Transcripts encoded by a homoeo box gene are restricted to dorsal tissues of Drosophila embryos

In Drosophila elaboration of positional identity along the anterior-posterior and dorsal-ventral embryonic body axes involves early zygotic gene functions that are expressed in response to maternal cues present in the unfertilized egg¹. Zygotic loci that are required for the specification of positional identity along the anterior-posterior body axis have been described in detail^2-9. Less is known about the zygotic loci responsible for differentiation of the dorsal-ventral pattern; however, several genes that might be involved have been identified^3-5,10. Zerkn̈llt (zen) is an example of a zygotic gene required for correct differentiation of dorsally derived embryonic tissues¹⁰. On the basis of homoeo box cross homology, we have now isolated a gene, called S60, that derives from the zen region of the Antennapedia complex (ANT-C)^7,10. Transcripts encoded by S60 transiently accumulate in the dorsal-most tissues of developing embryos. This pattern of expression suggests that S60 corresponds to zen. Since S60 contains a homoeo box, it is possible that differentiation of the anterior-posterior and dorsal-ventral embryonic patterns involves similar molecular mechanisms.