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No evidence for transcriptional imprinting of the 11p15 ribonucleotide reductase M1 subunit locus in Wilms' tumour
Abstracts
163
NO EVIDENCE FOR TRANSCRIPTIONAL IMPRINTING OF THE 11p15 RIBONUCLEOTIDE REDUCTASE M1 SUBUNIT LOCUS IN WlLMS' TUMOUR Jennifer A. Bvrne and Peter J. Smith. Queensland Cancer Fund Research Unit, Department of Pathology, University of Queensland Medical School, Herston 4006, Queensland, Australia. Studies of genetic abnormalities in Wilms' tumour (WT) have lead to the suggestion that genomic imprinting at chromosomal region 11p15 may play a role in the pathogenesis of WT. However, transcription of maternally and paternally inherited alleles at 11p15 has not been compared in WT or in other embryonal tumours. We have utilized the polymerase chain reaction (PCR) to amplify a transcribed Taql polymorphism in the ribonucleotide reductase M1 subunit gene, in cDNA from 6 WT, matched samples of normal kidney, one hepatoblastoma and matched normal liver. Taql digestion of PCR products revealed that both alleles were transcribed in all samples studied where both were present at the genomic level, and that there were no differences in the levels of transcription of the 2 alleles between tumour and somatic tissue. Thus rather than involving extensive regions of chromosome 11 p, imprinting may be applied in a gene specific manner at 11p15, or alternately imprinting may not contribute to tumourigenesis in all cases.
BECKWITH-WIEDEMANN SYNDROME, ASSOCIATED TUMORS, REGION 11p15.5, AND IMPRINTING. I. Henry (1), A. Puech (t), L. Ahnine (1), B. Horstemke (2), U. Claussen (3), C. Jeanpierre (1), C. Tones (4), C. Junien (1). (1) INSERM U73, G~n~tique et Pathologie foetale, 75016 Paris, France. (2) Institut fur Humangenetik, Essen, RFA. (3) Institut for Humangenetik, Erlangen, RFA. (4) Eleonore memorial institute for cancer center, Denver, CO, USA. The Beckwith-Wiedemann syndrome (BWS) is a malformative syndrome associated with predisposition to different types of tumors (Wilms' tumor WT, adrenocortical carcinoma ADCC) Cytogenetic and familial studies mapped BWS locus to 11p15.5. Using 11p markers we have compared constitutional and tumoral genotypes of 17 hereditary WT and 12 ADCC whether or not associated with BWS. This study allowed us to characterize two different subregions on 11p15 which could be involved in BWS, WT, and ADCC. One extends from HBB excluded to CALCA included, the other from HRAS1 excluded to IGF2/INS included. For 3 WT and 2 ADCC, a preferential loss of maternal alleles was observed suggesting that region 11p15 is submitted to genomic imprinting. To confirm the involvement of genomic imprinting in BWS, we used 11p15 specific markers to determine the parental origin of chromosome 11 in sporadic BWS. Probands in 3 out of 8 informative families displayed uniparental disomy for region 11p15.5. Moreover an overall significantly increased frequency of homozygosity for several 11p15.5 markers in a total of 23 sporadic BWS patients suggests that uniparental disomy probably accounts for an even higher proportion of BWS sporadic cases. Thus uniparental disomy can be associated with a genetic cancer predisposing syndrome. Imbalance of paternal versus maternal alleles could account for the clinical features and tumor development associated with the different etiological forms of BWS. Two different genomic libraries specific for region 11p15.5 were constructed and screened to isolate and characterize the gene(s) responsible for BWS and/or tumor progression. I) From a microdissection library, 19 clones were isolated and mapped using a panel of hybrids subdividing 11p15 in seven subregions. Seven clones are evolutionarily conserved. A cosmid and cDNA library are being screened to isolate the corresponding coding sequences. 2) Four clones from a genomic EMBL3 library established with hybrid J1.1 (only region 11p15) were shown to contain HTF islands or evolutionary conserved sequences. These clones are being used to more precisely map the region involved, in a series of BWS patients, and in tumors of different etiological forms.
163
NO EVIDENCE FOR TRANSCRIPTIONAL IMPRINTING OF THE 11p15 RIBONUCLEOTIDE REDUCTASE M1 SUBUNIT LOCUS IN WlLMS' TUMOUR Jennifer A. Bvrne and Peter J. Smith. Queensland Cancer Fund Research Unit, Department of Pathology, University of Queensland Medical School, Herston 4006, Queensland, Australia. Studies of genetic abnormalities in Wilms' tumour (WT) have lead to the suggestion that genomic imprinting at chromosomal region 11p15 may play a role in the pathogenesis of WT. However, transcription of maternally and paternally inherited alleles at 11p15 has not been compared in WT or in other embryonal tumours. We have utilized the polymerase chain reaction (PCR) to amplify a transcribed Taql polymorphism in the ribonucleotide reductase M1 subunit gene, in cDNA from 6 WT, matched samples of normal kidney, one hepatoblastoma and matched normal liver. Taql digestion of PCR products revealed that both alleles were transcribed in all samples studied where both were present at the genomic level, and that there were no differences in the levels of transcription of the 2 alleles between tumour and somatic tissue. Thus rather than involving extensive regions of chromosome 11 p, imprinting may be applied in a gene specific manner at 11p15, or alternately imprinting may not contribute to tumourigenesis in all cases.
BECKWITH-WIEDEMANN SYNDROME, ASSOCIATED TUMORS, REGION 11p15.5, AND IMPRINTING. I. Henry (1), A. Puech (t), L. Ahnine (1), B. Horstemke (2), U. Claussen (3), C. Jeanpierre (1), C. Tones (4), C. Junien (1). (1) INSERM U73, G~n~tique et Pathologie foetale, 75016 Paris, France. (2) Institut fur Humangenetik, Essen, RFA. (3) Institut for Humangenetik, Erlangen, RFA. (4) Eleonore memorial institute for cancer center, Denver, CO, USA. The Beckwith-Wiedemann syndrome (BWS) is a malformative syndrome associated with predisposition to different types of tumors (Wilms' tumor WT, adrenocortical carcinoma ADCC) Cytogenetic and familial studies mapped BWS locus to 11p15.5. Using 11p markers we have compared constitutional and tumoral genotypes of 17 hereditary WT and 12 ADCC whether or not associated with BWS. This study allowed us to characterize two different subregions on 11p15 which could be involved in BWS, WT, and ADCC. One extends from HBB excluded to CALCA included, the other from HRAS1 excluded to IGF2/INS included. For 3 WT and 2 ADCC, a preferential loss of maternal alleles was observed suggesting that region 11p15 is submitted to genomic imprinting. To confirm the involvement of genomic imprinting in BWS, we used 11p15 specific markers to determine the parental origin of chromosome 11 in sporadic BWS. Probands in 3 out of 8 informative families displayed uniparental disomy for region 11p15.5. Moreover an overall significantly increased frequency of homozygosity for several 11p15.5 markers in a total of 23 sporadic BWS patients suggests that uniparental disomy probably accounts for an even higher proportion of BWS sporadic cases. Thus uniparental disomy can be associated with a genetic cancer predisposing syndrome. Imbalance of paternal versus maternal alleles could account for the clinical features and tumor development associated with the different etiological forms of BWS. Two different genomic libraries specific for region 11p15.5 were constructed and screened to isolate and characterize the gene(s) responsible for BWS and/or tumor progression. I) From a microdissection library, 19 clones were isolated and mapped using a panel of hybrids subdividing 11p15 in seven subregions. Seven clones are evolutionarily conserved. A cosmid and cDNA library are being screened to isolate the corresponding coding sequences. 2) Four clones from a genomic EMBL3 library established with hybrid J1.1 (only region 11p15) were shown to contain HTF islands or evolutionary conserved sequences. These clones are being used to more precisely map the region involved, in a series of BWS patients, and in tumors of different etiological forms.