Bax phosphorylation association with nucleus and oligomerization after neonatal Hypoxia–ischemia

Neonatal hypoxia–ischemia (HI) is a common occurrence in preterm and low‐birth‐weight infants, and the incidence of low‐birth‐weight and preterm births is increasing. Characterization of brain injury after HI is of critical importance in developing new treatments that more accurately target the injury. After severe HI, neuronal cells undergo necrosis and secondary apoptosis of the surrounding cells as a result of neuroinflammation. We sought to characterize the biochemical pathways associated with cell death after HI. Bax, a cell death signaling protein, is activated after HI and translocates to the nucleus, endoplasmic reticulum, and mitochondria. The translocation patterns of Bax affect the resultant cell death phenotype (necrotic or apoptotic) observed. Although Bax is known to oligomerize once it is activated, less is known about the factors that control its translocation and oligomerization. We hypothesize that Bax kinase‐specific phosphorylation determines its oligomerization and intracellular localization. Using well‐established in vivo and in vitro models of neonatal HI, we characterized Bax oligomerization and multiorganelle translocation. We found that HI‐dependent phosphorylation of Bax determines its oligomerization status and multiorganelle localization, and, ultimately, the cell death phenotype observed. Understanding the mechanisms of Bax translocation will aid in the rational design of therapeutic strategies that decrease the trauma resulting from HI‐associated inflammation. © 2013 Wiley Periodicals, Inc.     

Defining the Epsilon‐Sarcoglycan (SGCE) Gene Phenotypic Signature in Myoclonus‐Dystonia: A Reappraisal of Genetic Testing Criteria

Mutations or exon deletions of the epsilon‐sarcoglycan (SGCE) gene cause myoclonus‐dystonia (M‐D), but a subset of M‐D patients are mutation‐negative and the sensitivity and specificity of current genetic testing criteria are unknown. We screened 46 newly enrolled M‐D patients for SGCE mutations and deletions; moreover, 24 subjects previously testing negative for SGCE mutations underwent gene dosage analysis. In our combined cohorts, we calculated sensitivity, specificity, positive and negative predictive values, and area under the curve of 2 published sets of M‐D diagnostic criteria. A stepwise logistic regression was used to assess which patients' characteristics best discriminated mutation carriers and to calculate a new mutation predictive score (“new score”), which we validated in previously published cohorts. Nine of 46 (19.5%) patients of the new cohort carried SCGE mutations, including 5 novel point mutations and 1 whole‐gene deletion; in the old cohort, 1 patient with a complex phenotype carried a 5.9‐Mb deletion encompassing SGCE. Current diagnostic criteria had a poor ability to discriminate SGCE‐positive from SGCE‐negative patients in our cohort; conversely, age of onset, especially if associated with psychiatric features (as included in the new score), showed the best discriminatory power to individuate SGCE mutation carriers, both in our cohort and in the validation cohort. Our results suggest that young age at onset of motor symptoms, especially in association with psychiatric disturbance, are strongly predictive for SGCE positivity. We suggest performing gene dosage analysis by multiple ligation‐dependent probe amplification (MLPA) to individuate large SGCE deletions that can be responsible for complex phenotypes. © 2013 Movement Disorder Society