PRNP polymorphisms in four Italian sheep breeds

Pubblicato su SPVet.it (ISSN 1592-1581) n.91/2015
PRNP polymorphisms in four Italian sheep breeds
Emiliano Lasagna1, Ludovica Curcio1,2, Carla Sebastiani2, Marcella Ciullo2, Piera Di Lorenzo1,
Simone Ceccobelli1, Francesca Maria Sarti1, Giovanni Pezzot 2, Massimo Biaget 2
1. Dipartimento di Scienze Agrarie, Alimentari e Ambientali, Università degli Studi di Perugia,
Borgo XX giugno 74, 06121, Perugia, Italy
2. Area Ricerca e Sviluppo, Istituto Zooprofilatco Sperimentale dell’Umbria e delle Marche, Via G.
Salvemini 1, 06126 Perugia, Italy
*Corresponding author: [email protected]
Introduction
Results and discussion
Susceptibility or resistance to classical scrapie is strongly
regulated by the polymorphisms at codons 136, 154 and
171 of the PRNP gene. The disease is especially associated
with the ARQ/ARQ genotype in sheep breeds where the
VRQ allele is rare or absent. In Mediterranean countries
such as Italy, Greece and Spain ARQ/ARQ is a very
frequent genotype detected in animals sick with scrapie,
but many authors reported ARQ-associated SNPs related
to scrapie-resistance.
Objectives
Four Italian sheep breeds (Appenninica, Bergamasca,
Comisana and Sarda) were investigated with the purpose
of checking new allelic variants in order to assess their
possible protective role against classical scrapie.
Allelic and genotypic frequencies for the main allelic
variants were calculated. ARQ was the predominant allele;
ARR, ARH, AHQ, and VRQ alleles were detected at lower
frequencies. The highest three genotypic frequencies were
ARR/ARR, ARR/ARQ, ARQ/ARQ. The AT 112RQ allele was
observed in all the analysed breeds (ranging from 6.3% to
31.8%) with the exception of Sarda sheep. The ARQK176
allele by contrast was observed only in Sarda breed (4.6%).
Moreover five non synonymous polymorphisms (Q101R,
G127S, L141F, H143R, H180Y) and two synonymous
polymorphisms at codons 231 and 237 were also found.
Table 1.
Allelic frequencies (%)
Methods
A total of 647 whole blood samples, only from females,
belonging to meat breeds as Appenninica and Bergamasca
and to dairy breeds as Comisana and Sarda were
collected. Genomic DNA was extracted using a semiautomatic extractor (Fig. 1).
Genotyping analysis of codons 136, 154, and 171 were
performed following the real time PCR protocol. A total of
146 homozygous ARQ animals were sequenced (Fig. 2).
Sarda breed
(n°=278)
Genomic DNA extraction
from blood
Appenninica breed
(n°=169)
Genotypic frequencies (%)
Comisana breed
(n°=100)
SNPs frequenciesa (%)
Bergamasca breed
(n°=100)
Figure 1. Animal sampling and DNA extraction
Real Time PCR
Sequence analysis by capillary
electrophoresis
aBreeds:
APN. Appenninica; BGS. Bergamasca; CMS. Comisana; SRD. Sarda
Conclusions
The results here obtained could be the basis for the
development of a genetic breeding programme aimed at
increasing scrapie-resistance of sheep populations and
preserving PRNP variability.
Acknowledges
Figure 2. Genotyping and sequencing analysis
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