Collaborative study of the molecular epidemiology of Tay-Sachs disease in Europe

Tay-Sachs disease is a lipidosis due to the deficiency of the lysosomal hexosaminidase A. In order to understand the molecular mechanisms of this enzyme deficiency we studied 42 patients of different ethnic origins diagnosed in Europe. The strategy used consists in HEXA cDNA amplification followed by allele-specific oligonucleotide analysis for the frequent mutations, and by chemical cleavage mismatch and denaturing gradient gel electrophoresis for the detection of new mutations. 90% of alleles were clarified in this way, showing a high heterogeneity of HEXA lesions in Tay-Sachs disease. 28 different mutations were found, 20 being identified for the first time in this group of patients.

Deletion of chromosome 11p13-11p15.5 sequences in invasive human ovarian cancer is a subclonal progression factor

In human ovarian cancer, multiple specific chromosomal deletions can be found by cytogenetic analysis or molecular techniques such as restriction fragment length polymorphism probing. This work confirms the loss of HRAS alleles in 1 out of 2 cases of invasive ovarian cancer as determined in 32 samples or cell lines derived from 19 patients. Results with other polymorphic probes indicate that a consensus deletion probably includes 11p15.5-11p13. Tumor suppressor genes might be located in the deleted area, and deletion of the gene might then play a role in disease progression. Examination of DNA from distinct tumor sites of individual patients indicates clonal heterogeneity in the malignant cell population, indicating that loss of 11p sequences is a late event in the disease progression. Loss of alternate 11p alleles at different disease sites in one patient is inconsistent with the current model of tumor suppressor gene inactivation. The 11p deletion seems to be limited to ovarian cancers in younger patients. Eight novel permanent ovarian cancer cell lines, previously not described in the literature and derived from tumor sites from five patients, were included in the current analysis.

Vasopressin and gonadotropin deficiency in a boy with the ectrodactyly-ectodermal dysplasia-clefting syndrome

A boy presented with ectrodactyly (lobster claw deformity), bilateral cleft lip and palate, semilobar holoprosencephaly and microcephaly, associated with congenital hypogonadotropic hypogonadism and central diabetes insipidus. Other aspects of pituitary function were normal. We suggest that the ectrodactyly-ectodermal dysplasia-clefting syndrome can be associated with a variety of hypothalamo-pituitary dysfunctions, in addition to the already described isolated growth hormone deficiency.

Pyruvate dehydrogenase (PDH) deficiency caused by a 21-base pair insertion mutation in the E1 alpha subunit

We report the molecular characterization of a case of a functional PDH-E1 (E1 subunit of pyruvate dehydrogenase) deficiency, a cause of severe congenital lactic acidosis. Residual PDH-E1 activity was reduced to 10% of normal values, although the subunit appeared to be quantitatively and qualitatively normal at the protein level as determined by Western blotting. The sequence of PDH-E1 alpha mRNA and the corresponding genomic DNA revealed an in-frame 21-bp insertion between codons 305 and 306 of the normal E1 alpha cDNA. The mutational insert commences with a novel GAT codon and is a nearly perfect tandem duplication of the wild type DNA sequence. A serine phosphorylation site regulating the activity of the PDH complex is altered by this insertion, which in all likelihood is responsible for the functional enzymatic deficiency leading to lactic acidosis.

Mitochondrial myopathy of childhood associated with depletion of mitochondrial DNA

We have studied five children with mitochondrial myopathy manifesting within or soon after the first year of life. Muscle biopsies showed ragged-red fibers and decreased respiratory chain activity. All five patients had a severe decrease (2 to 34% of normal) in the amount of muscle mitochondrial DNA (mtDNA). The depletion of mtDNA correlated with absence of mtDNA-encoded translation products and with loss of cytochrome c oxidase enzyme activity in individual muscle fibers. This mitochondrial myopathy of childhood illustrates one phenotypic expression of a novel pathogenetic mechanism in mitochondrial diseases, the specific depletion of mtDNA in affected tissues.

Analysis of the peripheral T-cell compartment in the MHC class II deficiency syndrome

To analyse the impact of lack of MHC class II expression on the composition of the peripheral T-cell compartment in man, the expression characteristics of several membrane antigens were examined on peripheral blood lymphocytes (PBL) and cultured T cells derived from an MHC-class-II-deficient patient. No MHC class II expression could be detected on either PBL or activated T cells. Moreover, the expression of MHC class I was reduced both on PBL and in vitro activated T cells compared to the healthy control. However, the reduced expression of CD26 observed on the PBL of the patient was restored after in vitro expansion. Despite the presumably class-II-deficient thymic environment, a distinct but reduced single CD4+ T-cell population was observed in the PBL of the patient. After in vitro expansion, the percentage of CD4+ cells dropped even further, most likely due to a proliferative disadvantage, compared to the single CD8+ T-cell population. However, proliferation analysis showed that T-cell activation via the TcR/CD3 pathway is not affected by the MHC class II deficiency.

Two unrelated children with partial trisomy 1q and monosomy 6p, presenting with the phenotype of the Larsen syndrome

Two unrelated children presented with similar clinical features (facial dysmorphism and multiple joint dislocations) suggesting the diagnosis of Larsen syndrome. Both carried an inherited unbalanced translocation resulting in partial trisomy 1q and partial monosomy 6p. Analysis of skin collagen from one of the probands disclosed a decreased alpha 1/alpha 2 chain ratio of collagen type I, increased thermal stability and increased hydroxylation of proline and lysine. The present findings suggest that, as a result of the chromosome rearrangements, both patients have a mutation on a gene involved in collagen production, located either on chromosome 1q or, more probably, on 6p. It is furthermore suggested that other cases of Larsen syndrome are the result of a similar mutation.

[Cordocentesis: experience in 391 initial samples]

The first diagnostic cordocentesis was performed in our unit in october 1985. Our 4-year experience is reported: 391 cordocentesis were performed in 360 patients during gestational weeks 14 to 42. The first attempt was successful in 90% of the procedures, 4 samplings failed, there were 4 fetal deaths within one week after diagnostic cordocentesis, one of them appears to be directly linked to the punction. A transient fetal bradycardia was observed in 9.9% of the cases, bleeding occurred in 19% of the cases. The indications for cordocentesis were: risk of fetal infection, karyotyping, hemopathy, search for paternity, assessment of fetal acid-base status, biochemical dosage. Our data confirm that cordocentesis is a safe and reliable diagnostic procedure providing guidelines for management of the pregnancy.

[Prenatal diagnosis using amniocentesis and chorionic villi sampling: comparative study of chromosomal findings]

The authors report the results of chromosomal analyses performed on 6235 amniocenteses and 559 choriocenteses. Whereas the frequencies of chromosomal anomalies observed respectively on amniocenteses and choriocenteses did not differ significantly, the comparison of the types of aberrations found revealed, in chorion villi, a relatively high proportion of lethal anomalies, never encountered in amniocyte cultures. Furthermore, chromosomal mosaicism was observed 10 times more frequently on chorion villi than on amniotic cells. These results are globally comparable to those reported in other surveys. In view of literature reports of discordances between fetal chorionic karyotypes, never found in amniocenteses, rapid karyotyping from chorion villi is not as reliable as from amniotic cells. Taking into account the risk of cytogenetic discordance specific to choriocentesis, it is recommended that this method be strictly limited to pregnancies with high genetic risk.

[The value of prenatal chromosomal diagnosis in cases of fetal abnormalities: results obtained in 468 pathological pregnancies]

The authors report the results of 468 foetal karyotypes performed on amniotic fluid or foetal blood samples after ultrasound discovery of foetal anomalies. A total of 46 chromosomal aberrations (10%) were detected. The rates of anomalies vary considerably according to the alarm sign; very high (greater than 30%) in cases of multiple malformations, foetal hydrops or foetal death, low (less than or equal to 2%) in cases of poly- or oligohydramnios and foetal growth retardation without detectable malformation. In addition to these chromosomal diagnoses, further investigations enabled in 9 cases the diagnosis of genetic autosomal recessive disorders. Our results which are comparable with those reported in the literature, demonstrate the importance of prenatal diagnosis in cases of pathological pregnancies, with regard to obstetrical and perinatal management as well as to genetic counseling.

[Chorionic villi sampling: experience of the initial 500 samples]

We report our experience in first trimester antenatal diagnosis since 1984. Transcervical chorionic villus sampling (CVS) was performed in 498 pregnancies. The rate of abnormal pregnancies was 6%, the rate of chromosomal abnormalities (trisomy) in the indication group "maternal age" was 2%. The fetal loss rate (until 28 weeks) was 3.4% (17 cases), the procedure related loss plus the background loss was 2.4% (12 cases). For 92.8% of the patients a diagnosis was available after 1 CVS procedure. Ultimately an antenatal diagnosis was given to 99% of the women through a second CVS procedure or an amniocentesis or a cordocentesis. No maternal complication was observed.

Trichothiodystrophy, mental retardation, short stature, ataxia, and gonadal dysfunction in three Moroccan siblings

Three sibs, a boy and two girls, born to Moroccan consanguineous parents, were affected with a syndrome characterized by brittle hair, mental retardation, short stature, ataxia, and gonadal dysfunction. The hair in these three patients displayed the morphological and biochemical hallmarks of trichothiodystrophy (TTD). Gonadal function tests showed abnormal gonadotropic responses to LHRH, consistent with delayed puberty in the male and ovarian failure in both females. Comparison with previously reported cases of TTD associated with mental retardation suggests genetic heterogeneity, although specific biochemical markers are needed in order to answer this question.

Carnitine deficiency with cardiomyopathy presenting as neonatal hydrops: successful response to carnitine therapy

A small-for-date infant presented at birth with severe non-immune hydrops, cardiac failure, metabolic acidosis and hypoglycaemia. Ultrasonography disclosed a cardiomyopathy. Initial therapy consisting of artificial ventilation, inotropes and diuretics resulted in partial disappearance of oedema without significant improvement in cardiac function. Episodes of hypoglycaemia recurred despite continuous glucose infusions. Total serum carnitine from cord blood was 1.65 nmoles/ml and was undetectable on day 20. Oral DL-carnitine supplements resulted in normoglycaemia, dramatic improvement in cardiac function and restoration of serum carnitine levels to normal values. The infant was thereafter maintained on carnitine therapy. Follow-up over 1 year showed moderate growth retardation and normal developmental milestones. In order to account for such a severe neonatal presentation of carnitine deficiency, a combination of defective pre- and postnatal carnitine supply with an inborn error of carnitine handling is considered. The present case illustrates the need for evaluation of carnitine status in fetuses and neonates presenting with hydrops associated with cardiac failure.

[Nanism with short limbs, dysmorphism, renal dysplasia, growth hormone deficiency with pituitary hypoplasia and psychomotor delay: a new syndrome?]

The authors present the case of a male infant affected with short limbed dwarfism already detected in utero by ultrasound. In addition, facial dysmorphism, bilateral hypoplasia and dysplasia of the kidneys with altered renal function, hypotonia and non-evolutive developmental delay are noted. Endocrine tests show a severe and isolated growth hormone deficiency. Metabolic investigations are negative, including peroxisomal functions. Prometaphase chromosomes are normal. Bone x-rays reveal generalized osteoporosis with absence of post-natal osseous maturation and the presence of wormian bones. Major pituitary hypoplasia is demonstrated by nuclear magnetic resonance. The present observation is compared to the case reported by Stratton & Parker (Am. J. Med. Genet., 1989, 32, 169-173). Available data do not allow either to affirm or to exclude the identity of the syndromes presented by these 2 isolated cases.

[Value of examining the placenta in pregnancies complicated by fetal malformations]

This investigation was undertaken to determine whether examination of the placenta contributed to a better understanding of the causes of fetal malformations. Specific histological abnormalities were found in triploidy and lysosomal storage disorders. Placentas from trisomies only showed a marked a specific retardation of villous maturation. The most frequent placental abnormalities detailed in cases presenting major fetal malformations with normal karyotype were: velamentous insertion of the umbilical cord, placental hypotrophy, single umbilical artery, marginal retroplacental hematoma and generalized perivillous fibrin deposition. Examination of the placenta after fetal malformation can provide helpful informations in counseling the parents and the perinatal team in the follow-up of any future child bearing.

Severe congenital cutis laxa with pulmonary emphysema: a family with three affected sibs

Clinical and morphologic findings in 3 sibs with congenital cutis laxa are presented. A severe urinary malformation in one affected infant is reported in detail. Elevated serum copper concentrations were observed in 2 of the sibs and in the healthy mother. However, the 64Cu uptake of fibroblast cells from tissue culture was not increased. Ultrastructural pathologic findings from skin biopsies have been studied and compared at birth and at age 2 years. The lack of junction between the 2 elastic fiber components was similar. Further evidence for clinical heterogeneity of this disease is stressed.

Familial trisomy 11p resulting from a balanced paternal translocation: 3 new cases including first trimester diagnosis

Three related new cases with almost complete trisomy 11p due to paternal balanced translocation 46, XY, t(7; 11) (q36.1; p11.1) are reported. The proband (Case 1) was a malformed stillborn with exomphalos, case 2 was diagnosed in the first trimester by direct chromosome preparations from chorionic villi, and confirmed on fetal products after termination of pregnancy. Case 3, a cousin to cases 1 and 2, was a 29-weeks-old fetus with omphalocele discovered at ultrasound. Literature reports of trisomy 11p are reviewed with regard to those new cases, and the possible relationship of this chromosome imbalance with the Beckwith-Wiedemann Syndrome is discussed.