Two dicentric Y isochromosomes, one without the Yqh heterochromatic segment

Abstract

Two women with primary amenorrhoea and few other stigmata of Turner's syndrome were found to be chromosome mosaics: 45,X/46,X,idic(Y). In Case 1, the dicentric isochromosome Y was found to have a long-arm breakpoint of formation. This structure was interpreted as containing two Y short arms and centromeres separated by a region derived from the proximal Y long arm. One of the centromeres in the Case 1--idic(Y) was suppressed in 80% of cells in blood, and in these cells it appeared as a regular Y-shaped chromosome. In Case 2 the idic(Y) was derived by a short-arm breakpoint of formation. In all the dicentrics of this case with one primary constriction (functional monocentrics) there was a single Cd band. In the 10% of dicentrics with two primary constrictions, there were two Cd bands. It is argued that the instability of sex isochromosomes is due to this functional dicentricity in some cells. These cases are compared with 42 other Y isochromosomes with various short- and long-arm breakpoints of formation. It is suggested that some of the nonheterochromatic, nonfluorescent Y chromosomes previously reported may be explained as dicentric i(Y) with proximal long-arm breakpoints of formation and one suppressed centromere.

47,X,idic(Y),inv dup(Y): A Non-Mosaic Case of a Phenotypically Normal Boy with Two Different Y Isochromosomes and Neocentromere Formation

“…If our proband's fertility turns out to be unimpaired as well, some of his offspring may have imbalanced karyotypes due to malsegregation after pairing and homologous recombination at PAR1 and PAR2. This may cause gonosomal disorders like Many cases of different forms of Y isochromosomes, most often isodicentrics involving long and short arms, have been reported during the last 3 decades [Daniel et al, 1980;Davis, 1981;Fryns et al, 1987;Haaf and Schmid, 1990;Hsu, 1994;Tuck-Muller et al, 1995;Stuppia et al, 1996;DesGroseilliers et al, 2006;Lange et al, 2009]. Most of these patients are mosaic for 45,X often showing variable clinical features including short stature and abnormal or ambiguous sexual development.…”

45, XO/46, X, dic(Yq) Mosaicism in Turner’s Phenotype with Endodermal Sinus Tumor of the Ovary

“…More than 30 cases of dicentric Y chromosome have been reported in the literature [1], In the individuals reported to have dicentric Y chromosome, the pheno typic sex and the gonadal differentiation have been vari able [4], Most cases of dicentric Y chromosome were found in association with an abundant 45,XO cell line [4], The karyotype of this case is 45,XO/46,X,dic(Yq) mosaicism. It is unquestionable now that a gene or genes on the short arm of the Y near the centromere play a crucial role in the development of the testis [5], How ever, this patient had some primordial follicles and no testicular cells in the gonads.…”

“…Many examples of abnormal sexual or gonadal differ entiation and structural anomalies of the Y chromosome have been reported [1,2]. Since Yunis [3] described the dicentric Y chromosome in 1965, more than 30 cases of dicentric Y chromosome have been reported.…”

Clonal origin of partially inactivated centromeres in a stable dicentric chromosome

“…Similarly, the instability observed in some dicentric cell lines may indi cate sporadic activation of a latent centromere (Hsu ct al., 1978: Dewald et al. 1979: Daniel et al. 1980: Ingand Smith.…”