Response of the corresponding author

To the Editors: In their recent publication, Swati S. Sathe and Peter J. Harte (Mech. Dev. 52,77-87, 1995) claim to have "reisolated' the extra sex combs (esc) gene of Drosophila from our published transgenic stock (Frei et aI., EMBO J. 4,979-987, 1985) by inverse PCR, using P element and rosy primers. This description is wrong because our published transgenic stock carried the esc trans gene within a 12 kb genomic fragment in the P-element vector Carnegie 4, which does not encode the rosy gene nor any other Drosophila marker. Moreover, the authors omitted to mention that 5 years ago (March, 1991) Harte had received from us also another esc rescue stock, which was unpublished but carried the esc transgene within a 4 kb genomic fragment, as pointed out to Harte at the time, I and hence identified the esc gene unambiguously. They thus convey to the reader of their paper a false impression of the ambiguity of the assignment of esc to a particular transcript. The unpublished esc rescue stock (published only recently (Gutjahr et aI., EMBO J. 14, 429~306, 1995) carried the 4 kb esc gene in the P-element vector Carnegie 20 which, in contrast to Carnegie 4, also carries the rosy marker.! If Sathe and Harte used rosy primers for their ore-isolation' of esc, as they have stated, then it appears that they used our unpublished stock, obtained from us together with the requested published stock for a different purpose; for Harte stated explicitly in his letter:! 'We are working on the trithorax (trx) gene and would like to use this chromosome2 as another esc 'duplication' for some gene dosage experiments with esc and trx.' In view of all these facts, we ask ourselves why Sathe and Harte went through the laborious ore-isolation' procedure to sequence the esc gene, as we have made the esc sequence available to numerous laboratories requesting it over the past 7 years.