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ObjectivesIn systemic lupus erythematosus (SLE) apoptotic chromatin is present extracellularly, which is most likely the result of disturbed apoptosis and/or insuffi cient removal. Released chromatin, modifi ed during apoptosis, activates the immune system resulting in the formation of autoantibodies. A study was undertaken to identify apoptosis-induced histone modifi cations that play a role in SLE. Methods The lupus-derived monoclonal antibody BT164, recently established by selection using apoptotic nucleosomes, was analysed by ELISA, western blot analysis and immunofl uorescence staining using chromatin, cells, plasma and renal sections. Random peptide phage display and peptide inhibition ELISA were used to identify precisely the epitope of BT164. The reactivity of plasma samples from lupus mice and patients with SLE with the epitope of BT164 was investigated by peptide ELISA. Results The epitope of BT164 was mapped in the N-terminal tail of histone H3 (27-KSAPAT-32) and included the apoptosis-induced trimethylation of K27. siRNA-mediated silencing of histone demethylases in cultured cells resulted in hypermethylation of H3K27 and increased nuclear reactivity of BT164. This apoptosisinduced H3K27me3 is a target for autoantibodies in patients and mice with SLE and is present in plasma and in glomerular deposits. Conclusion In addition to previously identifi ed acetylation of histone H4, H2A and H2B, this study shows that trimethylation of histone H3 on lysine 27 is induced by apoptosis and associated with autoimmunity in SLE. This fi nding is important for understanding the autoimmune response in SLE and for the development of translational strategies.

Recurrent submicroscopic deletions in genes affecting key cellular pathways are a hallmark of pediatric acute lymphoblastic leukemia (ALL). To gain more insight into the mechanism underlying these deletions, we have studied the occurrence and nature of abnormalities in one of these genes, the B-cell translocation gene 1 (BTG1), in a large cohort of pediatric ALL cases. BTG1 was found to be exclusively affected by genomic deletions, which were detected in 65 out of 722 B-cell precursor ALL (BCP-ALL) patient samples (9%), but not in 109 T-ALL cases. Eight different deletion sizes were identified, which all clustered at the telomeric site in a hotspot region within the second (and last) exon of the BTG1 gene, resulting in the expression of truncated BTG1 read-through transcripts. The presence of V(D)J recombination signal sequences at both sites of virtually all deletions strongly suggests illegitimate RAG1/RAG2-mediated recombination as the responsible mechanism. Moreover, high levels of histone H3 lysine 4 trimethylation (H3K4me3), which is known to tether the RAG enzyme complex to DNA, were found within the BTG1 gene body in BCP-ALL cells, but not T-ALL cells. BTG1 deletions were rarely found in hyperdiploid BCP-ALLs, but were predominant in other cytogenetic subgroups, including the ETV6-RUNX1 and BCR-ABL1 positive BCP-ALL subgroups. Through sensitive PCR-based screening, we identified multiple additional BTG1 deletions at the subclonal level in BCP-ALL, with equal cytogenetic distribution which, in some cases, grew out into the major clone at relapse. Taken together, our results indicate that BTG1 deletions may act as “drivers” of leukemogenesis in specific BCP-ALL subgroups, in which they can arise independently in multiple subclones at sites that are prone to aberrant RAG1/RAG2-mediated recombination events. These findings provide further evidence for a complex and multiclonal evolution of ALL.

With the growing use of selective serotonin reuptake inhibitor medications (SSRIs) for the treatment of depression during the perinatal period, questions have been raised about the longterm impact of these medications on development. We aimed to investigate how developmental SSRI exposure may alter affect-related behaviors and associated molecular processes in offspring using a rodent model of maternal stress and depression. For this purpose, prenatally stressed or non-stressed male offspring were exposed to fluoxetine (5 mg/kg/day) or vehicle, via lactation, until weaning. Primary results show that postnatal fluoxetine exposure differentially altered anxiety-like behavior by increasing anxiety in non-stressed offspring and decreasing anxiety in prenatally stressed offspring. In the hippocampus, developmental fluoxetine exposure decreased BDNF IV and TrkB mRNA expression. Prenatal stress alone also decreased escape behaviors and decreased hippocampal BDNF IV mRNA expression. These data provide important evidence for the long-term programming effects of early-life exposure to SSRIs on brain and behavior.

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