Cross-Species Genome-Wide Analysis Reveals Molecular and Functional Diversity of the Unconventional Interferon-? Subtype

Shields, Lauren E.; Jennings, Jordan; Liu, Qinfang; Lee, Jinhwa; Ma, Wenjun; Blecha, Frank; Miller, Laura C.; Sang, Yongming

Pigs (and cattle) have the largest expansion of type I IFNs regarding subtypes and total IFN-coding gene numbers (8, 9) . For example, porcine type I IFN gene loci contain 57 predictable IFN-coding genes (and 16 pseudogenes) spanning a nearly 1 Mbp genomic region and encoding at least 39 distinct IFN peptides assigned to 17 IFN-αs, 11 IFN-δs, 7 IFN-ωs, plus one each of IFN-β, IFN-ε, IFN-κ, and IFN-αω subtypes (9) . Single IFN-ωlike genes are identified in reptiles and birds, and multi-gene IFN-ω subtypes are present in most ungulate and bat species. Through phylogenic analysis we showed that porcine IFN-ωs are orthologous to the majority of IFN-ω gene products identified so far in different species (9, 13) . This further indicates porcine IFNω as a model to analyze functional novelty of this unconventional IFN subtype. Comparative genomic studies show that pigs have a molecular expansion of type I IFNs including IFN-ω genes, which are several-fold more than those in mice or humans (9, 13) .