Genetic Transmission of Bovine Spongiform Encephaolopathy in Cattle

Bovine spongiform encephalopathy (BSE) is a transmissible spongiform encephalopathy (TSE) of cattle.

Classical BSE is associated with ingestion of BSE-contaminated feed.

 H- and L-type BSE are collectively known as atypical BSE.

H and L type strains differ from classical BSE by displaying a different disease phenotype.

These strains have not been linked to the consumption of contaminated feed.

The 2006 US H-type atypical BSE animal had a polymorphism at codon 211 of the bovine prion gene resulting in a glutamic acid to lysine substitution (E211K).

Glutamic acid

Lysine:

This amino acid Glu to Lys substitution is analogous a human polymorphism associated with the most prevalent form of heritable TSE in humans, and it is considered to have caused BSE in the 2006 US atypical BSE animal.

To determine the amino acid mutation is a heritable trait in cattle, the prion alleles were sequenced from the only known offspring of this animal, a 2-year-old heifer.

Findings

Sequence analysis revealed that both the 2006 US atypical BSE animal and its 2-year-old heifer were heterozygous at bovine prion gene nucleotides 631 through 633 for GAA (glutamic acid) and AAA (lysine).

Both animals carry the E211K polymorphism, indicating that the allele is heritable and may persist within the cattle population.

Conclusion

This is evidence that the E211K polymorphism is a germline polymorphism, not a somatic mutation, suggesting BSE may be transmitted genetically in cattle.

In the event that E211K proves to result in a genetic form of BSE, this would be the first indication that all 3 etiologic forms of TSEs (spontaneous, hereditary, and infectious) are present in a non-human species.

Nicholson EM, Brunelle BW, Richt JA, Kehrli ME Jr, Greenlee JJ. 2008. Identification of a Heritable Polymorphism in Bovine PRNP Associated with Genetic Transmissible Spongiform Encephalopathy: Evidence of Heritable BSE. PLoS ONE 3(8): e2912. Retrieved October 4, 2010 from http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002912.

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