Sequence variation in exon 5 of the avian myxovirus-resistance (Mx) gene among Cameroon-reared chicken populations: a pilot study

ABSTRACT The avian myxovirus-resistance (Mx) gene encodes an interferon-inducible antiviral protein and has been investigated as a candidate locus in host responses to RNA viruses, including Newcastle disease virus (NDV). This pilot study characterised exon 5 sequence variation in 17 chickens reared in Cameroon from five local and improved chicken groups. Genomic DNA from blood was used to PCR-amplify a 284-bp exon 5 fragment, followed by Sanger sequencing. Alignment with White Leghorn and Rhode Island Red reference sequences identified 56 variable nucleotide positions, including a tri-allelic site at position 214. Several variants were fixed or nearly fixed within the sampled groups. Nucleotide diversity was higher in Brahma and Goliath and lower in Kabir and naked-neck chickens. Distance-based clustering and haplotype-network analysis grouped sequences by chicken group, and AMOVA attributed most observed variation to differences among groups rather than within groups. Thus, exon 5 of Mx was polymorphic, and its diversity was structured across this small sample. Because the study analysed only one gene fragment in 17 birds and did not measure NDV-response phenotypes, the detected variants cannot be interpreted as resistance markers. Broader sampling, full-gene sequencing and direct disease-related phenotyping are required to assess their biological and breeding relevance. Keywords: Mx gene, exon 5, SNP polymorphism, Newcastle disease virus, genetic diversity.