Common fragile sites in couples with recurrent spontaneous abortions

A new heritable fragile site at 15q13 in a three-generation family

Here, we describe a family ascertained through recurrent spontaneous abortions in which a new heritable fragile site located at 15q13 is segregating. The fragile site was present in nine members of a three-generation family and expressed spontaneously in a high proportion of the metaphases varying from 88 to 95% under standard culture conditions in all the carriers. This didn't change under folate deficiency.

Differential susceptibility to chromatid breaks induced by bleomycin in sub-fertile and fertile bovines

The rate of chromatid breaks was studied in cows with a history of sub-fertility by means of a test based on measurement of the average of breaks induced in lymphocytes of peripheral blood cultures. Fourteen female specimens were divided into two groups: fertile and sub-fertile. Peripheral blood lymphocytes were cultured and prepared for cytogenetic analysis. Two types of culture were established for each animal to evaluate the response of peripheral blood lymphocyte cultures to the genotoxic effects of bleomycin. The first culture did not receive bleomycin treatment (spontaneous chromosome aberrations). Our results showed that median breaks per cell (b/c) (+/-semirange) for spontaneous culture of the fertile and sub-fertile animals and bleomycin sensitivity assay for fertile and sub-fertile animals were 0.00+/-0.06, 0.02+/-0.03, 0.08+/-0.05 and 0.22+/-0.09, respectively. There was no significant difference (P>0.05) in the chromosomal breakage in lymphocytes not exposed to bleomycin; however, in comparing the number of chromatid breaks per cell in cultures treated with bleomycin, the sub-fertile group showed a significantly higher (P<0.05) level than the fertile group. These findings have implications both for identifying cattle with less than optimum fertility as well as for providing potential avenues to study the origins of sub-fertility.

Single cell chromosome rearrangements in indivuduals with reproductive failure

Single cell chromosome rearrangements (SCCR) are incidental findings in cell cultures. Nevertheless, some authors have implicated them in habitual abortion. Ninety individuals classified in four groups were prospectively studied: A) individuals with spontaneous abortions, malformed children or molar pregnancies (N = 36); B) azoospermic males (N = 14); C) individuals with one or more children with either de novo or inherited, constitutional, chromosome abnormalities (N = 26), and D) individuals with healthy children and no reproductive failure (control group, N = 14). Lymphocyte chromosome preparations were stained for GTG bands, and 50-100 metaphases were scored per individual. The rearrangements observed were translocations, deletions, duplications, isochromosomes, rings, fragments and markers. Thirty-four individuals (21 males, 13 females) had a range of 1-5 SCCR. Four had rearrangements only of chromosomes 7 and 14. SCCR frequency (with the exception of rearrangements involving chromosomes 7 and 14) was 0.0063, while that of rearrangements between chromosomes 7 and 14 was 0.0010. Statistical intergroup comparisons (<FONT FACE="Symbol">c</font>2 with Yates correction) did not show significant differences. Hence, the occurrence of SCCR in our sample was found to be independent of ascertainment mode and sex.

New heritable fragile site with spontaneous expression at 1q41

The report presents a family ascertained through recurrent spontaneous abortions in which a new heritable fragile site located at 1q41 is segregating. The fragile site is present in the mother and her son. It is expressed spontaneously in 100% of the metaphases from lymphocyte culture using standard conditions. The use of folate deficient medium and the addition of FUdR to the medium did not affect the appearance nor the level of expression of the fragile site.

6p23 deletion mosaicism in a woman with recurrent abortions and idiopathic hypoprolactinemia

A woman with a history of recurrent abortions, idiopathic hypoprolactinemia, and an apparent 6p partial deletion mosaicism is described. The breakpoint in the short arm of chromosome 6 was in the p23 region. This deletion could have been caused by a fragile site in 6p23.

Expression of common fragile sites on the X chromosome corresponds with active gene regions

The expression of common chromosomal fragile sites on human chromosomes has been proposed to be a cytogenetic expression of gene activity. Distinctive patterns of expression of two common fragile sites on the human X chromosome were observed in females. The fragile site at Xp22.31, located in a band region that contains genes which escape X inactivation, was expressed on both X chromosomes. By contrast, the fragile site at Xq22.1, in a region assumed to be subject to X inactivation, was expressed almost exclusively on one X, the active X chromosome. These findings provide evidence that common fragile site expression only occurs in regions with active genes.

Chromosome lesions which could be interpreted as "fragile sites" on the distal end of Xq

Chromosome lesions which could be interpreted as "fragile sites" on the distal end of the long arm of the X chromosome were identified during a cytogenetic study of 160 mentally retarded adult males with no apparent cause of their mental retardation and one normal adult female with a family history of fra (X) syndrome. Peripheral blood samples were cultured in either M199 or RPMI 1640 medium with FUdR or BrdU. Metaphases were examined for chromosome lesions or fragile sites on the distal end of Xq and 3 distinct sites were observed: Xq26, Xq27.2, and Xq27.3. Other chromosome lesions at Xq28 were observed and interpreted as nonspecific telomeric structural changes. Chromosome lesions were observed in cells from 14 of the 161 individuals. These included: 5 patients with an Xq26 site, 2 with the recently reported Xq27.2 site, 4 with the Xq27.3 site (characteristic of the fra (X) syndrome), 2 with nonspecific telomeric structural changes, and one individual with 2 lesions (a nonspecific telomeric structural change and an Xq26 site). Additional research is necessary to determine the frequency and clinical significance, if any, of lesions occurring in this region of the X chromosome and to distinguish among heritable fragile sites, constitutive fragile sites, and nonspecific telomeric structural changes.