Regulation of a remote Sonic hedgehog forebrain enhancer by the

YONGSU JEONG; FEDERICO COLUCCIO LESKOW; KENIA EL-JAICK; ERICH ROESSLER; MAXIMILIAN MUENKE; ANASTASIA YOCUM; CHRISTELE DUBOURG; XUE LI; XIN GENG; GUILLERMO OLIVER; DOUGLAS J. EPSTEIN

NATURE GENETICS

Nature Publishing Group

Lugar: London, UK; Año: 2008 vol. p. 1348 - 1353

1061-4036

In humans, SHH haploinsufficiency results in holoprosencephaly (HPE), a defect inanterior midline formation1,2. Despite the importance of maintaining SHHtranscript levels above a critical threshold, we know little about the upstreamregulators of SHH expression in the forebrain. Here we describe a rare nucleotidevariant located 460kb upstream of SHH in an individual with HPE that resulted inthe loss of Shh brain enhancer-2 (SBE2) activity in the hypothalamus of transgenicmouse embryos. Using a DNA affinity capture assay we screened SBE2 sequence forDNA binding proteins and identified members of the Six3/Six6 homeodomain familyas candidate regulators of Shh transcription. Six3 showed reduced binding affinityfor the mutant compared to wild type SBE2 sequence. Moreover, HPE causingmutations in Six3 failed to bind and activate SBE2. These data provide a direct linkbetween Six3 and Shh regulation during normal forebrain development and in thepathogenesis of HPE.