A modulatory role of the Rax homeobox gene in mature pineal gland function: Investigating the photoneuroendocrine circadian system of a Rax conditional knockout mouse

Deletion of Rax in the pineal gland did not affect its morphology, suggesting Rax is not essential for pineal gland development.

• Rax is crucial for eye development, leading to anophthalmia when deleted in the eye.
• The absence of Rax also results in the loss of the suprachiasmatic nucleus, indicating the importance of visual pathways for its development.
• Functional analyses showed a lack of a circadian clock in Rax conditional knockout mice.
• Aanat transcripts, which are vital for melatonin production, were undetectable in the knockout pineal gland under normal conditions.
• Isoproterenol injection induced some Aanat expression in the knockout mice, but levels remained significantly lower compared to Rax-proficient mice.
• These findings suggest that Rax may regulate pineal gene expression and influence melatonin synthesis through Aanat.

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