DISCOVERY OF MYOSIN GENES BY PHYSICAL MAPPING IN DICTYOSTELIUM

The diversity of the myosin family in a single organism, Dictyostelium discoideum, has been investigated by a strategy devised to rapidly id entify and clone additional members of a gene family. An ordered array of yeast artificial chromosome clones that encompasses the Dictyostel ium genome was probed at low stringency with conserved regions of the myosin motor domain to identify all possible myosin loci. The previous ly identified myosin loci (mchA, myoA-E) were detected by hybridizatio n to the probes, as well as an additional seven previously unidentifie d loci (referred to as myoF-L), Clones corresponding to four of these additional loci (myoF, myoH-J) were obtained by using the isolated yea st artificial chromosomes as templates in a PCR employing degenerate p rimers specific for conserved regions of the myosin head. Sequence ana lysis and physical mapping of these clones confirm that these PCR prod ucts are derived from four previously unidentified myosin genes. Preli minary analysis of these sequences suggests that at least one of the g enes (myoJ) encodes a member of a potentially different class of myosi ns. With the development of whole genome libraries for a variety of or ganisms, this approach can be used to rapidly explore the diversity of this and other gene families in a number of systems.