Hippocampal long-term potentiation (LTP) induced by theta-burst pairing of Schaffer collateral inputs and postsynaptic firing is associated with localized increases in synaptic strength and dendritic excitability. Using the same protocol, we now demonstrate a decrease in cellular excitability that was blocked by the h-channel blocker ZD7288. This decrease was also induced by postsynaptic theta-burst firing alone, yet it was blocked by NMDA receptor antagonists, postsynaptic Ca2+ chelation, low concentrations of tetrodotoxin, omega-conotoxin MVIIC, calcium/calmodulin-dependent protein kinase II (CaMKII) inhibitors and a protein synthesis inhibitor. Increasing network activity with high extracellular K+ caused a similar reduction of cellular excitability and an increase in h-channel HCN1 protein. We propose that backpropagating action potentials open glutamate-bound NMDA receptors, resulting in an increase in I(h) and a decrease in overall excitability. The occurrence of such a reduction in cellular excitability in parallel with synaptic potentiation would be a negative feedback mechanism to normalize neuronal output firing and thus promote network stability.

Dendritic, backpropagating action potentials (bAPs) facilitate the induction of Hebbian long-term potentiation (LTP).

Liquid biopsies, based on cell free DNA (cfDNA) and proteins, have shown the potential to detect early stage cancers of diverse tissue types. However, most of these studies were retrospective, using individuals previously diagnosed with cancer as cases and healthy individuals as controls. Here, we developed a liquid biopsy assay, named the hepatocellular carcinoma screen (HCCscreen), to identify HCC from the surface antigen of hepatitis B virus (HBsAg) positive asymptomatic individuals in the community population. The training cohort consisted of individuals who had liver nodules and/or elevated serum α-fetoprotein (AFP) levels, and the assay robustly separated those with HCC from those who were non-HCC with a sensitivity of 85% and a specificity of 93%. We further applied this assay to 331 individuals with normal liver ultrasonography and serum AFP levels. A total of 24 positive cases were identified, and a clinical follow-up for 6–8 mo confirmed four had developed HCC. No HCC cases were diagnosed from the 307 test-negative individuals in the follow-up during the same timescale. Thus, the assay showed 100% sensitivity, 94% specificity, and 17% positive predictive value in the validation cohort. Notably, each of the four HCC cases was at the early stage (<3 cm) when diagnosed. Our study provides evidence that the use of combined detection of cfDNA alterations and protein markers is a feasible approach to identify early stage HCC from asymptomatic community populations with unknown HCC status.

A diversity of ion channels contributes to the active properties of neuronal dendrites. From the apical dendrites of hippocampal CA1 pyramidal neurons, we recorded inwardly rectifying K ϩ channels with a single-channel conductance of 33 pS. The inwardly rectifying K ϩ channels were constitutively active at the resting membrane potential. The amount of constitutive channel activity was significantly larger in the apical dendrites than in the soma. Activities of these inwardly rectifying K ϩ channels were inhibited by Ba 2ϩ (200 M) and tertiapin (10 nM), both of which are believed to block G-protein-coupled inwardly rectifying K ϩ (GIRK) channels. Intracellularly applied GTP␥S (20 M) during dual dendritic recordings significantly increased constitutive channel activity. Baclofen (20 M), an agonist for the G-protein-coupled GABA B receptor, also significantly increased the level of channel activity. Therefore, these channels are GIRK channels, which are constitutively active at rest in the apical dendrites of CA1 pyramidal neurons and can be further activated via G-proteincoupled neurotransmitter receptors.

Copy number alteration (CNA) is a major contributor to genome instability, a hallmark of cancer. Here, we studied genomic alterations in single primary tumor cells and circulating tumor cells (CTCs) from the same patient. Single-nucleotide variants (SNVs) in single cells from both samples occurred sporadically, whereas CNAs among primary tumor cells emerged accumulatively rather than abruptly, converging toward the CNA in CTCs. Focal CNAs affecting the gene and the gene were observed only in a minor portion of primary tumor cells but were present in all CTCs, suggesting a strong selection toward metastasis. Single-cell structural variant (SV) analyses revealed a two-step mechanism, a complex rearrangement followed by gene amplification, for the simultaneous formation of anomalous CNAs in multiple chromosome regions. Integrative CNA analyses of 97 CTCs from 23 patients confirmed the convergence of CNAs and revealed single, concurrent, and mutually exclusive CNAs that could be the driving events in cancer metastasis.

Back-propagating action potentials (bAPs) are involved in associative synaptic plasticity and the modulation of dendritic excitability. We have used high-speed confocal and two-photon imaging to measure calcium and voltage signals associated with action potential propagation into oblique branches of CA1 pyramidal neurons in adult hippocampal slices. The spatial profile of the bAP-associated Ca 2+ influx was biphasic, with an initial increase in the proximity of the branch point followed by a progressive decrease. Voltage imaging in the branches showed that bAP amplitude was initially constant and then steadily declined with distance from the soma. To determine the role of transient K + channels in this profile, we used external Ba 2+ (150 μM) as a channel blocker, after characterizing its effect on A-type K + channels in the apical trunk. Bath application of Ba 2+ significantly reduced the A-type K + current in outside-out patches and nearly eliminated the distance-dependent decrease in bAP amplitude and its associated Ca 2+ signal. Finally, small amplitude bAPs at more distal oblique branch locations could be boosted by simultaneous branch depolarization, such that the paired Ca 2+ signal became nearly the same for proximal and distal oblique dendrites. These data suggest that dendritic K + channels regulate the amplitude of bAPs to create a dendritic Ca 2+ signal whose magnitude is inversely related to the electrotonic distance from the soma when bAPs are not associated with a significant amount of localized synaptic input. This distance-dependent Ca 2+ signal from bAPs, however, can be amplified and a strong associative signal is produced once the proper correlation between synaptic activation and AP output is achieved. We hypothesize that these two signals may be involved in the regulation of the expression and activity of dendritic voltage-and ligand-gated ion channels. The densities and properties of several dendritic voltageand ligand-gated ion channels are known to markedly vary depending upon their physical location within a given neuron (Hoffman et

Voltage-dependent K+ channels in the apical dendrites of CA1 pyramidal neurones play important roles in regulating dendritic excitability, synaptic integration, and synaptic plasticity. Using cell-attached, voltage-clamp recordings, we found a large variability in the waveforms of macroscopic K + currents in the dendrites. With single-channel analysis, however, we were able to identify four types of voltage-dependent K + channels and we categorized them as belonging to delayed-rectifier, M-, D-, or A-type K + channels previously described from whole-cell recordings. Delayed-rectifier-type K + channels had a single-channel conductance of 19 ± 0.5 pS, and made up the majority of the sustained K + current uniformly distributed along the apical dendrites. The M-type K + channels had a single-channel conductance of 11 ± 0.8 pS, did not inactivate with prolonged membrane depolarization, deactivated with slow kinetics (time constant 100 ± 6 ms at −40 mV), and were inhibited by bath-applied muscarinic agonist carbachol (10 µM). The D-type K + channels had a single-channel conductance of around 18 pS, and inactivated with a time constant of 98 ± 4 ms at +54 mV. The A-type K + channels had a single-channel conductance of 6 ± 0.6 pS, inactivated with a time constant of 23 ± 2 ms at +54 mV, and contributed to the majority of the transient K + current previously described. These results suggest both functional and molecular complexity for K + channels in dendrites of CA1 pyramidal neurones.

Purpose: Genomic analyses of small-cell lung cancer (SCLC) are limited by the availability of tumor specimens. This study aimed to investigate the suitability of single-cell sequencing of circulating tumor cells (CTC) as a method of inferring the evolution and progression of SCLCs.