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Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than one million visitors each month.

Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

WHO International Clinical Trials Registry Platform

The World Health Organization (WHO) has created a new Web site to help researchers, doctors and
patients obtain reliable information on high-quality clinical trials. Now you can go to one website and search all registers to identify clinical trial research underway around the world!




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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
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Home | Pregnancy Timeline | News Alerts |News Archive June 11, 2014


Cryptochromes (CRY) proteins along with Period (PER) proteins form
protein complexes which can be modified by a zinc ion to affect the
synchronization of the mouse circadian clock.

WHO Child Growth Charts




Found: Essential circadian clock protein

This discovery may provide the basis for treating circadian clock disorders with their associated metabolic problems.

Structural biologists have made important progress towards understanding the functioning of the circadian clock. The circadian or inner clock coordinates the sleep-wake rhythm and many other body processes that regulate, for example, metabolism, blood pressure, and the immune system.

The research is published in the journal Cell.

The research team was led by Professor Eva Wolf, Professor of Structural Biology the Institute of General Botany of Johannes Gutenberg University, Mainz (JGU), also Adjunct Director at the Institute of Molecular Biology (IMB).

Dr. Wolf has for the first time identified the molecular structure of a protein complex that plays an important role in regulating the circadian rhythm.

At the same time, they also made a surprising discovery: The protein complex contains a zinc ion, which apparently stabilizes it. These results could form the basis for new strategies for treating illnesses that are the result of circadian clock dysfunction.

"Our circadian clock controls many important physiologic functions," explains Professor Wolf. If our natural rhythm is disrupted, as in the case of people working in shifts, the likelihood of developing metabolic disorders, diabetes, or cancer is significantly increased. The fundamental research conducted by the Wolf group is focused on gaining insight into the molecular workings of our circadian clock.

The team investigated proteins called cryptochromes, which are associated with the mammalian circadian clock. In addition to regulating circadian rhythm, cryptochromes also control glucose stabilization as well as blood sugar levels. The Wolf team has just determined what the complex structure combining cryptochromes with another clock protein called period looks like.

X-ray analysis of the cryptochrome-period complex revealed atomic details of the interaction between cryptochrome and period proteins and also revealed that a zinc ion modifies these protein interactions.

"The [zinc] metal ion stabilized the complex and also appears to influence an adjacent disulfide bond,"
said Wolf. [In chemistry, a disulfide bond is a chemical bond made by the attraction between atoms. Wikipedia]

Cell studies conducted by Professor Achim Kramer's group showed that this is also the case in human cells.

Researchers didn't expect to find a disulfide bond in the cytoplasm or the cell nucleus. The disulfide bond is probably regulated by the zinc ion and acts like a sensor to indicate the metabolic status of the cell.

Wolf hopes that future discoveries about the cryptochrome-period complex will help her and her team figure out more clock protein interaction patterns. Knowing these patterns might lead to developing interventions to synchronise an otherwise out of synch human circadian clock.

•Crystal structure of mouse CRYPTOCHROME1 in complex with PERIOD2
•Mutually exclusive binding of PER2 and FBXL3 to CRY1
•Jointly coordinated zinc ion stabilizes CRY1/PER2 complex in vivo and in vitro
•Interdependent zinc binding and disulfide bond formation modulate CRY1/PER2 complex

Period (PER) proteins are essential components of the mammalian circadian clock. They form complexes with cryptochromes (CRY), which negatively regulate CLOCK/BMAL1-dependent transactivation of clock and clock-controlled genes. To define the roles of mammalian CRY/PER complexes in the circadian clock, we have determined the crystal structure of a complex comprising the photolyase homology region of mouse CRY1 (mCRY1) and a C-terminal mouse PER2 (mPER2) fragment. mPER2 winds around the helical mCRY1 domain covering the binding sites of FBXL3 and CLOCK/BMAL1, but not the FAD binding pocket. Our structure revealed an unexpected zinc ion in one interface, which stabilizes mCRY1-mPER2 interactions in vivo. We provide evidence that mCRY1/mPER2 complex formation is modulated by an interplay of zinc binding and mCRY1 disulfide bond formation, which may be influenced by the redox state of the cell. Our studies may allow for the development of circadian and metabolic modulators.


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