Pharmacological Inhibition of the Histone Lysine Demethylase KDM1A Suppresses the Growth of Multiple Acute Myeloid Leukemia Subtypes.

Lysine-specific demethylase 1 (KDM1A) is a transcriptional coregulator that can function in both the activation and repression of gene expression, depending upon context. KDM1A plays an important role in hematopoiesis and was identified as a dependency factor in leukemia stem cell populations. Therefore, we investigated the consequences of inhibiting KDM1A in a panel of cell lines representing all acute myelogenous leukemia (AML) subtypes using selective, reversible and irreversible KDM1A small-molecule inhibitors. Cell models of AML, CML, and T-ALL were potently affected by KDM1A inhibition, and cells bearing RUNX1-RUNX1T1 (AML1-ETO) translocations were especially among the most sensitive. RNAi-mediated silencing of KDM1A also effectively suppressed growth of RUNX1-RUNX1T1-containing cell lines. Furthermore, pharmacologic inhibition of KDM1A resulted in complete abrogation of tumor growth in an AML xenograft model harboring RUNX1-RUNX1T1 translocations. We unexpectedly found that KDM1A-targeting compounds not only inhibited the catalytic activity of the enzyme, but evicted KDM1A from target genes. Accordingly, compound-mediated KDM1A eviction was associated with elevated levels of local histone H3 lysine 4 dimethylation, and increased target gene expression, which was further accompanied by cellular differentiation and induction of cell death. Finally, our finding that KDM1A inhibitors effectively synergize with multiple conventional as well as candidate anti-AML agents affords a framework for potential future clinical application. Cancer Res; 76(7); 1975-88. ©2016 AACR.

The role of intracellular calcium stores in synaptic plasticity and memory consolidation.

Memory processing requires tightly controlled signalling cascades, many of which are dependent upon intracellular calcium (Ca(2+)). Despite this, most work investigating calcium signalling in memory formation has focused on plasma membrane channels and extracellular sources of Ca(2+). The intracellular Ca(2+) release channels, ryanodine receptors (RyRs) and inositol (1,4,5)-trisphosphate receptors (IP3Rs) have a significant capacity to regulate intracellular Ca(2+) signalling. Evidence at both cellular and behavioural levels implicates both RyRs and IP3Rs in synaptic plasticity and memory formation. Pharmacobehavioural experiments using young chicks trained on a single-trial discrimination avoidance task have been particularly useful by demonstrating that RyRs and IP3Rs have distinct roles in memory formation. RyR-dependent Ca(2+) release appears to aid the consolidation of labile memory into a persistent long-term memory trace. In contrast, IP3Rs are required during long-term memory. This review discusses various functions for RyRs and IP3Rs in memory processing, including neuro- and glio-transmitter release, dendritic spine remodelling, facilitating vasodilation, and the regulation of gene transcription and dendritic excitability. Altered Ca(2+) release from intracellular stores also has significant implications for neurodegenerative conditions.

Role for purinergic receptors in memory processing in young chicks.

The current study used a single trial bead discrimination task for the young chick to ascertain if inhibitors of P2 purinergic receptors would impair memory retention. Suramin and PPADS provided similar retention profiles. Loss of memory retention was evident by 60 min post-training. Both drugs caused persistent memory loss which was still evident 24h post-training. These findings suggest that P2 receptors have a role in memory processing.

Blocking SK channels impairs long-term memory formation in young chicks.

The role of small-conductance calcium-activated potassium (SK) channels in memory formation was explored in chicks trained on a single-trial discrimination avoidance task. Blockade of SK channels using apamin (1 nM, 0.02 ng/hem, i.c.) impaired long-term memory retention when administered between 10 min prior to, and 30 min after, training. Apamin (1 nM, 0.02 ng/hem, immediately post-training, i.c.) resulted in persistent impairment of retention during the long-term memory stage by 90 min post-training until at least 24 h post-training, indicating SK channels contribute to long-term memory.

Pharmacobehavioural evidence for nitric oxide and noradrenaline interactions with ryanodine receptors during memory formation in the young chick.

Impairment of nitric oxide (NO) production, ryanodine receptor (RyR) calcium channel function and adrenoceptor activation have been found to prevent the formation of the long-term memory stage in young chicks trained on a single-trial discrimination avoidance task. The current study investigated whether these three activities were linked, and if so, the sequence of activation. Young chicks were trained using either a strongly or weakly reinforced variant of the single-trial discrimination avoidance task, yielding either a persistent or labile memory trace, respectively. Following strongly reinforced training, retention loss induced by a RyR inhibitor was prevented by a NO donor or noradrenaline (NA). A RyR agonist also prevented retention loss induced by either NO synthase or ß1+2-adrenoceptor inhibition. These findings were interpreted to reflect the capacity of NO, RyR-dependent calcium release and NA to modulate memory by preventing retention loss. A second set of studies used weakly reinforced training. Although the administration of a RyR agonist promoted long-term memory formation, this facilitation was compromised in the presence of a ß1+2-adrenoceptor antagonist, but not a NO synthase inhibitor. Similarly, the inhibition of RyRs interfered with the facilitation of retention induced by a NO donor, but not NA. These differential findings with weakly reinforced training suggest that NO facilitates memory formation through mechanisms involving RyR-dependent calcium release. The findings also indicate that RyRs may promote memory formation through noradrenergic activation of ß2-adrenoceptors. This study demonstrates an intricate role for RyRs underlying memory formation.

A ryanodine receptor agonist promotes the consolidation of long-term memory in young chicks.

Young chicks were trained on a weakly reinforced variant of a single-trial discrimination avoidance task which typically fails to consolidate the long-term memory stage. The ryanodine receptor (RyR) agonist 4-chloro-m-cresol (500 microM, i.c.) persistently promoted high retention until at least 24 h post-training when administered between the time of training and 20 min post-training. The consolidation of the long-term memory stage by RyR activation implicates intracellular calcium release in triggering long-term memory.

Comparative physical mapping links conservation of microsynteny to chromosome structure and recombination in grasses.

Nearly finished sequences for model organisms provide a foundation from which to explore genomic diversity among other taxonomic groups. We explore genome-wide microsynteny patterns between the rice sequence and two sorghum physical maps that integrate genetic markers, bacterial artificial chromosome (BAC) fingerprints, and BAC hybridization data. The sorghum maps largely tile a genomic component containing 41% of BACs but 80% of single-copy genes that shows conserved microsynteny with rice and partially tile a nonsyntenic component containing 46% of BACs but only 13% of single-copy genes. The remaining BACs are centromeric (4%) or unassigned (8%). The two genomic components correspond to cytologically discernible "euchromatin" and "heterochromatin." Gene and repetitive DNA distributions support this classification. Greater microcolinearity in recombinogenic (euchromatic) than nonrecombinogenic (heterochromatic) regions is consistent with the hypothesis that genomic rearrangements are usually deleterious, thus more likely to persist in nonrecombinogenic regions by virtue of Muller's ratchet. Interchromosomal centromeric rearrangements may have fostered diploidization of a polyploid cereal progenitor. Model plant sequences better guide studies of related genomes in recombinogenic than nonrecombinogenic regions. Bridging of 35 physical gaps in the rice sequence by sorghum BAC contigs illustrates reciprocal benefits of comparative approaches that extend at least across the cereals and perhaps beyond.