Atm heterozygous mice are more sensitive to radiation-induced cataracts than are their wild-type counterparts.
It is important to know whether the human population includes genetically predisposed radiosensitive subsets. In vitro studies have shown that cells from individuals homozygous for ataxia telangiectasia (A-T) are much more radiosensitive than cells from unaffected individuals. Although cells heterozygous for the ATM gene (ATM(+/-)) may be slightly more radiosensitive in vitro, it remained to be determined whether the greater susceptibility of ATM(+/-) cells translates into an increased sensitivity for late effects in vivo, though there is a suggestion that radiotherapy patients that are heterozygous for the ATM gene may be more at risk of developing late normal tissue damage. We chose cataractogenesis in the lens as a means to assay for the effects of ATM deficiency in a late-responding tissue. One eye of wild-type, Atm heterozygous and homozygous knockout mice was exposed to 0.5-, 1.0-, 2.0-, or 4.0-Gy x rays. The animals were followed weekly for cataract development by conventional slit-lamp biomicroscopy. Cataract development in the animals of all three groups was strongly dependent on dose. The lenses of homozygous mice were the first to opacify at any given dose. Most important in the present context is that cataracts appeared earlier in the heterozygous versus wild-type animals. The data suggest that ATM heterozygotes in the human population may also be radiosensitive. This may influence the choice of individuals destined to be exposed to higher than normal doses of radiation, such as astronauts, and may also suggest that radiotherapy patients who are ATM heterozygotes could be predisposed to increased late normal tissue damage.
Worgul
Basil V
BV
Eye Radiation and Environmental Research Laboratory and Center for Radiological Research, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
Smilenov
Lubomir
L
Brenner
David J
DJ
Junk
Anna
A
Zhou
Wei
W
Hall
Eric J
EJ
D000818:Animals; D001260:Ataxia Telangiectasia / Q000235:genetics; D064007:Ataxia Telangiectasia Mutated Proteins; D002386:Cataract / Q000235:genetics*; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D004195:Disease Models, Animal; D006720:Homozygote; D051379:Mice; D018345:Mice, Knockout; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D011832:Radiation Injuries / Q000235:genetics*; D011836:Radiation Tolerance / Q000235:genetics*; D012016:Reference Values; D013997:Time Factors; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases