Low dose radiation’s harmful effects on fruit flies – implications for the human species
“These results may have broader implications beyond the model organism. In particular, they may indicate an increased risk of pathological response to radiation in humans carrying hypomorphic mutations of these genes in their genome (note that both genes are highly evolutionarily conserved). Such individuals may be more vulnerable than the bulk of the population to even low levels of radiation
Researchers reveal the secret of radiation vulnerability Medical EXpress, 15 May 14, The scientists – Boris Kuzin, Ekaterina Nikitina, Roman Cherezov, Julia Vorontsova, Mikhail Slezinger, Olga Zatsepina, Olga Simonova, Grigori Enikolopov and Elena Savvateeva-Popova – studied Drosophila flies, in whose genome weak mutations of two different genes were combined. They concluded that these mutations synergistically strengthen their mutual phenotypic expression. In other words, the aggregate effect of these mutations is much greater than that which can be produced by one of them individually.
The mutant flies bred by the scientists have a number of significant peculiarities. The experiments have shown that even low doses of X-ray irradiation (not exceeding 10 R) can cause serious defects in those flies’ legs.
In contrast, in the flies with normal (unchanged) genome such defects could not be caused even by doses of irradiation hundreds of times higher. What is more, the combination of the two mutations worsened the long-term memory impairment, earlier observed in the flies with only one of the mutations.
In addition, the mutant flies’ cells are less resistant to the so-called superoxide radicals.
Superoxide radicals are ions which appear in cells under both normal and pathological conditions. Superoxide radicals have very high rates of reactivity, which is why their excess damages many types of bio-molecules, including DNA. The mutations inDrosophilaflies’ cells lowered their ability to resist that damage.
What was already known
According to the scientists, mutations in the genome of the experimental flies affected two genes: CG5017 and spineless. Both these genes are involved in regulation of many different functions, a large number of which still remain unknown. The team of researchers from MIPT, RAS and Cold Spring Harbor Laboratory has set a goal to reduce this white spot. The scientists started with the already known facts, i.e., that the CG5017 gene mutations impair insects’ memory, and that mutations in spineless bring about a number of defects in morphogenesis. In Drosophila flies, spineless mutations affect leg and eye formation and disrupt the development of neuronal dendritic structure………
Spineless-controlled genes are responsible for the proper development of an animal. Even by the first half of the twentieth century,spineless gene mutations were ranked among the so-called homeotic mutations. Such mutations do not stop the process of the organism’s formation, but direct it in the wrong way.
“Where we expected to see antennae, there emerged leg morphological structures with altered segmentation. It later turned out that the formation of eye structures and nervous cells had also been disrupted,” said Boris Kuzin, the leading author of the article presenting the research……
What was discovered
The new research has shown the following: the spineless gene is also involved in long-term memory formation and detoxification. Spineless, and the proteins it controls, help the cell to get rid of exogenous toxins (i.e., originating outside the cell) and endogenous ones (in this case, those which were produced inside the cell following the irradiation). According to Boris Kuzin, the combination of the weak spineless and CG5017 gene mutations in a genome has a synergistic effect and results in the weakening of spineless (ss) products’ functions. The organisms of fruit flies with these particular mutations cannot manage the simultaneous processes of detoxification and morphogenesis.
“It seems that the disruption of detoxification leads to aggravation of the defects, which appear in the process of limb formation in response to even low radiation doses. It looks like these mutant flies lack the functionally active spineless (ss) products necessary for the simultaneous control of development and detoxification,” said Kuzin……….
What is means
The discovery, as the scientists state in their article, can shed some light on the problem of individual irradiation sensitivity. It is known that low doses of radiation sometimes result in serious inborn defects, and sometimes leave no traces. In part, it is connected with the a priori random nature of ionizing radiation, but there are also a number of genetically-based molecular-biological differences, many of which have not been yet defined.
“These results may have broader implications beyond the model organism. In particular, they may indicate an increased risk of pathological response to radiation in humans carrying hypomorphic mutations of these genes in their genome (note that both genes are highly evolutionarily conserved). Such individuals may be more vulnerable than the bulk of the population to even low levels of radiation………http://medicalxpress.com/news/2014-05-reveal-secret-vulnerability.html
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