Map of the Naip gene family array in C57BL/6J. The horizontal line depicts the chromosome and the named arrows beneath the lines indicate the relative position and direction of transcription of the C57BL/6J mouse Naip gene paralogs. In addition, some flanking genes are indicated to provide genomic context.Naip6/ΔNaip gene encodes a 3′ UTR with unspliced exons from a nearby rearranged and nonfunctional ΔNaiplocus. The exact structure of the Naip gene family array varies among mouse strains. For example, mice of the 129 background have an expanded central portion of the Naip array that contains two additional close relatives of theNaip6/ΔNaip gene locus (Endrizzi et al. 2000;Growney and Dietrich 2000). Interestingly, the human orthologous region also contains repeats of NAIP gene sequences, although the map is uncertain because of considerable interhaplotype variability in structure (for review, see Growney et al. 2000). The genetic interval for Lgn1, which contains only Naip2, Naip5, and the 3′ UTR of Naip6/ΔNaip, is indicated above the chromosome. Arrows below each Naip symbol point to some relevant information about each gene.