Genetics counseling Postnatal cytogenetics examination DNA examination FISH Prenatal diagnostics Other examinations Invasive examinations and operations Examination offered in prenatal cytogenetic diagnostics Actions Institute workers Home

DNA examination DNA laboratory dealing with examination of several genetically dependent diseases exists on our institute already 14 years, both on postnatal and prenatal level. Since 1995 the samples of Tuberous sclerosis (TSC) patients are collected on our institute from whole Czech Republic. Nowadays the number of affected families exceeded one hundred; most cases seem to be new mutations. Familial cases can be solved by linkage analysis using STR polymorphisms from chromosome 16 and 9. Former SSCP method, established for new mutations screening in 64 exons comprising two genes involved in TSC, is substituted by more efficient DGGE technique this year. Samples picked out by SSCP or DGGE are sequenced on capillary electrophoresis with fluorescently labelled dideoxynucleotides. Test of loss of heterozygozity (LOH) was established for detection of allele reduction of tested polymorphic markers in hamartomatous tissue. Our cooperating partners from DNA laboratory of Clinical Genetics, Erasmus University Rotterdam, support this work. The diagnostics and quantification of chromosome Y sequenties is pursued in prevention of gonadal tumours in Turner syndrome patients since 1998. In patients and their parents the X chromosome transfer is observed by chromosome X specific STR markers testing. The correlation between revealed findings on genetic level and clinical features (grade of neurocognitive dysfunction) is studied. For resolution of this problem the influence of gonozomal mosaic (45X/46XX and 45X/46XY) will be solved. In 1999 the examination of infertile patients was introduced, searching for micro deletions in AZF region, which can lead to non-obstructive azoospermia or oligospermia. For the detection of micro deletions testing of 10 STR loci was started: SY16, SY72, SY84, SY86, SY87, SY134, SY143, SY147, SY255 (DAZ) and SY158. To facilitate and speed up the examination, multiplex-PCR with fluorescently labelled primers was introduced for loci SY87, SY147 and SY158. Since 2000 the genetic analyser ABI Prism 310 is in operation, significantly extending and specifying DNA analysis. Genetic analyser enabled establishment of a new, fast and high efficient method – quantitative fluorescent PCR (QF PCR) of microsatellite DNA for testing of polymorphic markers localized on chromosomes going with most frequent trisomies. This method makes possible fast detection of most frequent chromosomal aberrations without foetal cell cultivation (on the contrary amniotic fluid sampling or placental biopsy followed by cultivation and chromosomal examination lasts for 2 to 3 weeks in average). Newly introduced procedure belongs to the most forward-looking methods of prenatal diagnostics. It enables to reveal aberration of chromosomal number ideally within 4 hours after amniotic fluid sampling from micro volumes of foetal cells without previous cultivation and substantially reduce patients stress duration. In 2004 following projects were started: 1) Monitoring of the dynamics of apoptotic and extra cellular foetal DNA concentration in maternal serum in course of pregnancy and after delivery and aimed DNA analysis of ploidy in normal and pathological pregnancies. It takes advantage of proven quantitative possibilities of capillary electrophoresis, sensitivity of innovative QF PCR technique and right combination of primers labelling. 2) Research of influence of sequential, repetitive and expression variability of TSPY gene on biological function in normal and pathological cells (testicular tumour, gonadoblastoma and prostate carcinoma) and in male with impaired fertility. Disputable paternities and identification tests are resolved by DNA profiling using microsatellite markers (STRs). These systems come out from international DNA profiles data basis CODIS, used both by American FBI and European ENFSI. Utilization of these systems can easily solve dispute paternity as guaranteed paternity index runs minimally into 500, but mostly is many times higher. Calculated paternity probability then always exceeds 99,8 %, largely over 99,99 %. Other genetical examinations can be mentioned: CAG expansion assessment in Huntington’s chorea diagnostics Mutation screening in Connexin 26 in patients with hearing loss Main mutations testing in Cystic fibrosis patients