A new role for hth in the early pre-blastodermic divisions in drosophila.

In drosophila, the preblastodermic syncytial nuclear divisions occur very fast. In this short period of time chromosomes must condense, segregate and decondense, in conditions governed by maternally provided RNAs and proteins. In this report, we show that the Homothorax (Hth) transcription factor is maternally provided and that its function is necessary for the proper assembly of the centric/centromeric heterochromatin during preblastodermic divisions. Embryos lacking the hth maternally-derived transcript, show abnormal localisation of the centromeric CID protein, and aberrant chromosomal segregation. In this syncytial context, Hth presumably acts together with its partner Extradenticle (Exd) and the RNA PolII, to facilitate transcription of satellite repeats. The transcripts derived from these sequences are needed for the correct assembly of the centric heterochromatin.