Heritable fragile sites and cancer: fra(16)(q22) in lymphocytes of an acute nonlymphocytic leukemia patient with inv(16)(p13q22)

Fragile site testing was performed on normal peripheral blood lymphocytes from three acute nonlymphocytic leukemia patients who carried inv(16)(p13q22) in malignant cells. Cultures were treated with BrdU, distamycin A, Hoechst 33258, or folic acid deprivation to induce fragile site expression. One patient was found to be a carrier of fra(16)(q22), but the expression was observed only by Hoechst 33258 treatment.     

Pericentric inversions inv(2)(p11q13) and inv(2)(p13q11) in 2 unrelated families.

Pericentric inversions in chromosome 2 were traced in 2 unrelated North American black families. In the case of inv(2)(p13q11) no effect on reproduction was observed. In the case of inv(2)(p11q13) some reproductive abnormalities were noted which might be related to the inversion.     

Constitutive fragile sites in fra(X) individuals

Recently, it was proposed that the constitutive fragile site at 3p14 be used as an "internal control" to indicate the effectiveness of the FUdR fragile site induction system. We have tested this hypothesis by determining the frequency of constitutive fragile sites at 1p31, 3p14, and 16q23 in cultures from 42 known fra(X) individuals. At least 50 cells were analyzed from each case. Seventy-four percent (31/42), 95% (40/42) and 90% (38/42) of the fra(X) individuals exhibited frequencies of less than 4% at constitutive fragile sites 3p14, 1p31 and 16q23, respectively. Of the 42 individuals tested, 12 or 28.6% showed no fragility at any of the 3 sites studied. On the other hand, at least one constitutive fragile site was observed in 50 cells studied from over 70% of the 42 people studied. It is suggested that "positive controls" continue to be used, while at the same time recording all fragile sites to identify a combination of constitutive fragile sites that may serve as an internal control indicator, and that DNA marker studies be used to complement cytogenetic testing.     

Normal blood lymphocytes from patients with adipose tissue tumors with rearrangements at 12q13-q14 do not express the fragile site fra(12)(q13.1)

An association between chromosomal fragile sites and cancer-specific breakpoints has been found to be statistically significant. Cancer patients have been shown to be carriers of fragile sites in chromosome regions involved in rearrangements in malignant cells. Based on these observations it has been hypothesized that fragile sites may be involved in the pathogenesis of human tumors. We have recently described a new recurrent cancer breakpoint at chromosomal region 12q13-q14 in adipose tissue tumors. The possible involvement in these tumors of the rare folate-sensitive fragile site 12q13.1 has been investigated in PHA-stimulated peripheral blood cells from three patients carrying the t(12;16)(q13;p11) in their liposarcoma cells and one patient with the t(3;12)(q28;q14) in his lipoma cells. No expression of the fragile site 12q13.1 could be detected in the blood lymphocytes of any of the patients. The involvement of the fragile site 12q13.1 in the pathogenesis of adipose tissue tumors with a 12q13-q14 breakpoint remains to be established.     

Direct intrachromosomal duplication of 16q and heritable fragile site fra (10) (q25) in the same patient

We describe a woman with profound mental retardation and a direct duplication of 16q and fragile site fra(10)(q25). The identification and possible origin of the duplicated 16q is discussed along with the clinical manifestations. To our knowledge this is the first direct duplication of 16q to be reported. The karyotype is shown to be 46,XX, dir dup (16) (q11.2----q13).     

The fragile X(q27) form of X-linked mental retardation: FUdR as an inducing agent for fra(X)(q27) expression in lymphocytes,fibroblasts, and amniocytes

The effect of FUdR on the expression of fra(X)(q27) was examined in lymphocytes and/or fibroblasts from 16 affected males and 5 carriers from 10 families; six different culture media were used: F10, 5% serum, pH 7.3(37°C); medium 199, 5% serum, pH 7.6(37°C); folate-free 199, 5% serum, pH 7.6(37°C), and these three media with FUdR (0.05 μm). In lymphocytes there was no significant difference in the percentage of fra(X) expressing cells between any of the FUdR-containing media. The highest percentage of expressing cells seen in lymphocytes with FUdR was 56%. The average enhancement in males with FUdR in the 199 and folate-free 199 media was 30%. This relative enhancement with FUdR was very much higher in a few blood specimens delayed in transit and FUdR may prevent some of the false-negative results obtained from mailed specimens. FUdR did not induce the marker in four obligate carriers with previously negative results. The fibroblasts from affected males were grown in the six specific media for the last 48 hr. Two of the six media yielded reproducibly positive results. These were 199-FUdR and folate-free 199-FUdR with mean percentages of expressing cells of 12.8 ± 7.1% and 11.3 ± 6.1%, respectively. F10-FUdR, which contains thymidine, did not permit expression of the marker in fibroblasts and there was no difference in the percentage of fra(X) expression in 199-FUdR media with or without folate. It was concluded that FUdR shows promise as an agent to permit prenatal diagnosis of the condition and to enhance the detection of the marker in lymphocyte cultures.     

Spontaneous expression of fra(11)(q23) in a patient with Ewing's sarcoma and t(11;22)(q23;q11)

Cytogenetic analysis of a Ewing's sarcoma revealed a 46,XX,t(8;18)(q11;q21.3), t(11;22)(q23–24;q11–12) chromosome pattern. Observation of t(11;22) is consistent with other reported cases of Ewing's sarcoma. One breakpoint in this translocation, 11q23, coincides with the location of a folate-sensitive fragile site. Examination of peripheral blood leukocyte chromosomes from the patient revealed a 46,XX chromosome pattern with spontaneous, fluorodeoxyuridine-, and Bactrim-induced expression of fra(11)(q23). This may be the first demonstration of constitutional fra(11)(q23) expression in a patient with a neoplasm that exhibits a chromosome rearrangement involving this breakpoint and the first observation of spontaneous expression of this fragile site. These results provide a basis for discussion of the relationship between fragile sites and chromosome rearrangements.     

Replication status of fragile X(q27.3) in 13 female heterozygotes.

Chromosome analysis, after bromodeoxyuridine incorporation and a sequential Leishman acridine orange staining method previously described, was used to assess the percentage of early or active fragile Xs compared with the overall total in informative cells in 13 heterozygous females. The percentage thus obtained was then used to calculate the percentage of early or active fragile X that would be expected in a culture without bromodeoxyuridine, that is: percentage active fragile X divided by 100 X percentage fra(X) in standard 199 or M culture. Five females were normal and eight of below normal intelligence. In one culture pokeweed mitogen was substituted for phytohaemagglutinin and the percentage of active fragile Xs obtained was compared with that obtained with phytohaemagglutinin. In the same female the effect of addition of fluorodeoxyuridine and methotrexate on the replication ratio of the X was also investigated. R banded and G banded cells from this subject were also scanned for the deletion of Xq27.3----qter.     

Expression of fra(10)(q25) in peripheral blood and bone marrow in familial neutropenia.

We report on the expression of fra(10)(q25) in a mother and daughter with familial chronic neutropenia. Differences in expression of the fragile site in bone marrow cells compared with peripheral blood lymphocytes were observed. Short term bone marrow cultures in complete medium showed high levels of spontaneous expression, whereas in 72 hour stimulated blood cultures it was virtually absent. There were also differences in the types of lesions found; chromosome type lesions predominated in the marrow and chromatid type in the blood. Apparent folate sensitivity of the fra(10)(q25) is also discussed.     

Rare interstitial deletion (2)(p11.2p13) in a child with pericentric inversion (2)(p11.2q13) of paternal origin.

An unbalanced 46,XY,der(2)del(2)(p11.2p13) inv(2)(p11.2q13) karyotype was found in a phenotypically abnormal child with a de novo interstitial deletion of band 2p12 associated with an inv(2)(p11.2q13) inherited from the father. The inv(2) is generally considered a benign familial variant without significant reproductive consequences. However, our findings led us to consider a previously proposed mechanism of unequal meiotic crossing over at the base of a parental inversion loop, which could lead to either a deletion or duplication of a segment adjacent to the inverted region in the offspring. This phenomenon has been reported in other inversions of chromosomes 1, 7, 13, 15, and 17 and may explain the origin of the deletion in our patient. Although repetitive sequences might be present around such inversions, which could predispose to de novo deletions independently of the inversion, current evidence including this case favors a proposed causal relationship between the parental inversion and the deletion in the child. Our review and results suggest there could be a small risk for a related imbalance to couples with an inv(2)(p11.2q13). For del(2)(p11.2p13), which is rare, a more distinct phenotype has been proposed herein. Our patient shared several findings with the three previously published cases, namely the broad nasal bridge, abnormal ears, high-arched palate, psychomotor retardation, and micrognathia. However, our patient also had sensorineural hearing loss and significant hypotonia, which have not been previously reported, thereby expanding our understanding of this rare deletion. Am. J. Med. Genet. 87:139-142, 1999. Published 1999 Wiley-Liss, Inc.     

Trisomy 13 due to rea(13q;13q) is caused by i(13) and not rob(13;13)(q10;q10) in the majority of cases

We have used 20 PCR-based DNA polymorphisms to determine whether trisomy 13 due to de novo rea(13q;13q) in six cases is caused by translocation (13q;13q) or isochromosome (13q;13q); to determine the parental origin of the rearrangements and the mechanisms of formation. The six probands were three liveborn children with clinical features characteristic of Patau's syndrome and three fetuses diagnosed prenatally by amniocentesis or CVS. Five cases were isochromosomes with two identical q arms, one of maternal and four of paternal origin. Only one case was a Robertsonian translocation of maternal origin.     

Translocation (X;5)(q13;q33) in essential thrombocythemia.

We report a novel chromosomal translocation (X;5)(q13;q33) in a woman with no history of prior chemotherapy or radiotherapy, found to have essential thrombocythemia. Aberrations in chromosome 5, mostly deletions of 5q, have been described in essential thrombocythemia; however, a t(X;5) translocation has not been reported.     

Two pericentric inversions, inv(2)(p11q13) and inv(5)(p13q13), in a patient referred for psychiatric problems

Two pericentric inversions were found in the karyotype of a male patient referred for psychiatric problems. Cytogenetic analysis, using conventional Giemsa staining and G and C banding techniques, revealed a pericentric inversion in chromosome 2, inv(2)(p11q13), and chromosome 5, inv(5)(p13q13) (fig 1). Subsequent family studies showed that the proband's father carried both inversions also (fig 2), while other members were found to be carriers of either the inverted 2 or the inverted 5. To our knowledge, this is the first report of two pericentric inversions to be found in the human genome.     

Familial t(11;13)(q21;q14) and the duplication 11q, 13q phenotype

Cases of duplication of distal 11q or proximal 13q have been reported independently. A specific translocation resulting in duplication of distal 11q, [der(22)t(11;22)(q23;q11)], has been documented in over 40 cases. We report on a male fetus with chromosomal excess of both distal 11q and proximal 13q resulting from a familial translocation. This case supports the causal association of duplication 11q with neural tube defects. © 1993 Wiley-Liss, Inc.     

Maternal translocation t(13:18)(q34:q11) and Edwar''s syndrome in a fetus: 47, XY, t(13:18)(q34:q11) + 18

A 32-year-old woman, who presented with four spontaneous abortions, was found to have a balanced translocation: 46,XX,t(13:18)(q34:q11). In the last pregnancy an amniocentesis was done. Abnormal constitution of the fetus had been detected: 47,XY,t(13:18)(q34:q11) + 18, and an abortion was induced. Examination of the fetal tissue confirmed the finding. The fetus showed the characteristics of Edward's syndrome. Through the patient's pedigree it was discovered that balanced translocation appeared in three generations.     

Inversion (X)(p22q13) in a uterine leiomyoma.

We report a case of uterine leiomyoma which showed a karyotype 46,X,inv(X)(p22q13) as the only clonal change in most of the cells. A few cells had an additional del(7), though del(7) has been found to be a primary change in leiomyomas. These findings indicate that the abnormality involving the X chromosome and particularly Xp22 can be considered as a primary chromosomal abnormality. We discuss the findings together with few reports of cases involving chromosome X in leiomyomas.     

Rare interstitial deletion (2)(p11.2p13) in a child with pericentric inversion (2)(p11.2q13) of paternal origin

An unbalanced 46,XY,der(2)del(2)(p11.2p13) inv(2)(p11.2q13) karyotype was found in a phenotypically abnormal child with a de novo interstitial deletion of band 2p12 associated with an inv(2)(p11.2q13) inherited from the father. The inv(2) is generally considered a benign familial variant without significant reproductive consequences. However, our findings led us to consider a previously proposed mechanism of unequal meiotic crossing over at the base of a parental inversion loop, which could lead to either a deletion or duplication of a segment adjacent to the inverted region in the offspring. This phenomenon has been reported in other inversions of chromosomes 1, 7, 13, 15, and 17 and may explain the origin of the deletion in our patient. Although repetitive sequences might be present around such inversions, which could predispose to de novo deletions independently of the inversion, current evidence including this case favors a proposed causal relationship between the parental inversion and the deletion in the child. Our review and results suggest there could be a small risk for a related imbalance to couples with an inv(2)(p11.2q13). For del(2)(p11.2p13), which is rare, a more distinct phenotype has been proposed herein. Our patient shared several findings with the three previously published cases, namely the broad nasal bridge, abnormal ears, high-arched palate, psychomotor retardation, and micrognathia. However, our patient also had sensorineural hearing loss and significant hypotonia, which have not been previously reported, thereby expanding our understanding of this rare deletion. Am. J. Med. Genet. 87:139–142, 1999. Published 1999 Wiley-Liss, Inc.     

Deletion (13)(q13q14.3) with retinoblastoma: confirmation and extension of a recognisable pattern of clinical features in retinoblastoma patients with 13q deletion.

A girl with retinoblastoma and a del(13)(q13q14.3) is presented. This case helps to confirm and extend our previous observations regarding a recognisable facial pattern in retinoblastoma patients with 13q deletion involving 13q14 and its adjacent segments.