Circadian rhythms have three key criteria: they have an endogenous period of approximately 24 hours, can be entrained by external cues, and exhibit temperature compensation. A key experiment involved transplanting the suprachiasmatic nucleus (SCN) between animals, discovering it controls circadian rhythms. The Clock gene was also discovered in 1994 as a central part of the circadian mechanism that involves transcriptional feedback loops. UT Southwestern Medical Center is a leading research institution with Nobel laureates, National Academy members, and over $415 million in annual funding supporting thousands of research projects.

1. Introduction to
Circadian Biology
By Isara Laothamatas

2. Three Criteria of Circadian Rhythm
• Rhythm has an endogenous free-running period
of approximately ~24h
• Rhythms are entrainable by external cues
• Rhythms exhibit temperature compensation

3. PLoS One. 2008;3(12):e3884. doi: 10.1371/journal.pone.0003884. Epub 2008 Dec 8

4. Phase Response Curve
http://www.docudharma.com/diary/15742/the-idea-of-order-in-the-celestial-clockwork

5. SCN Transplantation Experiment
2118 Sollars et al. J Neurosci. 1995 Mar;15(3 Pt 2):2109-22.

6. Discovery of Clock gene
Takahashi, et al. (1994)

7. Discovery of Clock gene
Takahashi, et al. (1994)

8. Discovery of Clock gene
Takahashi, et al. (1994)

9. Transcriptional Feedback Loop
Regulation

12. UT Southwestern Medical Center

13. UT Southwestern Medical Center
• Six Nobel laureates since 1985
• 23 members of the National Academy of Sciences
• 19 members of the National Academy of Medicine
• Funding from federal agencies, foundations, companies and
private donors provide approximately $415.5 million per year
to fund about 3,300 research projects
• 11 Howard Hughes Medical Institute investigators