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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.

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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 4, 2014

 

The location of brown fat in an adult. According to Rasmus Siersbaek, PhD:
"If we manage to find ways to make stem cells develop into brown rather than
white fat cells, it may be possible to reduce the development of obesity.
"






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How stem cells develop may help us fight obesity

The world has great expectations that stem cells will revolutionize medicine. But in order to exploit their potential, we need to understand how their development is regulated.

Stem cells can develop into different cell types throughout the body. In adult humans these cells play an important role in tissue regeneration, renewing tissue that would otherwise die. The hope is that this potential for repair can be manipulated for treating diseases caused by the death of specialized cells - such as Parkinson's or diabetes. But in order to manipulate stem cells, we need to know how they self regulate.

Now Danish researchers Rasmus Siersback, postdoc, professor Susanne Mandrup and Atefeh Rabiee, PhD, at the University of Southern Denmark, write in Cell Reports their insight into basic stem cell differentiation.


"An incredibly complex and previously unknown interplay between transcription factors takes place on locations we call 'hotspots,' in the cell's DNA. This interplay appears to be of great importance for the development of stem cells. When we understand these mechanisms better, we will have the tools to make a stem cell develop in the direction we want."

Rasmus Siersbaek, PhD, Department of Biochemistry and Molecular Biology at the University of Southern Denmark.


Siersbaek and colleagues made the discovery while studying how stem cells develop into fat cells.


"We know that there are two types of fat cells; brown and white. White fat cells store fat, while brown fat cells actually increase the burning of fat. Brown fat cells are found in infants, while adults have varying smaller amounts.

"If we manage to find ways to make stem cells develop into brown rather than white fat cells, it may be possible to reduce the development of obesity. Our findings open new possibilities to do this by focusing on the specific sites where transcription proteins work."

Rasmus Siersbaek, PhD


Researchers worked with a well-known cell line that can be induced to develop into fat cells using a cocktail of hormones. These factors control which genes are turned on and off by binding to places on the cell's genome referred to as 'hotspots'. Research also revealed several hotspots working together form super-enhancers which activate genes during fat cell development.


The study shows an extremely high degree of cooperation between transcription factors, which appear to direct the development of stem cells.


Transcription Factor Cooperativity in Early Adipogenic Hotspots and Super-Enhancers:

Highlights
•A combined proteomics and genomics approach identifies hotspot-associated factors
•Hotspots are highly enriched in early adipogenic super-enhancers
•(Super)-enhancer activity relies on extensive transcription factor cooperativity
•Transcription factors differ in their impact on super- and regular-enhancer activity

Summary
It is becoming increasingly clear that transcription factors operate in complex networks through thousands of genomic binding sites, many of which bind several transcription factors. However, the extent and mechanisms of crosstalk between transcription factors at these hotspots remain unclear. Using a combination of advanced proteomics and genomics approaches, we identify ∼12,000 transcription factor hotspots (∼400 bp) in the early phase of adipogenesis, and we find evidence of both simultaneous and sequential binding of transcription factors at these regions. We demonstrate that hotspots are highly enriched in large super-enhancer regions (several kilobases), which drive the early adipogenic reprogramming of gene expression. Our results indicate that cooperativity between transcription factors at the level of hotspots as well as super-enhancers is very important for enhancer activity and transcriptional reprogramming. Thus, hotspots and super-enhancers constitute important regulatory hubs that serve to integrate external stimuli on chromatin.

Authors
Rasmus Siersbæk, Atefeh Rabiee, Ronni Nielsen, Simone Sidoli, Sofie Traynor, Anne Loft, Lars La Cour Poulsen, Adelina Rogowska-Wrzesinska, Ole N. Jensen, and Susanne Mandrup.

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