Biomedical subjects

Maria Toledo-Rodriguez

Publications and source records attributed to Maria Toledo-Rodriguez.

7 recordsLinked to original sources

PubMed2005

Neuropeptide and calcium-binding protein gene expression profiles predict neuronal anatomical type in the juvenile rat.

Neocortical neurones can be classified according to several independent criteria: morphological, physiological, and molecular expression (neuropeptides (NPs) and/or calcium-binding proteins (CaBPs)). While it has been suggested that particular NPs and CaBPs characterize certain anatomical subtypes of neurones, there is also considerable overlap in their expression, and little is known about simultaneous expression of multiple NPs and CaBPs in morphologically characterized neocortical neurones. Here we determined the gene expression profiles of calbindin (CB), parvalbumin (PV), calretinin (CR), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), somatostatin (SOM) and cholecystokinin (CCK) in 268 morphologically identified neurones located in layers 2-6 in the juvenile rat somatosensory neocortex. We used patch-clamp electrodes to label neurones with biocytin and harvest the cytoplasm to perform single-cell RT-multiplex PCR. Quality threshold clustering, an unsupervised algorithm that clustered neurones according to their entire profile of expressed genes, revealed seven distinct clusters. Surprisingly, each cluster preferentially contained one anatomical class. Artificial neural networks using softmax regression predicted anatomical types at nearly optimal statistical levels. Classification tree-splitting (CART), a simple binary neuropeptide decision tree algorithm, revealed the manner in which expression of the multiple mRNAs relates to different anatomical classes. Pruning the CART tree revealed the key predictors of anatomical class (in order of importance: SOM, PV, VIP, and NPY). We reveal here, for the first time, a strong relationship between specific combinations of NP and CaBP gene expressions and the anatomical class of neocortical neurones.

Animals↗

PubMed2005

Cellular signalling properties in microcircuits.

Molecules and cells are the signalling elements in microcircuits. Recent studies have uncovered bewildering diversity in postsynaptic signalling properties in all areas of the vertebrate nervous system. Major effort is now being invested in establishing the specialized signalling properties at the cellular and molecular levels in microcircuits in specific brain regions. This review is part of the TINS Microcircuits Special Feature.

Animals↗

PubMed2004

Anatomical, physiological and molecular properties of Martinotti cells in the somatosensory cortex of the juvenile rat.

Whole-cell patch-clamp recordings followed by histochemical staining and single-cell RT-PCR were obtained from 180 Martinotti interneurones located in layers II to VI of the somatosensory cortex of Wistar rats (P13-P16) in order to examine their anatomical, electrophysiological and molecular properties. Martinotti cells (MCs) mostly displayed ovoid-shaped somata, bitufted dendritic morphologies, and axons with characteristic spiny boutons projecting to layer I and spreading horizontally across neighbouring columns more than 1 mm. Electron microscopic examination of MC boutons revealed that all synapses were symmetrical and most synapses (71%) were formed onto dendritic shafts. MCs were found to contact tuft, apical and basal dendrites in multiple neocortical layers: layer II/III MCs targeted mostly layer I and to a lesser degree layer II/III; layer IV MCs targeted mostly layer IV and to a lesser degree layer I; layer V and VI MCs targeted mostly layer IV and layer I and to a lesser degree the layer in which their somata was located. MCs typically displayed spike train accommodation (90%; n = 127) in response to depolarizing somatic current injections, but some displayed non-accommodating (8%) and a few displayed irregular spiking responses (2%). Some accommodating and irregular spiking MCs also responded initially with bursts (17%). Accommodating responses were found in all layers, non-accommodating mostly in upper layers and bursting mostly in layer V. Single-cell multiplex RT-PCR performed on 63 MCs located throughout layers II-VI, revealed that all MCs were somatostatin (SOM) positive, and negative for parvalbumin (PV) as well as vasoactive intestinal peptide (VIP). Calbindin (CB), calretinin (CR), neuropeptide Y (NPY) and cholecystokinin (CCK) were co- expressed with SOM in some MCs. Some layer-specific trends seem to exist. Finally, 24 accommodating MCs were examined for the expression of 26 ion channel genes. The ion channels with the highest expression in these MCs were (from highest to lowest); Cabeta1, Kv3.3, HCN4, Cabeta4, Kv3.2, Kv3.1, Kv2.1, HCN3, Caalpha1G, Kv3.4, Kv4.2, Kv1.1 and HCN2. In summary, this study provides the first detailed analysis of the anatomical, electrophysiological and molecular properties of Martinotti cells located in different neocortical layers. It is proposed that MCs are crucial interneurones for feedback inhibition in and between neocortical layers and columns.

Action Potentials↗

PubMed2004

Correlation maps allow neuronal electrical properties to be predicted from single-cell gene expression profiles in rat neocortex.

The computational power of the neocortex arises from interactions of multiple neurons, which display a wide range of electrical properties. The gene expression profiles underlying this phenotypic diversity are unknown. To explore this relationship, we combined whole-cell electrical recordings with single-cell multiplex RT-PCR of rat (p13-16) neocortical neurons to obtain cDNA libraries of 26 ion channels (including voltage activated potassium channels, Kv1.1/2/4/6, Kvbeta1/2, Kv2.1/2, Kv3.1/2/3/4, Kv4.2/3; sodium/potassium permeable hyperpolarization activated channels, HCN1/2/3/4; the calcium activated potassium channel, SK2; voltage activated calcium channels, Caalpha1A/B/G/I, Cabeta1/3/4), three calcium binding proteins (calbindin, parvalbumin and calretinin) and GAPDH. We found a previously unreported clustering of ion channel genes around the three calcium-binding proteins. We further determined that cells similar in their expression patterns were also similar in their electrical properties. Subsequent regression modeling with statistical resampling yielded a set of coefficients that reliably predicted electrical properties from the expression profile of individual neurons. This is the first report of a consistent relationship between the co-expression of a large profile of ion channel and calcium binding protein genes and the electrical phenotype of individual neocortical neurons.

Action Potentials↗

PubMed2004

Interneurons of the neocortical inhibitory system.

Mammals adapt to a rapidly changing world because of the sophisticated cognitive functions that are supported by the neocortex. The neocortex, which forms almost 80% of the human brain, seems to have arisen from repeated duplication of a stereotypical microcircuit template with subtle specializations for different brain regions and species. The quest to unravel the blueprint of this template started more than a century ago and has revealed an immensely intricate design. The largest obstacle is the daunting variety of inhibitory interneurons that are found in the circuit. This review focuses on the organizing principles that govern the diversity of inhibitory interneurons and their circuits.

Animals↗

PubMed2002

Anatomical, physiological, molecular and circuit properties of nest basket cells in the developing somatosensory cortex.

Anatomical, electrophysiological and molecular diversity of basket cell-like interneurons in layers II-IV of rat somatosensory cortex were studied using patch-clamp electrodes filled with biocytin. This multiparametric study shows that neocortical basket cells (BCs) are composed of three distinct subclasses: classical large (LBC) and small (SBC) basket cells and a third subclass, the nest basket cell (NBC). Anatomically, NBCs were distinct from LBCs and SBCs in that they formed simpler dendritic arbors and an axonal plexus of inter-mediate density, composed of a few long, smooth axonal branches. Electrophysiologically, NBCs exhibited diverse discharge responses to depolarizing current injections including accommodation, non-accommodation and stuttering. Single-cell multiplex RT-PCR revealed distinct mRNA expression patterns for the calcium binding proteins parvalbumin (PV), calbindin (CB) and calretinin (CR), and the neuropeptides somatostatin (SOM), vasoactive intestinal peptide (VIP), cholecystokinin (CCK) and neuropeptide Y (NPY) for each BC-subclass. SBCs lacked NPY expression but invariably expressed VIP, whereas neither VIP, CR nor SOM expression was detected in LBCs, and VIP and CR expression was absent in NBCs. Electro-physiologically distinct types of NBCs formed GABAergic synapses with specific dynamics onto pyramidal cells (PCs) and received either strongly facilitating or depressing synaptic inputs from PCs. Finally, NBCs were found to be the most common basket cell in layers II/III, while LBCs were the most common in layer IV. These data provide multiparametric distinguishing features of three major subclasses of basket cells and indicate that NBCs are powerful interneurons that provide most of the (peri-)somatic inhibition in the supragranular layers.

Animals↗

PubMed2002

Nir2, a novel regulator of cell morphogenesis.

Cell morphogenesis requires dynamic reorganization of the actin cytoskeleton, a process that is tightly regulated by the Rho family of small GTPases. These GTPases act as molecular switches by shuttling between their inactive GDP-bound and active GTP-bound forms. Here we show that Nir2, a novel protein related to Drosophila retinal degeneration B (RdgB), markedly affects cell morphology through a novel Rho-inhibitory domain (Rid) which resides in its N-terminal region. Rid exhibits sequence homology with the Rho-binding site of formin-homology (FH) proteins and leads to an apparent loss of F-actin staining when ectopically expressed in mammalian cells. We also show that Rid inhibits Rho-mediated stress fiber formation and lysophosphatidic acid-induced RhoA activation. Biochemical studies demonstrated that Nir2, via Rid, preferentially binds to the inactive GDP-bound form of the small GTPase Rho. Microinjection of antibodies against Nir2 into neuronal cells markedly attenuates neurite extension, whereas overexpression of Nir2 in these cells attenuates Rho-mediated neurite retraction. These results implicate Nir2 as a novel regulator of the small GTPase Rho in actin cytoskeleton reorganization and cell morphogenesis.

3T3 Cells↗