Regulation of a remote Shh forebrain enhancer by the Six3 homeoprotein.
In humans, SHH haploinsufficiency results in holoprosencephaly (HPE), a defect in anterior midline formation. Despite the importance of maintaining SHH transcript levels above a critical threshold, we know little about the upstream regulators of SHH expression in the forebrain. Here we describe a rare nucleotide variant located 460 kb upstream of SHH in an individual with HPE that resulted in the loss of Shh brain enhancer-2 (SBE2) activity in the hypothalamus of transgenic mouse embryos. Using a DNA affinity-capture assay, we screened the SBE2 sequence for DNA-binding proteins and identified members of the Six3 and Six6 homeodomain family as candidate regulators of Shh transcription. Six3 showed reduced binding affinity for the mutant compared to the wild-type SBE2 sequence. Moreover, Six3 with HPE-causing alterations failed to bind and activate SBE2. These data suggest a direct link between Six3 and Shh regulation during normal forebrain development and in the pathogenesis of HPE.
Department of Genetics, University of Pennsylvania School of Medicine, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA.
Yongsu
Y
Jeong
Federico Coluccio
FC
Leskow
Kenia
K
El-Jaick
Erich
E
Roessler
Maximilian
M
Muenke
Anastasia
A
Yocum
Christele
C
Dubourg
Xue
X
Li
Xin
X
Geng
Guillermo
G
Oliver
Douglas J
DJ
Epstein
D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D005136:Eye Proteins / Q000378:metabolism*; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D016142:Holoprosencephaly / Q000235:genetics / Q000473:pathology; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding; D015534:Trans-Activators; D000097607:Homeobox Protein SIX3
D005136:Eye Proteins; D053823:Hedgehog Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D015534:Trans-Activators; D000097607:Homeobox Protein SIX3; C114419:Six6 protein, mouse