Further information and requests for resources and reagents should be directed to and will be fulfilled by the Lead Contact, Eileen E.M. Furlong ( furlong@embl.de ). Embryos were collected from heterozygous adult flies containing the lncRNA deletion in trans to a balancer chromosome harboring GFP under the control of an early enhancer. The following genotypes of the heterozygous stocks were used: Hatched flies were crossed 1 on 1 withand progeny was screened for DsRed positive flies.