Novel approach to the molecular diagnosis of Marfan syndrome: application to sporadic cases and in prenatal diagnosis.

Marfan syndrome is an autosomal dominant disorder affecting the skeletal, ocular, and cardiovascular systems. Defects in the gene that encodes fibrillin-1 (FBN1), the main structural component of the elastin-associated microfibrils, are responsible for the disorder. Molecular diagnosis in families with Marfan syndrome can be undertaken by using intragenic FBN1 gene markers to identify and track the disease allele. However, in sporadic cases, which constitute up to 30% of the total, DNA-based diagnosis cannot be performed using linked markers but rather requires the identification of the specific FBN1 gene mutation. Due to the size and complexity of the FBN1 gene, identification of a causative Marfan syndrome mutation is not a trivial undertaking. Herein, we describe a comprehensive approach to the molecular diagnosis of Marfan syndrome that relies on the direct analysis of the FBN1 gene at the cDNA level and detects both coding sequence mutations and those leading to exon-skipping, which are often missed by analysis at the genomic DNA level. The ability to consistently determine the specific FBN1 gene mutation responsible for a particular case of Marfan syndrome allows both prenatal and pre-implantation diagnosis, even in sporadic instances of the disease.

Transcobalamin II deficiency with methylmalonic aciduria in three sisters.

Transcobalamin II (TC II) is a plasma protein that binds vitamin B12 (cobalamin, Cbl) and facilitates cellular Cbl uptake by receptor-mediated endocytosis. In autosomal recessive TC II deficiency, intracellular Cbl deficiency results in an early onset of megaloblastic anaemia that may be accompanied by neurological abnormalities. Inadequate treatment may lead to neurological abnormalities. We describe three sisters, the daughters of first cousins of Moroccan origin, with TC II deficiency requiring continuous and long-term vitamin B12 treatment. The diagnosis was suspected from the finding of low unsaturated vitamin B12 binding capacity and confirmed by absence of detectable TC II by radioimmunoassay and by inability of cultured fibroblasts to synthesize TC II.

Predictive value of family data for the management of infantile bilateral partial cataract.

PURPOSE: To examine the data on outcome of surgery performed over a wide age range in members of a family affected by familial infantile bilateral partial cataract, with the purpose of assessing their predictive value concerning the timing of surgery. METHODS: A retrospective clinical study was carried out of a family with dominant inheritance of familial infantile bilateral partial cataract. The family spanned four generations and consisted of 53 members, 31 of whom were examined in our department. Of these, 18 were affected. Cataract surgery was performed in 26 eyes of 15 patients, whose ages ranged from 6 to 58 years at the time of operation. As the surgical procedures spanned the years from 1978 to 1996, different techniques were used. RESULTS: In 24 eyes (92%) the post-operative visual acuity was 6/9 or better. One eye achieved 6/12 and another 6/15. CONCLUSIONS: In this particular family there was no relationship between the post-operative visual acuity and the age at which surgery was performed. In deciding when to operate on family members with infantile bilateral partial cataract with similar morphology, in addition to the commonly used criteria the family data should also be taken into account. In infants and young children, delaying surgery may allow better development of visual acuity aided by accommodation, stabilisation of binocularity and more precise determination of the power of an intraocular lens. Success of very early surgery in such cases may not be attributable to the timing of the operation.

Demonstration of a new pathogenic mutation in human complex I deficiency: a 5-bp duplication in the nuclear gene encoding the 18-kD (AQDQ) subunit.

We report the cDNA cloning, chromosomal localization, and a mutation in the human nuclear gene encoding the 18-kD (AQDQ) subunit of the mitochondrial respiratory chain complex I. The cDNA has an open reading frame of 175 amino acids and codes for a protein with a molecular mass of 23.2 kD. Its gene was mapped to chromosome 5. A homozygous 5-bp duplication, destroying a consensus phosphorylation site, in the 18-kD cDNA was found in a complex I-deficient patient. The patient showed normal muscle morphology and a remarkably nonspecific fatal progressive phenotype without increased lactate concentrations in body fluids. The child's parents were heterozygous for the mutation. In 19 other complex I-deficient patients, no mutations were found in the 18-kD gene.

Microcephaly due to fetal brain disruption sequence. Case report.

A case of microcephaly that developed intrauterine is described. Since it began three weeks after a car accident during second trimester of pregnancy, we attribute it to "brain disruption sequence" resulting in an arrest of brain development after the injury.

Cytogenetic analysis of fetal chondrocytes: a comparative study.

Progress in the prevention and prenatal detection of birth defects has led to a relative increase in the number of interruption of pregnancies associated with chromosomal abnormalities. There is an inverse relationship between the rate of success of fetal cell cultures and the interval between fetal demise and the initiation of culture. This report describes the cytogenetic analyses of cultured fetal chondrocytes compared with tissue cultures of fetal skin, fetal membranes, and placenta. The results show that cells obtained from the fetal chondrocostal junction and/or patella from missed abortions, intrauterine fetal deaths, or stillbirths can be cultured and successfully karyotyped. Since cartilage cells remain viable for some time after fetal demise, the culture of fetal chondrocytes is a complementary method for fetal chromosome analysis, especially in cases of tissue maceration after fetal demise. The success rate of chondrocyte cultures is similar to that of conventional fetal tissue cultures.

Familial café au lait spots: a variant of neurofibromatosis type 1.

Café au lait spots (CALS) are a frequent and one of the early manifestations of neurofibromatosis 1 (NF1). However, there are patients with isolated CALS who do not meet the diagnostic criteria for NFI. There are several reports of families in which CALS are inherited as an autosomal dominant trait, without any other features of NFI. In one reported family with dominantly inherited CALS linkage to the NF1 locus was ruled out. In order to elucidate the relationship between familial CALS and NF1 further, we performed a linkage analysis in a large kindred with 11 subjects with CALS in three generations and established close linkage between CALS and five NF1 intragenic polymorphisms. We propose that in this family the trait of CALS is allelic to NF1, it is fully penetrant, and it does not confer a risk of other NF1 symptoms.

H19 expression and tumorigenicity of choriocarcinoma derived cell lines.

Certain embryonal tumors demonstrate a loss of heterozygosity at the parentally imprinted region of chromosome 11p15.5. It has been hypothesized that this implicates a tumor suppressor gene at this locus. The human H19 gene maps to 11p15.5, is expressed in fetal tissues including the placenta and is paternally imprinted. Here we show that the abundance of H19 transcripts in cells of two choriocarcinoma derived cell lines (JAr and JEG-3) differs greatly. While JAr cells express high levels of H19 RNA, the expression of H19 in JEG-3 cells is much lower than that of normal trophoblasts. Cells of these two cell lines were subcutaneously injected into nude mice with subsequent tumor formation. A fivefold increase in the H19 RNA level was measured in tumors derived from JEG-3 cell lines as compared to these cells before injection. However this increase in H19 RNA did not alter the clonogenicity in soft agar nor the growth rate of the cells derived from these tumors as compared to the original JEG-3 cells. Nevertheless, the cells retaining the elevated level of H19 transcripts were more tumorigenic than the original cells. We propose that there is a selection of cells expressing high levels of H19 from the total JEG-3 cell population during the microevolution of tumor formation. These observations, together with our previous publications on H19 expression in human cancers, do not support the notion of a tumor suppressor role for the H19 gene.

Neurofibromatosis type I (NFI) in Israeli families: linkage analysis as a diagnostic tool.

Linkage analysis of 18 neurofibromatosis type I (NFI) families was performed using intragenic and flanking polymorphic markers. The aims of the analysis were prenatal diagnosis of at-risk fetuses, and of asymptomatic individuals who were relatives of NFI patients. Prenatal diagnosis was performed in 9 pregnancies of 7 families; 5 fetuses were diagnosed as affected. In 6 families with an affected spouse, the request was to identify informative polymorphisms to be used in future pregnancies. Presymptomatic diagnosis was performed in 4 families. One individual, a brother of an NFI patient, was found to have Lisch nodules as the only NFI symptom. Linkage analysis indicated that if this person is a carrier of the NFI gene, he must be a product of intragenic crossover. In 2 individuals with a new NFI mutation, the origin of the NFI-bearing chromosomes was paternal. The same observation was noted by others. A summary of published cases shows that some 90% of the NFI-bearing chromosomes of patients with new mutations were of paternal origin. We therefore suggest that for the purpose of prenatal diagnosis in carriers of NFI new (and unidentified) mutations, the paternal chromosome will be considered as the NFI-bearing chromosome.

Aplasia cutis congenita, elevated alpha-fetoprotein, and a distinct amniotic fluid acetylcholinesterase electrophoretic band.

Aplasia cutis congenita affecting the elbows, knees, hips, and gluteal area was observed in a female newborn, product of a twin pregnancy. One of the twins was a fetus papyraceous detected at 15 weeks of pregnancy. During the course of the pregnancy, maternal thrombocytosis was diagnosed and treated with aspirin. alpha-Fetoprotein was elevated in maternal serum and amniotic fluid, and a distinct electrophoretic acetylcholinesterase band was seen in amniotic fluid. These findings are in agreement with the classification of aplasia cutis congenita as proposed by Frieden et al in which type V is related to the presence of a fetus papyraceous or placental infarcts. The findings in the present case may be explained by the effect of the dead twin on the surviving fetus and the extensive denuded skin areas. Long-term follow-up of the infant showed that the lesions were cured, most of them with minimal scars. Increased risk for aplasia cutis congenita should be considered when elevated maternal and amniotic fluid alpha-fetoprotein and a distinct electrophoretic band of acetylcholinesterase are found. Especially when one of the twins is dead.

Homozygosity for inversion (2)(p12q14).

Two healthy adults, brother and sister, who are homozygotes for inv2(p12q14) are reported. As this is the first report of homozygosity for this inversion the authors ask to be informed of any further known cases.

[Huntington's disease: ethical aspects of presymptomatic testing].

Huntington's disease is an autosomal dominant entity with onset mostly in middle age. Neurological signs and psychosis evolve without possibility of treatment or alleviation. Genetic counseling of relatives of patients has changed since the development of presymptomatic testing. Ethical issues and dilemmas associated with the application of this technological advance are reviewed as a result of a request by a mother to perform presymptomatic testing in her young daughter whose father has Huntington's disease.

Further delineation of the acrocallosal syndrome.

The acrocallosal syndrome (ACS) was recognized by Schinzel in 1979 as a specific entity, characterized by the association of craniofacial anomalies, total or partial agenesis of corpus callosum, polysyndactyly and mental retardation. The inheritance is autosomal recessive, based on instances of recurrence in siblings and cousins and parental consanguinity. A large inbred kindred with recurrent ACS is presented. This family further strengthens the hypothesis of autosomal recessive inheritance for this syndrome. The array of clinical manifestations in this sibship and those previously reported exemplify the phenomenon of inter- and intrafamilial variability that must be considered when defining ACS. Based on a review of published reports and the present family, essential, additional and occasional findings are distinguished. Attention is drawn to geographical clustering of the families.