[Determination of sex chromatin and Y body in the diagnosis of sex chromosome abnormalities].
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A reliable technique has been developed for the production of good quality G-banded chromosome preparations from 6- to 8-day-old human blastocysts (20-800 cell stage) from an in vitro fertilization programme. The technique involves a thymidine cell division synchronization step to reduce the exposure time to colcemid, in conjunction with a simple 70% acetic acid disaggregation procedure to produce discrete metaphases for analysis. Of 105 blastocysts processed by this technique, 9 were lost during handling and 10 showed no dividing cells. The remaining 86 produced useful separate metaphases with a mean mitotic activity of 6.5%. A full G-banded karyotype was obtained from 1-6 cells in 55 blastocysts (64%), incomplete G-banded analysis but with full information of ploidy was obtained from 18 blastocysts (21%), with 13 (15%) producing no useful cytogenetic results. Abnormalities observed included polyploidy, diploid/polyploid mosaicism, non-mosaic trisomy 16 (2 cases), 46,Xdel(X)-(q21)/46,XX (1 case) and several single cells with trisomies or structural anomalies in otherwise normal blastocysts. Variable levels of structural chromosome damage, with apparent interchanges, chromosome branching and anomalous chromatid pairing were also seen.
Specific constitutional chromosome rearrangements have been described in a small number of individuals with two solid childhood tumors, retinoblastoma and Wilms' tumor. On the basis of these observations, a causal relationship between these chromosome abnormalities and tumorigenesis has been postulated. Though a specific constitutional chromosome abnormality has yet to be reported in association with neuroblastoma, another childhood tumor, we now confirm the involvement of a particular chromosome segment in structural abnormalities in cells from this tumor. Deletions or rearrangements of chromosome 1p were found in preparations from four of six neuroblastomas from individuals with normal constitutional karyotypes and in three of four permanent neuroblastoma cell lines. Structural abnormalities resulting in the loss or rearrangement of material from 1p (with the most frequent break point being 1p32 and with all rearrangements involving the apparent loss or rearrangement of material distal to 1p31, always including 1p34 to 1pter), represent the single most common class of chromosome aberrations in neuroblastoma. This suggests that the distal portion of 1p contains at least one gene involved in the development of neuroblastoma.
Comparative genomic hybridization (CGH) was used to evaluate and map genomic aberrations in 50 hepatocellular carcinomas (HCCs) from patients chronically infected with hepatitis B virus (HBV). CGH clearly detected nonrandom genomic imbalances. Losses were most prevalent on chromosome regions 4q (70%), 8p (65%), 16q (54%), 17p (51%), 13q and 6q (37% each), and lp (30%). The most frequent gains occurred on 8q (60%), 1q (58%), and 6p and 17q (33% each). In a few cases, sequence amplifications were detected that were mapped to bands 11q12, 12p11, 14q12, and 19q13.1. This study represents the first analysis of primary liver cancers by CGH, and it confirms the presence of previously known chromosomal aberrations in HCC and highlights new quantitative abnormalities and sequence amplifications. These findings should lead to the characterization of new loci involved in liver cancer pathogenesis.
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Comparative genomic hybridization (CGH) is a recent molecular cytogenetic method that detects and localizes gains or losses in DNA copy number across the entire tumor genome. We used CGH to examine 9 glioma cell lines and 20 primary and 10 recurrent glioblastoma tumors. More than 25% of the primary tumors had gains on chromosome 7; they also had frequent losses on 9p, 10, 13 and Y. The losses on chromosome 13 included several interstitial deletions, with a common area of loss of 13q21. The recurrent tumors not only had gains on chromosome 7 and losses on 9p, 10, 13 and Y but also frequent losses on 6 and 14. One recurrent tumor had a deletion of 10q22-26. Cell lines showed gains of 5p, 7 and Xp; frequent amplifications at 8q22-24.2, 7q21-32 and 3q26.2-29 and frequent losses on 4, 10, 13, 14 and Y. Because primary and recurrent tumors and cell lines showed abnormalities of DNA copy number on chromosomes 7, 10, 13 and Y, these regions may play a fundamental role in tumor initiation and/or progression. The propensity for losses on chromosomes 6 and 14 to occur in recurrent tumors suggests that these aberrations play a role in tumor recurrence, the development of resistance to therapy or both. Analysis of common areas of loss and gain in these tumors and cell lines provides a basis for future attempts to more finely map these genetic changes.
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