Is radon emission in caves causing deletions in satellite DNA sequences of cave-dwelling crickets?

The most stable isotope of radon, 222Rn, represents the major source of natural radioactivity in confined environments such as mines, caves and houses. In this study, we explored the possible radon-related effects on the genome of Dolichopoda cave crickets (Orthoptera, Rhaphidophoridae) sampled in caves with different concentrations of radon. We analyzed specimens from ten populations belonging to two genetically closely related species, D. geniculata and D. laetitiae, and explored the possible association between the radioactivity dose and the level of genetic polymorphism in a specific family of satellite DNA (pDo500 satDNA). Radon concentration in the analyzed caves ranged from 221 to 26,000 Bq/m3. Specimens coming from caves with the highest radon concentration showed also the highest variability estimates in both species, and the increased sequence heterogeneity at pDo500 satDNA level can be explained as an effect of the mutation pressure induced by radon in cave. We discovered a specific category of nuclear DNA, the highly repetitive satellite DNA, where the effects of the exposure at high levels of radon-related ionizing radiation are detectable, suggesting that the satDNA sequences might be a valuable tool to disclose harmful effects also in other organisms exposed to high levels of radon concentration.

Conocimiento del estado vascular para la toma de decisiones terapéuticas en el ictus isquémico agudo: ¿cuál es el papel de la neurosonología? / Knowledge of vascular status for therapeutic decision-making in acute ischemic stroke: which is the role of neurosonology?

Existe en los últimos años un interés creciente en el conocimiento del estado vascular de los pacientes con ictus agudo. La detección y localización de una oclusión arterial resultan de gran interés para un enfoque pronóstico adecuado y la selección del tratamiento recanalizador agudo más apropiado. La neurosonología constituye una herramienta diagnóstica útil en el estudio del estado vascular del paciente con ictus agudo. En el presente trabajo se revisan diversas situaciones en las que los ultrasonidos aportan información diagnóstica valiosa, como en el caso de la oclusión de la arteria cerebral media (ACM), oclusión ‘en T’ de la arteria carótida interna (ACI), oclusión ‘en tándem’ ACI-ACM, monitorización de oclusiones de arterias intracraneales, oclusión aguda de la ACI extracraneal y presencias de trombos flotantes intracarotídeos. La neurosonología aporta ventajas evidentes frente a otras técnicas diagnósticas: es rápida, dinámica, económica, inocua, accesible, permite la monitorización del estado vascular del paciente en tiempo real, evita retrasos en la administración de tratamientos agudos y posee un efecto terapéutico (sonotrombólisis). Por todo ello, la neurosonología ocupa un papel fundamental en el diagnóstico del estado vascular y en la toma de decisiones terapéuticas en el paciente con ictus isquémico agudo (AU)

In the last years there is an increasing interest in the knowledge of vascular status in patients with acute stroke. Detection and localization of an artery occlusion is of great interest for an accurate prognosis and the selection of the most appropriate recanalizing therapy. Neurosonology is a useful diagnostic tool for vascular status study in patients with acute stroke. Different situations where ultrasounds offer a valuable diagnostic information are reviewed, such as middle cerebral artery (MCA) occlusion, ‘T’ internal carotid artery (ICA) occlusion, ‘tandem’ ICA-MCA occlusion, monitoring of intracranial artery occlusions, acute occlusion of extracranial ICA, and free-floating thrombus in the ICA. Neurosonology offers evident advantages compared with other diagnostic techniques: it is faster, dynamic, cheaper, harmless, and accessible, allows real-time monitoring of patients vascular status, avoids delays in acute treatments and has a therapeutic effect (sonothrombolysis). Neurosonology has an essential role in the diagnosis of vascular status and in therapeutic decisionmaking of acute ischemic stroke patients (AU)

Knockout of glutelin genes which form a tandem array with a high level of homology in rice by gamma irradiation.

In the course of evolution, a gene is often duplicated in tandem, resulting in a functional redundancy. The analysis of function of these genes by raising double mutant might be difficult because they are very tightly linked. We described here a mutant of such a tandem duplicated gene. glu1 is a gamma-ray-induced rice mutant, which lacks an acidic subunit of glutelin, a major seed storage protein. We found that glu1 harbors a 129.7-kb deletion involving two highly similar and tandem repeated glutelin genes, GluB5 and GluB4. The deletion eliminated the entire GluB5 and GluB4 gene except half of the first exon of GluB5. GluB5 and GluB4 have the same amino acid sequence in the acidic subunit, suggesting that only the mutation involving both GluB5 and GluB4 results in the lack of the glutelin acidic subunit deleted in glu1. Our finding suggests that gamma-ray can be an effective mutagen to analyze tandem repeated and functionally redundant genes.

Radiation-induced mutation at tandem repeat DNA Loci in the mouse germline: spectra and doubling doses.

The spectra and dose response for mutations at expanded simple tandem repeat (ESTR) loci in the germline of male mice acutely exposed to low-LET X or gamma rays at pre-meiotic stages of spermatogenesis were compared in five strains of laboratory mice. Most mutation events involved the gain or loss of a relatively small number of repeat units, and the distributions of length changes were indistinguishable between the exposed and control males. Overall, a significant bias toward gains of repeats was detected, with approximately 60% of mutants showing gains. The values for ESTR mutation induction did not differ substantially between strains. The highest values of doubling dose were obtained for two genetically related strains, BALB/c and C.B17 (mean value 0.98 Gy). The estimates of doubling dose for three other strains (CBA/H, C57BL/6 x CBA/H F1 and 129SVJ x C57BL/6) were lower, with a mean value of 0.44 Gy. The dose response for ESTR mutation across all five strains was very close to that for the specific loci (Russell 7-locus test). The mechanisms of ESTR mutation induction and applications of this system for monitoring radiation-induced mutation in the mouse germline are discussed.

Gamma radiation-induced heritable mutations at repetitive DNA loci in out-bred mice.

Recent studies have shown that expanded-simple-tandem-repeat (ESTR) DNA loci are efficient genetic markers for detecting radiation-induced germline mutations in mice. Dose responses following irradiation, however, have only been characterized in a small number of inbred mouse strains, and no studies have applied ESTRs to examine potential modifiers of radiation risk, such as adaptive response. We gamma-irradiated groups of male out-bred Swiss-Webster mice with single acute doses of 0.5 and 1.0 Gy, and compared germline mutation rates at ESTR loci to a sham-irradiated control. To test for evidence of adaptive response we treated a third group with a total dose of 1.1 Gy that was fractionated into a 0.1 Gy adapting dose, followed by a challenge dose of 1.0 Gy 24h later. Paternal mutation rates were significantly elevated above the control in the 0.5 Gy (2.8-fold) and 1.0 Gy (3.0-fold) groups, but were similar to each other despite the difference in radiation dose. The doubling dose for paternal mutation induction was 0.26 Gy (95% CI = 0.14-0.51 Gy). Males adapted with a 0.1 Gy dose prior to a 1.0 Gy challenge dose had mutation rates that were not significantly elevated above the control, and were 43% reduced compared to those receiving single doses. We conclude that pre-meiotic male germ cells in out-bred Swiss-Webster mice are sensitive to ESTR mutations induced by acute doses of ionizing radiation, but mutation induction may become saturated at a lower dose than in some strains of inbred mice. Reduced mutation rates in the adapted group provide intriguing evidence for suppression of ESTR mutations in the male germline through adaptive response. Repetitive DNA markers may be useful tools for exploration of biological factors affecting the probability of heritable mutations caused by low-dose ionizing radiation exposure. The biological significance of ESTR mutations in terms of radiation risk assessment, however, is still undetermined.

A novel single molecule analysis of spontaneous and radiation-induced mutation at a mouse tandem repeat locus.

Expanded simple tandem repeat (ESTR) loci include some of the most unstable DNA in the mouse genome and have been extensively used in pedigree studies of germline mutation. We now show that repeat DNA instability at the mouse ESTR locus Ms6-hm can also be monitored by single molecule PCR analysis of genomic DNA. Unlike unstable human minisatellites which mutate almost exclusively in the germline by a meiotic recombination-based process, mouse Ms6-hm shows repeat instability both in germinal (sperm) DNA and in somatic (spleen, brain) DNA. There is no significant variation in mutation frequency between mice of the same inbred strain. However, significant variation occurs between tissues, with mice showing the highest mutation frequency in sperm. The size spectra of somatic and sperm mutants are indistinguishable and heavily biased towards gains and losses of only a few repeat units, suggesting repeat turnover by a mitotic replication slippage process operating both in the soma and in the germline. Analysis of male mice following acute pre-meiotic exposure to X-rays showed a significant increase in sperm but not somatic mutation frequency, though no change in the size spectrum of mutants. The level of radiation-induced mutation at Ms6-hm was indistinguishable from that established by conventional pedigree analysis following paternal irradiation. This confirms that mouse ESTR loci are very sensitive to ionizing radiation and establishes that induced germline mutation results from radiation-induced mutant alleles being present in sperm, rather than from unrepaired sperm DNA lesions that subsequently lead to the appearance of mutants in the early embryo. This single molecule monitoring system has the potential to substantially reduce the number of mice needed for germline mutation monitoring, and can be used to study not only germline mutation but also somatic mutation in vivo and in cell culture.