Mutations of the DNA repair gene PNKP in a patient with microcephaly, seizures, and developmental delay (MCSZ) presenting with a high-grade brain tumor.

Polynucleotide Kinase-Phosphatase (PNKP) is a bifunctional enzyme that possesses both DNA 3'-phosphatase and DNA 5'-kinase activities, which are required for processing termini of single- and double-strand breaks generated by reactive oxygen species (ROS), ionizing radiation and topoisomerase I poisons. Even though PNKP is central to DNA repair, there have been no reports linking PNKP mutations in a Microcephaly, Seizures, and Developmental Delay (MSCZ) patient to cancer. Here, we characterized the biochemical significance of 2 germ-line point mutations in the PNKP gene of a 3-year old male with MSCZ who presented with a high-grade brain tumor (glioblastoma multiforme) within the cerebellum. Functional and biochemical studies demonstrated these PNKP mutations significantly diminished DNA kinase/phosphatase activities, altered its cellular distribution, caused defective repair of DNA single/double stranded breaks, and were associated with a higher propensity for oncogenic transformation. Our findings indicate that specific PNKP mutations may contribute to tumor initiation within susceptible cells in the CNS by limiting DNA damage repair and increasing rates of spontaneous mutations resulting in pediatric glioma associated driver mutations such as ATRX and TP53.

Neurological disorders associated with DNA strand-break processing enzymes.

The termini of DNA strand breaks induced by reactive oxygen species or by abortive DNA metabolic intermediates require processing to enable subsequent gap filling and ligation to proceed. The three proteins, tyrosyl DNA-phosphodiesterase 1 (TDP1), aprataxin (APTX) and polynucleotide kinase/phosphatase (PNKP) each act on a discrete set of modified strand-break termini. Recently, a series of neurodegenerative and neurodevelopmental disorders have been associated with mutations in the genes coding for these proteins. Mutations in TDP1 and APTX have been linked to Spinocerebellar ataxia with axonal neuropathy (SCAN1) and Ataxia-ocular motor apraxia 1 (AOA1), respectively, while mutations in PNKP are considered to be responsible for Microcephaly with seizures (MCSZ) and Ataxia-ocular motor apraxia 4 (AOA4). Here we present an overview of the mechanisms of these proteins and how their impairment may give rise to their respective disorders.

Induction of adaptive response in mice exposed to 900MHz radiofrequency fields: application of micronucleus assay.

Adult male ICR mice were pre-exposed to non-ionizing radiofrequency fields (RF), 900MHz at 120µW/cm(2) power density for 4h/day for 7 days (adaptation dose, AD) and then subjected to an acute whole body dose of 3Gy γ-radiation (challenge dose, CD). The classical micronucleus (MN) assay was used to determine the extent of genotoxicity in immature erythrocytes in peripheral blood and bone marrow. The data obtained in mice exposed to AD+CD were compared with those exposed to CD alone. The results indicated that in both tissues, the MN indices were similar in un-exposed controls and those exposed to AD alone while a significantly increased MN frequency was observed in mice exposed to CD alone. Exposure of mice to AD+CD resulted in a significant decrease in MN indices compared to those exposed to CD alone. Thus, the data suggested that pre-exposure of mice to non-ionizing RF is capable of 'protecting' the erythrocytes in the blood and bone marrow from genotoxic effects of subsequent γ-radiation. Such protective phenomenon is generally described as 'adaptive response' (AR) and is well documented in human and animal cells which were pre-exposed to very low doses of ionizing radiation. It is interesting to observe AR being induced by non-ionizing RF.

The effect of combined exposure of 900 MHz radiofrequency fields and doxorubicin in HL-60 cells.

Human promyelocytic leukemia HL-60 cells were pre-exposed to non-ionizing 900 MHz radiofrequency fields (RF) at 12 µW/cm(2) power density for 1 hour/day for 3 days and then treated with a chemotherapeutic drug, doxorubicin (DOX, 0.125 mg/L). Several end-points related to toxicity, viz., viability, apoptosis, mitochondrial membrane potential (MMP), intracellular free calcium (Ca(2+)) and Ca(2+)-Mg(2+) -ATPase activity were measured. The results obtained in un-exposed and sham-exposed control cells were compared with those exposed to RF alone, DOX alone and RF+DOX. The results indicated no significant differences between un-exposed, sham-exposed control cells and those exposed to RF alone while treatment with DOX alone showed a significant decrease in viability, increased apoptosis, decreased MMP, increased Ca(2+) and decreased Ca(2+)-Mg(2+-)ATPase activity. When the latter results were compared with cells exposed RF+DOX, the data showed increased cell proliferation, decreased apoptosis, increased MMP, decreased Ca(2+) and increased Ca(2+)-Mg(2+)-ATPase activity. Thus, RF pre-exposure appear to protect the HL-60 cells from the toxic effects of subsequent treatment with DOX. These observations were similar to our earlier data which suggested that pre-exposure of mice to 900 MHz RF at 120 µW/cm(2) power density for 1 hours/day for 14 days had a protective effect in hematopoietic tissue damage induced by subsequent gamma-irradiation.

Adaptive response in mice exposed to 900 MHz radiofrequency fields: primary DNA damage.

The phenomenon of adaptive response (AR) in animal and human cells exposed to ionizing radiation is well documented in scientific literature. We have examined whether such AR could be induced in mice exposed to non-ionizing radiofrequency fields (RF) used for wireless communications. Mice were pre-exposed to 900 MHz RF at 120 µW/cm(2) power density for 4 hours/day for 1, 3, 5, 7 and 14 days and then subjected to an acute dose of 3 Gy γ-radiation. The primary DNA damage in the form of alkali labile base damage and single strand breaks in the DNA of peripheral blood leukocytes was determined using the alkaline comet assay. The results indicated that the extent of damage in mice which were pre-exposed to RF for 1 day and then subjected to γ-radiation was similar and not significantly different from those exposed to γ-radiation alone. However, mice which were pre-exposed to RF for 3, 5, 7 and 14 days showed progressively decreased damage and was significantly different from those exposed to γ-radiation alone. Thus, the data indicated that RF pre-exposure is capable of inducing AR and suggested that the pre-exposure for more than 4 hours for 1 day is necessary to elicit such AR.

[Chronotoxicology of fenvalerate on the male rats reproductive system].

OBJECTIVE: To study the chronotoxicity and mechanism of fenvalerate (Fen) on the male reproductive system. METHODS: Forty-nine healthy clean SD rats in a 12h: 12h light-dark photoperiod, which were divided into seven groups: control group and six Fen groups (Fen 2, Fen 6, Fen 10, Fen 14, Fen 18, Fen 22). Fen groups were administered by intra-gastric injection of Fen (12 mg/kg BW) respectively at corresponding zeitgeber time (ZT 02, ZT 06, ZT 10, ZT 14, ZT 18, ZT 22) for 30 days. The control group rats were administered with equal volume of edible blend oil. One side testicular was used to make HE paraffin slice. Germ cell (Daily sperm production, DSP. Sperm live rate, SLR. Abnormal sperm rate, ASR), the activities testicular mark enzymes and the levels of Sex hormones (testosterone, T, estradiol, E2) in testicular were measured. RESULTS: Compared with the control group, Fen cause the pathological changes of testicular tissue in rats, and the most serious injuries occurred in ZT 18. DSP, SLR, ACP and T in testicular were decreased, ASR and E2 were increased. Results from Cosinor analysis showed that Circadian rhythms of the changes compared to the control group in DSP, SLR and ACP were validated, and sensitive point in time to Fen was respectively at ZT 04, ZT 14, ZT 23. CONCLUSION: The results suggested that the effects of Fen on male reproductive function were time-dependent in a circadian day.

Mortality Factor Survey of Severe Acute Respiratory Syndrome in Taiwan.

BACKGROUND: Severe acute respiratory syndrome (SARS) is a new respiratory tract infectious disease caused by the highly contagious coronavirus (SARS-CoV). Its propagation and symptom progress are very rapid. This study evaluated the clinical characteristics, laboratory results and mortality factors of probable SARS cases. METHODS: This study was adopted with a retrospective research design to study probable SARS cases from the Chang Gung Memorial Hospital in Linkou and Kaoshiung from August 2003 to February 2004, with a total of 78 cases (average age, 44 years; standard deviation, 18 years; age range, 13-84 years) including 24 males (30.8%) and 54 females (69.2%). RESULTS: Most of the 78 cases involved nosocomial infection (56.4%). A total of 24 patients died, and the mortality rate was as high as 30.8%. Logistic regression analysis found that intubation (odds ratio, 115; p < 0.001) was the mortality forecast factor. CONCLUSION: The mortality rate of intubation patients was 115 times higher than that of those who did not require intubation. Therefore, special care must be taken with SARS disease with severe infiltration chest X-ray images and respiratory distress. Positive medical treatment should be performed to lower the mortality rate.