Three types of polymorphisms in exon 14 in porcine Mx1 gene

Much is known about the antiviral activity of Mx proteins in species such a s mouse and human. In the mouse, loss of resistibility to influenza virus h as been shown to be due to specific polymorphisms in the Mx gene. This gene is therefore an interesting candidate gene for disease resistance in farm animals. The porcine Mx1 gene has already been identified and characterized based on its homology with mouse Mx1; however until now no evidence of pol ymorphisms in the porcine gene has been reported. In this study, we have fo und two new polymorphisms in exon 14 of porcine Mx I by DNA sequencing and confirmed their presence in different breeds, using polymerase chain reacti on (PCR)-restriction fragment length polymorphisms (RFLP) with NarI and Nae I restriction enzymes. On the basis of the deduced amino acid sequence, one allele contains a deletion that may result in a frameshift to yield severa l amino acid substitutions and extension of the carboxyl terminal region of Mx1 protein. The deletion allele, Mx1(c), was found to be segregating in L andrace, Berkshire, Duroc, Hampshire, and Yucatan miniature pig. A second p oint mutation, Mx1(b), was detected in Meishan and two Vietnamese native pi g breeds. All other breeds tested were fixed for the Mx1(a) allele that is identical to the sequence reported previously. It will be interesting to de termine if the Mx1(c) deletion is associated with variation in resistance t o the myxovirus family in the pig.