UC Davis School of Veterinary Medicine Veterinary Genetics Laboratory
Goat Scrapie Susceptibility - S146 and K222

Introduction

Scrapie is a fatal, infectious neurodegenerative disease that affects sheep and goats.  The disease results from infection with pathogenic agents known as “prions” which change the normal prion protein (PrPC) to the improperly folded, disease-associated form (PrPSc).  The abnormal PrPSc is resistant to the protein turnover process and forms deposits in the central nervous system and some peripheral tissues that lead to progressive neurodegeneration. Goat scrapie is similar to a group of prion diseases that includes Creutzfeldt-Jakob disease in humans, bovine spongiform encephalopathy (BSE) in cattle, sheep scrapie and chronic wasting disease in cervids. The disease impacts animal health and welfare, animal movement and trade.

Natural mutations (also called variants or alleles) in the prion protein gene (PRNP) of sheep and goats have been identified which confer susceptibility or resistance to scrapie. In the goat, S146 and K222 variants have been confirmed, experimentally and in the field, to confer genetic resistance against classical scrapie. These variants are named for the amino acid changes in the PRNP protein. S146 indicates serine (S) at position 146 instead of normal asparagine (N) and K222 indicates lysine (K) instead of normal glutamine (Q) at position 222. Serine-146 or Lysine-222 forms of PrPC are more resistant to conversion to the abnormal PrPSc.

The VGL offers a DNA test for classical scrapie in goats to screen for presence/absence of the resistance alleles S146 and K222. Information from the test can be used by breeders to select breeding stock to increase frequency of beneficial alleles in their herds. Breeding for resistance is an effective means to control classical scrapie in goats at the herd and population levels. This test is applicable to goats of all types and breeds, including those raised in the U.S.

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Allow 6 - 10 business days for results.

Results are reported as:

146
222
Interpretation of Results
NN
QQ
No copies of protective variants. Susceptible to classical scrapie.
NN
 
QK
One copy of K222 protective variant. Increased resistance to classical scrapie.
NN
  
KK
Two copies of K222 protective variant. Increased resistance to classical scrapie.
NS
QQ
One copy of S146 protective variant. Increased resistance to classical scrapie.
NS
QK
One copy each of S146 and K222 protective variants. Increased resistance to classical scrapie.
SS
QQ
Two copies of S146 protective variant. Increased resistance to classical scrapie.

Reference:

White SN, Reynolds JO, Waldron DF, Schneider DA, O'Rourke KI. Extended scrapie incubation time in goats singly heterozygous for PRNP S146 or K222. Gene. 2012 Jun 10;501(1):49-51. doi: 10.1016/j.gene.2012.03.068.

White S, Herrmann-Hoesing L, O’Rourke K, Waldron D, Rowe J, Alverson J. Prion gene (PRNP) haplotype variation in United States goat breeds. Genet. Sel. Evol. 2008, 40:553-561.

 
Veterinary Genetics Laboratory, Tel 530-752-2211, Email VGL