A twenty strain survey and backcross localization of the erythrocytic GTP concentration determining locus Gtpc on mouse chromosome 9

Erythrocyte nucleotide concentrations were surveyed among 20 inbred strains of mice in order to further assess the variability in GTP concentration. T here was no significant difference in erythrocytic ATP concentration (Schef fe's test at P = 0.01), 678-1154 nmol/mL packed cells, among the strains su rveyed. Two groups were distinguishable with respect to erythrocytic GTP co ncentration, 8 strains having high GTP, 215 +/- 44 nmole/ml packed cells, a nd 12 strains having low GTP, 34 +/- 12 nmole/ml packed cells. The erythroc ytic GTP concentration determining trait Gtpc was previously shown to be li nked to transferrin, Trf, on chromosome 9. Analysis of 232 [(B6 x WB) F-1 x B6] backcross individuals for Gtpc and 8 microsatellite markers restricted the localization of Gtpc to a 5.6 +/- 2.1 cM region. The gene order and ge netic distances in cM I SE are: (D9Mit14) 0.4 +/- 0.4 (D9Mit24) 1.7 +/- 0.8 (Gtpc, D9Mit51, D9Mit116, D9Mit212) 3.9 +/- 1.3 (D9Mit200) 3.0 +/- 1.1 (D9 Mit20) 7.8 +/- 1.8 (D9Mit18). The GTP concentration determining trait appea rs to be a property of erythrocytes as no differences were observed for GTP /ATP ratios of brain, kidney, liver, and tongue from a low GTP strain, C3H/ HeHa x Pgk-1(a) acid a high GTP strain. C57BL/6J.