Although these analyses were conducted in naive mice (not experimentally challenged with a pathogen or immunogen), upregulation of CD44 and downregulation of CD62L are indicative of T cells that have been antigen exposed. death of erythroid and neuronal cells.5 The generation of chimaeric or tissue-specific revealed a critical role for BCL-XL in the survival of developing lymphocytes5 and platelets.6, 7 embryos die before implantation (E3.5),8 but conditional deletion models have demonstrated an essential role for MCL-1 in the survival of haematopoietic stem cells, lymphocytes, neurons and cardiomyocytes.9, 10, 11, 12, 13, 14, 15 mice have impaired spermatogenesis.16, 17 A1 remains the only pro-survival BCL-2 family member for which a knockout mouse strain has not been developed. A1 was first discovered as a GM-CSF-inducible gene Rabbit Polyclonal to c-Met (phospho-Tyr1003) with significant sequence similarity to BCL-2 and Bretylium tosylate MCL-1, 18 and its human Bretylium tosylate homologue BFL-1 was later identified in fetal liver.19 Overexpression of A1 protected an IL-3-dependent cell line from growth factor deprivation-induced apoptosis, thus demonstrating its pro-survival function.20 In mice, A1 expression is restricted to the haematopoietic compartment.18 Human BFL-1 expression is more widespread, but also predominantly haematopoietic. 21 A1 can be upregulated by NF-and and are nearly identical at both the DNA and protein levels, but their expression patterns vary between cell types and particular functions for each isoform are yet to be delineated.27 Mice lacking the isoform have been generated, but showed only minor defects in neutrophils and mast cells,28, 29 suggesting functional redundancy between the different isoforms. Other studies of A1 involved knockdown of all functional isoforms using transgenic expression of an shRNA.30, 31, 32, 33 A1 knockdown caused a reduction in B cells, mast cells and dendritic cells, but knockdown in these models was usually incomplete and hence not equivalent to a knockout. Herein we describe the characterisation of a novel mouse strain lacking all A1 proteins, with a focus Bretylium tosylate on the immune cell subsets that have previously been proposed to rely on A1 for their survival. Our results demonstrate that complete loss of A1 has only a minor impact, with only conventional dendritic cells (cDCs) being substantially affected. These findings have important implications for the regulation of haematopoietic cell survival, and also inform on toxicities that may be expected from therapeutic targeting of A1. Results Generation of A1-deficient mice The mouse strain was generated by sequential deletion of each isoform (and (((to allow for its conditional deletion. Antibiotic resistance markers were removed by flippase-mediated recombination to yield the conditional knockout allele (and but has flanked by loxP sites. Two independent ES cell clones were used to generate the mice were crossed with mice, in which the CRE recombinase is expressed ubiquitously and constitutively. This produced the final knockout allele (mice generated the complete knockout mice (isoforms was confirmed by PCR using primers for each individual locus (Figure 1a, Supplementary Figure S1c and Supplementary Table S2). mice were born at the expected Mendelian frequency (Supplementary Table S1) and proved fertile. They appeared outwardly normal up to 12 months of age and are currently being monitored further. Open in a separate window Figure 1 Generation and validation of gene locus and the three targeting constructs for (((and are constitutively deleted after Flpe recombination, and is flanked by loxP sites. Intercrossing mice carrying the conditional knockout allele with the transgenic mouse enabled CRE-mediated recombination to remove for the constitutive knockout. The and or Bretylium tosylate sites were used for diagnostic deletion tests through the multiple rounds of gene targeting. Numbers and dotted lines indicate sites for PCR primers, described in Supplementary Table S2. (b) FACS-sorted T and B lymphocytes from the spleens of wild-type and mice were stimulated for the times indicated and cell lysates were then prepared for western blotting. T cells were treated with antibodies against CD3 and CD28. B cells were treated with anti-IgM antibody fragments in the presence of IL-4 and IL-5. Per lane, 20?cells depicted). Ratios are determined from the average MFIs of cells stimulated from three mice of each genotype Western blotting was.