Welcome to The Visible Embryo

Home- - -History-- -Bibliography- -Pregnancy Timeline- --Prescription Drugs in Pregnancy- -- Pregnancy Calculator- --Female Reproductive System- News Alerts -Contact

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 ' million visitors each month.


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!



Home

History

Bibliography

Pregnancy Timeline

Prescription Drug Effects on Pregnancy

Pregnancy Calculator

Female Reproductive System

Contact The Visible Embryo

News Alerts Archive

Disclaimer: The Visible Embryo web site is provided for your general information only. The information contained on this site should not be treated as a substitute for medical, legal or other professional advice. Neither is The Visible Embryo responsible or liable for the contents of any websites of third parties which are listed on this site.
Content protected under a Creative Commons License.

No dirivative works may be made or used for commercial purposes.

Return To Top Of Page
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
Click weeks 0 - 40 and follow fetal growth
Google Search artcles published since 2007
 
Home--History--Bibliography- -Pregnancy Timeline- Prescription Drugs/Pregnancy- Pregnancy Calculator - Reproductive System- -News Alerts

March 1, 2012--------News Archive Return to: News Alerts

Protein subunits 9a and 9b found in the mustard plant Arabidopsis thaliana by
IU biologists play a role in how different RNA polymerases work, including
performing RNA-directed DNA methylation. Altered DNA methylation is
involved in genetic disorders and diseases that include cancer.
Print-Quality Photo

WHO Child Growth Charts

What Is Your BMI?

       

How Protein Machine Systems Tweak Gene Expression

Unique enzyme structures offer insights into which genes get turned on or off

Indiana University biologists have found that specific types of RNA polymerase enzymes, the molecular machines that convert DNA into RNA, can differ in function based on variation in the parts - in this case protein subunits - used to assemble those machines.

The new findings on the synthesis and function of different RNA polymerases (Pols), including two RNA polymerases that lead author Craig Pikaard discovered over a decade ago - the plant-specific enzymes Pol IV and Pol V - indicate that subunit composition of the polymerases plays a role in selecting how some genes are silenced while others are not.

All eukaryotes - a group that includes plants, animals, fungi and all other organisms with nuclei - contain life-essential Pols I, II and III that are each built from different combinations of 12 to 17 protein subunits, with each of the three enzymes assigned specific, unique tasks in the cell. In 1999 while analyzing the newly sequenced genome of Arabidopsis thaliana, a member of the mustard family considered a model organism for experimentation in plant biology, Pikaard identified Pol IV and Pol V.

Pikaard's work has since shown that while the Pol IV and Pol V enzymes are not essential to life and are actually specialized forms of Pol II (the RNA polymerase responsible for generating RNAs that encode proteins), they play important roles in RNA-directed DNA methylation, a process that silences mobile genetic elements known as retrotransposons that can cause trouble if allowed to spread.

"In fact, most of the 12 protein subunits present in Pols II, IV and V are encoded by the same genes," Pikaard said. "Interestingly, among these common subunits are alternative forms of the ninth subunit, and the two forms of the ninth subunit (9a and 9b) are extremely similar, differing in only 8 of their 114 amino acids."

This high degree of similarity suggested 9a and 9b proteins might be redundant, but the Pikaard lab's new research found this to be only partially true.

"When you remove both proteins, the plants die as embryos; but if they lack just one of the proteins, they still survive, which is evidence that the two alternative forms of the protein are redundant for survival," he said. "But despite this, plants missing either 9a or 9b have different physical characteristics, such as leaf shape, suggesting that Pol II built using 9a does not function exactly the same as Pol II assembled using 9b."

Another unique feature found between the two protein subunits involves the functionality of Pol V and its ability to conduct RNA-directed DNA methylation: The Pol V polymerase built using 9b facilitates methylation, while the 9a-built Pol V does not.

"This is the first evidence showing that different functional subtypes of nuclear RNA polymerases are generated using alternative subunits, and there are multiple subunits for which more than one variant is produced," Pikaard said. "The results also show for the first time that the ninth subunit has a role in RNA-directed DNA methylation."

With new evidence from other research that RNA-directed DNA methylation and transposon silencing also takes place in the sperm-forming cell lineage in mammals, and not just in plants, Pol II transcription is implicated in methylation in both plants and animals.

"Alterations in DNA methylation and gene silencing are involved in multiple genetic disorders and diseases, including cancer," Pikaard said. "Our studies of RNA Pol IV and Pol V may tell us important things about their cousin, Pol II, that may not be possible to know otherwise, including how RNA synthesis can help specify sites of DNA methylation."

Pikaard is the Carlos O. Miller Professor of Plant Growth and Development in the IU Bloomington College of Arts and Sciences' Department of Biology and Department of Molecular and Cellular Biochemistry. Last year he was also named as an investigator of the Howard Hughes Medical Institute and the Gordon and Betty Moore Foundation along with 14 other scientists as part of a $75 million plant science initiative.

Co-authors with Pikaard were University of California Davis postdoctoral researcher Ek Han Tan, IU Bloomington postdoctoral researcher Todd Blevins, and University of Wisconsin postdoctoral researcher Thomas S. Ream. All were Pikaard students while he was at Washington University in St. Louis prior to his coming to IU in 2009.

For more information or to speak with Pikaard, please contact Steve Chaplin, IU Communications, at 812-856-1896 orstjchap@iu.edu. Tweeting IU science news: @IndianaScience

"Functional consequences of subunit diversity in RNA Polymerases II and V," published March 1, 2012, in Cell Reports, authors Ek Han Tan, Todd Blevins, Thomas S. Ream and Craig S. Pikaard.

Original article: http://newsinfo.iu.edu/news/page/normal/21461.html?emailID=21461