A genetic analysis ofbx bxd cis double mutants in theDrosophila Ultrabithorax gene

Abstract

The Ultrabithorax (Ubx) gene of Drosophila melanogaster includes two functionally distinguishable regions. One is the Ubx transcription unit, which gives rise by alternative splicing to a family of morphogenetic Ubx proteins (UBX). The other is its upstream bithoraxoid (bxd) region. On the basis of genetic and molecular studies, it is generally assumed that the Ubx transcription unit contains internal positively acting cis-regulatory elements controlling UBX expression in the T3a compartment of the body of Drosophila, while the bxd region contains positive cis-regulatory elements controlling UBX expression in the T3p and A1a compartments. We have performed a genetic analysis of bx bxd cis double mutant chromosomes containing one mutation (bx alleles) affecting the Ubx unit, and a second (bxd alleles) affecting the bxd region of the Ubx gene. Our study of different bx bxd/bx combinations shows that bxd alleles partially rescue the adult mutant phenotypes of bx alleles, which suggests that the bxd region contains a negative cis-regulatory element involved in the control of the activity of the Ubx gene in the T3a compartment.

Physical and Genetic Interactions Link Hox Function with Diverse Transcription Factors and Cell Signaling Proteins

“…Our analysis exploited a gypsy insertion line, Ubx bx-34e , that decreases the concentration of UBX protein in the haltere in a temperature-dependent manner (43). Heterozygotes for the Ubx bx-34e lesion have a normal haltere phenotype but reduced UBX concentrations, and thus the halteres are poised to be more easily transformed into a winglike phenotype (Fig.…”

“…A genetic interaction between Ubx and Hairy is observable at elevated temperatures at which the ectopic expression of the partner protein increases (45) and the expression of UBX in flies harboring the Ubx bx-34e genetic element further decreases (43). At room temperature, Hairy overexpression generated shriveled wings with large ectopic bristles (Fig.…”

Glycosphingolipids are linked to elevated neurotransmission and neurodegeneration in a Drosophila model of Niemann Pick type C

“…We next found that Npc1a; brn double mutants have elevated synaptic transmission of the same magnitude as the individual brn and Npc1a single mutants, further indicating that brn and Npc1a likely function within the same pathway to increase presynaptic neurotransmission. Such double mutant genetic assays are a powerful approach to test whether two genes operate in the same pathway (no additional change) or in different, parallel pathways (additive phenotypes) ( Haber et al, 2013 ; Martínez-Laborda et al, 1996 ). Importantly, our results indicate that brn is not sufficient to alter the elevated synaptic transmission in Npc1a nulls, and thus that accumulation of either MacCer or GlcCer may be responsible for the Npc1a neurotransmission phenotype.…”

Homeotic Genes: Clustering, Modularity, and Diversity

“…Since the CRMs maintain required levels of Ubx in T3, their absence leads to a lack of expression of the gene. This loss of function causes T3 to anteriorize into a copy of T2 ( Little et al, 1990 ; Martínez-Laborda et al, 1996 ). It was a remarkable achievement for two reasons – (1) All three mutations were within a span of 100 kb of each other and were therefore extremely difficult to obtain in cis- through the genetic crossing.…”