Comparative analysis of the Shadoo gene between cattle and buffalo reveals significant differences.
BACKGROUND
While prions play a central role in the pathogenesis of transmissible spongiform encephalopathies, the biology of these proteins and the pathophysiology of these diseases remain largely unknown. Since no case of bovine spongiform encephalopathy (BSE) has ever been reported in buffalo despite their phylogenetic proximity to cattle, genetic differences may be driving the different susceptibilities of these two species to BSE. We thus hypothesized that differences in expression of the most recently identified member of the prion family or Shadoo (SPRN) gene may relate to these species-specific differences.


RESULTS
We first analyzed and compared the polymorphisms of the SPRN gene (~4.4 kb), including the putative promoter, coding and 3' regions, and further verified the entire ORF and putative promoter. This yielded a total of 117 fixed differences, remarkably: 1) a 12-bp insertion/deletion polymorphism in the hydrophobic domain of the cattle but not buffalo gene, introducing a four amino acid expansion/contraction in a series of 5 tandem Ala/Gly-containing repeats; 2) two fixed missense mutations (102Ser→Gly and 119Thr→Ala), and three missense mutations (92Pro>Thr/Met, 122Thr>Ile and 139Arg>Trp) in the coding region presenting different (P<0.05) genotypic and allelic frequency distributions between cattle and buffalo; and, 3) functional luciferase-reporter experiments for the predicted promoter region, consistent with a significantly higher activity in buffalo than cattle. Supporting these findings, immunoblotting revealed higher relative expression levels of Sho protein in cerebrum from buffalo than from cattle. In addition, for cattle, highest Sho expression was detected in obex, as compared to cerebrum or cerebellum.


CONCLUSIONS
Our findings support Sho as a non-PrP specific marker for prion infections, with obex as the best tissue source for the detection of Sho in TSE rapid tests. Moreover, these discoveries may prove advantageous for further understanding the biology of prion diseases.
Laboratory for Conservation and Utilization of Bio-resource, Yunnan University, Kunming, People's Republic of China.
Hui
H
Zhao
Lin-Lin
LL
Liu
Shou-Hui
SH
Du
Si-Qi
SQ
Wang
Ya-Ping
YP
Zhang
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D002020:Buffaloes / Q000235:genetics*; D002417:Cattle / Q000235:genetics*; D016643:Encephalopathy, Bovine Spongiform / Q000235:genetics*; D040461:Gene Components; D015870:Gene Expression; D005787:Gene Frequency; D017930:Genes, Reporter; D054643:INDEL Mutation; D049410:Luciferases, Renilla / Q000096:biosynthesis / Q000235:genetics; D020125:Mutation, Missense; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009928:Organ Specificity; D011110:Polymorphism, Genetic; D017434:Protein Structure, Tertiary; D012091:Repetitive Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
D009419:Nerve Tissue Proteins; D049410:Luciferases, Renilla