OMIA:001079-9940 : Yellow fat in Ovis aries (sheep)

In other species: horse , pig , taurine cattle , rabbit

Categories: Adipose tissue phene

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 611740 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2010

Species-specific description: The presence of three xanthophylls (lutein, lutein-5-6-epoxide, and flavoxanthin) in sheep fat, presumably due to the inability to oxidise xanthophylls. Inherited as a single-locus autosomal recessive trait. The paper by Niu et al. (2017) reports a genetically-modified organism (GMO)

Molecular basis: Vage and Boman (2010): "the coding region of the BCMO1 and the BCO2 gene were sequenced in yellow fat individuals and compared to the corresponding sequences from control animals with white fat. In the yellow fat individuals a nonsense mutation was found in BCO2 nucleotide position 196 (c.196C>T), introducing a stop codon in amino acid position 66." Kent et al. (2021): "In spælsau we detected an aberration in BCO2 mRNA. Nanopore sequencing of genomic DNA revealed the insertion of a 7.9 kb endogenous Jaagsiekte Sheep Retrovirus (enJSRV) sequence in the first intron of the BCO2 gene. Close examination of its cDNA revealed that the BCO2 genes first exon was spliced together with enJSRV-sequence immediately downstream of a potential -AG splice acceptor site at enJSRV position 415. The hybrid protein product consists of 29 amino acids coded by the BCO2 exon 1, one amino acid coded by the junction sequence, followed by 28 amino acids arbitrary coded for by the enJSRV-sequence, before a translation stop codon is reached."

Genetic engineering: Yes - in addition to the occurrence of natural variants, variants have been created artificially, e.g. by genetic engineering or gene editing
Have human generated variants been created, e.g. through genetic engineering and gene editing

Breed: spælsau (Sheep) (VBO_0001617).
Breeds in which the phene has been documented. (If a likely causal variant has been documented for the phene, see the variant table breeds in which the variant has been reported).

Associated gene:

Symbol Description Species Chr Location OMIA gene details page Other Links
BCO2 beta-carotene oxygenase 2 Ovis aries 15 NC_056068.1 (22198102..22268616) BCO2 Homologene, Ensembl , NCBI gene


By default, variants are sorted chronologically by year of publication, to provide a historical perspective. Readers can re-sort on any column by clicking on the column header. Click it again to sort in a descending order. To create a multiple-field sort, hold down Shift while clicking on the second, third etc relevant column headers.

WARNING! Inclusion of a variant in this table does not automatically mean that it should be used for DNA testing. Anyone contemplating the use of any of these variants for DNA testing should examine critically the relevant evidence (especially in breeds other than the breed in which the variant was first described). If it is decided to proceed, the location and orientation of the variant sequence should be checked very carefully.

Since October 2021, OMIA includes a semiautomated lift-over pipeline to facilitate updates of genomic positions to a recent reference genome position. These changes to genomic positions are not always reflected in the ‘acknowledgements’ or ‘verbal description’ fields in this table.

OMIA Variant ID Breed(s) Variant Phenotype Gene Allele Type of Variant Source of Genetic Variant Reference Sequence Chr. g. or m. c. or n. p. Verbal Description EVA ID Year Published PubMed ID(s) Acknowledgements
1333 spælsau (Sheep) yellow fat BCO2 insertion, gross (>20) Naturally occurring variant 15 "insertion of a 7.9 kb endogenous Jaagsiekte Sheep Retrovirus (enJSRV) sequence in the first intron of the BCO2 gene" (Kent et al. 2021) 2021 34193038
320 spælsau (Sheep) Yellow fat BCO2 nonsense (stop-gain) Naturally occurring variant Oar_rambouillet_v1.0 15 g.25024133C>T c.196C>T p.(Q66*) Oar_v3.1 position is g.21947481C>T rs1090867485 2010 20122251 Variant coordinates obtained from or confirmed by EBI's Some Effect Predictor (VEP) tool

Cite this entry

Nicholas, F. W., Tammen, I., & Sydney Informatics Hub. (2024). OMIA:001079-9940: Online Mendelian Inheritance in Animals (OMIA) [dataset].


Note: the references are listed in reverse chronological order (from the most recent year to the earliest year), and alphabetically by first author within a year.

2021 Kent, M., Moser, M., Boman, I.A., Lindtveit, K., Árnyasi, M., Sundsaasen, K.K., Våge, D.I. :
Insertion of an endogenous Jaagsiekte sheep retrovirus element into the BCO2 - gene abolishes its function and leads to yellow discoloration of adipose tissue in Norwegian Spælsau (Ovis aries). BMC Genomics 22:492, 2021. Pubmed reference: 34193038. DOI: 10.1186/s12864-021-07826-5.
2017 Niu, Y., Jin, M., Li, Y., Li, P., Zhou, J., Wang, X., Petersen, B., Huang, X., Kou, Q., Chen, Y. :
Biallelic β-carotene oxygenase 2 knockout results in yellow fat in sheep via CRISPR/Cas9. Anim Genet 48:242-244, 2017. Pubmed reference: 27862083. DOI: 10.1111/age.12515.
2010 Vage, DI., Boman, IA. :
A nonsense mutation in the beta-carotene oxygenase 2 (BCO2) gene is tightly associated with accumulation of carotenoids in adipose tissue in sheep (Ovis aries). BMC Genet 11:10, 2010. Pubmed reference: 20122251. DOI: 10.1186/1471-2156-11-10.
1985 Baker, R.L., Steine, T., Vabeno, A.W., Breines, D. :
The inheritance and incidence of yellow fat in Norwegian sheep Acta Agriculturae Scandinavica 35:389-397, 1985.
1972 Gedde-Dahl, T.W. :
[Reduction of the yellow fat incidence by different breeding plans for sheep]. Nord Vet Med 24:620-30, 1972. Pubmed reference: 4666502.
1962 Hill, F. :
Xanthophyll pigmentation in sheep fat. Nature 194:865-6, 1962. Pubmed reference: 13907341.
1934 Castle, W.E. :
Yellow fat in sheep Journal of Heredity 25:246-247, 1934.

Edit History

  • Created by Frank Nicholas on 13 Oct 2010
  • Changed by Frank Nicholas on 14 Sep 2011
  • Changed by Frank Nicholas on 09 Dec 2011
  • Changed by Frank Nicholas on 24 Nov 2016
  • Changed by Frank Nicholas on 12 May 2017
  • Changed by Imke Tammen2 on 11 Aug 2021
  • Changed by Imke Tammen2 on 12 Dec 2023
  • Changed by Imke Tammen2 on 27 Feb 2024