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
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
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-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
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
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.