Environmental and Molecular Mutagenesis - Legacy Tobacco ...

370 1989 EMS Abstracts
MOLECULAR PATTERNS OF APRT GENE REARRANGEMENTS . M . MEUTH, G . SARGENT, C. MILES, AND Notes
G . PHEAR, IMPERIAL CANCER RESEARCH FUND, Clare Hall Laboratories, South Mimms, Herts .
EN6 3LD, U .K .
Deletions and other gene rearrangements appear to be an important step in the
process of oncogenesis and are a result of many forms of DNA damage, but very little
is known of the mechanisms responsible for these mutations . We have been studying
gene rearrangements at the hamster adenine vhosnhoribosvl transferase . (anrt)locus with
the intention of identifying sequence featurea and functions involved in such
alterations . A striking feature of deletions at aprt is the directionality of the
mutations . Deletion breakpoints frequently occur within aprt and often upstream of
the locus but rarely downstream . This suggests that an essential function or structure
lies downstream from the locus and limits the mutations recoverable . On the other hand
this directionality aids molecular analysis by providing a "tag" for deletion junction
fragments allowing their cloning or recovery by the polymerase chain reaction . Many
types of rearrangements (both small and very large deletions as well as several
insertion mutants) have now been characterized at base sequence level . These
alterations have a number of distinctive properties which will be discussed in detail .
371
INSTABILITY OF CHROMOSOMES CONTAINING AMPLIFIED REGIONS IN CHINESE BAMSTER CELLS .
M . Miele, S . Bonatti, G . Fronza, L . Ottaggio, S . Yiaggi,and A . Abbondandolo, National In
stitute for Research on Cancer, Genova (Italy), University-of Genova (Italy), and UO of
CNR, Pisa (Italy)
With the aim to study the effect of gross morphological modifications on chromosome
stability, the behaviour of chromosomes carrying amplified CAD (carbamyl phosphate synthetase-aspartate
transcarbamylase-dihydroorotase) or DH7R (dihydrofolate reductase) genas
was studied in V79 Chinese hamster cell derivatives resistant to PALA (N-phospohacetyl-
-L-aspartate) and MTX (methotrexate), respectively . In both metaphase chromosomes and in_
terphase nuclei, amplified regions were localized by in s1 u hybridisation . In MTX-resis_
tant cells, the amplification bearing chromosomes was lagging behind at anaphase and gaw
rise in interphase nuclei to bud-shaped formations . Apparently, these buds could eventually
separate as micronuclei . In both MTX- and PALA- resistant cells, micronuelei in in_
terphase and displaced chromosomes in metaphase, both containing amplified DNA, were ob
served . The presence of chromosomes in micronuclei was confirmed by fluorescent staining
with antikinetochore antibodies . Finally, amplification,bearing dicentric chromosomes
were found at high frequencies in both drug-resistant call lines . All together, these ob
servations indicate that the presence of an amplified region makes chromosomes unstabla,
since : (i) they tend to be excluded from cells, and (ii) they rearrange sare frequently
than normal chromosomes .
372
SPONTANEOUS AND IN VITRO RADIATION-INDUCED CHROMOSOME ABERRATIONS IN HUMAN SPERMATOZOA :
APPLICATION OF A NEW METHOD
Mikamo, K., Kamiguchi, Y. and Tateno, H . : Department of Biological Sciences, Asahikawa
Medical College, Asahikawa 078, JAPAN
Chromosomes of the spermatozoon can be analyzed only after they replicate and become
condensed in the ootid as male pronuclear chromosomes . Therefore, difficulty of using
human oocytes had long been a severe limitation for the human sperm chromosome study .
Fortunately, however, development of the interspecific in vitro fertilization system
using zona-free hamster oocytes made It possible to carry out a large scale study of
human sperm chromosomes without relying upon human oocytes . In the present talk, we
describe briefly the procedure of our lmproved method and the results thereby obtained
in the in vitro experiments . (1) Spontaneous incidences of human sperm chromosome
aberrations in a total of 9280 spermatozoa from 87 samples of 26 men. Incidences of
aneuploidy and structural anomaly were 1 .35 Z(hyperhaploidy, 0.68 x; hypohaploidy,
0.67 x) and 13.9 x, respectively. The latter incidence varied considerably among the
donors, ranging from 3.6 x to 21 .5 2. (2) Radiation (X-, y- and 8-rays)-induced human
sperm chromosome aberrations in a total of 6974 spermatozoa from 57 samples of 12 men .
Incidences of spermatozoa with structural chromosome aberrations increased linearly
with increase of radiation dosage . The slope of the dose-effect equation was nearly
the same between the three kinds of radiation . The incidence of breakage-type
aberrations was far higher than that of exchange-type aberrations, both of them showing
linear dose-dependent increases .
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