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.
Jeong
Yongsu
Y
Department of Genetics, University of Pennsylvania School of Medicine, 415 Curie Boulevard, Philadelphia, Pennsylvania 19104, USA.
Leskow
Federico Coluccio
FC
El-Jaick
Kenia
K
Roessler
Erich
E
Muenke
Maximilian
M
Yocum
Anastasia
A
Dubourg
Christele
C
Li
Xue
X
Geng
Xin
X
Oliver
Guillermo
G
Epstein
Douglas J
DJ
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