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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 in 1993 as a first generation internet teaching tool consolidating human embryology teaching for first year medical students.

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.


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Pregnancy Timeline by SemestersFemale Reproductive SystemFertilizationThe Appearance of SomitesFirst TrimesterSecond TrimesterThird TrimesterFetal 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 HemispheresEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterDevelopmental Timeline
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December 24, 2012--------News Archive Return to: News Alerts


Gene expression wave in the lower part of the growing
column of vertebrae in a mammalian embryo.

As the wave moves from tail to head, new pre-vertebrae are formed
and the future vertebral column elongates.






WHO Child Growth Charts

       

Synced to Grow

Oscillating pattern of gene activity may underlie how embryos grow proportionately throughout body plan


In Brief

Size of pre-vertebrae in a mammalian embryo is controlled by a wave-like gene expression pattern along its back

The size of each pre-vertebra is proportional to the speed of the wave: the faster the wave, the bigger the vertebra

Embryonic cells coordinate gene activities with each other to adapt the size of pre-vertebrae to the overall size of the embryo


From a single-cell egg to a fully functional body: as embryos develop and grow, they must form organs that are in proportion to the overall size of the embryo. The exact mechanism underlying this fundamental characteristic, called scaling, is still unclear.

However, a team of researchers from EMBL Heidelberg is now one step closer to understanding how scaling works.

They have discovered that scaling of newly forming vertebrae in a mouse embryo is controlled by how the expression of some specific genes oscillate, in a coordinated way, between neighbouring cells. Published in Nature, their findings highlight how important this oscillatory pattern, and its regulation, is to ensure that embryos grow up to become well-proportioned animals.


Neighbouring cells in the future vertebral column
of an embryo coordinate to turn specific genes
on and off in turn, thus generating a wave
of gene expression similar to the ‘Slide to unlock’
animation on your smart phone.

To study this process, and determine its impact
on how the relative sizes of the future vertebrae are
maintained, the researchers developed a new technique.


“Using this new assay, we were able to film this wave of gene expression in real time with high precision, and to identify whether this pattern could change according to the overall size,” explains Alexander Aulehla who coordinated the study at EMBL Heidelberg. “There is a clear link: when the embryo is smaller, the number of segments formed remains the same, but each segment is smaller and the expression waves are proportionally slower.”


The speed of the wave seems to be the essential
characteristic to predict the size of the future vertebra:

the faster the wave, the bigger the vertebra.

Similar expression waves have been observed in
several vertebrates and also in insect species,
so this communication pattern amongst
embryonic cells seems to be very wide-spread.

However, scientists haven’t yet figured out how the
speed of the wave is controlled at a molecular level.


The technique developed in this study might be the key to helping the team understand this complex and fundamental mechanism.

In order to make observation easier, the scientists grew only one layer of embryonic stem cells to which a specific marker was added, to follow the expression of the Notch genes. The combination of the monolayer and marking made real-time observation of gene expression possible. In the future this new technique might help researchers understand the details of how embryonic cells sync to grow.

More information on the research of the Aulehla Group
Source Article
Scaling of embryonic patterning based on phase-gradient encoding - Volker M. Lauschke, Charisios D. Tsiairis, Paul François & Alexander Aulehla – Published online in Nature on 19 December, 2012.
Article Abstract

A fundamental feature of embryonic patterning is the ability to scale andmaintain stable proportions despite changes in overall size, for instance during growth. A notable example occurs during vertebrate segment formation: after experimental reduction of embryo size, segments form proportionally smaller, and consequently, a normal number of segments is formed. Despite decades of experimental and theoretical work, the underlying mechanism remains unknown. More recently, ultradian oscillations in gene activity have been linked to the temporal control of segmentation; however, their implication in scaling remains elusive. Here we show that scaling of gene oscillation dynamics underlies segment scaling. To this end, we develop a new experimental model, an ex vivo primary cell culture assay that recapitulates mouse mesoderm patterning and segment scaling, in a quasi-monolayer of presomitic mesoderm cells (hereafter termed monolayer PSM or mPSM). Combined with real-time imaging of gene activity, this enabled us to quantify the gradual shift in the oscillation phase and thus determine the resulting phase gradient across the mPSM. Crucially, we show that this phase gradient scales by maintaining a fixed amplitude across mPSM of different lengths. We identify the slope of this phase gradient as a single predictive parameter for segment size, which functions in a size- and temperature-independent manner, revealing a hitherto unrecognized mechanism for scaling. Notably, in contrast to molecular gradients, a phase gradient describes the distribution of a dynamical cellular state. Thus, our phase-gradient scaling findings reveal a new level of dynamic information-processing, and provide evidence for the concept of phase-gradient encoding during embryonic patterning and scaling.

Original article: http://www.embl.de/aboutus/communication_outreach/
media_relations/2012/121219_Heidelberg/index.html