Two-tier analysis of histone H2AX phosphorylation allows the identification of Ataxia Telangiectasia heterozygotes.
OBJECTIVE
Ataxia Telangiectasia (A-T) heterozygotes constitute 0.36-1% of the general population. They have a higher risk of developing several types of cancer and may be more likely to suffer side-effects following radiotherapy than the general population. Their identification is both labor- and time-consuming and the sensitivity and specificity of the methods employed has not been evaluated. This paper describes a new approach to the identification of A-T heterozygotes based on a two-tier analysis of histone H2AX phosphorylation.


METHODS
We compared the T-cell phenotype after exposure to 2 Gy in nine obligate A-T heterozygotes and 17 normal donors. Examined end points were histone H2AX phosphorylation by flow cytometry 1 h after irradiation (kinase proficiency) and the residual gamma-H2AX foci by confocal microscopy 72 h after irradiation (DSB repair proficiency).


RESULTS
The sequential use of these two methods results in 100% positive predictive value (PPV), 67% negative predictive value (NPV), 78% sensitivity, and 100% specificity. The overall hit rate, i.e. the ratio between the true positives plus the true negatives and the total number of observations was 85%.


CONCLUSIONS
A-T heterozygotes can be identified by analysing irradiated T-cell H2AX phosphorylation level and residual gamma-H2AX foci.
Porcedda
Paola
P
Department of Clinical and Biological Sciences, University of Turin, Italy. paola.porcedda@unito.it
Turinetto
Valentina
V
Orlando
Luca
L
Lantelme
Erica
E
Brusco
Alfredo
A
De Marchi
Mario
M
Amoroso
Antonio
A
Ricardi
Umberto
U
Gregori
Dario
D
Giachino
Claudia
C
D000328:Adult; D001260:Ataxia Telangiectasia / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D006579:Heterozygote; D006657:Histones / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D010770:Phosphotransferases; D012680:Sensitivity and Specificity
D006657:Histones; D010770:Phosphotransferases