A highly polymorphic CA/GT repeat (LIMK1GT) within the Williams syndrome critical region.
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Biomedical subjects
Publications and source records attributed to G Novelli.
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We report a personal experience of first-trimester prenatal diagnosis of Ellis-van Creveld (EvC) syndrome based on typing of microsatellite markers flanking the EvC locus. An heterozygous fetus was diagnosed with a diagnostic accuracy of 96 per cent. The DNA prediction was confirmed by ultrasound at 22 weeks of gestation and by clinical evaluation at birth.
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Tricuspid atresia has not been reported in 22q11 microdeletions causing DiGeorge and velo-cardio-facial syndromes. We investigated the prevalence of 22q11 hemizygosity in 26 children with tricuspid atresia. Fluorescent hybridization with the Sc11.1 probe demonstrated a 22q11 microdeletion in 2 patients, one with and another without transposition of the great arteries. Both deletion patients had minor facial anomalies characteristic of DiGeorge syndrome. The present observations suggest that tricuspid atresia should be included in the list of cardiac malformations seen in del22q11 syndromes.
Despite the importance of cholesterol metabolism in the central nervous system, only relatively few studies have dealt with the cerebral uptake and transport of lipids into the brain compartment. These functions are mediated by the endothelium of brain microvessels, which forms the anatomical basis of the blood-brain barrier. By a reverse transcriptase PCR study of messenger RNA expression we could show, in bovine brain microvessels, the presence of transcripts of native low-density lipoprotein receptor and of both type I and II scavenger receptors. Brain microvessels therefore appear to play an active role in the uptake of native and modified low-density lipoproteins.
In order to investigate the spinal muscular atrophy (SMA) disease processes, the expression of the survival motor neuron gene (SMN) has been analyzed in human fetal tissues using RT-PCR and in situ hybridization. These studies allowed the detection of SMN RNA in all the examined tissues, with no significant variation between different developmental stages. In particular, SMN mRNA was detected in spinal cord (dorsal and ventral portions), skeletal muscle, lung, heart, kidney, liver, and spleen. Moreover, RT-PCR studies demonstrated that the expression pattern of SMN isoforms was similar to that observed in adult tissues. The present data confirm a housekeeping role for the SMN protein and may have implications on the search for early therapeutic strategies.
Childhood SMAs are common neuromuscular disorders, due to the occurrence of large genomic deletions encompassing the SMN gene and often extending to involve the NAIP gene. Although NAIP deletions are more frequently observed in patients affected by the acute form of the disease, it is not possible to establish an unambiguous correlation between deletion size and clinical severity. We have investigated the effects of gender on the association between NAIP gene deletion and disease severity. NAIP deletions were screened in 197 Italian SMA patients lacking SMN; the results obtained were correlated with disease severity in male and female samples separately. No significant relationship between deletion size and clinical phenotype was observed among male subjects, whereas in females the absence of NAIP was strongly associated with a severe phenotype (p <0.0001). These results provide a possible molecular explanation for the sex-dependent phenotype variation observed in SMA patients.
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The present genome era is characterized by speedy progress and prompt transfer of results into clinical practice. This creates the need for rapid disclosure of results and renewal of laboratory's protocols. Molecular cytogenetics has provided and increased ability to identify chromosomes, correlate chromosome structure with gene location, find out cryptic aberrations, and detect specific DNA sequences. These advances have allowed the confident discovery of a number of contiguous gene syndromes. The positional cloning and positional candidate strategies have greatly expedited the search process of disease genes, and become relevant methods for genes' discovery. Understanding the molecular basis of diseases has shown an unpredicted wide genetic heterogeneity, which has splitted single disorders into many clinically similar conditions, and added complexity to the nosology of human diseases. The opposite process, allelism, where clinical diversity results from allelic mutations, has lumped together many distinct disorders, by showing that different clinical entities are not necessarily due to mutations in different genes. Dynamic mutations have provided the molecular understanding of interindividual and intrafamilial variability including anticipation, in a number of diseases. The discovery of distinct correlations between the molecular pattern and disease severity is providing a unique opportunity for using molecular results to assess the clinical outcome. Diagnostic, presymptomatic and predictive molecular testing are becoming widely used and provide enormous opportunities for improving the lot of our patients.
The CATCH 22 acronym outlines the main clinical features of 22q11.2 deletions (cardiac defects, abnormal facies, thymic hypoplasia, cleft palate and hypocalcemia), usually found in DiGeorge (DGS) and velo-cardio-facial (VCFS) syndromes. Hemizygosity of this region may also be the cause of over 100 different clinical signs. The CATCH 22 locus maps within a 1.5 Mb region, which encompasses several genes. However, no single defect in 22q11.2 hemizygous patients can be ascribed to any gene so far isolated from the critical region of deletion. We have identified a gene in the CATCH 22 critical region, whose functional features and tissue-specific expression suggest a distinct role in embryogenesis. This gene, UFD1L, encodes the human homolog of the yeast ubiquitin fusion degradation 1 protein (UFD1p), involved in the degradation of ubiquitin fusion proteins. Cloning and characterization of the murine homolog (Ufd1l) showed it to be expressed during embryogenesis in the eyes and in the linear ear primordia. These data suggest that the proteolytic pathway that recognizes ubiquitin fusion proteins for degradation is conserved in vertebrates and that the UFD1L gene hemizygosity is the cause of some of the CATCH 22-associated developmental defects.
We present clinical data on 558 patients with deletions within the DiGeorge syndrome critical region of chromosome 22q11. Twenty-eight percent of the cases where parents had been tested had inherited deletions, with a marked excess of maternally inherited deletions (maternal 61, paternal 18). Eight percent of the patients had died, over half of these within a month of birth and the majority within 6 months. All but one of the deaths were the result of congenital heart disease. Clinically significant immunological problems were very uncommon. Nine percent of patients had cleft palate and 32% had velopharyngeal insufficiency, 60% of patients were hypocalcaemic, 75% of patients had cardiac problems, and 36% of patients who had abdominal ultrasound had a renal abnormality. Sixty-two percent of surviving patients were developmentally normal or had only mild learning problems. The majority of patients were constitutionally small, with 36% of patients below the 3rd centile for either height or weight parameters.
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We carried out a genotype-phenotype correlation study, based on clinical findings in 465 patients with myotonic dystrophy (DM), in order to assess [CTG] repeat number as a predictive test of disease severity. Our analysis showed that the DM subtypes defined by strict clinical criteria fall into three different classes with a log-normal distribution. This distribution is useful in predicting the probability of specific DM phenotypes based on triplet [CTG] number. This study demonstrates that measurement of triplet expansions in patients' lymphocyte DNA is highly valuable and accurate for prognostic assessment.
In a low-risk pregnant patient at 21 weeks' gestation, ultrasound revealed shortening of fetal long bones compatible with achondroplasia. Funipuncture was performed and DNA analysis of fetal blood demonstrated the presence of the GR380R fibroblast growth factor receptor 3 (FGFR3), which is specifically associated with achondroplasia. After termination of the pregnancy, necropsy confirmed the prenatal diagnosis. A certain sonographic diagnosis of fetal de novo achondroplasia is rarely possible prior to viability. The specificity of the FGFR3 causative mutation has added a new diagnostic option which can be applied prenatally for diagnostic validation.
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Multicopy dinucleotide repeats have been characterized in the spinal muscular atrophy (SMA) region on chromosome 5q13, which reveal deletions in some SMA patients. 119 Italian and Spanish SMA families have been analysed using the C272 and C212 markers. Seventy percent of these families were informative. We found 9.4% de novo deletions in SMA I and 1.5% in SMA II families. A single inherited deletion segregating in a Spanish pedigree was detected in three affected brothers. A SMA II patient showed deletion only of C272. The data presented in this study are relevant to the molecular diagnosis of SMA families in Italy and Spain and provide additional insights toward the understanding of the molecular pathology of SMA.
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