Biomedical subjects

Ken Sugino

Publications and source records attributed to Ken Sugino.

5 recordsLinked to original sources

PubMed2006

Probing the transcriptome of neuronal cell types.

Distinct neuronal cell types acquire and maintain their identity by expressing different genes. Recently it has become feasible to measure this cell type specific expression by isolating and amplifying mRNA from small populations of fluorescently labeled neurons and probing this mRNA with microarrays. Prior to this, most neuronal gene expression studies used tissue homogenates or randomly selected single cells and were, therefore, not well suited to studying transcriptional differences between cell types. Microarray studies of purified cell types have enabled investigators to identify the transcriptional signatures of, for example, subtypes of pyramidal neurons and interneurons in the neocortex, modulatory dopaminergic and serotonergic neurons, and the striatal neurons that form the so-called 'direct' and 'indirect' pathways through the basal ganglia. These studies are opening up new approaches to understanding brain circuitry, plasticity and pathology and are refining the concept of the neuronal cell type.

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PubMed2006

The problem of neuronal cell types: a physiological genomics approach.

Neural circuits within the vertebrate brain are composed of highly diverse cell types. The exact extent of this diversity is a matter of continuing debate. For example, do cortical interneurons comprise a few, dozens or >100 distinct cell types? Recently, several groups have used microarrays to measure genome-wide gene expression profiles for specific neuronal cell types. These methods can offer an objective basis for neuronal classification. In this review, we argue that this approach should now be carried out more broadly and that it should be coupled to large-scale efforts to generate mouse driver lines in which tools for genetic manipulation, such as the Cre recombinase, are expressed in identified cell types within the brain. This would enable neuroscientists to begin to investigate more systematically the roles of specific genes in establishing particular cellular phenotypes, and also the roles of particular cell types within brain circuits. This review is part of the TINS special issue on The Neural Substrates of Cognition.

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PubMed2005

Molecular taxonomy of major neuronal classes in the adult mouse forebrain.

Identifying the neuronal cell types that comprise the mammalian forebrain is a central unsolved problem in neuroscience. Global gene expression profiles offer a potentially unbiased way to assess functional relationships between neurons. Here, we carried out microarray analysis of 12 populations of neurons in the adult mouse forebrain. Five of these populations were chosen from cingulate cortex and included several subtypes of GABAergic interneurons and pyramidal neurons. The remaining seven were derived from the somatosensory cortex, hippocampus, amygdala and thalamus. Using these expression profiles, we were able to construct a taxonomic tree that reflected the expected major relationships between these populations, such as the distinction between cortical interneurons and projection neurons. The taxonomic tree indicated highly heterogeneous gene expression even within a single region. This dataset should be useful for the classification of unknown neuronal subtypes, the investigation of specifically expressed genes and the genetic manipulation of specific neuronal circuit elements.

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PubMed2003

The NMDA-to-AMPA ratio at synapses onto layer 2/3 pyramidal neurons is conserved across prefrontal and visual cortices.

To better understand regulation of N-methyl-d-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor complements across the cortex, and to investigate NMDA receptor (NMDAR)-based models of persistent activity, we compared NMDA/AMPA ratios in prefrontal (PFC) and visual cortex (VC) in rat. Whole cell voltage-clamp responses were recorded in brain slices from layer 2/3 pyramidal cells of the medial PFC and VC of rats aged p16-p21. Mixed miniature excitatory postsynaptic currents (mEPSCs) having AMPA receptor (AMPAR)- and NMDAR-mediated components were isolated in nominally 0 Mg2+ ACSF. Averaged mEPSCs were well-fit by double exponentials. No significant differences in the NMDA/AMPA ratio (PFC: 27 +/- 1%; VC: 28 +/- 3%), peak mEPSC amplitude (PFC: 19.1 +/- 1 pA; VC: 17.5 +/- 0.7 pA), NMDAR decay kinetics (PFC: 69 +/- 8 ms; VC: 67 +/- 6 ms), or degree of correlation between NMDAR- and AMPAR-mediated mEPSC components were found between the areas (PFC: n = 27; VC: n = 28). Recordings from older rats (p26-29) also showed no differences. EPSCs were evoked extracellularly in 2 mM Mg2+ at depolarized potentials; although the average NMDA/AMPA ratio was larger than that observed for mEPSCs, the ratio was similar in the two regions. In nominally 0 Mg2+ and in the presence of CNQX, spontaneous activation of NMDAR increased recording noise and produced a small tonic depolarization which was similar in both areas. We conclude that this basic property of excitatory transmission is conserved across PFC and VC synapses and is therefore unlikely to contribute to differences in firing patterns observed in vivo in the two regions.

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PubMed2002

Multi-unit spike-triggered averaging: a method for probing the physiology of central synapses.

We describe the ongoing development of a method that combines multi-unit extracellular recording with intracellular recording to probe unitary synaptic connections in the central nervous system. In multi-unit spike-triggered averaging (multi-unit STA), intracellular recordings are averaged based on extracellularly recorded action potentials from multiple units to rapidly screen large numbers of neuronal pairs for rare synaptic connections. High throughput is achieved by using many extracellular electrodes and online, automated analysis. Using this approach, we were able to screen dozens of candidate pairs per hour. About 1-2% of these were synaptically connected, and for some of these presynaptic unit isolation was sufficient to accurately quantify synaptic properties such as latency, conductance, kinetics and transmission failure rate. Since it requires only a single intracellular recording, multi-unit STA might be a suitable method for probing unitary synaptic connections in the intact brain, where obtaining multiple intracellular recordings is not feasible.

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