Molecular characterization of a ring chromosome 16 from a patient with bilateral cataracts.

A four-month-old white female, who was referred to us for genetic evaluation because of severe developmental delay, dysmorphic features, and bilateral cataracts, was found by routine cytogenetic analysis to have ring chromosome 16 in almost all cells analyzed. Ring chromosome 16 was confirmed and further delineated by fluorescence in situ hybridization (FISH). Breakpoints between loci D16S521 and KG8 on the short arm and D16S3121 and D16S303 on the long arm of chromosome 16 were determined by polymerase chain reaction (PCR) analysis. The deleted chromosome was of maternal origin. To our knowledge, this is the first case of ring chromosome 16 associated with bilateral cataracts. Comparison of previously reported cases with deletion of chromosome 16 and our case suggests the presence of cataract locus within 1 Mb of the terminus of 16q.     

Fluorescence in situ hybridization detection of two telomeres on the short arm of a derived chromosome 16 in an infant with thrombocytopenia

We report a case of severe thrombocytopenia with an abnormal bone marrow karyotype described by G-banding analysis as t(16;21)(p?13;q11). Using fluorescence in situ hybridization (FISH) analysis with whole chromosome paints, the chromosome rearrangement was shown to be more complex, with the additional cryptic involvement of the long arm of chromosome 3. The chromosome rearrangement involved the breakpoints 3q26, 16p13.3, and 21q11; this rearrangement has not been previously described. The size of genomic material translocated from the chromosome 16 homologue was too small to be detected by chromosome paint. A 16p-specific telomeric probe was hybridized to locate the translocated 16p material. The 16p telomeric unique sequence DNA was retained on the der(16) chromosome, indicating a more distal breakpoint. This study demonstrates that telomeric translocations can occur that would be undetected by telomeric-specific FISH probes.     

Molecular characterization of a ring chromosome 16 from a patient with bilateral cataracts

A four‐month‐old white female, who was referred to us for genetic evaluation because of severe developmental delay, dysmorphic features, and bilateral cataracts, was found by routine cytogenetic analysis to have ring chromosome 16 in almost all cells analyzed. Ring chromosome 16 was confirmed and further delineated by fluorescence in situ hybridization (FISH). Breakpoints between loci D16S521 and KG8 on the short arm and D16S3121 and D16S303 on the long arm of chromosome 16 were determined by polymerase chain reaction (PCR) analysis. The deleted chromosome was of maternal origin. To our knowledge, this is the first case of ring chromosome 16 associated with bilateral cataracts. Comparison of previously reported cases with deletion of chromosome 16 and our case suggests the presence of cataract locus within 1 Mb of the terminus of 16q. © 2001 Wiley‐Liss, Inc.     

Defining regions of loss of heterozygosity of 16q in breast cancer cell lines

The loss of heterozygosity (LOH) of chromosome 16 was assessed in 21 breast cancer cell lines and two nontumorigenic breast epithelial cell lines by typing microsatellite markers distributed on this chromosome. In addition, dual-color fluorescence in situ hybridization was used to metaphase spreads of these cell lines using chromosome 16 paint and region specific probes. Eleven of the cell lines had LOH for chromosome 16, two for the entire chromosome, three for the long arm, and six had LOH for restricted regions of the long arm. The results supported evidence that there are two predominant regions of LOH, 16q22.1 and 16q24.3. The cell lines with chromosome 16 LOH can be used for screening candidate tumor suppressor genes at 16q in breast cancer.     

Spectral karyotypic study of the HL-60 cell line: detection of complex rearrangements involving chromosomes 5, 7, and 16 and delineation of critical region of deletion on 5q31.1.

Interstitial deletions of the q arm of chromosome 5 have been associated with acute myelogenous leukemia (AML); therefore, accurate identification of rearrangements of this chromosome in a model cell line, HL-60, is important for understanding the critical genes involved in this disease. In this study, we employed a newly developed technology termed spectral karyotyping to delineate chromosomal rearrangements in this cell line. Our study revealed a derivative of chromosome 7 that resulted from translocations of chromosome arms 5q and 16q to 7q; that is, der(7)t(5;7)(?;q?)t(5;16)(?;q?). Interestingly, both chromosomes 5 and 7 were also involved in translocations with chromosome 16 in der(16) t(5;16)(q?;q?22-24) and der(16)t(7;16)(?;q?22-24), respectively. Other notable chromosomal abnormalities that were not previously reported in the HL-60 included an insertion of chromosome 8 in the q arm of chromosome 11, a translocation between chromosomes 9 and 14, and a translocation between chromosomes 14 and 15. In an attempt to define the loss of the 5q31.1 region in HL-60, we performed fluorescence in situ hybridization analysis by utilizing bacterial artificial chromosomes BAC1 and BAC2 that spanned the IL9 and EGR1 gene interval, which was previously shown to be a critical region of loss in AML. We showed that a copy of both BAC1 (spanning the D5S399 locus) and BAC2 (spanning the D5S393 locus centromeric to BAC1) were present in the normal chromosome 5, but a second copy of BAC1 was lost and a second copy of BAC2 was inserted in the der(16)t(7;16) chromosome. Thus, not only was this study the first to use the new 24-color karyotyping technique to identify several novel chromosomal rearrangements in HL-60, but it also narrowed the 5q31.1 critical region of deletion to the region represented by BAC1.     

Trisomy 16q in a female newborn with a de novo X;16 translocation and hypoplastic left heart

We report a case of a newborn female with minor dysmorphic features and hypoplastic left heart. Chromosome studies showed that she was the carrier of an unbalanced translocation between the X-chromosome and chromosome 16, resulting in monosomy for Xp and trisomy for 16q. Only a handful of partial trisomy 16q cases have been reported in the literature among liveborns. The great majority of these cases have had significant anomalies in contrast to what has been seen in our patient. The absence of dysmorphic features and other significant abnormalities in this case (with the exception to the hypoplastic left heart), suggested that the inactivation of the derivative X chromosome might have played a role in the mild phenotype of this patient. Conventional cytogenetic studies were conducted in this patient in conjunction with fluorescent in situ hybridization studies, which were used to characterize the X inactivation pattern. The studies revealed that the X chromosome material in the derivative chromosome was inactive while the chromosome 16 derived material in the derivative chromosome was early replicating and active in all cells studied. Am. J. Med. Genet. 82:128–131, 1999. © 1999 Wiley-Liss, Inc.     

Chromosome 16 inversion-associated translocation: two new cases.

Two patients with chromosome 16 inversion-associated translocation were studied with conventional cytogenetic and fluorescence in situ hybridization (FISH) techniques. The same chromosome 16 was involved in inversion and translocation in both patients. The chromosome translocation breakpoint was located within the heterochromatin of chromosome 16 but outside the alpha satellite domain in the t(10;16) of the first patient, whereas it was outside the heterochromatin area in the second case with t(1;16). These two types of rearrangements may be due to different mechanisms and illustrate the possible difficulties in recognizing the chromosome 16 inversion without FISH studies.     

Novel chromosome 16 abnormality--der(16)del(16) (q13)t(16;21)(p11.2;q22)--associated with acute myeloid leukemia.

Inversion of chromosome 16 is a common feature of acute myeloid leukemia (AML) M4, while t(16;21), although also associated with AML, appears to be a separate entity. We present a patient with myelodysplastic syndrome (MDS) who transformed to AML-M1. The karyotype was normal at diagnosis; at 15 months, hematological evidence of transformation was present, and repeat cytogenetics showed a novel rearrangement of one chromosome 16. Two breaks had occurred; one in the short arm at 16p11, with translocation of the segment distal to this onto chromosome 21q, and the other in the long arm at 16q22 with subsequent deletion of the segment from 16q22-->qter. Fluorescence in situ hybridization (FISH) confirmed the abnormalities detected by cytogenetics and excluded involvement of the AML1 gene on 21q22. While the 16q22 breakpoint was at the usual site for the inv(16), the 16p11 was not. The patient is more characteristic of t(16;21) than inv(16), and adds to the spectrum of chromosome 16 abnormalities in AML.     

Noninvolvement of chromosome 16 in karyotype evolution of acute myeloid leukemia in a patient with a heritable fragile site on 16q22

A fragile site on the long arm of chromosome #16 (q22) was detected in a 24-year-old man with pancytopenia. During the course of the disease he developed an inverted duplication of region q11-12 of chromosome #1 and a translocation between chromosomes #9 and #13: t(9;13)(p22;q32). These abnormalities, as well as an additional iso-like marker chromosome that consisted of one normal 9p and the abnormal 9p arm, were detected in Epstein-Barr nuclear antigen-positive B-cell cultures. Two years later, evolution of the abnormal clone with loss of chromosome #7 and, subsequently, chromosome #22 occurred in connection with development of acute myeloid leukemia. Although the heritable fragile site on chromosome #16 was present in all cell populations investigated, it was not involved in the evolution of the abnormal karyotype. This fragile chromosome #16 also was found in 4 of 11 family members in whom chromosome analysis was performed, thus suggesting this aberration was inherited in a dominant autosomal pattern. The incidence of the heritable fragile site in normal and leukemic cells of the patient, as well as stimulated blood cultures of his relatives, are reported. In addition, the possible relationship between this constitutional chromosome breakage syndrome and the occurrence of leukemia is analyzed.     

High resolution mapping of interstitial long arm deletions of chromosome 16: relationship to phenotype.

The breakpoints of seven interstitial deletions of the long arm of chromosome 16 and two ring chromosomes of this chromosome were mapped by in situ hybridisation or by analysis of mouse/human somatic cell hybrids containing the deleted chromosome 16. Use of a high resolution cytogenetic based physical map of chromosome 16 enabled breakpoints to be assigned to an average resolution of at least 1.6 Mb. In general, interstitial deletions involving q12 or q22.1 have broadly similar phenotypes though there are differences in specific abnormalities. Deletions involving regions more distal, from 16q22.1 to 16q24.1, were associated with relatively mild dysmorphism. One region of the long arm, q24.2 to q24.3, was not involved in any deletion, either in this study or in any previous report. Presumably, monosomy for this region is lethal. In contrast, patients with deletions of 16q21 have a normal phenotype. These results are consistent with the proposed distribution of genes, frequent in telomeric Giesma light band regions but infrequent in G positive bands.     

Molecular studies of non-disjunction in trisomy 16.

The origin of the additional chromosome in 26 trisomy 16 spontaneous abortions was studied using DNA probes for chromosome 16, including a probe for centromeric alpha sequences. We were able to determine the parent and meiotic stage of origin of trisomy in 22 cases, with all being attributable to maternal meiosis I non-disjunction. Furthermore, in each of the remaining four cases the results were compatible with this origin. Thus, it is likely that the high incidence of trisomy 16 results from an abnormal process acting at maternal meiosis I which more frequently involves chromosome 16 than other similar sized chromosomes. In studies of recombination, we found little evidence for an association between reduced or absent recombination and chromosome 16 non-disjunction; however, we were unable to rule out an effect of hyperrecombination.     

Simultaneous chromosome 1q gain and 16q loss is associated with steroid receptor presence and low proliferation in breast carcinoma.

We applied comparative genomic hybridization (CGH) to 46 breast carcinoma samples, collected from 1993 to 1995, in order to detect chromosome 1q gains and 16q losses and to define whether samples showing both these alterations had distinct biopathologic features and different clinical outcome. A total of 22 samples (48%) had simultaneous chromosome 1q gain and 16q loss, which was always associated with other genetic changes. In total, 23 samples had various chromosome imbalances (including chromosome 1q gain independent of chromosome 16q loss and vice versa) and one sample did not show detectable alterations. Samples having chromosome 1q gain/16q loss were compared to the other samples with regard to neoplasm size, lymph-node status, histologic and nuclear grade, estrogen and progesterone receptor presence, Ki-67, pRB, Cyclin D1, Cyclin A, p53, p21 and p27 expression as detected by immunohistochemistry. The samples showing chromosome 1q gain/16q loss had high steroid hormone receptor expression (P=0.02), low cell growth fraction (Ki-67, P=0.03) and high p27 expression (P<0.001). No statistical correlation with disease-free survival and overall survival or response to hormonal therapy was found. We conclude that simultaneous chromosome 1q gain/16q loss is a frequent event in invasive breast cancer, which occurs in a subset of both intermediate- and high-grade breast carcinomas. Although the final chromosome 1q and 16q imbalances might have originated from different chromosome alterations in low- and high-grade samples, the gene-dosage effect might be important in conferring peculiar biopathologic characteristics to this subset of samples. The cytogenetic and molecular mechanisms underlying these chromosome changes deserve further investigations.     

Two loci for Tuberous Sclerosis: one on 9q34 and one on 16p13

32 families informative for the segregation of Tuberous sclerosis (TSC) have been examined for genetic markers on chromosomes 9, 11, 12 and 16. In one large family there was clear evidence of linkage to markers on chromosome 16p13.3 (lodscore with D16S291 of 4·7 at θ= 0) but other families were too small to give individually convincing lodscores. Combined results for all families gave positive results with ABO/DBH on chromosome 9 (max lod 2·63) and with D16S291 on chromosome 16 (max lod 3·98) at values of theta of 0·2 in each case. Further analysis showed strong evidence for heterogeneity with approximately half the families linked to a locus TSC1 on chromosome 9 between ASS and D9S298 and half to TSC2 on chromosome 16 close to D16S291. There was no definite support for a third locus although in many families this could not be excluded. In three families the segregation pattern of TSC remains unexplained. In two of these the family apparently segregates for TSC1 but in each case a single affected individual appeared to exclude the whole of the candidate region. Preliminary analysis of clinical features did not reveal any definite differences in incidence of mental handicap between individuals in different linkage groups or with different sex of the parent of origin. The frequencies of periungual fibromas and facial angiofibromas were also similar in both linkage groups. The difficulties of detecting linkage in small families where there is locus heterogeneity are discussed. The program ZZ was found to be helpful in this respect.     

Inversion-associated translocations in acute myelomonocytic leukemia with eosinophilia

Cytogenetic studies of three acute myelomonocytic leukemias with bone marrow eosinophilia (M4EO) revealed chromosome 16 inversion associated with additional abnormalities. The inverted chromosome 16 was involved in two patients. Fluorescence in situ hybridization (FISH) experiments with a YAC probe detecting inv(16) showed that the translocation breakpoints involving chromosome 16 did not implicate the inversion breakpoints. FISH can thus distinguish between true variant translocations and translocations with other breakpoints on chromosome 16 in M4EO.     

Assignment of three human markers in chromosome 21q11 to mouse chromosome 16

Three unique sequence microclones from human chromosome region 21q11 were assigned to mouse chromosome 16 using a mouse/Chinese hamster cell hybrid 96Az2 containing a single mouse chromosome 16. This comparative mapping provides further homology between human chromosome 21 and mouse chromosome 16 to include the very proximal portion of the long arm of human chromosome 21. Since this part of human chromosome 21 is associated with mental retardation in Down syndrome individuals, its homologous mouse region should also be included in the construction of mouse models for studying Down syndrome phenotypes including mental retardation.     

Ring chromosome 13 and haptoglobin heterozygosity

Two patients with congenital ring 13 chromosome abnormality as identified by tritiated thymidine autoradiography and Giemsa banding were heterozygous for the haptoglobin locus. The ring chromosome of one patient was appreciably smaller than those from which Hp deletion was claimed. Evidence for and against the presence of the haptoglobin locus on chromosome 13 and evidence favouring chromosome 16 as the site of this locus are reviewed.     

Mapping the chromosome 16 cadherin gene cluster to a minimal deleted region in ductal breast cancer

The cadherin family of cell adhesion molecules has been implicated in tumor metastasis and progression. Eight family members have been mapped to the long arm of chromosome 16. Using radiation hybrid mapping, we have located six of these genes within a cluster at 16q21-q22.1. In invasive lobular carcinoma of the breast frequent LOH and accompanying mutation affect the CDH1 gene, which is a member of this chromosome 16 gene cluster. CDH1 LOH also occurs in invasive ductal carcinoma, but in the absence of gene mutation. The proximity of other cadherin genes to 16q22.1 suggests that they may be affected by LOH in invasive ductal carcinomas. Using the mapping data, microsatellite markers were selected which span regions of chromosome 16 containing the cadherin genes. In breast cancer tissues, a high rate of allelic loss was found over the gene cluster region, with CDH1 being the most frequently lost marker. In invasive ductal carcinoma a minimal deleted region was identified within part of the chromosome 16 cadherin gene cluster. This provides strong evidence for the existence of a second 16q22 suppressor gene locus within the cadherin cluster.     

Demonstration of the translocation der(16)t(1;16)(q12;q11.2) in interphase nuclei of ewing tumors

The der(16)t(1;16) has been detected cytogenetically in a number of malignancies including Ewing tumors (ETs). To enable fast and reliable analysis of der(16) chromosomes, we established an interphase cytogenetic approach. By using two DNA probes hybridizing to the heterochromatic portions on the long arms of chromosomes 1 and 16, this technique allows the detection of this chromosomal aberration in nonproliferating cells. Formation of the der(16) leads to partial excess of 1 q material and partial loss of the long arm of chromosome 16. Double-target fluorescence in situ hybridization (FISH) experiments were performed on cytospin slides of 13 ETs, near-triploid tumor cells and normal cells to assess whether the FISH technique used permits the discrimination of nuclei harboring this aberration from nuclei without a der(16) chromosome. In five ETs, we found evidence for the presence of one or two der(16)t(1;16) chromosomes both by FISH and by conventional cytogenetics. Tumor cells displayed two signals for intact chromosomes 1, one or two additional fused signals for the der(16) chromosomes, and one signal for the intact chromosome 16. In one case without fused signals, the presence of a der(16) was demonstrated by hybridizing a painting probe for chromosome 16 simultaneously with the paracentromeric probe for chromosome 1. Our results suggest that double-target FISH on interphase nuclei offers an ideal tool for analyzing tumors prospectively and retrospectively to assess the biological role and the possible prognostic impact of the der(16) in ETs and in other solid tumors. Genes Chromosom Cancer 17:141–150 (1996) © 1996 Wiley-Liss, Inc.