Glossary

This is an index of new, innovative and/or complex methods, ideas or terms that are used in the studies I review.

Optical Intrinsic Signal Imaging: When neurons are active, their optical reflective properties change (ie the amount of light they reflect changes). So by providing some kind of input to a population of cells, say by giving a visual stimulus to the eye and monitoring the visual cortex, it is possible to change the reflective properties of that population of neurons, and thus that of the area of brain where those cells reside. The analysis of the change in reflective properties of the cells can be done with low resolution imaging (for example, a 2.5x objective). Generally, a stimulus will be presented at a specific frequency, and the area of the brain where the changes in reflection match the frequency of the stimuli is identified as the area where that stimulus is being processed.

Tet On/ Tet Off: Tetracycline-Mediated Transcription Activation: Tet-On/Tet-Off transcription activation is used to induce transcription of a transgene of interest. The systems use a tetracycline transactivator (tTA or rtTA),  the tet-Operator (tetO), and doxycycline, an analogue of tetracycline.

In nature, tetracycline activated repressor controls the transcription of a gene that produces a tetracycline pump called TetA, which removes tetracycline from bacterial cells.

The Tet On/Tet Off systems employ a fusion of the tetracycline repressor and the VP16 activation domain. In contrast to the natural tet repressor, this fusion protein, called tTA or “tetracycline transactivator,” activates transcription from the tetO that is inserted upstream of the transgene of interest, leading to transcription of the transgene.

Both Tet On and Tet Off involve activation by tTA; the On/Off differentiation refers to the systems’ respective responses to doxycycline, a tetracycline analogue. In Tet On transcription activation, reverse tTA (rtTA) binds to the operator only when it is bound to doxycycline. On the other hand, in Tet Off, tTA is normally bound to the operator, activating trascription, and falls of when doxycycline binds to it. Thus doxyxline turns transcription of the transgene on for Tet On, and it turns transcription off for Tet Off.

2 Responses to Glossary

  1. Pingback: In Depth: A Map of 16,000 Fruit Fly Neurons |

  2. Pingback: In Depth: Neurons that Change Shape! Implications for Treatment of Depression? |

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