Characterization of three new deletions in the ß-globin gene cluster during a screening survey in two French urban areas.

BACKGROUND: Deletions represent about 5% of the mutations in the ß-globin gene cluster. We report here the screening for such deletions in the two French urban areas of Paris and Lyon between 2003 and 2010. METHODS: Semi-quantitative PCR methods were used for the first screening of deletions. Thereafter, a specific gap-PCR, eventually followed by DNA sequencing, was used for precise identification. RESULTS: 285 patients bore a deletion or recombination event in the ß-globin gene cluster. Hbs Lepore or anti-Lepore were detected in 99 patients. Among the remaining 186 patients, 132 bore a deletion that could be fully identified. The most prevalent deletions were the Ghanaian HPFH-2 (n=46), the Sicilian (δß)(0)-thal (n=22) and the Spanish (δß)(0)-thal (n=12). The other characterized deletions were the: HPFH-3, HPFH-1, Filipino, Senegalese, Corfu, Kabilian, -1.39 kb, Indian -619 bp and -468 bp. Interestingly, three new deletions were fully characterized: a -7719 bp deletion, a -27,825 bp deletion with a 25 bp insertion and a -125 bp deletion. CONCLUSIONS: The present study emphasizes the importance to detect deletions in the ß-globin gene cluster, particularly for at risk couples. The new -27,825 bp deletion illustrates the complexity to understand the transcriptional regulation of fetal to adult hemoglobin switch.

A novel PCR approach for prenatal detection of the common NEMO rearrangement in incontinentia pigmenti.

OBJECTIVES: Incontinentia pigmenti (IP) is a rare X-linked dominant genodermatosis that is usually lethal in males in the prenatal period. Largely 80% of cases are accounted for by a large-scale deletion encompassing exons 4 to 10 of the NEMO gene. The aim of this work was to facilitate prenatal diagnosis of IP by devising a novel test for detection of the prevalent NEMO deletion. METHODS: We devised a sensitive and reproducible multiplex PCR test enabling simultaneous amplification of the deleted and wild-type NEMO genes in IP female individuals. RESULTS: Combination of this DNA test, with Xq28 linkage analysis and X-inactivation pattern study enabled us to offer an IP prenatal diagnosis in 15 of the 16 couples at a 50% risk to have an affected offspring. CONCLUSION: A current approach to IP prenatal diagnosis is proposed on the basis of the previously mentioned molecular tools.

NDP gene mutations in 14 French families with Norrie disease.

Norrie disease is a rare X-inked recessive condition characterized by congenital blindness and occasionally deafness and mental retardation in males. This disease has been ascribed to mutations in the NDP gene on chromosome Xp11.1. Previous investigations of the NDP gene have identified largely sixty disease-causing sequence variants. Here, we report on ten different NDP gene allelic variants in fourteen of a series of 21 families fulfilling inclusion criteria. Two alterations were intragenic deletions and eight were nucleotide substitutions or splicing variants, six of them being hitherto unreported, namely c.112C>T (p.Arg38Cys), c.129C>G (p.His43Gln), c.133G>A (p.Val45Met), c.268C>T (p.Arg90Cys), c.382T>C (p.Cys128Arg), c.23479-1G>C (unknown). No NDP gene sequence variant was found in seven of the 21 families. This observation raises the issue of misdiagnosis, phenocopies, or existence of other X-linked or autosomal genes, the mutations of which would mimic the Norrie disease phenotype.