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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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August 14, 2012--------News Archive Return to: News Alerts

Cohesinopathies are associated with defects in sister chromatid cohesion.
The cohesion complex, Smc1/Smc3, Scc1/Scc3, is loaded onto chromatin by Scc2/Scc4.
During replication Smc3 is acetylated by Eco1. In metaphase cohesion is removed
by cleavage of Scc1. ESCO2 is one of the two human orthologs of Eco in yeast.

WHO Child Growth Charts

       

Mutations Disrupt Cell Recycling Causing Genetic Disease

Researchers identify new gene in Cornelia deLange syndrome which causes intellectual disability, limb deformations and other disabilities resulting from impairments in early development

Genetics researchers at the Children's Hospital of Philadelphia have identified that when the gene HDAC8 is mutated, the rare multisystem disorder Cornelia deLange syndrome (CdLS) is triggered.

"As we better understand how CdLS operates at the level of cell biology, we will be better able to define strategies for devising treatments for CdLS, and possibly for related disorders," said study leader Matthew A. Deardorff, M.D., Ph.D., a pediatric genetics clinician and scientist at The Children's Hospital of Philadelphia. Deardorff also is in the Perelman School of Medicine at the University of Pennsylvania.

Deardorff and co-corresponding author Katsuhiko Shirahige, Ph.D., of the Research Center for Epigenetic Disease at the University of Tokyo, published their study online in the journal Nature.

A group led by Ian Krantz, M.D., and Laird Jackson, M.D., both of The Children's Hospital of Philadelphia, announced in 2004 that mutations in the NIPBL gene are the primary cause of CdLS, accounting for roughly 60 percent of the "classical" cases of the disease. In 2007, Deardorff described mutations in two additional genes, SMC1A and SMC3.


First described in 1933,
Cornelia deLange syndrome
(CdLS)
affects an estimated 1 in 10,000 children.


The CdLS research team at Children's Hospital has focused on the cohesin complex, a group of proteins that form a bracelet-like structure that encircles pairs of chromosomes, called sister chromatids.

Deardorff: "Cohesin has two roles. It keeps sister chromatids together during cell division, and it allows normal transcription—the transmission of information from DNA to RNA."

Deardorff added that mutations that perturb normal cohesin function can interfere with normal human development. Such is the case in CdLS, which exemplifies a newly recognized class of diseases called cohesinopathies.

In the current study, the scientists investigated both acetylation—how an acetyl molecule is attached to part of the cohesin complex¬—and deactylation, the removal of that molecule. Normally, deactylation helps recycle cohesin to make it available during successive rounds of cell division.


The study team found that mutations
in the HDAC8 gene threw off
normal cellular recycling of cohesin.


Mutations in the gene cause loss of HDAC8 protein activity, and consequently decrease the amount of "recharged" cohesin available to properly regulate gene transcription. This, in turn, the researchers suggest, impairs normal embryonic development and gives rise to CdLS.

The researchers showed in cell cultures that mutations in HDAC8 lead to a decrease in cohesin binding to genes, similar to that seen for cells deficient in the NIPBL gene. They also identified HDAC8 mutations in approximately 5 percent of patients with CdLS.


Because mothers of children with CdLS
may carry mutations in the HDAC8 gene,
identifying these mutations will be very useful
in accurately counseling families of
the likelihood of having
a subsequent child with CdLS.


Furthermore, added Deardorff, by providing biological details of the underlying defect in CdLS, the current research suggests future approaches to treating the genetic disease.

Deardorff: "By concentrating downstream on the biological pathway in the cohesin cycle rather than focusing on the defective gene, we may be able to eventually screen for small-molecule drugs that could be used to intervene in CdLS."

Deardorff and colleagues will continue investigate CdLS and possible therapies. Last month, the Doris Duke Charitable Foundation chose Deardorff to receive a Clinical Scientist Development Award. This three-year award, totaling $486,000, is directed to further studies of cohesin abnormalities in human disease. Deardorff is a member of Children's Hospital's Center for Cornelia deLange Syndrome and Related Diagnoses, one of the world's leading programs in studying and treating CdLS.

Financial support for this study came from the National Institutes of Health (grants HD055488, GM49758, and HD052860), the U.S.A. Cornelia deLange Syndrome Foundation, institutional funding from The Children's Hospital of Philadelphia, intramural funding from the University of Lubeck, and the Research Program of Innovative Cell Biology by Innovative Technology. Co-authors with Deardorff and Shirahige included researchers from the United States, Japan, Canada, France, Belgium, Germany, Greece and Denmark.

"HDAC8 mutations in Cornelia deLange Syndrome affect the cohesin acetylation cycle," Nature, advance online publication Aug. 12, 2012. http://dx.doi:10.1038/nature11316

About The Children's Hospital of Philadelphia: The Children's Hospital of Philadelphia was founded in 1855 as the nation's first pediatric hospital. Through its long-standing commitment to providing exceptional patient care, training new generations of pediatric healthcare professionals and pioneering major research initiatives, Children's Hospital has fostered many discoveries that have benefited children worldwide. Its pediatric research program is among the largest in the country, ranking third in National Institutes of Health funding. In addition, its unique family-centered care and public service programs have brought the 516-bed hospital recognition as a leading advocate for children and adolescents. For more information, visit http://www.chop.edu.

Original article: http://www.eurekalert.org/pub_releases/2012-08/chop-mdc080912.php