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N-Myc amplification at chromosome band 1p32 in neuroblastoma cells as investigated by in-situ hybridization
Abstracts 29
163 LINKAGE ANALYSIS IN FAMILIES WITH HEREDITARY RETINOBLASTOMA. H. Scheffer1, Y. C. M. Kruize ~, J. H. M. van den Berg~, D. Penninga~, K. E. W. P. Tan2, G. J. te Meerman~, and C. H. C. M. Buys1. Department of Human Genetics~, State University of Groningen, and Department of Ophthalmology2, State University of Utrecht, The Netherlands.
We have analyzed the segregation of several markers, both within and flanking the retinoblastoma gene, in 19 families (69 meioses) with hereditary retinoblastoma. The intragenic markers [1] were informative in 69%. The use of flanking markers from the same chromosomal region caused an increase of the total informativity to 91%. In one family an inherited deletion involving one of the RB1 alleles was detected. In two families a carrier was identified who showed nonpenetrance of the mutation predisposing to retinoblastoma. In these families we could not find any genomic alteration upon an analysis of Southern blots with the RB1 cDNA clones. A variety of possible mutations makes the use of DNA markers the proper method to follow the inheritance of the predisposition to retinoblastoma through further generations. Our findings emphasize the use of a combination of both intragenic and flanking markers to obtain the highest reliability of carrier detection in families with hereditary retinoblastoma. REFERENCE 1. Wiggs et al. (1988): N Engl J Med 318:151-157.
30
AMPLIFICATION OF INT1 IN RETINOBLASTOMAS. K. Arheden, N. Tommerup, N. Mandahl, S. Heim and F. Mitelman. Department of Clinical Genetics, Lund University Hospital, S-221 85 Lund, Sweden.
The human putative oncogene INT1 has been found to be amplified in two of four retinoblastomas. The degree of amplification was 10 to 15-fold in one tumor, and 100-fold in the other. Both cases showed local invasion of the choroid and development of metastases. Similar increased tumor aggressiveness was not detectable in the other two tumors in which INT1 was not amplified. The results indicate that INT1 amplification might be a feature of tumor progression in retinoblastomas.
31
N-MYC AMPLIFICATION AT CHROMOSOME BAND lp32 IN NEUROBLASTOMA CELLS AS INVESTIGATED BY IN-SITU HYBRIDIZATION. L. Lonso*, H. Christiansen°, N. M. Panlsen*, P. CornagliaFerraris*, F. Lampert°. * G. Gaslini Children's Hospital, Genoa, Italy/°Department of Pediatrics, University of Giessen, FRG/*lnstitute of Genetics, University of Giessen, FRG.
The most common karyotypic change in neuroblastoma (NB) cells is the terminal deletion of the short arm of chromosome I (lp32). Furthermore Double Minute Chromosomes (DMs) and Homogeneously Staining Regions (HSRs), found in this malignancy more often than any other, have been described as the cytogenetic manifestations of N-myc oncogene amplification. Here we report the molecular and in-situ hybridization studies of a newly established NB cell line (GI-LIN) which displayed two marker chromosomes 1-besides a normal one both bearing HSR at the band lp32 instead of the segment 1p32-pter. Southern-blot analysis showed multiple copies of N-myc oncogene, the rate of amplification being 30-fold as determined by the DNA-dot.blot procedure. 52 metaphases were scored for the in-situ hybridization analysis. 81 out of 230 (=35.2%) labelled sites were detected on the HSRs, while 15 out of 230 (=6.5%) grains were localized on the short arm of chromosome 2, which contains the normal Nmyc sane locus. An uneven distribution of grains with an higher density of signals at the distal part of the HSRs was observed. This finding may be explained by a particular mechanism of N-myc amplification causes hybridizing and non-hybridizing HSR segments or may reflect local variations in probe accessibility or chromatin compaction. Our results confirm the presence of amplified N-myc units in the HSR associated with NB tumors and seem to indicate that the lp deletion occurred before the appearance of the HSR in this cell line. This study was supported by the Deutsche Forschungsgemeinschaft (SFB-AT) and carried out in the Department of Pediatrics, University of Giessen, FRG.
163 LINKAGE ANALYSIS IN FAMILIES WITH HEREDITARY RETINOBLASTOMA. H. Scheffer1, Y. C. M. Kruize ~, J. H. M. van den Berg~, D. Penninga~, K. E. W. P. Tan2, G. J. te Meerman~, and C. H. C. M. Buys1. Department of Human Genetics~, State University of Groningen, and Department of Ophthalmology2, State University of Utrecht, The Netherlands.
We have analyzed the segregation of several markers, both within and flanking the retinoblastoma gene, in 19 families (69 meioses) with hereditary retinoblastoma. The intragenic markers [1] were informative in 69%. The use of flanking markers from the same chromosomal region caused an increase of the total informativity to 91%. In one family an inherited deletion involving one of the RB1 alleles was detected. In two families a carrier was identified who showed nonpenetrance of the mutation predisposing to retinoblastoma. In these families we could not find any genomic alteration upon an analysis of Southern blots with the RB1 cDNA clones. A variety of possible mutations makes the use of DNA markers the proper method to follow the inheritance of the predisposition to retinoblastoma through further generations. Our findings emphasize the use of a combination of both intragenic and flanking markers to obtain the highest reliability of carrier detection in families with hereditary retinoblastoma. REFERENCE 1. Wiggs et al. (1988): N Engl J Med 318:151-157.
30
AMPLIFICATION OF INT1 IN RETINOBLASTOMAS. K. Arheden, N. Tommerup, N. Mandahl, S. Heim and F. Mitelman. Department of Clinical Genetics, Lund University Hospital, S-221 85 Lund, Sweden.
The human putative oncogene INT1 has been found to be amplified in two of four retinoblastomas. The degree of amplification was 10 to 15-fold in one tumor, and 100-fold in the other. Both cases showed local invasion of the choroid and development of metastases. Similar increased tumor aggressiveness was not detectable in the other two tumors in which INT1 was not amplified. The results indicate that INT1 amplification might be a feature of tumor progression in retinoblastomas.
31
N-MYC AMPLIFICATION AT CHROMOSOME BAND lp32 IN NEUROBLASTOMA CELLS AS INVESTIGATED BY IN-SITU HYBRIDIZATION. L. Lonso*, H. Christiansen°, N. M. Panlsen*, P. CornagliaFerraris*, F. Lampert°. * G. Gaslini Children's Hospital, Genoa, Italy/°Department of Pediatrics, University of Giessen, FRG/*lnstitute of Genetics, University of Giessen, FRG.
The most common karyotypic change in neuroblastoma (NB) cells is the terminal deletion of the short arm of chromosome I (lp32). Furthermore Double Minute Chromosomes (DMs) and Homogeneously Staining Regions (HSRs), found in this malignancy more often than any other, have been described as the cytogenetic manifestations of N-myc oncogene amplification. Here we report the molecular and in-situ hybridization studies of a newly established NB cell line (GI-LIN) which displayed two marker chromosomes 1-besides a normal one both bearing HSR at the band lp32 instead of the segment 1p32-pter. Southern-blot analysis showed multiple copies of N-myc oncogene, the rate of amplification being 30-fold as determined by the DNA-dot.blot procedure. 52 metaphases were scored for the in-situ hybridization analysis. 81 out of 230 (=35.2%) labelled sites were detected on the HSRs, while 15 out of 230 (=6.5%) grains were localized on the short arm of chromosome 2, which contains the normal Nmyc sane locus. An uneven distribution of grains with an higher density of signals at the distal part of the HSRs was observed. This finding may be explained by a particular mechanism of N-myc amplification causes hybridizing and non-hybridizing HSR segments or may reflect local variations in probe accessibility or chromatin compaction. Our results confirm the presence of amplified N-myc units in the HSR associated with NB tumors and seem to indicate that the lp deletion occurred before the appearance of the HSR in this cell line. This study was supported by the Deutsche Forschungsgemeinschaft (SFB-AT) and carried out in the Department of Pediatrics, University of Giessen, FRG.