title: Somatic mutations in GLI3 and OFD1 involved in sonic hedgehog signaling cause hypothalamic hamartoma.
abstract: Hypothalamic hamartoma (HH) is a congenital anomalous brain tumor. Although most HHs are found without any other systemic features, HH is observed in syndromic disorders such as Pallister-Hall syndrome (PHS) and oral-facial-digital syndrome (OFD). Here, we explore the possible involvement of somatic mutations in HH.
  
  
  
  We analyzed paired blood and hamartoma samples from 18 individuals, including three with digital anomalies, by whole-exome sequencing. Detected somatic mutations were validated by Sanger sequencing and deep sequencing of target amplicons. The effect of GLI3 mutations on its transcriptional properties was evaluated by luciferase assays using reporters containing eight copies of the GLI-binding site and a mutated control sequence disrupting GLI binding.
  
  
  
  We found hamartoma-specific somatic truncation mutations in GLI3 and OFD1, known regulators of sonic hedgehog (Shh) signaling, in two and three individuals, respectively. Deep sequencing of amplicons covering the mutations showed mutant allele rates of 7-54%. Somatic mutations in OFD1 at Xp22 were found only in male individuals. Potential pathogenic somatic mutations in UBR5 and ZNF263 were also identified in each individual. Germline nonsense mutations in GLI3 and OFD1 were identified in each individual with PHS and OFD type I in our series, respectively. The truncated GLI3 showed stronger repressor activity than the wild-type protein. We did not detect somatic mutations in the remaining 9 individuals.
  
  
  
  Our data indicate that a spectrum of human disorders can be caused by lesion-specific somatic mutations, and suggest that impaired Shh signaling is one of the pathomechanisms of HH.
authors.affiliation: Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama 236-0004 Japan; Department of Biochemistry Hamamatsu University School of Medicine Hamamatsu 431-3192 Japan.
authors.forename: Hirotomo
authors.initials: H
authors.lastname: Saitsu
authors.affiliation: Department of Functional Neurosurgery Epilepsy Center Nishi-Niigata Chuo National Hospital Niigata 950-2085 Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Sonoda
authors.affiliation: Department of Functional Neurosurgery Epilepsy Center Nishi-Niigata Chuo National Hospital Niigata 950-2085 Japan.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Higashijima
authors.affiliation: Department of Functional Neurosurgery Epilepsy Center Nishi-Niigata Chuo National Hospital Niigata 950-2085 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shirozu
authors.affiliation: Department of Functional Neurosurgery Epilepsy Center Nishi-Niigata Chuo National Hospital Niigata 950-2085 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Masuda
authors.affiliation: Department of Child Neurology Nishi-Niigata Chuo National Hospital Niigata 950-2085 Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Tohyama
authors.affiliation: Department of Pediatrics Showa University School of Medicine Tokyo 142-8666 Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kato
authors.affiliation: Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama 236-0004 Japan.
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Nakashima
authors.affiliation: Clinical Research Institute Kanagawa Children's Medical Center Yokohama 232-8555 Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Tsurusaki
authors.affiliation: Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama 236-0004 Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mizuguchi
authors.affiliation: Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama 236-0004 Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Miyatake
authors.affiliation: Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama 236-0004 Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Miyake
authors.affiliation: Department of Functional Neurosurgery Epilepsy Center Nishi-Niigata Chuo National Hospital Niigata 950-2085 Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kameyama
authors.affiliation: Department of Human Genetics Yokohama City University Graduate School of Medicine Yokohama 236-0004 Japan.
authors.forename: Naomichi
authors.initials: N
authors.lastname: Matsumoto