title: Gene dosage as a relevant mechanism contributing to the determination of ovarian function in Turner syndrome.
abstract: OBJECTIVE
  What is the burden of X chromosome mosaicism in the occurrence of spontaneous menarche (SM) in Turner syndrome (TS)?
  
  
  CONCLUSIONS
  SM was significantly associated with X chromosome mosaicism in the TS patients; a mosaicism with around 10% euploid cell line may predict spontaneous pubertal development when determined by molecular-cytogenetic techniques on uncultivated tissues.
  
  
  BACKGROUND
  Spontaneous puberty can be observed in a minority of patients with TS, more frequently, but not exclusively, in those with a high level of 46,XX/45,X mosaicism at standard karyotype. The genetic mechanisms contributing to ovarian function in TS patients are still not determined. However, submicroscopic X-linked and autosomal copy number variations (CNVs) have recently emerged as an important genetic risk category for premature ovarian insufficiency and may be involved in modulating the TS ovarian phenotype.
  
  
  METHODS
  A group of 40 patients with a diagnosis of TS at conventional karyotyping participated in the study; 6 patients had SM and 34 patients had primary amenorrhoea (PA). All clinical data and the patients' DNA samples were collected over the years at a single paediatric clinic.
  
  
  METHODS
  The patients' samples were used to perform both genetic (Copy Number Assay) and molecular-cytogenetic (array-CGH and iFISH, interphase-FISH) analyses in order to evaluate the X chromosome mosaicism rate and to detect possible rare CNVs of genes with a known or predicted role in female fertility.
  
  
  RESULTS
  All TS patients showed variable percentages of the 46,XX lineage, but these percentages were higher in the SM group (P < 0.01). A mosaicism around 10% for the euploid cell line may predict spontaneous pubertal development when determined by molecular-cytogenetic techniques performed in uncultivated tissues. A few CNVs involving autosomal and X-linked ovary-related loci were identified by array-CGH analysis and confirmed by real-time quantitative PCR, including a BMP15 gene duplication at Xp11.22, a deletion interrupting the PAPPA gene at 9q33.1, and an intragenic duplication involving the PDE8A gene at 15q25.3.
  
  
  CONCLUSIONS
  This is a pilot study on a relatively small sample size and confirmation in larger TS cohorts may be required. The ovarian tissue could not be studied in any patients and in a subgroup of patients, the mosaicism was estimated in tissues of different embryonic origin.
  
  
  CONCLUSIONS
  The combined determination of X chromosome mosaicism by molecular and molecular-cytogenetic techniques may become useful for the prediction of SM in TS. The detection of CNVs in both X-linked and autosomal ovary-related genes further suggests gene dosage as a relevant mechanism contributing to the ovarian phenotype of TS patients. These CNVs may pinpoint novel candidates relevant to female fertility and generate further insights into the mechanisms contributing to ovarian function.
  
  
  BACKGROUND
  This study was funded by Telethon Foundation (grant no: GGP09126 to L.P.), the Italian Ministry of the University and Research (grant number: 2006065999 to P.F.) and a Ministry of Health grant 'Ricerca Corrente' to IRCCS Istituto Auxologico Italiano (grant number: 08C704-2006). The authors have no conflict of interest to declare.
authors: Medical Cytogenetics and Molecular Genetics Lab, IRCSS Istituto Auxologico Italiano, 20145 Milan, Italy.
authors: Chiara
authors: C
authors: Castronovo
authors: Raffaella
authors: R
authors: Rossetti
authors: Daniela
authors: D
authors: Rusconi
authors: Maria P
authors: MP
authors: Recalcati
authors: Chiara
authors: C
authors: Cacciatore
authors: Elena
authors: E
authors: Beccaria
authors: Valeria
authors: V
authors: Calcaterra
authors: Pietro
authors: P
authors: Invernizzi
authors: Daniela
authors: D
authors: Larizza
authors: Palma
authors: P
authors: Finelli
authors: Luca
authors: L
authors: Persani
mesh_terms: D000293:Adolescent; D002648:Child; D041321:Chromosomes, Human, X; D055028:Comparative Genomic Hybridization; D005260:Female; D005298:Fertility; D018628:Gene Dosage; D006801:Humans; D007621:Karyotyping; D008572:Menarche / Q000235:genetics*; D009030:Mosaicism; D010049:Ovarian Diseases / Q000473:pathology*; D010053:Ovary / Q000502:physiology*; D011627:Puberty; D014424:Turner Syndrome / Q000235:genetics*
keywords: BMP15; Turner syndrome; X chromosome; copy number variations; ovary