GAD65Cre Drives Reporter Expression in Multiple Taste Cell Types

Area of Science:

• Neuroscience
• Cell Biology
• Sensory Biology

Background:

• Type I cells constitute 50-60% of taste bud cells, primarily exhibiting glial-like functions.
• Emerging evidence suggests Type I cells possess sensory and signaling roles, including salt transduction and neurotransmitter release.
• Understanding Type I cell function is hindered by the lack of a specific reporter system.

Purpose of the Study:

• To evaluate the specificity of the GAD65Cre mouse line as a reporter for Type I taste cells.
• To validate the utility of GAD65Cre mice for studying taste transduction and signaling.

Main Methods:

• Crossed GAD65Cre mice with floxed tdTomato and Channelrhodopsin (ChR2) reporter lines.
• Utilized immunochemistry, chorda tympani recordings, and calcium imaging to assess transgene expression and cell activity.
• Examined tdTomato expression in relation to known Type I cell markers (NTPDase2) and other taste cell markers (Gustducin, SNAP25).

Main Results:

• tdTomato expression was observed in NTPDase2-positive cells but also in Gustducin and SNAP25-positive taste cells.
• Channelrhodopsin (ChR2) expression was detected in cells outside the primary fungiform taste buds.
• Chorda tympani recordings from GAD65Cre/ChR2 mice showed significant responses to blue light stimulation.
• Isolated tdTomato-positive cells exhibited calcium influx upon KCl depolarization, indicating functional voltage-gated calcium channels.

Conclusions:

• The GAD65Cre driver exhibits broader expression than anticipated, labeling multiple taste cell populations.
• GAD65Cre mice are not specific to Type I taste cells and therefore are unreliable for studying their unique functions.
• Further development of specific genetic tools is necessary for precise investigation of Type I taste cell physiology.