Klaus Grade

Acceptability of carrier screening for cystic fibrosis during pregnancy in a German population

A pilot project offering voluntary heterozygote screening for the ΔF508 mutation causing cystic fibrosis (CF) to 638 pregnant women attending two antenatal clinics in the eastern part of Berlin was carried out from 1990–1993. Participation was invited using an information leaflet and inclusion in the study was conditional on written informed consent. Of those invited to participate, only one refused to be tested, on the grounds of non-acceptance of prenatal diagnosis. Eighteen pregnant women were identified as carriers of the ΔF508 mutation. All of them and their male partners accepted counselling in which the genetics of CF, its prognosis and treatment were explained, with emphasis on the meaning of heterozygosity, the fact that carriers are healthy, and the risk of an affected fetus when only one parent is identified as a heterozygote. All partners agreed to be tested for the ΔF508 R553X and G551D mutations and a second counselling session was carried out after this test result was available. No problems were observed during initial testing but, as in other studies, we found considerable anxiety on being given the result in all couples where the woman tested positive; this was reduced substantially by counselling and when the partner tested negative. All probands found to be carriers stated that they found screening acceptable. In contrast to the cautious statement by the German Berufsverband Medizinische Genetik and the hostile reaction from a representative of the CF self-support organisation towards community-based heterozygote screening for CF, this study shows that CF screening is generally acceptable in this German population and that it is actively taken up by most pregnant women when offered.

BRCA1 mutations in German breast‐cancer families

We analyzed germline mutations of the BRCAI gene in 20 German breast/ovarian‐cancer families. BRCAI mutations co‐segregating with breast‐cancer susceptibility were identified in 3 of these families. All mutations were found to generate a premature stop codon leading to the synthesis of truncated BRCAI proteins of different length. Nine polymorphisms were detected in BRCAI, 4 of which have not been described previously. Analysis of familial tumors for LOH revealed that only the disease‐related allele of BRCAI was present.

Identification of three novel mutations in the CFTR gene using temperature-optimized non-radioactive conditions for SSCP analysis

Optimal temperature conditions for the detection of 28 known mutations on 15 exons of the human cystic fibrosis transmembrane conductance regulator gene by single strand conformation polymorphism analysis using the Diagen TGGE Apparatus were established. This procedure was applied to the detection of unknown mutations in 58 non-deltaF508 chromosomes. Three novel mutations,-471del3 (5′ flanking region), 3171insC (exon 17a) and 4700(T)8/9 (3′ non-translated region) of the CFTR gene were found. Mutation 3171insC occured in conjunction with the delta F508 mutation on the other allele of a child presenting with severe pathology. Mutation -471 del3 has so far only been found in one healthy individual and her father, and 4700(T)8/9 is a DNA sequence polymorphism.

A pooling strategy for heterozygote screening of the ΔF508 cystic fibrosis mutation

SummaryA theoretical and practical approach to economize the analysis of large DNA sample numbers for identifying heterozygosity of the ΔF508 mutation causing cystic fibrosis is presented. Sample pooling can reduce the number of polymerase chain reaction (PCR) tests for this mutation by up to 77%. Based on a mathematical model, the optimal number (n) of samples to be united in one pool is 24 for a German population with a ΔF508 heterozygosity incidence of about 1/35. We show that the PCR method is sufficient to detect one heterozygote for the ΔF508 mutation in a pool of up to 49 non-delated DNA samples.

BRCA1 mutations and phenotype

More than 100 mutations have been described for the breast-cancer-susceptibility geneBRCA1. The paper describes phenotypical aspects of three selected mutations located at the beginning, in the middle, and at the end of the gene. A remarkable decrease of the age of diagnosis of the mammary carcinoma is observed with increasing length of the putative gene product, combined with greater severity of the disease.

BRCA1 mutation update and analysis.

The discovery of theBRCA1 gene involved in the development of human hereditary breast cancer led to extensive international efforts to identify the mutations leading to the disease. The new listing covers 127 mutations published in the indicated papers before 30 April 1996; 55% of the mutations are localized in exon 11, followed by exons 2 (5.5%), 5 and 16 (4.7% each).

First analysis of the F508 deletion in cystic fibrosis patients from the GDR

SummaryCystic fibrosis (CF) patients (n = 157) from the GDR were analysed for the occurrence of the recently discovered 3bp deletion causing CF. About 50% of all investigated patients were homozygotes and about 30% heterozygotes for this deletion. Of the analysed CF chromosomes from these patients, 62% carry the deletion, which is in strong linkage disequilibrium with the KM19 restriction fragment length polymorphism allele 2 and the 1/2 XV2c/KM19 haplotype.