An X;9 translocation, primary amenorrhea, and hypothalamic dysfunction

Cytogenetic evaluation of patients with clinical spectrum of Turner syndrome

AIM:

The objective of this study was to correlate the genotype, of female patients, withshort stature and primary amenorrhea.

MATERIALS AND METHODS:

One hundred and forty-six subjects were recruited during 2005-2012. Microscopic and automated karyotyping analyses were done by using chromosomes isolated from the lymphocytes using Giemsa banding (GTG) to identify chromosome abnormalities.

RESULTS:

A total of 146 clinically suspected Turner syndrome (TS) subjects were recruited for the study, of which, 61 patients were identified to have chromosome abnormalities. The chromosomal abnormalities detected were as follows: Monosomy X (n = 19, 13.01%), triple X syndrome (n = 4, 2.7%), mosaic TS (n = 12, 8.21%), XY gonadal dysgenesis (n = 13, 8.9%), and structural abnormalities including X chromosome (n = 15, 10.27%) and one patient each with autosomal changes involving 9qh inversion and translocation of chromosomes 12 and 14.

CONCLUSION:

Karyotype abnormalities accounting for 46% in this study emphasize the need for karyotype testing in cases of short stature with primary amenorrhea.

A dominant X-linked QTL regulating pubertal timing in mice found by whole genome scanning and modified interval-specific congenic strain analysis

BACKGROUND

Pubertal timing in mammals is triggered by reactivation of the hypothalamic-pituitary-gonadal (HPG) axis and modulated by both genetic and environmental factors. Strain-dependent differences in vaginal opening among inbred mouse strains suggest that genetic background contribute significantly to the puberty timing, although the exact mechanism remains unknown.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a genome-wide scanning for linkage in reciprocal crosses between two strains, C3H/HeJ (C3H) and C57BL6/J (B6), which differed significantly in the pubertal timing. Vaginal opening (VO) was used to characterize pubertal timing in female mice, and the age at VO of all female mice (two parental strains, F1 and F2 progeny) was recorded. A genome-wide search was performed in 260 phenotypically extreme F2 mice out of 464 female progeny of the F1 intercrosses to identify quantitative trait loci (QTLs) controlling this trait. A QTL significantly associated was mapped to the DXMit166 marker (15.5 cM, LOD = 3.86, p<0.01) in the reciprocal cross population (C3HB6F2). This QTL contributed 2.1 days to the timing of VO, which accounted for 32.31% of the difference between the original strains. Further study showed that the QTL was B6-dominant and explained 10.5% of variation to this trait with a power of 99.4% at an alpha level of 0.05.The location of the significant ChrX QTL found by genome scanning was then fine-mapped to a region of approximately 2.5 cM between marker DXMit68 and rs29053133 by generating and phenotyping a panel of 10 modified interval-specific congenic strains (mISCSs).

CONCLUSIONS/SIGNIFICANCE

Such findings in our study lay a foundation for positional cloning of genes regulating the timing of puberty, and also reveal the fact that chromosome X (the sex chromosome) does carry gene(s) which take part in the regulative pathway of the pubertal timing in mice.

Functional disomies of the X chromosome influence the cell selection and hence the X inactivation pattern in females with balanced X-autosome translocations: a review of 122 cases

We reviewed 122 cases of balanced X-autosome translocations in females, with respect to the X inactivation pattern, the position of the X break point and the resulting phenotype. In 77% of the patients the translocated X chromosome was early replicating in all cells analysed. The break points in these cases were distributed all along the X chromosome. Most of these patients were either phenotypically normal or had gonadal dysgenesis, some had single gene disorders, and less than 9% had multiple congenital anomalies and/or mental retardation. In the remaining 23% of the cases the translocated X chromosome was late replicating in a proportion of cells. In these cells only one of the translocation products was reported to replicate late, while the remaining portion of the X chromosome showed the same replication pattern as the homologous part of the active, structurally normal X chromosome. The analysis of DNA methylation in one of these cases confirmed noninactivation of the translocated segment. Consequently, these cells were functionally disomic for a part of the X chromosome. The presence of disomic cells was highly prevalent in translocations with break points at Xp22 and Xq28, even though spreading of X inactivation onto the adjacent autosomal segment was noted in most of these cases. This suggests that selection against cells with a late replicating translocated X is driven predominantly by a functional disomy X, and that the efficiency of this process depends primarily on the position of the X break point, and hence the size of the noninactivated region.(ABSTRACT TRUNCATED AT 250 WORDS)

Whole-arm t(X;17) (Xp17q;Xq17p) and gonadal dysgenesis. A further exception to the critical region hypothesis

A 19-year-old female patient with gonadal dysgenesis and a de novo t(X;17) (Xp17q;Xq17p) is described. Since the critical segment Xq13----q26 was intact, this case is a further exception to the critical region hypothesis.

Effect of balanced X/autosome translocations on sexual and physical development. A personal experience in 4 patients

Four different balanced X/autosome translocations: 46,X,t(X;9)(p11;q13); 46,X,t(X;12) (p11;q12); 46,X,t(X;15)(q12;p11) and 46,X,t(X;19)(q26;p12) are described in four female patients. The effect of X/autosome translocations on physical and sexual development of these women and their offspring is discussed.