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Gene Discovery May Shed Light On Kidney Diseases; Second Gene Found For Alagille Syndrome May Have Broader Role
In a finding that may have
broader implications for understanding kidney disorders, genetics
researchers at The Children's Hospital of Philadelphia have identified a
second gene that gives rise to Alagille syndrome, a genetic developmental
disease that affects multiple organs. The Children's Hospital team
previously discovered the first gene associated with this disease.
The researchers found that mutations in the NOTCH2 gene were linked to
kidney abnormalities in patients and families. "While Alagille syndrome is
relatively rare, organ diseases are not rare, and our findings suggest that
genes on this biological pathway may have a broader role in kidney
disorders," said study leader Nancy B. Spinner, Ph.D., a geneticist at The
Children's Hospital of Philadelphia.
The study appears in the July issue of the American Journal of Human
Genetics.
Dr. Spinner led the Children's Hospital team that identified mutations
in the JAG1 gene as a cause of Alagille syndrome in 1997. Like the NOTCH2
gene analyzed in the current study, JAG1 is part of a signaling pathway
that governs important processes in early human development.
Alagille syndrome, estimated to occur in one in 20,000 individuals, is
a complex disorder, primarily affecting the liver, heart, eyes, face and
skeleton. Some patients with Alagille syndrome have very mild symptoms or
isolated problems, while others may have severe, life-threatening heart or
liver defects.
Both the JAG1 and the NOTCH2 genes participate in the Notch signaling
pathway. JAG1 codes for the ligand Jagged1, a signaling protein that
triggers receptors in the pathway. The NOTCH2 gene codes for Notch2, which
is one of those receptors. The pathway as a whole is active during
embryonic development, and transmits signals to cells to develop into
specialized organs. Mutations in those genes are thought to disrupt normal
development, by, for instance, causing the defective bile ducts found in
the livers of many patients with Alagille syndrome.
"Ligands and receptors are like keys and locks," said Dr. Spinner. "If
either one is defective, it may interfere with normal growth and
development."
Dr. Spinner's team previously determined that 94 percent of patients
diagnosed with Alagille syndrome had mutations in the JAG1 gene. In the
current study, they analyzed 11 patients with Alagille syndrome who did not
have the JAG1 mutation, and found that two of them had mutations in NOTCH2.
Furthermore, the patients had three family members, all mildly affected,
who also had the same mutation. All five individuals had kidney disease.
Because their study identified only two families with NOTCH2 mutations,
said Dr. Spinner, it is not definitive in establishing that those mutations
cause a distinct variety of Alagille syndrome. However, it is the first
study to report that mutations in the NOTCH2 gene cause human disease. Dr.
Spinner is planning further studies to better characterize the role of
NOTCH2 mutations and the Notch signaling pathway in the wider population of
patients with kidney disorders.
She also will investigate liver involvement in Alagille syndrome under
the Rare Diseases Clinical Research Network, recently established by the
National Institutes of Health. "Part of the rationale for this research
network is that, collectively, relatively rare diseases added together
constitute a significant portion of the population," said David A. Piccoli,
M.D., chief of Gastroenterology and Nutrition at Children's Hospital and a
co-author of the study. "Another rationale is that studying relatively rare
diseases may offer insights into more common diseases and into health in
general."
The National Institute for Diabetes and Digestive Diseases supported
this study, as did the Fred and Suzanne Biesecker Center at The Children's
Hospital of Philadelphia. Co-authors with Drs. Spinner and Piccoli, all
from Children's Hospital and the University of Pennsylvania School of
Medicine, were Ian Krantz, M.D.; Ryan McDaniell, Daniel M. Warthen, Pedro
A. Sanchez-Lara and Athma Pai.
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 second in National Institutes of Health funding. In
addition, its unique family-centered care and public service programs have
brought the 430-bed hospital recognition as a leading advocate for children
and adolescents. For more information, visit http://www.chop.edu.
The Children's Hospital of Philadelphia
http://www.chop.edu
Gene Discovery mai reflecte renal boli; Gene În al doilea rând pentru Alagille Sindromul poate fi mai ample Rolul - Gene Discovery May Shed Light On Kidney Diseases; Second Gene Found For Alagille Syndrome May Have Broader Role - articole medicale engleza - startsanatate