A simple and reliable method for claustrum localization across age in mice.

Area of Science:

• Neuroscience
• Anatomy
• Molecular Biology

Background:

• The rodent claustrum's anatomical boundaries are poorly defined, hindering functional studies.
• Existing methods for claustrum identification often lack specificity or completeness, particularly during development.

Purpose of the Study:

• To develop a reliable immunolabelling method for identifying rodent claustrum projection neurons.
• To differentiate the claustrum from adjacent cortical structures using molecular markers.

Main Methods:

• Juxtaposing expression patterns of claustrum-enriched markers (Nurr1, Nr2f2) and a cortical marker (Tle4).
• Utilizing retrograde tracing to verify claustrum projection neuron characteristics.
• Assessing neuronal activation via c-Fos expression in response to environmental novelty.

Main Results:

• Claustrum cells expressing Nurr1/Nr2f2 were found to be Tle4-negative, enabling clear differentiation from cortical cells.
• This Nurr1-positive/Tle4-negative profile effectively identified claustrum projection neurons, including during neonatal development (7-21 days).
• Environmental novelty increased c-Fos expression in the claustrum, primarily in Nurr1-positive cells.

Conclusions:

• The proposed immunolabelling method provides a robust tool for studying the rodent claustrum.
• This technique enhances the ability to investigate claustrum anatomy and function across different developmental stages.
• The findings support the claustrum's role in processing environmental novelty.