title: Microsatellite analysis in Turner syndrome: parental origin of X chromosomes and possible mechanism of formation of abnormal chromosomes.
abstract: Turner syndrome is a chromosomal disorder in which all or part of one X chromosome is missing. The meiotic or mitotic origin of most cases remains unknown due to the difficulty in detecting hidden mosaicism and to the lack of meiotic segregation studies. We analyzed 15 Turner patients, 10 with a 45,X whereas the rest had a second cell line with abnormal X-chromosomes: a pseudodicentric, an isochromosome, one large and one small ring, and the last with a long arm deletion. Our aims were: to detect X cryptic mosaicism in patients with a 45,X constitution; to determine the parental origin of the abnormality; to infer the zygotic origin of the karyotype and to suggest the timing and mechanism of the error(s) leading to the formation of abnormal X chromosomes from maternal origin. Molecular investigation did not revealed heterozygosity for any microsatellite, excluding X mosaicism in the 45,X cases. Parental origin of the single X chromosome was maternal in 90% of these patients. Three of the structurally abnormal Xs were maternally derived whereas the other two were paternal. These results allowed us to corroborate breakpoints in these abnormal X chromosomes and suggest that the pseudodicentric chromosome originated from post-zygotic sister chromatid exchange, whereas the Xq deleted chromosome probably arose after a recombination event during maternal meiosis.
authors.affiliation: Servicio de Genética, Hospital General de México/Facultad de Medicina, UNAM, México, D.F, México.
authors.forename: Nancy
authors.initials: N
authors.lastname: Monroy
authors.forename: Marisol
authors.initials: M
authors.lastname: López
authors.forename: Alicia
authors.initials: A
authors.lastname: Cervantes
authors.forename: Diana
authors.initials: D
authors.lastname: García-Cruz
authors.forename: Gildardo
authors.initials: G
authors.lastname: Zafra
authors.forename: Sonia
authors.initials: S
authors.lastname: Canún
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Zenteno
authors.forename: Susana
authors.initials: S
authors.lastname: Kofman-Alfaro
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002871:Chromosome Banding; D004247:DNA / Q000235:genetics; D005192:Family Health; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007621:Karyotyping; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D010375:Pedigree; D012729:Sex Chromosome Aberrations; D014424:Turner Syndrome / Q000235:genetics*; D014960:X Chromosome / Q000235:genetics
chemical_list: D004247:DNA