Molecular analysis of mammalian timeless

Area of Science:

• Chronobiology
• Molecular Biology
• Genetics

Background:

• The circadian clock relies on molecular feedback loops for daily rhythm regulation.
• Drosophila melanogaster has a well-characterized circadian clock involving timeless (tim) and period (per) genes.
• Mammalian homologs of these genes are crucial for understanding circadian rhythms in mammals.

Purpose of the Study:

• To clone and characterize the mouse homolog of the Drosophila timeless gene (mTim).
• To investigate the expression patterns and potential role of mTim in the mammalian circadian clock.
• To explore interactions between mTim and mammalian period (mPER) proteins.

Main Methods:

• Cloning of mouse cDNA for mTim.
• Quantitative analysis of mTim RNA expression in various tissues (SCN, PT, eyes, spleen, testis).
• Yeast two-hybrid assays to examine protein-protein interactions between mTim and mPER proteins.

Main Results:

• mTim shares significant homology with Drosophila TIM.
• mTim is robustly expressed in the hypophyseal pars tuberalis (PT) but weakly in the suprachiasmatic nuclei (SCN).
• mTim RNA levels do not oscillate in the SCN and are unaffected by light. Yeast two-hybrid assays showed mPER-mPER interactions but no mPER-mTIM interactions.

Conclusions:

• The mammalian circadian clock may utilize PER-PER interactions instead of PER-TIM dimers found in Drosophila.
• mTim's distinct expression pattern and lack of oscillation suggest a different role in mammalian circadian regulation compared to Drosophila TIM.
• These findings provide insights into the evolution and diversification of circadian clock mechanisms.