title: A novel HESX1 splice mutation causes isolated GH deficiency by interfering with mRNA processing.
abstract: OBJECTIVE
  Mutations in HESX1 represent a rare cause of GH deficiency (GHD) associated with a broad spectrum of other anomalies. We searched for causative mutations in a cohort of 244 Italian patients affected by combined and isolated GHD (IGHD).
  
  
  METHODS
  The HESX1 gene-coding region and exon-intron boundaries were screened by denaturing HPLC scanning.
  
  
  RESULTS
  A novel mutation adjacent to the invariant donor splice site of intron 2 (c.357+3G>A) was identified at the heterozygous state in an IGHD patient. The in vitro and in vivo mRNA analysis of the wild-type HESX1 allele revealed the presence of the whole cDNA and two isoforms lacking exon 2 and exons 2-3 respectively. The mutant HESX1 allele yielded only two splicing products, the whole cDNA and the cDNA missing exons 2-3, whereas the mRNA lacking exon 2 was absent. An in vitro assay demonstrated that the exon 2-deleted mRNA, predicting a prematurely truncated protein, is subjected to nonsense-mediated mRNA decay (NMD).
  
  
  CONCLUSIONS
  The c.357+3G>A mutation prevents the generation of one of the alternative isoforms normally produced by the wild-type allele, predicting a truncated HESX1 protein. The mutation is likely to cause IGHD in the heterozygous patient by interfering with the downregulation of HESX1 expression mediated by alternative splicing and NMD. Our results open new insight into the mechanism of HESX1 regulation suggesting that the coupling of alternative splicing and NMD might play a fundamental role in directing the HESX1 expression, and that the alteration of this process might lead to severe consequences.
authors.affiliation: Laboratorio di Oncologia Ospedale Santa Croce e Carle, 12100 Cuneo, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Vivenza
authors.forename: Michela
authors.initials: M
authors.lastname: Godi
authors.forename: Maria Felicia
authors.initials: MF
authors.lastname: Faienza
authors.forename: Simona
authors.initials: S
authors.lastname: Mellone
authors.forename: Stefania
authors.initials: S
authors.lastname: Moia
authors.forename: Anna
authors.initials: A
authors.lastname: Rapa
authors.forename: Antonella
authors.initials: A
authors.lastname: Petri
authors.forename: Simonetta
authors.initials: S
authors.lastname: Bellone
authors.forename: Stefania
authors.initials: S
authors.lastname: Riccomagno
authors.forename: Luciano
authors.initials: L
authors.lastname: Cavallo
authors.forename: Mara
authors.initials: M
authors.lastname: Giordano
authors.forename: Gianni
authors.initials: G
authors.lastname: Bona
mesh_terms: D000293:Adolescent; D000483:Alleles; D017398:Alternative Splicing / Q000235:genetics*; D000818:Animals; D016466:CHO Cells; D002648:Child; D002675:Child, Preschool; D006224:Cricetinae; D003412:Cricetulus; D004393:Dwarfism, Pituitary / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007223:Infant; D008297:Male; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D055815:Young Adult
chemical_list: C489736:HESX1 protein, human; D018398:Homeodomain Proteins; D012333:RNA, Messenger