Translocations1 are induced in hematopoietic stem cells2
after irradiation of fetal mice3
Mammalian fetuses are considered to be highly sensitive to radiation, but in studies oflymphocyte4 chromosomes5 in the blood of in-utero exposed, A-bomb survivors as adults,
no increase in frequency of chromosomal translocations was observed with increased
radiation dose. That situation lends support to the hypothesis that chromosomal
aberrations in fetal hematopoietic cells do not occur or, if they do, the cells withabnormalities disappear before adulthood.
In this study, pregnant mice (12.5–15.5 days after fertilization) were whole-body irradiatedwith 2 gray (Gy)6 of X-ray irradiation. Subsequently, 24 hours later, hematopoietic stem cells
from maternal mice and their fetuses were isolated. From a single hematopoietic stem cellof both the mother and the fetus, the chromosomes of clone cells (genetically identicalcells) proliferated in vitro (within test tubes) were examined.
As a result, fetal mouse hematopoietic stem cells were observed to have chromosomal
aberrations (translocations), although the frequency was lower than that in the maternal
mice 24 hours after their exposure. Based on that finding, it is believed that hematopoietic
stem cells with translocations are generated in fetal mice but then disappear by the timethe mice become adults, resulting in a translocation frequency around the same level asthat found in non-irradiated mice. Further research is needed regarding this process
marked by the disappearance of hematopoietic stem cells with translocation-type
chromosomal aberrations caused by radiation exposure.
Notes
1
Translocations: Refers to the phenomenon of partial replacement of chromosomes thatcan occur after chromosome breakage caused by cell damage from radiation, etc.22
Hematopoietic stem cells: Cells that reside in the bone marrow and can form all thedifferent types of blood cells (white blood cells, red blood cells, and platelets) and supply
blood throughout life.
3
Mouse fetus: A baby mouse residing in the mother’s body.
4
Lymphocytes: A type of white blood cell, one component of blood, that is involved inimmune function.
5
Chromosomes: Chromosomes, comprised of DNA, are biological material responsible forthe expression and transmission of cellular genetic information. Human somatic cells
contain 23 pairs of chromosomes (46 total chromosomes).
6
Gray (Gy): Gray (1 gray = 1,000 milligray) is a unit of radiation that represents the amountof radiation dose absorbed by a substance when it is exposed to radiation. The average
dose for RERF’s LSS participants is around 140–200 milligray (0.14–0.2 Gy). As reference,
the average annual amount of radiation we are all exposed to in our daily lives, including
medically, is estimated to be around 2–6 milligray (0.002–0.006 Gy).
doi. org/10.1093/jrr/rrac078(Doi are permanent, content-specific numbers assigned to most digital information and, in
this case, can be used to link to published abstracts and/or full papers.)
RERF’s objective with this brief outline is to succinctly explain our research for the lay public.
Much of the technical content of the original paper has been omitted. For further details about
the study, please refer to the full paper published by the journal.