A novel missense mutation and two microrearrangements in the FOXC2 gene of three families with lymphedema-distichiasis syndrome.

Lymphedema-distichiasis (LD) syndrome is a rare autosomal dominant disorder of the FOXC2 gene, which codes for a forkhead transcription factor. Most of the mutations described in this gene to date are deletions or insertions, suggesting a mechanism of haploinsufficiency. We studied three independent families with LD presenting with both lymphedema and distichiasis. Two microrearrangements (one 8-bp deletion and one 7-bp duplication) occurring in a GC-rich genomic region (c.893-930) known to be prone to mutations were identified. A new missense mutation (p.Lys132Glu) located in a highly conserved sequence, the forkhead domain, was also identified. Mutations in this domain have been previously shown to impair FOXC2 transactivation ability. At a genetic level, this study confirms the heterogeneity of mutations responsible for LD and is consistent with a mechanism of haploinsufficiency. At a clinical level, it reinforces the importance of genetic testing in subjects with familial lymphedema or distichiasis, since measures can be taken at an early stage to prevent complications and to reduce the progression of lymphedema or delay its occurrence.

[Molecular biology usefulness for rapid diagnosis of Down's syndrome and common aneuploidies]. / Intérêt de la biologie moléculaire dans le diagnostic rapide de la trisomie 21 et des aneuploïdies les plus fréquentes.

OBJECTIVE: Trisomy of chromosome 13, 18, 21 and sex chromosome aneuploidies are the most common chromosomal abnormalities encountered in prenatal screening and are responsible for polymaformative syndrome associated with severe mental retardation. This high degree of morbidity justifies the prenatal diagnosis of these aneuploidies. Fetal nuchal translucency measurement and maternal serum biochemical marker assessment are the method of choice used for antenatal screening of aneuploidies. This prenatal screening leads to numerous maternal samplings followed by karyotyping which is cost-effective, time consuming, while results are generally returned between 2 and 3 weeks. Our study describes the research of common aneuploidies by molecular biology. We have used on one hand the MLPA kit (MRC Holland) based on amplification of specific DNA probes that hybridize with chromosomes 13, 18, 21, X, Y. On the other hand we have developed multiplex fluorescent PCR, amplifying microsatellite DNA sequences. PATIENTS AND METHODS: We have evaluated the efficiency of these two techniques to detect chromosomal abnormalities by screening 400 amniotic fluids or chorionic villi samples obtained from pregnant women presenting a high risk of chromosomal aneuploidy. RESULTS: We have found four trisomies 21, one trisomy 13, one monosomy 13, one trisomy 18, two triploidies, one trisomy X and one Klinefelter syndrome. DISCUSSION AND CONCLUSION: In our study we have detected by molecular biology, in less than 48 h, 100% of common chromosomal aneuploidies without false positive or false negative results which could lead molecular biology as a method of choice for the rapid detection of common aneuploidies in addition to fetal karyotyping.