleles in the Bleke parents P11, P14 and P15 and three amplifying alleles in the commercial line parents P31, P34 and P35, ranging in size from 619 bp to 763 bp (table 2). Sequence-analysis revealed that the SCARB1-2 alleles comprise the zeste consensus motif [T/C]GAG[T/C][G/T]. The repetitive zeste-elements and their corresponding amplified alleles in the Bleke and the commercial Atlantic salmon parents are shown in table 2. Size determination of the SCARB1-2 alleles using fluorescently labelled oligonucleotides and capillary electrophoresis yielded no amplification products in parents P31, P34 and P35. These 'failed' amplifications were declared as '/' genotypes, and when combined with the genotype patterns observed in the F2 progeny, it was possible to infer F1 parent genotypes with alleles, and therefore Mendelian segregation in the F2 families. This strategy, however, meant that it was impossible to distinguish / genotypes from failed amplifications in F2 progeny. Nevertheless, based on high quality size standard profiles, and previous amplification success with other markers, / genotypes were inferred when no peaks were observed. SCARB1-2 mapped to chromosome 1 of the Atlantic salmon map [29] (Figure 2). Large differences in recombination rate were observed in the male and female maps, with the female map consisting of two unlinked segments (Chr1-F1 and Chr1-F2), while the male map had a higher level of recombination between marker OtsG83 and CL9726 than the female map.


Characterisation of a novel paralog of scavenger receptor class B member I (SCARB1) in Atlantic salmon (Salmo salar).

Sundvold H, Helgeland H, Baranski M, Omholt SW, Våge DI - BMC Genet. (2011)

Position of SCARB1-2 on the male and female chromosome 1 linkage maps. The relative position of SCARB1-2 on the male(M) and female(F) chromosome 1 linkage maps used in this study. Chr1-F1 and Chr1-F2 represent two unlinked segments in the female map.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3118963&req=5

Figure 2: Position of SCARB1-2 on the male and female chromosome 1 linkage maps. The relative position of SCARB1-2 on the male(M) and female(F) chromosome 1 linkage maps used in this study. Chr1-F1 and Chr1-F2 represent two unlinked segments in the female map.
Mentions: Genotyping of the six founding parents in the SALBANK population and the F2 progeny resulted in four amplifying alleles in the Bleke parents P11, P14 and P15 and three amplifying alleles in the commercial line parents P31, P34 and P35, ranging in size from 619 bp to 763 bp (table 2). Sequence-analysis revealed that the SCARB1-2 alleles comprise the zeste consensus motif [T/C]GAG[T/C][G/T]. The repetitive zeste-elements and their corresponding amplified alleles in the Bleke and the commercial Atlantic salmon parents are shown in table 2. Size determination of the SCARB1-2 alleles using fluorescently labelled oligonucleotides and capillary electrophoresis yielded no amplification products in parents P31, P34 and P35. These 'failed' amplifications were declared as '/' genotypes, and when combined with the genotype patterns observed in the F2 progeny, it was possible to infer F1 parent genotypes with alleles, and therefore Mendelian segregation in the F2 families. This strategy, however, meant that it was impossible to distinguish / genotypes from failed amplifications in F2 progeny. Nevertheless, based on high quality size standard profiles, and previous amplification success with other markers, / genotypes were inferred when no peaks were observed. SCARB1-2 mapped to chromosome 1 of the Atlantic salmon map [29] (Figure 2). Large differences in recombination rate were observed in the male and female maps, with the female map consisting of two unlinked segments (Chr1-F1 and Chr1-F2), while the male map had a higher level of recombination between marker OtsG83 and CL9726 than the female map.

Bottom Line: Red flesh colour is a unique trait found in some salmonid genera.A better understanding of the molecular mechanisms underlying the cellular uptake and deposition of carotenoids could potentially be used to improve the low muscle deposition rate that is typically found in farmed Atlantic salmon.A total of seven different SCARB1-2 alleles comprising repetitive enhancer of zeste motifs (EZH2) were identified in the founding parents of a resource Atlantic salmon population.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Integrative Genetics, Dept. of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, 1432 Aas, Norway. Hilde.Sundvold@oslo-universitetssykehus.no

ABSTRACT

Background: Red flesh colour is a unique trait found in some salmonid genera. Carotenoid pigments are not synthesized de novo in the fish, but are provided by dietary uptake. A better understanding of the molecular mechanisms underlying the cellular uptake and deposition of carotenoids could potentially be used to improve the low muscle deposition rate that is typically found in farmed Atlantic salmon. In addition, from an evolutionary point of view, the establishment and maintenance of this trait is still poorly understood. It has been demonstrated in several species that scavenger receptor class B, member 1 (SCARB1) is involved in intestinal absorption of carotenoids, which makes this gene a possible source of genetic variation in salmonid flesh pigmentation.

Results: In this study, a novel paralog of SCARB1 (SCARB1-2) was detected through screening for genetic variation in Atlantic salmon SCARB1. Full length SCARB1-2 encodes a protein with 89% identity to Atlantic salmon SCARB1, except for the C-terminal cytoplasmic tail that shows only 12% identity. The most prominent site of SCARB1 mRNA expression was in the mid gut, while a five-fold lower level was detected in Atlantic salmon skeletal muscle and liver. The SCARB1-2 mRNA was equally expressed in liver, muscle and mid gut, and at a lower level than SCARB1 mRNA. A total of seven different SCARB1-2 alleles comprising repetitive enhancer of zeste motifs (EZH2) were identified in the founding parents of a resource Atlantic salmon population. We mapped the SCARB1-2 paralog to a region on Atlantic salmon chromosome 1, containing a putative QTL for flesh colour. Addition of the SCARB1-2 marker increased the significance of this QTL, however the large confidence interval surrounding the QTL precludes confirmation of SCARB1-2 as a causative gene underlying variation in this trait.

Conclusion: We have characterised a novel paralog of SCARB1 (SCARB1-2), have mapped it to Atlantic salmon chromosome 1 and have described its expression in various tissues. Mapping with SCARB1-2 alleles added further evidence for a QTL affecting flesh colour on this chromosome, however further studies are needed to confirm a functional role for this gene in flesh colour pigmentation.

Show MeSH