title: Identification of a novel mutation in the exon 2 splice donor site of the POU1F1/PIT-1 gene in Japanese identical twins with mild combined pituitary hormone deficiency.
abstract: BACKGROUND
  To date, approximately 35 different POU1F1 mutations have been described in patients with familial and sporadic combined pituitary hormone deficiency (CPHD) from different ethnic backgrounds. The majority are missense mutations clustered within the conserved POU-specific and POU-homeo domains, encoded by exons 4 and 6, respectively.
  
  
  OBJECTIVE
  This study aimed to identify the molecular basis and clinical characteristics of a Japanese CPHD family with a novel POU1F1 mutation.
  
  
  METHODS
  The POU1F1 gene was sequenced in identical twin brothers with mild CPHD. The mutation identified was also evaluated in family members as well as 188 Japanese controls and then examined in functional studies.
  
  
  RESULTS
  A novel heterozygous splice site mutation (Ex2 + 1G>T; c.214 + 1G>T) was detected. This mutation was also present in their undiagnosed mother, but not in any of the controls. In vitro splicing studies suggested this mutation to result in an in-frame skipping of exon 2, thus producing an internally deleted protein lacking most of the R2 transactivation subdomain (TAD-R2). Heterologous expression studies of the mutated POU1F1 protein showed only modest reductions in its transactivation activities in HEK293T cells, while acting as a dominant-negative inhibitor of the endogenous activities of POU1F1 in pituitary GH3 cells.
  
  
  CONCLUSIONS
  This is the first report of a mutation at the exon 2 donor splice site of POU1F1, affecting TAD-R2. The addition of this mutation to the growing list of pathological POU1F1 mutations may provide deeper insights into clinical heterogeneity in the expressions of individual mutations and a better understanding of the structure-function relationships of POU1F1.
authors: Diabetes Therapeutics and Research Center, Institute for Genome Research, The University of Tokushima, Tokushima, Japan. hinoue@genome.tokushima-u.ac.jp
authors: Hiroshi
authors: H
authors: Inoue
authors: Tokuo
authors: T
authors: Mukai
authors: Yukiko
authors: Y
authors: Sakamoto
authors: Chizuko
authors: C
authors: Kimura
authors: Natsumi
authors: N
authors: Kangawa
authors: Mitsuo
authors: M
authors: Itakura
authors: Tsutomu
authors: T
authors: Ogata
authors: Yoshiya
authors: Y
authors: Ito
authors: Kenji
authors: K
authors: Fujieda
mesh_terms: D000328:Adult; D000818:Animals; D044466:Asian People; D019556:COS Cells; D002675:Child, Preschool; D002522:Chlorocebus aethiops; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005091:Exons / Q000235:genetics*; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007223:Infant; D008297:Male; D009154:Mutation; D010907:Pituitary Hormones / Q000172:deficiency* / Q000235:genetics; D011485:Protein Binding; D021381:Protein Transport; D022821:RNA Splice Sites / Q000235:genetics*; D050817:Transcription Factor Pit-1 / Q000235:genetics / Q000378:metabolism*; D014430:Twins, Monozygotic
chemical_list: C494187:POU1F1 protein, human; D010907:Pituitary Hormones; D022821:RNA Splice Sites; D050817:Transcription Factor Pit-1; D004247:DNA