First-trimester prenatal diagnosis of cystic fibrosis using the polymerase chain reaction: report of eight cases

Traditional Prenatal Diagnosis: Past to Present

In the nearly 60 years since prenatal diagnosis for genetic disease was first offered, the field of prenatal diagnosis has progressed far past rudimentary uterine puncture to provide fetal material to assess gender and interpret risk. Concurrent with the improvements in invasive fetal sampling came technological advances in cytogenetics and molecular biology that widened both the scope of genetic disorders that could be diagnosed and also the resolution at which the human genome could be interrogated. Nowadays, routine blood work available to all pregnant women can determine the risk for common chromosome abnormalities; chorionic villus sampling (CVS) and amniocentesis can be used to diagnose nearly all conditions with a known genetic cause; and the genome and/or exome of a fetus with multiple anomalies can be sequenced in an attempt to determine the underlying etiology. This chapter will discuss some of the major advances in prenatal sampling and prenatal diagnostic laboratory techniques that have occurred over the past six decades.

Rapid DNA-based prenatal diagnosis by genetic linkage in three families with Alport's syndrome

Alport's syndrome (AS) is a clinically and genetically heterogeneous progressive inherited glomerulonephritis characterized by hematuria, sensorineural hearing loss, ocular lesions, and specific alterations of the glomerular basement membrane. Typically, AS shows an X-linked dominant pattern of inheritance, with mutations affecting the collagen type IV alpha5 chain gene (COL4A5) at Xq22. Rarely, AS is caused in some families by mutations of the COL4A3/A4 genes on chromosome 2q, showing an autosomal recessive transmission. Very few families have been described with possible autosomal dominant AS, but no mutations in any of the COL4 genes have been found. We describe three unrelated families affected with a severe AS phenotype in which DNA-based prenatal diagnosis by linkage analysis was made in fetuses at risk for the disease. In two families, the pedigree structure and the clinical picture were consistent with typical X-linked dominant AS. In these families, autosomal inheritance was also ruled out molecularly. In one family, despite careful clinical and molecular evaluation, the mode of transmission could not be firmly established. We used tightly linked and intragenic COL4A5 markers, as well as COL4A3/A4-linked markers. A chromosome Y-specific marker for fetal sex determination was simultaneously used. In all the families, before the fetal analysis, the putative at-risk X haplotype was identified with high diagnostic accuracy. We diagnosed a healthy male fetus in one family, and female but carrier fetuses in the other two kindreds, who decided not to terminate their pregnancies. We used rapid nonisotopic polymerase chain reaction-based methods, and the results were available within 2 to 3 days. The genetic results significantly affected the reproductive decisions of the parents. This report illustrates the application of genetic linkage analysis as an additional tool for molecular diagnosis in AS, and also addresses the issue of the attitudes of the families toward prenatal testing. To our knowledge, prenatal diagnosis of AS using a genetic linkage approach has not been previously reported.

Concepts, principles, and applications of selected molecular biology techniques in clinical biochemistry

The myriad molecular techniques that have been developed and are undergoing refinement have advanced our knowledge of disease processes and made available strategies for detection. While the greatest impact of molecular techniques in the diagnostic laboratory has been in the realm of infectious diseases, techniques such as flow cytometry, FISH, and multiplex-nested PCR followed by direct DNA sequencing are increasing the scope of cancer detection and treatment. The facile typing of HLA-class II genes is a major advance in the matching of donors to recipients of organ transplantation. With advances in genosensor technology and robotic automation, molecular biology techniques are clearly poised to enter the diagnostic clinical biochemistry laboratory for multiple applications.

Effect of introducing prenatal diagnosis on the reproductive behaviour of families at risk for cystic fibrosis. A cohort study

We studied 101 couples to determine how far their reproductive behaviour was affected by the diagnosis of cystic fibrosis (CF) on its first occurrence in the couple's progeny and by the availability of prenatal diagnosis (PD). The couples were all resident in the Veneto and Trentino regions and attending the Verona CF Centre. CF had been diagnosed in the first affected child, during the period 1 January 1980-1 July 1990, before the age of 1 year. Couples received a questionnaire regarding socio-demographic status, reproduction data, and awareness of PD. Reproductive history was divided into three phases: prior to diagnosis of CF in the first affected child; from this time until PD was made available; and after the couples had learned of PD. In phase 2 (awareness of the genetic risk but not of PD), 54 couples showed a marked decrease in reproduction, none of the few pregnancies that occurred being taken to term. When couples became aware of PD, some resumption of reproductive activity occurred and 11 per cent of the 101 couples had another child; PD was used in 65 per cent of pregnancies and the abortion rate decreased to 35 per cent. All couples who opted for PD had no children without CF.

Prenatal diagnosis of autosomal dominant polycystic kidney disease using flanking DNA markers and the polymerase chain reaction

A prenatal diagnosis was carried out on a 9-week-old fetus at risk for autosomal dominant polycystic kidney disease (ADPKD). Ten members of the family were previously typed using five DNA markers linked to the PKD1 locus on chromosome 16, and one marker linked to the putative PKD2 locus on chromosome 2. The polymerase chain reaction (PCR) was used to amplify the D16S125 locus. Pairwise and multipoint lod scores indicated that the family was most likely segregating a PKD1 mutation. The fetus inherited the disease haplotype from the affected parent. Diagnostic accuracy was greater than 99 per cent, taking into account the possibility of genetic heterogeneity.

Isolation of fetal trophoblast cells from peripheral blood of pregnant women

Fetal trophoblast cells were isolated from maternal peripheral blood by means of murine monoclonal antibodies of high specificity and affinity for human syncytiotrophoblast and nonvillous cytotrophoblast cells. The cells were isolated in sufficient numbers to allow polymerase chain reaction (PCR) amplification of the Y-chromosome-specific DNA sequence from the peripheral blood of thirteen pregnant women. The fetal sex predicted by PCR analysis of the isolated trophoblast cells accorded with that ascertained by karyotyping of chorionic villus samples in eleven of twelve women studied in early pregnancy and with the sex of the baby on delivery in one woman studied at 34 weeks' gestation. Isolation of these fetal cells could allow noninvasive diagnosis of a wide range of inherited disorders.

The genotype of a new linked DNA marker, MP6d-9, is related to the clinical course of cystic fibrosis

The clinical symptoms of a cohort of cystic fibrosis patients were related to their genotypes using RFLPs shown with MspI and the closely linked DNA marker MP6d-9. In the majority of CF chromosomes, the restriction site for MspI was present, and the genotype 2/2 was found most often in patients who were severely affected by the disease. The genotype 1/2 was significantly over-represented in patients with very mild clinical manifestations, including pancreatic sufficiency, absence of meconium ileus, and absence of Pseudomonas colonisation. When pancreatic dysfunction was present, the 1/2 genotype was associated with a mild form, while the 2/2 genotype was found in patients with severe insufficiency. None of our patients had the 1/1 genotype. These results indicate that the newly isolated MP6d-9 marker correlates with some important symptoms of cystic fibrosis.