Isolation of a yeast artificial chromosome clone that spans the (12;16) translocation breakpoint characteristic of myxoid liposarcoma.

Cytogenetic analysis of liposarcomas has demonstrated that translocation (12;16) (q13.3;p11.2) is characteristic of the myxoid subtype of this adipose tissue tumor. Our previous results suggested that the GLI gene is close to the translocation breakpoint on chromosome 12. We now describe a yeast artificial chromosome (YAC) that contains GLI and spans the chromosome 12 region involved in the t(12;16) breakpoint. This clone will permit rapid definition of the genetic region surrounding the breakpoint and allow isolation of the gene presumably affected by the translocation.     

Identification of a BAC clone overlapping the t(6p12.3) breakpoint in the cell line ESS-1 derived from an endometrial stromal sarcoma

A major subgroup of endometrial stromal sarcomas (ESS) is characterized by translocations involving chromosome 6 with consistent breakpoints at 6p11 approximately p21. As part of an ongoing positional cloning effort to identify the genes affected by these translocations, this article reports on the delineation of the 6p breakpoint in the cell line ESS-1 derived from an ESS. The G- and 4',6-diamidino-2-phenylindole-banded karyotypes showed an unbalanced translocation described originally as der(3)t(3;6) (q29;p21.1). Fluorescence in situ hybridization using probes derived from contigous yeast artificial chromosome, bacterial artificial chromosome (BAC), and P1-derived artificial chromosome clones specific to 6p12.3 approximately p21.1 located the breakpoint at 6p to the BAC clone RP11-337K13 mapping to 6p12.3. The DNA sequence of the breakpoint region contained in RP11-337K13 will serve as a candidate locus for further molecular genetic analyses to isolate the gene(s) altered in ESS with 6p rearrangement.     

Involvement of the HMGI(Y) gene in a microfollicular adenoma of the thyroid.

Follicular thyroid adenomas are epithelial tumors characterized by subgroups with specific chromosomal aberrations. Here we present a case with translocation t(1;6)(p35;p21). In 1p35 and 6p21, two genes of the high-mobility group of proteins are located. With P1-derived Artificial Chromosome (PACs) derived from the HMG17 gene located at 1p35 and HMGI(Y) located at 6p21, fluorescence in situ hybridization was performed. The breakpoints were located distal to HMG17 and proximal to HMGI(Y), but no rearrangement of the genes was shown by FISH. However, an overexpression of the HMGI(Y) gene was detected by RT-PCR as well as by immunohistochemistry techniques. This suggests a breakpoint in the proximity of the HMGI(Y) deregulating HMGI(Y) gene expression, a situation found in a variety of human benign mesenchymal tumors with involvement of chromosome band 6p21.     

Fish mapping of a translocation breakpoint at 6q21 (or q22) in a patient with heterotaxia

Summary Heterotaxia is a congenital lateralization defect of visceral organs. As several single-genes that act on the formation of left-right asymmetry during embryogenesis have been identified in animals, a defect in the similar system may play a role in heterotaxia in man. We previously reported a Japanese girl with heterotaxia associated with ade novo balanced translocation (6;18)(q21 or q22;q21.3 or q22). In the present study, based on a hypothesis that one of the putative situs-determining genes is disrupted at a breakpoint of the translocation, we first isolated a yeast artificial chromosome (YAC) clone covering a breakpoint, 6q21 (or q22) of the translocation. Then, using STSs mapped on the YAC, we isolated bacterial artificial chromosome (BAC) clones spanning the breakpoint. FISH analysis using the BAC clones as probes revealed that the breakpoint is confined to a segment between two STS loci, WI-4066 and the CHLC.GATA6B06.192, within a genetic distance of 1.4 cM. The human connexin43 gene was not disrupted in our patient, although mutations of this gene have been reported in patients with complex heart disease and heterotaxia. The molecular localization of the translocation breakpoint in our patient may contribute to the positional cloning of a putative heterotaxia gene.     

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.     

Tandem Y/6 translocation with partial deletion 6 (p23→pter)

An infant with multiple malformations had a de novo tandem translocation of the Y chromosome to chromosome 6. The karyotype 45,X,tan(Y;6) (q12;p23) resulted in a partial monosomy of 6p23----pter. Many of the effects of ring chromosome 6 are present in this case.     

Molecular assignment of a translocation breakpoint in acute myeloid leukemia with t(8;21)

An 8;21 translocation is a common chromosome abnormality associated with acute myeloblastic leukemia with maturation (M2 of French-American-British (FAB) classification). We have isolated chromosome 21 Notl linking clones; pulsed field gel electrophoresis analysis with one clone (LL263) detected an altered fragment of Notl-digested leukemic cell DNA carrying t(8;21). The altered fragment was shown to be produced by the 8;21 translocation. The breakpoint in chromosome 21 was located about 13 kb to 100 kb proximal to the LL263 Notl site. Because the LL263 clone has a CpG island and is a short distance from the breakpoint, the clone itself may be considered as a candidate for part of the t(8;21) associated gene.     

Atypical breakpoint in a t(6;17) translocation case of acampomelic campomelic dysplasia

Campomelic dysplasia (CD) is a skeletal dysplasia characterized by Pierre Robin sequence (PRS), shortened and bowed long bones, airway instability, and the potential for sex reversal. A subtype of CD, acampomelic CD (ACD), is seen in approximately 10% of cases and preserves long bone straightness. Both syndromes are caused by alterations in SOX9, with translocations and missense mutations being overrepresented in ACD cases. We report a term infant with PRS, severe cervical spine abnormalities, eleven rib pairs, hypoplastic scapulae, and female genitalia. Chromosome analysis identified a 46,XY,t(6;17)(q25;q24) karyotype. FISH analysis with a series of BAC probes localized the translocation breakpoints to 6q27 and a region at 17q24.3 in the range of 459–379 kb upstream of SOX9. Therefore, this case extends the region classified as the proximal breakpoint cluster. In addition, the comorbidity of acampomelia, complete sex reversal, and severe spinal anomalies in our patient underscores the variability in the level of malformation in the CD/ACD family of disorders.     

HMGI(Y) expression in human uterine leiomyomata. Involvement of another high-mobility group architectural factor in a benign neoplasm.

Chromosomal rearrangements involving 6p21 have been observed in uterine leiomyomata and a variety of other benign tumors. The gene for HMGI(Y), a member of the high-mobility group (HMG) family of proteins, has been localized to 6p21. To determine whether rearrangements observed in this area alter HMGI(Y) expression, we analyzed HMGI(Y) DNA-binding activity in protein extracts from uterine leiomyoma and normal myometrium tissues. This report describes a uterine leiomyoma specimen with an inv(6)(p21q15). A genomic P1 clone that contains the HMGI(Y) region of chromosome 6 is found to span the inversion breakpoint by fluorescent in situ hybridization of metaphase chromosomes. Expression of HMGI(Y) protein in this leiomyoma specimen is increased dramatically as compared with the matching normal myometrial tissue. Elevated HMGI(Y) expression was also found in 8 of 16 leiomyomas without cytogenetically detectable chromosome 6p21 aberrations but not in any of the 9 matching myometrial tissues. Analysis of the genetic events involved in the pathobiology of these benign tumors will provide a basis for understanding the process of improper cellular growth and might be important in deciphering the multistep pathway of tumorigenesis.     

HMGI-C and HMGI(Y) immunoreactivity correlates with cytogenetic abnormalities in lipomas, pulmonary chondroid hamartomas, endometrial polyps, and uterine leiomyomas and is compatible with rearrangement of the HMGI-C and HMGI(Y) genes

High-mobility group (HMG) proteins are nonhistone nuclear proteins that play an important role in the regulation of chromatin structure and function. HMGI-C and HMGI(Y) are members of the HMGI family of HMG proteins, and their expression in adult tissues generally correlates with malignant tumor phenotypes. However, HMGI-C and HMGI(Y) dysregulation as a result of specific rearrangements involving 12q15 and 6p21, the respective chromosomal sites in which the HMGI-C and HMGI(Y) genes are located, is also identified in a variety of common benign mesenchymal tumors, such as lipomas and uterine leiomyomata. The general prevalence of HMGI-C and HMGI(Y) protein expression and its correlation with chromosomal alterations in these benign tumors are unknown. We analyzed 95 human tumors (20 lipomas, 21 pulmonary chondroid hamartomas, 26 uterine leiomyomata, and 28 endometrial polyps) representing a selection of the benign lesions in which karyotypic alterations involving the chromosomal regions 12q15 and 6p21 are frequently detected. All cases were successfully karyotyped and some of them analyzed by fluorescent in situ hybridization with probes spanning the HMGI-C and HMGI(Y) genes. The results of this study demonstrate that expression of HMGI-C or HMGI(Y) is a common occurrence in lipomas, pulmonary chondroid hamartomas, leiomyomata, and endometrial polyps; that it correlates with 12q15 and 6p21 chromosomal alterations (p < 0.001); and that it is compatible with rearrangement of the HMGI-C and HMGI(Y) genes. The expression pattern and cellular localization of the immunoreactivity support the view that in biphasic lesions composed of a mixture of both stromal and epithelial cells, such as pulmonary chondroid hamartoma and endometrial polyps, the mesenchymal component is the site of the HMGI genetic alterations.     

Familial t(6;21)(p21.1;p13) translocation associated with male-only sterility

A 38-year-old male with primary infertility was referred for cytogenetic investigation. Karyotype analysis revealed a 46,XY,t(6;21)(p21.1;pl3) translocation. The Ag-nucleolar organizer regions (NORs) banding technique demonstrated that the 21p NORs were retained in the derivative and actively transcribed. Family studies showed that three brothers, two sisters and their mother carried the t(6;21). All carrier males suffered from primary infertility with severe oligoasthenoteratospermia or azoospermia, whereas at least two of the three carrier women were fertile. The region of the translocation breakpoint was narrowed down cytogenetically and by fluorescence in situ hybridisation as 21p13 and 6p21.1. Southern blot analysis showed that the gene ZNF165, which maps to this region and which is specifically expressed in the testis, was not disrupted by the translocation. However, studies performed on testicular biopsy showed spermatocyte meiosis anomalies. We discuss the possible mechanisms by which the translocation might affect meiosis in spermatogenesis and lead to infertility.     

New translocation t(2;13)(p12;q34) and rearrangement of the MLL gene in a childhood leukemia cell line

Here we report the case of a 7-month-old boy who presented with biphenotypic acute leukemia, but with leukemia cells of B-cell phenotype present at the time of relapse. Two cell lines were derived from bone marrow specimens obtained at relapse, and immunophenotyping and analysis of antigen receptor gene configuration revealed concordance between the patient's leukemic cells and the cell lines. Cell line PER-377 shows a new chromosomal abnormality, t(2;13)(p12;q34), a molecular rearrangement at chromosome band 11q23 in the absence of a cytogenetically detectable abnormality of this band, and deletion of the genes for IGK.     

FISH characterization of the Xq21 breakpoint in a translocation carrier with premature ovarian failure

A panel of ordered YAC clones, isolated using STSs in the Xq13-Xq23 region, was used to characterize by Fluorescent In Situ Hybridization (FISH) the Xq21 breakpoint in a t(X;1)(q21;p34) translocation female with premature ovarian failure. The YAC 949E11 was found to span the breakpoint, but also to join the two non-overlapping YACs 36CB1 and 40AB3, proximal and distal, respectively, to the patient's Xq21 breakpoint.     

Partial trisomy 6q, due to balanced maternal translocation (6;22) (q21; p13) or (q21; pter)

We report a stillborn infant with partial trisomy 6q who had several major congenital malformations not previously associated with this chromosomal aberration. These included occipital encephalocele, ambiguous genitalia with imperforate anus, omphalocele and unilateral hydronephrosis. The infant's karyotype was 46, XY,-22, der(22), t(6;22)(q21; p13) or (q21;pter)mat. The mother and maternal grandmother are balanced translocation carriers.