Shwachman-Diamond syndrome (SDS) is a relatively rare genetic disorder that occurs in approximately one in 50,000 births. SDS affects many organs in the body. Primary features of SDS include a defect in the pancreas that leads to difficulties in digesting food, hematologic (blood) problems with inadequate production of some types of white blood cells, skeletal abnormalities, and short stature. The hematologic problems make people with SDS prone to severe, sometimes fatal infections, and some die from blood complications such as leukemia or bone marrow failure.
"The identification of the gene is important because it will allow for accurate diagnosis and screening of Shwachman-Diamond syndrome. It will also help us to determine what goes wrong at the molecular level, and this will open the door to the development of new therapies," said Dr. Johanna Rommens, the study's principal investigator, an HSC senior scientist and associate professor of Molecular and Medical Genetics at U of T.
"This discovery will aid in the clinical management of Shwachman-Diamond syndrome," said Dr. Peter Durie, co-principal investigator of the study, an HSC gastroenterologist and senior scientist, and a professor of Paediatrics at U of T. "It is also very important to the families affected by this disease. We have received patient samples from around the world, and the Shwachman-Diamond parent groups from many countries supported this research financially."
Shwachman-Diamond syndrome is an autosomal recessive disease, meaning that a child needs to inherit two mutated genes (one from each parent) in order to have the disease. The SDS gene resides in a region of the human genome that was very difficult to map because it contains a lot of highly repetitious DNA sequence. It was found that in the normal state, every chromosome 7 has two copies of the SDS gene - a functional gene and a non-functional gene relic, called a 'pseudogene'.
"We have determined that the type of genetic mutation that causes Shwachman-Diamond syndrome is gene conversion, in that a piece of the non-functional pseudogene has been introduced into the good copy of the gene, thus disrupting its function. These types of mutations have been seen in more than 90 per cent of SDS patients," said Graeme Boocock, the study's lead author and a University of Toronto graduate student. Boocock is a recipient of a Canadian Institutes of Health Research doctoral research award.
Other members of the research team are Jodi Morrison, Maja Popovic, Nicole Richards, and Lynda Ellis, all from The Hospital for Sick Children.
This research was supported by the Canadian Institutes of Health Research, Shwachman-Diamond Syndrome Canada, Shwachman-Diamond Syndrome International, Shwachman-Diamond Support of Great Britain, The Harrison Wright Appeal, Shwachman-Diamond Syndrome Support of Australia, Paediatric Consultants Inc., Canadian Genetic Diseases Network of Centres of Excellence, and The Hospital for Sick Children Foundation.
The Hospital for Sick Children, affiliated with the University of Toronto, is Canada's most research-intensive hospital and the largest centre dedicated to improving children's health in the country. Its mission is to provide the best in family-centred, compassionate care, to lead in scientific and clinical advancement, and to prepare the next generation of leaders in child health. For more information, please visit www.sickkids.ca.
Further information for families affected by Shwachman-Diamond syndrome is available on the HSC Web site at http://www.sickkids.ca/mediaroom/custom/SDSgeneQA.asp.
For more information, please contact:
Laura Greer, Public Affairs (away December 24-January 6)
The Hospital for Sick Children
Lisa Lipkin, Public Affairs
The Hospital for Sick Children