Deletion of PS1 expression starts at DP stage and reduces activity of gamma-secretase as well as expression of Deltex-1/2 genes. DNA from DN, DP, SP4, or SP8 thymocytes as well as from CD4, CD8, or B splenocytes from control or PS KO animals was used to evaluate the deletion of presenelin-1 gene by PCR with specific primers (A). Protein extracts from control or PS KO thymocytes were used to measure the amount of PS1 and NIC proteins by Western blot (B). cDNA from DN, DP, SP4, or SP8 thymocytes was analyzed by real-time PCR for Deltex-1/2 gene expression (C). Representative of 3 independent experiments.