Genomic organization of IgH gene compared with the expression of Bcl-2 gene
in t(14;18)-positive lymphoma
R Amakawa, S Fukuhara, H Ohno, F Matsuyama, I Kato, S Tanabe, P Sideras, TR Mizuta, T Honjo and M Okuma
Department of Internal Medicine, Faculty of Medicine, Kyoto University,
Japan.
In three lymphoma cell lines carrying t(14;18), named FL-18, FL-218, and
FL-318, the genomic organization of IgH gene was compared with the
expression of bcl-2 gene; the t(14;18) of the FL-18 cells occurred
downstream from the major breakpoint cluster region (mbr) of a bcl-2 gene,
and that of the FL-218 and FL-318 cells within the mbr. The FL- 318
expressed the normal-sized bcl-2 transcript of 8.5-kb mRNA having the
noncoding region 3 to the mbr, which was found in the FL-18, and the FL-218
lacking the intact bcl-2 gene did not. This finding suggests that in
t(14;18)-positive lymphoma having the breakpoint within the mbr,
transcription of the nontranslocated bcl-2 allele is not necessarily
silent. In addition, the FL-218 and FL-318 expressed aberrant bcl-2
transcripts and heterogenous IgH transcripts lacking the VH region, and the
bcl-2 transcripts each comigrated with parts of the sterile IgH mRNAs. The
FL-318, which did not exhibit switch recombination on either IgH allele,
contained abundant amounts of l gamma mRNAs, a prerequisite for the
recombination into the C gamma locus. One of the I-mRNA species comigrated
with the aberrant bcl-2 transcript. The FL-18 and FL-218 lacking the I
gamma mRNAs had completed switch recombination of both IgH alleles. This
result raises a possibility that deregulated bcl-2 transcription caused by
t(14;18) is capable of playing a role in class switch recombination of IgH
gene.
Volume 77,
Issue 9,
pp. 1970-1976,
05/01/1991
Copyright © 1991 by The American Society of Hematology
