Isolation and characterization of DNA fragments corresponding to the deletion in chromosome 7 of Albino deletion mutant mice

A series of overlapping deletions in chromosome 7 (C7) of the mouse at and in the proximity of the albino locus (c) have been shown to cause failure of expression of various hepatocyte-specific genes in newborn lethal deletion homozygotes including TAT, PepCK, SDH, glucose-6-phosphatase, P450, cytochione etc. (Gluecksohn-Waelsch, Cell 16: 225-237 (1979)). More recent work has suggested that sequences corresponding to the deletions encode trans-acting factor(s) involved in the transcriptional control of such genes, which map on other chromosomes. The smallest deletion, c high 14CoS, used in our studies, comprises about 1.5 cM. In attempts to characterize DNA sequences involved in the regulation of such genes, a microclone library enriched for the central segment (i.e. 20%) of C7 has been established using translocation Rb(7;18)9-Lub. mouse cell karyotype preparations harboring C7 "tagged" with C18, thus permitting the identification of C7. Three microclones were isolated which hybridize with normal but not with c high 14CoS mouse DNA. These microclones are apparent sigle copy non-overlapping DNA fragments, of which one cross-hybridizes with several EcoRI restriction fragments located within the deletion. Isolated microclones and a tyrosinase-specific probe are utilized for PFGE mapping experiments in order to identify deletion-specific "HTF islands". The cloneas are being used as multiple entry points for chromosomal waking and jumping strategies. To assay for biological activity of isolated DNA sequences, SV40 virus immortalized homozygous c high 14CoS mutant newborn mouse hepatocyte lines were established. The cells multiply in chemically defined medium with insulin, retained some hepatic functions (e.g. albumin, AFP, arginine syntheses etc.) but not others (e.g. TAT), thus reflecting important properties of mutant liver. These lines (Paul et al., J.Cell. Physiol. in press) may be useful for complementation studies to identify regulatory sequences which confer hepa