DELETION MAP OF THE COLOBOMA (CM) LOCUS ON MOUSE CHROMOSOME-2

The extent of the semidominant coloboma (Cm) mutation on mouse Chromos ome 2 was determined by deletion mapping using interspecific hybrid mi ce. The Cm deletion mutation results in ophthalmic dysmorphology and b ehavioral deficits, including profound hyperactivity, and has been sho wn to encompass the gene Snap. In addition to Snap, the gene encoding phospholipase C beta-1 (Plcb-1), which maps 0.60 +/- 0.60 cM proximal to Snap, and simple sequence repeat (SSR) loci D2Mit19, D2Mit46, D2Mit 28, and D2Mit136 were shown to be deleted at the Cm locus. In contrast , analysis of other closely linked SSRs and genes either proximal (Bmp -2a) or distal (Nec-1) to Snap, as well as a complementation test with the closely linked mutation lethal milk (lm), indicates that these ge ne sequences are unaffected by the Cm mutation. These data demonstrate that the Cm deletion represents a contiguous gene defect encompassing 1.1 to 2.2 cM that may be probed for genes, both in the mouse and in the syntenic region of human Chr 20, that independently affect element s of neurological behavior and eye development. (C) 1994 Academic Pres s, Inc.