[Analysis of cell free fetal DNA fragmentation rate in pregnant women during the course of gravidit]

AIM OF STUDY

To assess cell free fetal DNA (cffDNA) fragmentation rate in pregnant women during the course of gravidity.

STUDY DESIGN

QF PCR efficiency in cffDNA and quantitative analyses in particular cffDNA molecular size fractions.

SETTING

The study was performed at Department of Medical Genetics and Fetal Medicine, University Hospital Olomouc.

METHOD

1. 363 plasma DNA samples from women in different week of pregnancy (from 4th w.g. to 37th w.g.) were tested for QF PCR efficiency in particular STRs and AMELX/Y. 2. Size fractionated cff DNA (150-300 bp, 300-500 bp, 500-760 bp) was quantified by QF PCR in 91 pregnant women (from 9th w.g. to 40th w.g.). 3. Size fractionated cff DNA from male fetuses was quantified by real time PCR (SRY/internal control) in 22 pregnant women (from 9th w.g. to 36th w.g.).

RESULTS

1. QF PCR efficiency decreased from longer to shorter molecules. 2. The only 500 -760 bp fraction showed cffDNA increase in relation to week of gravidity. 3. Indirect relation between amount of cffDNA and week of gravidity was found in 150-300 bp fraction by Real-time PCR.

CONCLUSION

Assembling of all 3 approaches indicates increase of longer cffDNA molecules during the gravidity while level of the short cffDNA molecule fragments probably remains from the approximately 9th w.g. the same.

[Noninvasive fetal sex detection from maternal plasma in pregnant women]

OBJECTIVE

Objective of our study was optimization of noninvasive fetal sex detection from maternal plasma in pregnant women.

STUDY DESIGN

Molecular DNA quantitative analyses in gonosomal loci.

SETTING

The study was performed at Department of Medical Genetics and Fetal Medicine, University Hospital Olomouc.

METHODS

Together 475 DNA samples isolated from maternal plasma in different weeks of pregnancy ranging from 4th w.g. to 37th w.g. Y chromosomal sequences in AMELY and TSPY were tested by refined quantitative fluorescent PCR using capillary electrophoresis.

RESULTS

The method is able to distinguish 1% of Y chromosomal sequences of artificial mixtures. Investigation and assessment in cell free fetal DNA samples achieved 4.05% of false positivity and 7.15% of false negativity in Y sequence detection.

CONCLUSION

Established method allows detecting fetal sex with high sensitivity and specificity. The method is possible to use also for quantitative purposes.

[Paternity testing based on the analysis of DNA and its revision]

Paternity testing is nowadays mostly based on the analysis of DNA short tandem repeats (STR). Number and selection of STR loci differ according to identification kit producers and also particular laboratories. This article refers a revision of formerly excluded paternity. The cause of the mismatch was revealed by the enlargement of STR loci panel and reciprocal evaluation of samples and paternity was on the contrary confirmed. Different possibilities of failures, their consequences and preventions are also discussed.

[Molecular genetic study of causes of the Prader-Willi and Angelman syndrome]

BACKGROUND

Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are distinctive diseases with severe impairment of psychomotoric development and behaviour. Both syndromes are caused by the loss of paternal (PWS) or maternal (AS) gene expression of chromosomal region 15q11-13. The work reveals the various causes of this loss. The choice of the most suitable method for screening of the genome mutations in the patients suspected of PWS and AS is another purpose of the work.

METHODS AND RESULTS

The methyl specific analysis (MS PCR) in locus SNRPN, short tandem repeat (STR) analysis and fluorescent in situ hybridization (FISH) were used. In the group of 55 patients tested for PWS and AS only maternal allele was present in 11 patients and only paternal allele was present in 1 patient in the locus SNRPN: 10 microdeletions 15q11-13, 1 UPD(15)mat and 1 UPD(15)pat.

CONCLUSIONS

MS PCR seems to be the most profitable method for the first step of selection of PWS patients. In positive cases is inevitable to use also additional tests of molecular diagnosis to distinguish the particular mechanism leading to the disorders. In AS patients is also MSPCR recommended as the first step although it is necessary to exclude mutation in UBE3A gene in case of MS PCR negativity.

[Angiomyolipoma--its role in prenatal diagnosis of tuberous sclerosis]

Tuberous sclerosis (TSC) is a frequent hereditary autosomal-dominant disease characterised by hamartomas developing in many organs. The disorder is caused by mutations affecting either of the tumor-suppressor genes, TSC1 and TSC2. Tumorogenesis is triggered by the loss of second functional gene copy, mostly accompanied by loss of heterozygosity (LOH) of flanking polymorphic markers. Search for causing mutations is very laborious, time consuming and low effective. Prenatal diagnosis is often hampered by lack of detection of causing mutation. Detection of LOH in hamartomatous tissue suggests which gene is involved in particular case of disease and specifies which of homologous chromosomes carries germinal mutation. Examination of LOH is useful for prenatal diagnostics especially when time is lacking due to patient's pregnancy or in case of mutation screening failure.

[Increased sensitivity for detection of mutations in exon 15 of the APC gene in patients with familial adenomatous polyposis]

BACKGROUND

Protein Truncation Test (PTT) was used to detect mutations in exon 15 of the APC gene in patients with Familial Adenomatous Polyposis. This method is limited by its ability to detect polypetide chains up to a certain minimum length. The aim of this study was to increase the sensitivity of detection of mutations in this region by using the technique of Denaturing Gradient Gel Electrophoresis (DGGE).

METHODS AND RESULTS

Study were performed on 122 patients without detected mutations in the APC gene. The patients were divided into two independent groups 15A and 15A+15B (with 51 and 71 patients respectively). All the patients were tested with the DGGE and the positive findings were confirmed with sequencing. No mutation was detected in the group 15A (0%). In group 15A+15B one (1.4%) polymorphism and four (5.63%) patients with nonsense mutations were detected.

CONCLUSIONS

DGGE is an effective method for detecting mutations in the first part of exon 15 of APC gene. It allows detecting any change in DNA strand. DGGE complements PTT in scanning of the whole exon 15 of APC gene.

[Microdeletion of the azoospermia factor as one of the causes of male infertility]

One of the possible causes of male infertility is microdeletion of the Y chromosome in the Yq11.23 region--named the azoospermia factor. These deletions are associated with azoospermia or severe oligozoospermia. In these cases, testicular histopathological findings comprise a wide spectrum, from total absence of germ cells, through arrest of their maturation to decreased sperm production. Most Y-chromosome microdeletions arise de novo but transmission from the father is also possible, either by the natural way or by assisted reproduction. In relation to the assisted reproduction, the relationship between the Y-deletions and presence of spermatozoa in testis, fertilization capability and embryo quality were examined. Heredity of the deleted Y chromosome is holandric and therefore all sons of males with deletions will carry the same defect and will probably have fertility problems. Another negative influence of deletions on a man's health has not yet been identified.

[Analysis of specific sequences in female patients with Turner syndrome--initial study]

BACKGROUND

DNA sequences from chromosome Y can cause gonadoblastoma development in patients with Turner syndrome (TS). Estimated risk is about 30%. The aim of the study is detection of Y-sequences of DNA level, calculation of mosaicism and its cytogenetic location. Clinical result of the study is the recommendation to gonadectomy of proved positive patients.

METHODS AND RESULTS

Samples from 110 patients were collected. The PCR method and analysis of products on agarose gel was compared with analysis of DNA fragments from quantitative fluorescent (QF) PCR on capillary electrophoresis. The loci DYZ3, AMGX/Y and SRY were used for detection. The method QF PCR was effected for DYZ3 and AMGX/Y loci. The positive cases were examined by FISH method. Five (4.5%) and 3 (2.7%) positive cases were detected in DYZ3 and SRY resp. loci by electrophoresis on agarose gel. Seventeen (15.5%) and 7 (6.4%) positive cases were detected in DYZ3 and AMGX/Y resp. by capillary electrophoresis. The estimated mosaicism ranged from 1:5 to 1:100,000.

CONCLUSIONS

QG PCR is the most sensitive method for diagnostics of Y-sequences. Simultaneously the incidence of Y-positive cells can be estimated. The positive cases with marker in karyotype were confirmed by FISH.

[DNA analysis of chromosome Y in the area of the azoospermia factor (AZF) in infertile men]

OBJECTIVE

Establishment of investigation of sterile male DNA in AZF region--choice of loci and primers for investigation, optimization of PCR conditions (polymerase chain reaction).

DESIGN

For practice.

SETTING

Department of Medical Genetics and Foetal Medicine, Faculty of Medicine, Palacky University and Faculty Hospital Olomouc.

METHODS

PCR amplification of DNA isolated from blood of sterile men and consequential electrophoresis of synthesized DNA fragments to appoint microdeletions in AZF.

RESULTS

From January to June 2000 were detected the microdeletions in AZF of 3 out of 79 sterile men (3.80%) by means of the Experteam firm kit. From July to December 2000 were tested and optimized conditions of amplification of 10 AZF loci to substitute the kit and they were used for examination of the first 20 sterile men of our collection.

CONCLUSION

In our laboratory was established routine examination male sterility related to microdeletions in AZF. With our collection of loci was substituted the original Experteam firm kit and was widened spectrum of observed loci.

[DNA diagnosis in Czech patients with tuberous sclerosis]

BACKGROUND

Tuberous sclerosis complex (TSC) is an autosomal dominant disease characterised by mental retardation, epilepsy, facial angiofibromas, lesions in the CNS and the occurrence of hamartomata in different tissues. There are two genes responsible (TSC1 and TSC2). The aim of the study is to adopt a diagnosis of the disease on DNA level.

METHODS AND RESULTS

111 DNA samples were collected from 45 families with 54 clinically diagnosed patients. Three families with multiple incidence are linked to chromosome 9. In one case a large deletion was found using TSC2 specific cDNA probes. Most TSC mutations are supposed to be small mutations, identifiable by SSCP method. Using this method we examined all 23 TSC1 exons and 20 out of 41 TSC2 exons. In the TSC1 gene we found 1 nonsense and 2 frameshift mutations and 2 intragenic polymorphisms useful for linkage. In the TSC2 exons was identified so far 6 aberrations, cause of which is being checked by sequencing.

CONCLUSIONS

DNA mutation analysis is effective namely in families with multiple incidence. In such families the linkage can be used and there is more TSC1 cases which are easily identifiable. Analysis is not economical for differential diagnosis. Total number of revealed mutations (6.7%) matches last reports. No correlation between phenotype and type of mutation was found.