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frequencies (
P
nominal value
¼
0.0087;
P
¼
0.0435 after Bonferroni correction)
was obtained for the
GPX5
SNP.
30.4 Discussion
We analyzed polymorphisms in five candidate genes for prolificacy of sows to
detect association with FTNUM of ITLW.
CTSL
encodes a lysosomal proteinase
with a potential role in embryo implantation, while
EPOR
controls the differentia-
tion of red blood cells in the fetus and is a candidate for uterine capacity (Vallet
et al.
2005
).
ESR2
is essential for ovulation and embryo development (Mu˜oz et al.
2004
).
STAT5B
encodes a protein involved in signal transduction of hormones and
cytokines (Ballester et al.
2006
).
GPX5
encodes a glutathione peroxidase involved
mainly in sperm quality and male fertility, and it was a considered a positional
candidate gene for fertility due its location in a chromosomal region encompassing
QTL for reproductive traits. The analyzed polymorphisms, except for the
CTSL
(Fontanesi et al.
2010
) and
ESR2
SNPs (Dall'Olio et al.
2010
), have not been
investigated in ITLW before. All polymorphisms segregate in this breed; for this
reason, it was possible to use these markers in association studies. The results
indicated that the
GPX5
SNP is associated with FTNUM variability in ITLW
(
P
0.01). The allele that showed a favorable effect on teat numbers (
GPX5:
AF124818:g.1939 T) was the less frequent in the breed (group 1
<
¼
0.34, group
2
0.40, Table
30.2
). From a physiological point of view, it seems that there is no
direct relation between GPX5 function and the number of teats. The analyzed SNP
of the
GPX5
gene (Bertani et al.
1999
), located in the 3
0
-UTR, could affect mRNA
stability even if this role seems unlikely. Therefore, considering also the function of
this gene, it is possible that
GPX5
does not have a direct effect on the number of
teats, but its association may be due to linkage disequilibrium with a functional
allele within another gene on chromosome 7. However, the obtained result opens up
interesting perspectives, as this trait is related to the mothering ability of the sows.
We are evaluating whether the same markers analyzed in this study are associated
with prolificacy in Italian Large White sows.
¼
Acknowledgments This work was funded by the Ministry of Agriculture and Forestry
(MIPAAF) SELMOL project.
References
Ballester M, Sardina MT, Folch JM (2006) Polymorphism and chromosomal localization of the
porcine signal transducer and activator of transcription 5B gene (
STAT5B
). J Anim Breed
Genet 123:284-287
Bertani GR, Marklund S, Hu ZL, Rothschild MF (1999) Rapid communication: mapping of the
glutathione-peroxidase-5 (
GPX5
) gene to pig chromosome 7. J Anim Sci 77:2855-2856
