A Novel MGC4607/CCM2 Gene Mutation Associated with Cerebral Spinal and Cutaneous Cavernous Angiomas

Cerebral cavernous malformations (CCMs) are vascular abnormalities that may cause seizures, headaches, intracerebral hemorrhages, and focal neurological deficits; they can also be clinically silent and occur as a sporadic or an autosomal dominant condition. Three genes have been identified as causing familial CCM: KRIT1/CCM1, MGC4607/CCM2, and PDCD10/CCM3, mapping, respectively, on chromosomes 7q, 7p, and 3q. Here, we report an Italian family affected by CCM due to a MGC4607 gene mutation, on exon 4. All the affected subjects suffered from seizures, and some of them underwent surgery for removal of a cavernous angioma. Brain MRI showed multiple lesions consistent with CCMs in all patients. Spinal and cutaneous cavernous angiomas were present too. This report underlines the need for a careful interdisciplinarity among neurologists, neuroradiologists, neurosurgeons, geneticists, ophthalmologists, and dermatologists for a total evaluation of the different manifestations of familial CCM. This points out that only referral centers are organized to offer a multidisciplinary management of this disease.

A novel dominant missense mutation--D179N--in the GJB2 gene (Connexin 26) associated with non-syndromic hearing loss

Mutations of the GJB2 gene, encoding Connexin 26, are the most common cause of hereditary congenital hearing loss in many countries, and account for up to 50% of cases of autosomal-recessive non-syndromic deafness. By contrast, only a few GJB2 mutations have been reported to cause an autosomal-dominant form of non-syndromic deafness. We report on a family from southern Italy in whom dominant, non-syndromic, post-lingual hearing loss is associated with a novel missense mutation in the GJB2 gene. Direct sequencing of the gene showed a heterozygous G-->A transition at nucleotide 535, resulting in an aspartic acid to asparagine amino acid substitution at codon 179 (D179N). This mutation occurred in the second extracellular domain (EC2), which would seem to be very important for connexon-connexon interaction.

Genetic diagnosis by chorionic villus sampling before 8 gestational weeks: efficiency, reliability, and risks on 317 completed pregnancies

Transabdominal chorionic villus sampling (TA-CVS) was attempted in 328 high-risk pregnancies at 6-7 weeks of gestation. Sampling was feasible in 97.7 per cent of cases; chorionic tissue specimens of more than 10 mg were obtained in 94.4 per cent of cases at the first needle insertion and in 100 per cent after a second attempt. Fetal karyotyping succeeded in 99.4 per cent of cases, while no diagnostic failures were reported in enzymatic and DNA analyses. Fetal loss rate in the first 4 weeks after CVS was significantly higher than in the later CVS series (7.2 vs. 2.5 per cent), but 50 per cent of losses were observed within 2 weeks in cases of inviable aneuploidies. A high incidence of severe limb abnormalities (1.6 per cent) was detected in pregnancies intended to continue, confirming the aetiological role of early CVS. Unclear visualization of the placental limits and poor control of the needle path are thought to be the main reasons for the vascular disruption of the chorionic plate, and thereby hypoxic embryo tissue damage. A better selection of cases, together with high-resolution vaginal ultrasound visualization, and analytical techniques requiring a minimal amount of tissue should avoid any teratogenic effect of early CVS.

Carrier detection and prenatal diagnosis of hemophilia A: 5-years experience at a hemophilia center

The identification of carriers and the prenatal diagnosis of hemophilia A have greatly improved with knowledge of the structure of the factor VIII gene. This has permitted the defect to be traced in families by using restriction fragment length polymorphisms. This study summarizes 5 years' experience at A. Bianchi Bonomi Hemophilia and Thrombosis Center and the problems encountered. One hundred and forty-four women at risk of hemophilia A from 93 families were referred to our center for DNA analysis. Carrier detection was performed in 95 women, including 11 who were pregnant. Prenatal diagnosis was performed at 7-14 weeks' gestation in 56 pregnant women. We employed two intragenic restriction fragment length polymorphisms (XbaI and BclI) and the two extragenic restriction fragment length polymorphisms (TaqI and BglII). Combining the results of intra and extragenic restriction fragment length polymorphisms with pedigree analysis, a diagnosis was reached in approximately 90% of cases. Of the 33 male fetuses, 11 were affected and 19 not affected. Two cases of recombination between extragenic restriction fragment length polymorphisms and the factor VIII locus were found.

Molecular characterization of hemoglobin C in Sicily

Analysis of polymorphisms of the beta-globin gene cluster was performed on 12 families and on one unrelated individual of Sicilian origin who carried hemoglobin C (Hb C). Two different haplotypes were found in association with beta c Sicilian alleles, corresponding to haplotypes I and II previously described in American blacks. In our population, the more frequent one (haplotype I) was linked to the lack of a polymorphic HpaI site 3' to the beta gene (13.0-kb fragment), similarly to haplotype I in blacks, while the less frequent one was linked to a 7.0-kb HpaI fragment attributable to a site that had never been previously described in linkage with beta c alleles. In Italy, these two haplotypes have been found in rare cases in association with beta A alleles. These findings provide new insights into the origin of Hb C present in Sicily, suggesting that (1) the beta c mutation detected in Sicily derived from African black chromosomes and does not represent a new mutation; and (2) Hb C may have originated either by multiple mutational events on separate chromosomes or by mutation in the HpaI site 3' to the beta gene in a pre-existing beta c chromosome.

Prenatal diagnosis of fetal hemoglobin Lepore-Boston disease on maternal peripheral blood

Molecular diagnosis of hemoglobin (Hb) Lepore-Boston in the fetus was successfully accomplished using maternal blood as a source for fetal cells in three pregnancies at risk for beta-thalassemia/Hb Lepore disease. Taking advantage of the possibility of amplifying Lepore-specific DNA fragments by polymerase chain reaction and of families in which Hb Lepore was inherited by the paternal side, we demonstrated in two cases and excluded in one case the presence of this hemoglobinopathy in the fetus directly on maternal DNA. The diagnosis was concordant with that obtained by traditional approaches in all three cases. Our results unequivocally show that nucleated fetal cells are present in maternal blood during pregnancy, and demonstrate for the first time that prenatal diagnosis of a genetic disease may be feasible without invasive procedures.

Caffeine interactions with methyl methanesulphonate, hycanthone, benlate, and cadmium chloride in chromosomal meiotic segregation of Saccharomyces cerevisiae

Interactions of caffeine with chemicals known for their effects on chromosomal segregation during meiosis of Saccharomyces cerevisiae were studied. It appears that caffeine does interfere with the action of other compounds during the different phases of meiosis. Treatments with methyl methanesulphonate (MMS) and cadmium chloride (CdCl2) resulted in a synergistic effect consisting of an increase in the frequency of recombination. The greatest effects were found on the induction of diploid spores: MMS, hycanthone, and distamycin demonstrated strong, benlate little synergistic action. CdCl2 demonstrated antagonism to caffeine by counter-inhibiting its effect on the induction of diploids. Concerning disomic induction: caffeine reduced (or left unchanged) the effect on non-disjunction when MMS and hycanthone were used. Simple additive effects were caused in conjunction with distamycin, benlate, and (in small doses) CdCl2. 2 mg of caffeine/ml in treatments with CdCl2 resulted in a very high frequency of disomic clones.