Transcription factor involved in imaginal disks development. Isoform rn is required in the wings, antenna, haltere, proboscis and legs disks, while isoform roe is required in the eye disk. Together with nab corepressor, it is involved in the initiation and maintenance of wingless (wg) expression in the wing hinge, by limiting the expression of wg to this compartment. Also required for the epithelial-mesenchymal transition branch of basolateral junctions signaling.

(UniProt, Q9VI93)

All alleles are viable as homozygotes. Both males and females are sterile; sterility is not germ line dependent. Two transcripts from the rotund region of Drosophila show similar positional specificities in imaginal disc tissues. Adult defects are restricted to homologous distal parts of the appendages, i.e., the antennae, legs, wings, halteres, and proboscis. In the antenna the basal capsule is missing and the third antennal segment is reduced in size; all other antennal and eye disc derivatives are normal. In all three pairs of legs abnormalities caused by the lack of rn+ product are localized specifically in the tarsus; instead of five individual tarsal segments, a single tarsus-like segment differentiates. The distal claw and proximal leg articulations (tibia, femur, trochanter, and coxa) are unaffected. Incomplete and duplicated joints seen at the presumptive positions of the tarsus 1-2 and 4-5 joints; intermediate joints virtually absent (Held, Duarte, and Derakhshanian, 1986, Wilhelm Roux's Arch. Dev Biol. 195: 145-57). Of the wing disc derivatives, the medial and distal costa are fused and the corresponding region in the posterior wing, the alula, is smaller, making the wing as a whole appear shorter; distal wing and mesonotum are formed as in wild type. Vein L5 and to a lesser extent L2 interrupted (rn3). Specific and localized deficiencies of labial and haltere disc derivatives are also evident. Genital and abdominal patterns are indistinguishable from wild-type patterns; however, seminal receptacles shorter than in wild-type females. Examination of the imaginal discs from third-instar rn larvae shows localized cell death in regions determined from fate maps to give rise to distal appendage parts (Cavallin).

Dominant mutation with complete penetrance and high expressivity. In Dipr/+ flies the distal wing blade reduced to two-thirds normal length; triple row replaced by two to three rows of irregularly sized bristles resembling those found on costa; occasionally these bristles may be bracted as are those of proximal costa. Posterior row of marginal bristles absent distally. Venation in proximal portion of wing irregular and crowded but more nearly normal distally. Trichomes of wing blade organized into whorls. Capitellum of haltere covered with small adventitious bristles and sometimes pedicellar-like sensilla. Pleura, coxa, trochanter, femur, tibia, and fifth tarsal segment unaffected; other tarsal segments reduced; tarsal segments two to four variably fused; ectopic sex combs form on second tarsal segment in 70-90% of forelegs. Basal cylinder of antenna reduced or missing; replaced by bristle elements at third-segment-arista junction resembling those on third segment. Proboscis contains five to seven rows of pseudotracheae rather than normal twelve; replaced by bristles laterally. Kerridge suggests transformation of distal into more proximal appendage elements. Homozygotes survive and are more extreme.

Produces a slight roughening of the eye owing to the irregular disposition of the facets; interommatidial bristles lost from posterior portion of the eye. Extreme expression in mutant/deficiency heterozygotes and more so in deficiency homozygotes; enhanced roughening and posterior loss of ommatidial bristles; in addition the eye is reduced in size and remaining interommatidial bristles are clumped. RK1.