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

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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 Oct 25, 2013

 

Study results show that Smek1, a regulatory subunit of PP4, regulates neuronal differentiation but also reveals an unreported function of PP4 in mammalian neurogenesis.
PP4 to Par3 during mitosis negatively regulates Par3 function in neurogenesis.







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How do humans and other mammals get so brainy?

Researchers put on their thinking caps to explain how neural stem and progenitor cells turn into neurons and related cells called glia.

USC researcher Wange Lu, PhD, and his colleagues shed new light on this question in a paper published in Cell Reports on October 24.

Neurons transmit information through electrical and chemical signals; glia surround, support and protect neurons in the brain and throughout the nervous system.

Glia do everything:

hold neurons in place
supply neurons with nutrients and oxygen
protect neurons from pathogens.


By studying early mouse embryo neural stem cells in a petri dish, Lu and his colleagues discovered that a protein called SMEK1 promotes differentiation of neural stem and progenitor cells. At the same time, SMEK1 keeps these cells in check by suppressing their uncontrolled proliferation.

They also determined that SMEK1 doesn't act alone: it works together with Protein Phosphatase 4 to suppress the activity of a third protein called PAR3 which discourages neurogenesis — the birth of new neurons.

With PAR3 out of the picture, neural stem cells and progenitors are free to differentiate into neurons and glia.


"These studies reveal the mechanisms of how the brain keeps the balance of stem cells and neurons when the brain is formed," said Wange Lu, associate professor of biochemistry and molecular biology at the Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC. "If this process goes wrong, it leads to cancer, or mental retardation or other neurological diseases."

Neural stem and progenitor cells offer tremendous promise as a future treatment for neurodegenerative disorders. Understanding their differentiation is the first step towards harnessing therapeutic potential. This could offer new hope for patients with Alzheimer's, Parkinson's and many other currently incurable diseases.

Abstract Highlights
Smek1 promotes neuronal differentiation
Subcellular localization of Smek1 changes dynamically during the cell cycle
Smek1 mediates Par3 dephosphorylation
Smek1 negatively regulates Par3 in neurogenesis
Summary

Neural progenitor cells (NPCs) are multipotent cells that can self-renew and differentiate into neurons and glial cells. However, mechanisms that control their fate decisions are poorly understood. Here, we show that Smek1, a regulatory subunit of the serine/threonine protein phosphatase PP4, promotes neuronal differentiation and suppresses the proliferative capacity of NPCs. We identify the cell polarity protein Par3, a negative regulator of neuronal differentiation, as a Smek1 substrate and demonstrate that Smek1 suppresses its activity. We also show that Smek1, which is predominantly nuclear in NPCs, is excluded from the nucleus during mitosis, allowing it to interact with cortical/cytoplasmic Par3 and mediate its dephosphorylation by the catalytic subunit PP4c. These results identify the PP4/Smek1 complex as a key regulator of neurogenesis.

Co-authors from the Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC include: Vicky Yamamoto, PhD; Si Ho Choi, PhD; and Zhong Wei, PhD. Co-authors Hee-Ryang Kim and Choun-Ki Joo, PhD are from the Catholic University of Korea in Seoul, and first author Jungmook Lyu, PhD, is affiliated with both institutions.

Funding for this study came from National Institutes of Health grant 5R01NS067213.

Original press release:http://www.eurekalert.org/pub_releases/2013-10/embl-co101113.php