To reflex or not: additional BRCA1/2 testing in Ashkenazi Jewish individuals without founder mutations.

This study determined the prevalence of non-Ashkenazi Jewish BRCA1/2 mutations in the Ashkenazi Jewish population in the state of Michigan, current provider testing practices, and the use of mutation probability models in determining which Ashkenazi Jewish individuals should be offered further analysis following negative BRCA1/2 founder testing. Testing patterns, mutation probabilities, and testing results were assessed for 327 Ashkenazi Jewish individuals seen for BRCA1/2 counseling in the state of Michigan who underwent testing for the Ashkenazi Jewish founder mutations. Only one (0.6 %) Ashkenazi Jewish individual with sequencing after negative founder analysis was found to have a non-founder mutation; no rearrangements were identified. Testing patterns varied by clinic, with the proportion of Ashkenazi Jewish individuals undergoing additional sequencing ranging from 22.2 to 92.9 %. In Ashkenazi Jewish individuals with a pre-test BRCAPRO risk calculation, the mean risk was significantly higher in those with follow-up sequencing compared to those who did not pursue additional testing. The low prevalence of non-founder BRCA1/2 mutations in Ashkenazi Jewish individuals does not warrant automatically reflexing to full analysis after negative mutation testing. Increased use of mutation probability models may aid in determining which cases warrant additional testing.

Platelet-activating factor stimulates cytoplasmic alkalinization and granule acidification in human eosinophils.

The effects of platelet-activating factor (PAF) and IL-5 on intracellular pH were investigated in human eosinophils. Purified peripheral blood eosinophils were loaded with the ratiometric fluorescent pH indicator BCECF-AM ester. Stimulation of eosinophils with PAF produced time-dependent alkalinization of the cytoplasm from an initial pH of 7.1+/-0.04 to 7.5+/-0.05. A similar alkalinization response was produced by the calcium ionophore, ionomycin and by the calcium ATPase inhibitor, thapsigargin. These compounds as well as PAF produce significant increases in cytoplasmic calcium ([Ca2+]i). In contrast, IL-5 and the protein kinase C (PKC) activator phorbol myristate acetate (PMA) did not produce cytoplasmic alkalinization and had no effect on [Ca2+]i in eosinophils. PAF-stimulated alkalinization was not inhibited under conditions that blocked plasma membrane Na+-H+ exchange, proton channel or plasma membrane H+-ATPase activities. Measurements of intragranule pH with a cell permeant pH indicator (LysoSensor Yellow/Blue DND-160), which partitions into intracellular acidic compartments, revealed that PAF-stimulated cytosolic alkalinization correlated with intragranule acidification. These results suggest that the increase in [Ca2+]i after PAF stimulation activates a H+-ATPase present in the granule membranes, leading to enhanced granule acidification and cytoplasmic alkalinization. We propose that granule acidification is an important step in solubilization of major basic protein crystals, which are stored within the granule core, in preparation for degranulation and release of these proteins.