Epigenetic mutations of the imprinted IGF2-H19 domain in Silver–Russell syndrome (SRS): results from a large cohort of patients with SRS and SRS-like phenotypes
- D Bartholdi1,
- M Krajewska-Walasek2,
- K Õunap3,4,
- H Gaspar1,
- K H Chrzanowska2,
- H Ilyana5,
- H Kayserili6,
- I W Lurie5,7,
- A Schinzel1,
- A Baumer1
- 1Institute of Medical Genetics, University of Zürich, Schwerzenbach, Switzerland
- 2Department of Medical Genetics, The Children’s Memorial Health Institute, Warsaw, Poland
- 3Department of Genetics, United Laboratories, Tartu University Hospital, Estonia
- 4Department of Pediatrics, University of Tartu, Estonia
- 5Belorussian Research Institute of Hereditary Diseases, Minsk, Belorus
- 6Department of Medical Genetics, Istanbul Medical Faculty, Istanbul University, Turkey
- 7Maryland Physicians Associates, Baltimore, Maryland, USA
- Dr D Bartholdi, Institute of Medical Genetics, University of Zürich, Schorenstrasse 16, 8603 Schwerzenbach, Switzerland;
- Received 3 August 2008
- Revised 15 November 2008
- Accepted 19 November 2008
- Published Online First 9 December 2008
Background: Silver–Russell syndrome (SRS) is a clinically and genetically heterogeneous condition characterised by severe intrauterine and postnatal growth retardation. Loss of DNA methylation at the telomeric imprinting control region 1 (ICR1) on 11p15 is an important cause of SRS.
Methods: We studied the methylation pattern at the H19-IGF2 locus in 201 patients with suspected SRS. In an attempt to categorise the patients into different subgroups, we developed a simple clinical scoring system with respect to readily and unambiguously assessable clinical features. In a second step, the relationship between clinical score and epigenetic status was analysed.
Results and conclusions: The scoring system emerged as a powerful tool for identifying those patients with both a definite SRS phenotype and carrying an epimutation at 11p15. 53% of the 201 patients initially enrolled fulfilled the criteria for SRS and about 40% of them exhibited an epimutation at the H19-IGF2 locus. Methylation defects were restricted to patients who fulfilled the diagnostic criteria for SRS. Patients carrying epimutations had a more severe phenotype than either the SRS patients with mUPD7 or the idiopathic SRS patients. The majority of patients with methylation abnormalities showed hypomethylation at both the H19 and IGF2 genes. However, we also identified SRS patients where hypomethylation was restricted to either the H19 or the IGF2 gene. Interestingly, we detected epimutations in siblings of normal parents, most likely reflecting germ cell mosaicism in the fathers. In one family, we identified an epimutation in an affected father and his likewise affected daughter.
Competing interests: None.
Funding: The study was supported in part by the Swiss National Science Foundation (Grant number: 3200B0-105536, to AB).
Patient consent: Not required