Gene Dmel\dpp

dpp is a complex locus affecting numerous developmental events. Mutations fall into three major genetic and phenotypic groupings: called shortvein (shv), Haplo-insufficiency (Hin) and imaginal disk-specific (disk). Each group maps to a different region of the dpp gene. Hin-region mutations have two distinguishing features: they are defective in normal dorsal-ventral patterning of the embryo, and they generally fail to complement mutations of the shv and disk types. shv-region mutations all show recessive defects in longitudinal wing vein formation. disk-region mutations exhibit pattern deletions in the adult epidermal derivatives of the imaginal disks. The phenotypes of most shv/disk heterozygotes suggest partial or full complementation of the shv and disk lesions. Within each of the three major groupings, several phenotypic classes of alleles have been identified. Complementation between certain combinations of dpp alleles is transvection sensitive (Gelbart, 1982, Proc. Nat. Acad. Sci. USA 79: 2636-40). The genetic properties of the several classes of dpp mutations are outlined below. For a given class, the prototypical recessive phenotypes are inferred from examinations of trans heterozygotes for two different alleles of that class. This procedure obviates possible complications due to the frequent association of dpp mutations with gross chromosomal rearrangements. Particular allelic combinations may deviate from the prototypical descriptions. Hin-region emb: Embryonic lethal mutation. Homozygous viable, but recessive lethal in combination with hin-r alleles, and, in the latter background, exhibits the same weakly ventralized phenotype as hin-r homozygotes. Completely complements all shv- and disk-region mutations. The sole emb allele is associated with a small deletion in Hin-region. Hin: Haplo-insufficient mutations. Hin/+ heterozygotes exhibit dominant embryonic lethality with the same weakly ventralized phenotype as hin-r homozygotes. Dominant lethality is rescued by duplication of dppHin+. Homozygotes are defective in gastrulation and die as embryos with completely ventralized cuticle. In general, Hin alleles do not complement any other dpp mutations. However, Hin alleles associated with small deletions or point mutations exhibit transvection effects in heterozygotes with small deletions or insertions in the shv and disk-regions. Hin mutations are considered the null alleles of the dpp gene. Hin alleles are associated with breakpoints, small deletions or point mutations in the Hin-region. Hin-Df: Haplo-insufficient mutations which are behave identically to breakoint Hin mutations, except that Hin-Df lesions are gross deletions removing the entire dpp gene and adjacent vital loci. hin-r: Recessive mutations behaving as milder versions of the Hin lesions. In homozygotes, hin-r mutations exhibit embryonic lethality with weak ventralization effects (identical to emb/hin-r or Hin/+ heterozygotes). All hin-r mutations engender temperature-sensitive mutant phenotypes when heterozygous with shv- and disk-region mutations. Phenotypes elicited in heterozygotes with small deletions, or insertions in the shv and disk regions are transvection sensitive. All hin-r mutations are cytologically normal and show no alterations in their restriction maps. Some have been associated with point mutations in the Hin-region. shv-region shv-lc: Recessive larval-lethal shortvein alleles which complement all disk-region mutations. Exhibit mutant phenotypes in heterozygotes with all shv, Hin, and hin-r mutations. Mutations generally associated with rearrangement breakpoints. shv-lnc: Recessive larval-lethal shortvein alleles which do not complement disk-region mutations. Also exhibit mutant phenotypes in heterozygotes with all shv, Hin, and hin-r mutations. Mutations generally associated with rearrangement breakpoints. shv-p: Recessive shortvein alleles surviving at least to pharate adult. Only two alleles are known; one (s11) is adult viable; exhibits strong venation defects, and variable head capsule defects, including loss of palps, and misarranged vibrissae. Allelic to all shv, Hin, and hin-r mutations. Complement all disk-region mutations. Both alleles are associated with rearrangement breakpoints. shv-w: Recessive viable and fertile shortvein alleles exhibiting only venation defects. Associated with small deletions of the shv-region. Venation phenotype allelic to all shv, Hin, and hin-r mutations. shv-w/Hin, and shv-w/hin-r mutant phenotypes are transvection sensitive. Only two alleles are known; both are associated with small deletions in the shv-region. Tg: A dominant gain-of-function allele in which the tegula on the wing appears duplicated. Tg/+ wings are held out and down. Distinct in phenotype from heldout (d-ho) homozygotes. Tg completely complements all dpp mutations. The dominant effects of Tg can be reverted by superimposing shv, Hin, or hin-r mutations on the Tg chromosome. The one Tg allele is associated with a rearrangement breakpoint in or near the shv-region. disk-region disk-blk: Recessive viable and fertile allele in which the only mutant phenotype is loss of 80-90% of ommatidia in eye; hence this allele was designated blink by Sparrow (unpublished). Exhibits mutant eye phenotypes in heterozygotes with disk-III, disk-V, Hin, and hin-r mutations. Can exhibit transvection effects. The one disk-blk allele is associated with a small deletion within the disk-region. disk-ho: Recessive viable and fertile alleles in which the only mutant phenotypes are heldout wings and loss of the Sc25 on the dorsal base of the wing. Heldout phenotype displayed in heteroyzgotes with all disk-region mutations except d-blk, and with Hin and hin-r mutations. Can exhibit transvection effects. In addition to the one mutant allele listed here, which is associated with a small deletion within the disk-region, several cytologically normal disk-ho alleles have been associated with mobilization of hobo mobile elements residing in the disk-region. disk-II: Recessive viable alleles. Homozygotes exhibit reductions in wing blade, haltere and male genitalia. Elicit mutant phenotypes in heterozygotes with all disk-region mutations except d-blk, and with Hin and hin-r mutations. Mildest class of disk-region alleles associated with rearrangement breakpoints. disk-III: Recessive viable alleles. Homozygotes exhibit multiple pattern abnormalities in epidermis of head, thorax, and terminalia. Structures absent or reduced include labial palps, arista, eye, wing blade, capitellum of haltere, tarsal claws, male terminalia, and female analia. Elicit mutant phenotypes in heterozygotes with all disk-region mutations, and with Hin and hin-r mutations. Intermediate class of disk-region alleles associated with rearrangement breakpoints. disk-V: Recessive early pupal lethal alleles. Homozygous larvae have greatly reduced imaginal disks. Elicit mutant phenotypes in heterozygotes with all disk-region mutations and with Hin and hin-r mutations. Most severe class of disk-region alleles associated with rearrangement breakpoints. t: Recessive larval-lethal alleles. Allelic to all disk, Hin, and hin-r mutations. The only two known alleles of this class behave identically to disk-V lesions, except for the earlier recessive lethal period. Tentatively classified as part of the disk-region. These two mutations are associated with breakpoints which map between the two tRNAtyr genes residing at the Hin-disk-V boundary. Hence the t designation is used to describe these alleles.