The replacement of cytogenetic analysis by direct chorionic villi sampling preparation with quantitative fluorescence PCR.

AIM: The aim of this study is to assess the replacement of chromosomal analysis of chorionic villi (CV) direct preparation samples (DIR) by quantitative fluorescence PCR (QF-PCR) and to determine its advantages in routine prenatal diagnosis. METHODS: From a total of 4,020 CV samples, rapid results were obtained either by conventional cytogenetic analysis of DIR in 2,770 samples, or by QF-PCR analysis in 1,250 samples. The final results were given after long-term culture (LTC). RESULTS: The frequencies of unbalanced fetal karyotypes were not significantly different, being 4.8% by DIR-LTC and 4.3% by QF-PCR-LTC. No false-negative or false-positive results were obtained from either approach. CONCLUSION: QF-PCR can replace chromosomal analysis of CV-DIR in most cases during routine prenatal diagnosis, requiring smaller CV samples and being more labor effective. Coupled with LTC, it is a robust diagnostic approach with high predictive value for the most frequent fetal trisomies.

Loss of the Y chromosome PAR2 region and additional rearrangements in two familial cases of satellited Y chromosomes: cytogenetic and molecular analysis.

Two cases of rare structural aberrations of the Y chromosome were detected: a del(Y) (q12) chromosome in a child with mild dysmorphic features, obesity and psychomotor delay, and two identical satellited Y chromosomes (Yqs) in a normal twin, which were originally observed during routine prenatal diagnosis. In both cases a Yqs chromosome was detected in the father which had arisen from a reciprocal translocation involving the short arm of chromosome 15 and the heterochromatin of the long arm of the Y chromosome (Yqh). Cytogenetic and molecular studies demonstrated that in the reciprocal product of chromosomes 15 and Y PAR2 could not be detected, showing that PAR2 had been deleted. It is discussed whether the translocation of the short arm of an acrocentric chromosome to the heterochromatin of the long arm of the Y chromosome causes instability of this region which results either in loss of genetic material or interference with the normal mechanism of disjunction.

Rare XXY/XX mosaicism in a phenotypic male with Klinefelter syndrome: case report.

Klinefelter syndrome represents the most commonly found human sex chromosomal abnormality. It is characterized by small, firm testes with hyalinization of the seminiferous tubules, elevated gonadotropins and azoospermia. Males with Klinefelter syndrome may have a 47,XXY or a mosaic 47,XXY/46,XY constitutional karyotype and varying degrees of spermatogenic failure. Mosaicism 47,XXY/46,XX with clinical features suggestive of Klinefelter syndrome, is very rare and so far only 10 cases have been described in literature [1,2,5,8,10,15,22,23,25,44]. We report here a case of a mosaic 47,XXY/46,XX infertile male in whom detailed cytogenetic, histological and molecular studies were performed. Cytogenetic analysis revealed 80% and 50% mosaicism for the 46,XX cell line in blood lymphocytes and in skin fibroblasts, respectively, and the presence of 47,XXY cells only, in cultured testicular tissue. Testicular histopathology revealed atrophy of the testes with no spermatogenesis and absence of germ cells. Molecular analysis showed paternal inheritance of the extra X chromosome.

Prenatal diagnosis of hypochondroplasia: report of two cases.

Hypochondroplasia (HCH) is an autosomal dominant skeletal dysplasia characterized by short extremities, short stature and lumbar lordosis, usually exhibiting a phenotype similar to but milder than achondroplasia (ACH). Mutations in the fibroblast growth factor receptor 3 (FGFR3) gene are present in a significant proportion of HCH patients. Reports of prenatal diagnosis of HCH are very rare and the phenotype/genotype correlation in these patients is poor. Here we present two sporadic cases with second trimester ultrasound findings consistent with a diagnosis of a non-lethal skeletal dysplasia. Ultrasound evaluation after 23 weeks of gestation showed a decreased rate of development of the femora (femur length

The implications of using mutagenic primers in combination with Taq polymerase having proofreading activity.

Polymerases with proofreading activity provide high fidelity PCR amplifications. In this study we examined the consequences of using a Taq polymerase with proofreading activity, such as Optimase Taq polymerase, in combination with 4 different mutagenic reverse primers for the amplification of a 345-bp FII PCR product. The amplifications were performed with Optimase Taq polymerase (Transgenomic), and Taq DNA polymerase-recombinant (Invitrogen), without proofreading activity. Mutation screening was carried out by DHPLC and restriction fragment analysis. The usage of Optimase Taq polymerase results in complete reversion of the first and second mutated nucleotide introduced at the 3' end of the mutagenic reverse primer. It also partially reverses the missense nucleotide introduced in the third position of the mutagenic primer and leads to misleading DHPLC and restriction fragment analysis patterns. Nevertheless it cannot perform such an activity when an abnormal nucleotide is introduced in the fourth position.

The impact of heterozygosity for the factor V Leiden and factor II G20210A mutations on the risk of thrombosis in Greek patients.

AIM: There is growing evidence that a number of genetic risk factors predispose independently to venous thrombosis and the coexistence of defective genes is involved in the manifestation and recurrence of thrombotic events. The goal of this study was to examine the efficiency of the selection criteria for performing a genetic test for the factor V G1691A (Leiden) and factor II G20210A mutations. METHODS: Blood samples were drawn from 119 patients referred to us by their physicians. FV and prothrombin (FII) mutations were detected by polymerase chain reaction (PCR) followed by digestion with restriction endonucleases MnlI (FV), HindIII and MspI (FII). RESULTS: Patient carrier frequencies were 16.8% and 10.08% for FV Leiden and FII G20210A, respectively. Heterozygosity for FII G20210A was observed in 10.0% of FV Leiden carriers whereas FV Leiden homozygosity was noted in 1.68% of the patients. Genotype frequencies were in conformity with Hardy-Weinberg equilibrium by the chi square goodness of fit test. CONCLUSION: The obtained data provided a substantial genetic explanation of the thrombotic phenotype in approximately 25% of the patients and thus the physicians selection criteria were sufficient for genetic testing. Furthermore, coinheritance of both genetic defects were significantly associated with increased thrombosis risk and that of recurrent thrombosis.

A modified mutagenic PCR-RFLP method for K-ras codon 12 and 13 mutations detection in NSCLC patients.

Evidence from many investigators has shown that mutations in the first exon of K- ras gene occur at elevated frequencies in lung, pancreatic and colon carcinoma and seem to be of prognostic importance. The aim of this study was to develop an effective method for the detection of K- ras mutations in codons 12 and 13 in non-small-cell lung cancer (NSCLC) patients in order to investigate correlation with clinical outcome. DNA was extracted from tumour and neighbouring non-neoplastic lung tissues from 70 patients and screened for codon 12 and 13 mutations. We applied a mutagenic PCR-restriction fragment length polymorphism for both codon 12 and 13 mutation detection. Codon 12 mutation was identified in 20% of NSCLC patients, whereas no codon 13 mutation was detected. As expected, the respective non-neoplastic tissues exhibited no mutations. We observed an increased codon 12 mutation prevalence in adenocarcinoma comparing to other types of carcinomas. Follow-up for 29 patients with a mean time of 12 months indicates an increased relapse rate in NSCLC patients with the K- ras codon 12 mutation. Furthermore, a trend towards increased percentage of mutant samples was observed in the advanced stage group of patients. We provide evidence that our approach is a fast and reliable method for screening K- ras exon 1 mutations in tumour samples from NSCLC patients.

Identification of an alleged offender of murder by VNTR analysis: case report.

DNA typing was used to demonstrate that three human body pieces found disposed of in the countryside around Athens and the suspicions about the perpetrator's identity were connected. Reverse paternity testing was attempted by comparative typing of three variable number tandem repeats loci in the remains, as well as in the presumptive parents and sister of the decedent, demonstrating Mendelian inheritance of the alleles of the loci analyzed. Confronting the results of the abovementioned analysis, the suspect accepted the accusation.

A study of five variable number tandem repeat (VNTR) loci in the Greek population.

The use of hypervariable tandem repeat loci for population genetic studies, genetic analysis of inherited disease and individual identification purposes requires establishment of a genetic database for each reference population. In the present study we have analysed variability at five tandem repeat loci (D1S80, D17S5, 3'-hvr/apoB, F8vWF and D6S89)in a representative sample (88 to 156 individuals of greek ancestry), using polymerase chain reaction amplification. Between nine and 19 alleles were resolved throughout the five polymorphic loci. Heterozygosity indices for these loci in the greek population ranged from 0.68 to 0.85. Allele frequencies follow a bimodal discrimination (pd) and allelic diversity (h) values ranged from 0.84 to 0.94 and 0.85 to 0.91, respectively, and indicated that these loci are highly informative and can be used for population studies, forensic purposes and parentage and family testing. Comparison of observed and expected genotype frequencies by the conventional chi-square test indicated conformity to Hardy-Weinberg predictions.