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ARTICLE |
Cellular/Molecular
Antideath Transcription Factors
Sp1 and Sp3 Are Oxidative Stress-Inducible, Antideath
Transcription Factors in Cortical Neurons
Hoon Ryu, Junghee Lee, Khalequz Zaman, James Kubilis, Robert J. Ferrante, Brian D. Ross, Rachael Neve, and Rajiv R. Ratan (see pages 3597-3606)
Cells react to oxidative stress with a complex tapestry of
adaptive responses. "Antideath" molecules can counteract this
cellular stress by reducing reactive oxygen species and repairing DNA
damage. Because oxidative stress can alter the expression of antideath genes, the role of transcription factors in regulating this process has
come under increasing scrutiny. A report this week from Ryu et al.
shows that the zinc finger transcription factors Sp1 and Sp3 are
redox-regulated in neurons. In cultured cortical neurons, oxidative
stress dramatically increased the low basal DNA-binding activity of Sp1
and Sp3, an early response that was prevented by antioxidants and
appeared to follow cellular increases in Sp1 and Sp3 protein.
Furthermore, overexpression of the zinc finger DNA-binding proteins
prevented oxidative stress- or DNA damage-induced neuronal death. To
investigate the activity of Sp1 proteins in vivo, the
authors used a transgenic and a chemical mouse model of Huntington's
disease; Sp1 and Sp3 levels were increased in both model systems.
Together, these results suggest that the Sp1 and Sp3 transcription
factors form one thread of a compensatory neuronal response to
oxidative stress.
Development/Plasticity/Repair
Dendritic Patterns in Drosophila
Distinct Developmental Modes and Lesion-Induced
Reactions of Dendrites of Two Classes of Drosophila
Sensory Neurons
Kaoru Sugimura, Misato Yamamoto, Ryusuke Niwa, Daisuke Satoh,
Satoshi Goto, Misako Taniguchi, Shigeo Hayashi, and Tadashi Uemura
(see pages 3752-3760)
Many neurons, such as Purkinje cells, can be instantly
recognized by their distinct dendritic arbors, yet the mechanisms
underlying the extent of dendritic fields and branching patterns is far
from clear. Advances in imaging technology are helping to answer such questions. Sugimura et al. generated cell-specific markers and then
used time-lapse videomicroscopy to watch dendritic development in class
I and class IV sensory neurons in the peripheral nervous system of the
Drosophila embryo. They followed dendrite maturation in
larva and the response to branch severing. They saw distinct branching
behaviors in the dendritic arborization of class I and class IV
neurons, which differ in their arbor complexity and morphology. Their
analysis was aided by the fact that these neurons form largely two-dimensional dendritic arbors. One interesting property of class IV
sensory neurons is the complete but minimal-overlapping innervation of
their receptive fields, called "tiling." Several signaling
molecules have been identified recently as important to dendritic arbor
formation. The current work, through laser ablation of dendritic
branches, seems to confirm that a class-specific intercellular
inhibitory communication between class IV neurons is necessary and
sufficient for tiling. This system should be a useful model to
investigate the underlying molecular mechanisms.
Behavioral/Systems/Cognitive
Neural Correlates of Remembering
Functional Dissociation among Components of Remembering:
Control, Perceived Oldness, and Content
Mark E. Wheeler and Randy L. Buckner (see pages
3869-3880)
In an investigation of human brain function, Wheeler and
Buckner used functional magnetic resonance imaging to examine specific components of that treasured cortical function, memory, and to define
the cortical areas that mediate it. The very nature of remembering (the
ability to recall events experienced at some time in
one's past) requires multiple interdependent elements. Here, Wheeler
and Buckner examined three such elements: control, the intentional
retrieval of information; perceived oldness, the realization that
information is in fact not new; and content, the actual "stuff" of
the memory, which can be given context by the modality in which it was
experienced. They separated the three components by manipulating the
study content, the presentation, and the conditions of the retrieval
tasks. They found distinct areas associated with each component. The
control element correlated with activity in the left prefrontal cortex,
whereas activity in parietal and frontal regions accompanied perceived
oldness and activity in inferior temporal regions was content-related.

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Word cues paired with pictures or sounds were used to test
components of remembering. This image is taken from Figure 1 of this
article.
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