# The tilt ( tt ) mutation of Drosophila melanogaster maps to the cis-regulatory region of the Iroquois Complex (Iro-C) located in the sosondowah ( sowah) gene

## TL;DR

This paper identifies the genetic location of the tilt mutation in fruit flies and links it to regulatory elements of the Iroquois Complex genes.

## Contribution

The study maps the tilt mutation to the cis-regulatory region of the Iroquois Complex within the sosondowah gene.

## Key findings

- The tilt mutation is located in the sosondowah gene, which regulates the Iroquois Complex genes araucan and caupolican.
- A gtwin retrotransposon with su(Hw) insulator binding sites is associated with the tilt mutation.
- Mutations in su(Hw) suppress the tilt phenotype, suggesting a functional link.

## Abstract

The
tilt
(

tt

) mutation first described by Morgan and Bridges in 1915 has adult visible phenotypes in wing posture and vein formation. We have mapped

tt

to a genomic region within the
sosondowah
(

sowah

) gene that houses the cis-regulatory elements that control expression of the Iroquois Complex genes
araucan
(

ara

) and

caup
olican

(

caup

) in the wing hinge and wing veins. Sequence analysis of the

tt
1

allele has identified a gtwin retrotransposon containing su(Hw) insulator binding sites within this region of

sowah

. We find that mutations in
su(Hw)
suppress the
tilt
phenotype, providing a potential mechanism for the insertion to affect the function of the Iroquois Complex.