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Molecular markers for diagnosis of Prader-Willi syndrome in thai patients by fish
Sirilak Wiriyaukaradecha1, Pimpicha Patmasiriwat, Pornswan Wasant
1Department of Microscopy, Faculty of Medical Technology, Mahidol University, Bangkok, Thailand.
Abstract:
Paternal microdeletion of chromosome 15 at q11-q13 has been reported in 75% of Prader-Willi syndrome (PWS) patients in western countries. Diagnosis of PWS in Thailand is mainly based on clinical observation and, in some cases, confirmed by conventional cytogenetic analysis. Loss of a tiny segment in this region (microdeletion) has made it difficult to discriminate from the normal karyotype. An attempt to solve this problem has been made by using a high resolution chromosome culture. However, this method is a tedious and time-consuming technique which is suitable for only experienced cytogeneticists. We report molecular cytogenetic analysis for PWS in Thai patients using FISH in addition to standard GTG- banding chromosome analysis. Nine Thai patients clinically diagnosed or with a suspicion of PWS were investigated. The FISH probes consist of the region-specific probes (SNRPN or D15S10 probe) and two chromosome 15-specific control probes (D15Z1 centromeric and PML chromosome 15 long arm probe). Bright field and FISH programs of an automatic karyotyper were applied to facilitate the efficiency of the chromosome analysis. We found that 2 out of 9 patients showed a deletion at 15q11-q13 region by standard GTG chromosome analysis while 4 out of 9 patients showed a delation in this region by FISH. Consistent losing of SNRPN and D15S10 signals in FISH was observed in these patients. This forty-four per cent deletion is considerably lower than those reported from western countries. We propose that DNA methylation at SNRPN promoter as well as structural abnormalities in other chromosome regions might also play a role in the etiology of this disorder in Thais, which should be investigated further.
Insights
Paternal microdeletion of chromosome 15 causes Prader-Willi syndrome (PWS). FISH analysis identified deletions in 44% of Thai PWS patients, a lower rate than in Western countries, suggesting other genetic factors may be involved.
Area of Science:
- Genetics
- Molecular Biology
- Cytogenetics
Background:
- Prader-Willi syndrome (PWS) is often caused by paternal microdeletions on chromosome 15q11-q13.
- PWS diagnosis in Thailand relies on clinical observation and conventional cytogenetics, which can be challenging due to small deletion sizes.
- High-resolution chromosome culture is effective but labor-intensive and requires expert cytogeneticists.
Purpose of the Study:
- To investigate the prevalence of PWS-associated 15q11-q13 deletions in Thai patients using molecular cytogenetics.
- To compare the diagnostic efficiency of FISH with standard GTG-banding for PWS detection in a Thai cohort.
- To explore potential reasons for lower deletion rates observed in Thai PWS patients compared to Western populations.
Main Methods:
- Molecular cytogenetic analysis including standard GTG-banding and Fluorescence In Situ Hybridization (FISH) was performed on nine Thai patients with suspected PWS.
- FISH utilized region-specific probes (SNRPN, D15S10) and control probes (D15Z1, PML) for chromosome 15.
- An automatic karyotyper with bright field and FISH programs was employed to enhance analysis efficiency.
Main Results:
- Standard GTG-banding identified deletions in 2 out of 9 patients (22%).
- FISH analysis detected deletions in 4 out of 9 patients (44%), with consistent loss of SNRPN and D15S10 signals.
- The observed deletion rate of 44% in Thai patients is lower than the 75% reported in Western countries.
Conclusions:
- FISH analysis is a more sensitive method than standard GTG-banding for detecting 15q11-q13 microdeletions in Thai PWS patients.
- The lower frequency of 15q11-q13 deletions in Thai PWS patients suggests that other genetic mechanisms, such as DNA methylation abnormalities or structural variations in different chromosomal regions, may contribute to PWS etiology in this population.
- Further investigation into DNA methylation at the SNRPN promoter and other chromosomal abnormalities is warranted for Thai PWS patients.
