Proximity of the Mep-1 Gene to H-2D on chromosome 17 in mice

The Mep-1 gene on chromosome 17 in mice controls the activity of meprin, a kidney brush border metalloendopeptidase. Most inbred mouse strains of the k haplotype (e.g., CBA, C3H, AKR) are markedly deficient in meprin activity; these mice carry the Mep-1^ballele. Mouse strains in which meprin activity levels are normal are designated Mep-1^a Studies using congenic and recombinant strains mapped the Mep-1 gene telomeric to H-2D near the Tla gene. To further study the relationship between the major histocompatibility complex and Mep-1, a linkage study was conducted. Mep-1^a F₁ hybrids [C3H.A (K^kD^d) × C3H.OH (K^dD^k)] were backcrossed with Mep-1^b C3H.OH (K^dD^k) parents. The progeny were assayed for H-2D markers, Pgk-2 isozymes, and meprin activity. Recombination between H-2D and Mep-1 occurred in 6 out of 284 mice, a crossover frequency of 2.1%. Mep-1 is therefore 2.1 crossover units telomeric to H-2D and approximately 0.6 crossover units from Tla. The Mep-1 locus provides a new genetic marker for the future mapping of this important area of the mouse genome.