A European multicenter study of phenylalanine hydroxylase deficiency: classification of 105 mutations and a general system for genotype-based prediction of metabolic phenotype.

Phenylketonuria (PKU) and mild hyperphenylalaninemia (MHP) are allelic disorders caused by mutations in the gene encoding phenylalanine hydroxylase (PAH). Previous studies have suggested that the highly variable metabolic phenotypes of PAH deficiency correlate with PAH genotypes. We identified both causative mutations in 686 patients from seven European centers.

Mutational analysis of the FMR1 gene in 118 mentally retarded males suspected of fragile X syndrome: absence of prevalent mutations.

Fragile X syndrome is usually caused by expansion of a trinucleotide (CGG) repeat in the 5'-untranslated region of the FMR1 gene. However, both deletions and point mutations in FMR1 have been identified as rare causes of the fragile X syndrome. We have screened the FMR1 gene for mutations by single-stranded conformational polymorphism analysis in 118 mentally retarded males who were referred to us for fragile X testing, and who had a CGG repeat number in the normal size range.

Non-disjunction of chromosome 18.

A sample of 100 trisomy 18 conceptuses analysed separately and together with a published sample of 61 conceptuses confirms that an error in maternal meiosis II (MII) is the most frequent cause of non-disjunction for chromosome 18. This is unlike all other human trisomies that have been studied, which show a higher frequency in maternal meiosis I (MI). Maternal MI trisomy 18 shows a low frequency of recombination in proximal p and medial q, but not the reduction in proximal q observed in chromosome 21 MI non-disjunction.

Characterization of a supernumerary small marker X chromosome in two females with similar phenotypes.

We describe two female patients mosaic for a cell line with an extra marker X chromosome in addition to a normal 46,XX cell line. To our knowledge, these cases are the first reports of females who had a cell line with a supernumerary marker X chromosome in addition to a normal cell line. They also had strikingly similar manifestations, including small hands and feet, minor facial anomalies, obesity, and mental retardation.

A molecular survey of phenylketonuria in Iceland: identification of a founding mutation and evidence of predominant Norse settlement.

Iceland was settled during the late 9th and early 10th centuries AD by Vikings who arrived from Norway and the British Isles. Although it is generally acknowledged that the Vikings brought with them Celtic slaves, the relative contribution of these peoples to the modern Icelandic gene pool has been a matter of considerable discussion. Most population genetic studies using classical markers have indicated a large Irish genetic contribution.

The genetic basis for Prader-Willi syndrome: the importance of imprinted genes.

The genetic basis of Prader-Willi syndrome involves imprinted genes on the proximal long arm of chromosome 15. The basic defect appears to be the absence of function of genes that are normally expressed in a monoallelic fashion only from the paternal chromosome. In 60-70% of patients with Prader-Willi syndrome, the genetic defect is a deletion in the area of 15q11-13 on the paternal chromosome.

Deletion of all CGG repeats plus flanking sequences in FMR1 does not abolish gene expression.

The fragile X syndrome is due to the new class of dynamic mutations. It is associated with an expansion of a trinucleotide repeat (CGG) in exon 1 of the fragile X mental retardation gene 1 gene (FMR1). Here we present a fragile X family with an unique female patient who was rendered hemizygous for the FRAXA locus due to a large deletion of one X chromosome.

Accuracy of cytogenetic findings on chorionic villus sampling (CVS)--diagnostic consequences of CVS mosaicism and non-mosaic discrepancy in centres contributing to EUCROMIC 1986-1992.

Of 62,865 karyotyped chorionic villus (CV) samples that were reported to EUCROMIC 1986-1992, 98.5 per cent showed either a normal karyotype (true negative result; 94.8 per cent of the total) or a non-mosaic chromosomal aberration (true positive non-mosaic result; 3.

Clinical features and molecular genetic analysis of a boy with Prader-Willi syndrome caused by an imprinting defect.

Prader-Willi syndrome (PWS) is a neuroendocrine disorder caused by a non-functioning paternally derived gene(s) within the chromosome region 15q11-q13. Most cases result from microscopically visible deletions of paternal origin, or maternal uniparental disomy of chromosome 15. In both instances no recurrence has been reported.

European collaborative research on mosaicism in CVS (EUCROMIC)--fetal and extrafetal cell lineages in 192 gestations with CVS mosaicism involving single autosomal trisomy.

Cytogenetic information on cells from cytotrophoblast, villus mesenchyme, and one or more fetal tissues was available for 192 gestations with mosaicism or non-mosaic fetoplacental discrepancy involving a single autosomal trisomy in the chorionic villus sample (CVS), registered in a collaborative study (EUCROMIC) during the period 1986-1994. In order to identify predictors of confined placental mosaicism (CPM), generalized mosaicism and/or uniparental disomy (UPD), distribution of the mosaic and nonmosaic aneuploid cell lines in the different fetal and extrafetal cell lineages were analyzed. Data were related to existing hypotheses on mechanisms leading to fetoplacental discrepancies and early extraembryonic cell differentiation.

Investigation of deletions at 7q11.23 in 44 patients referred for Williams-Beuren syndrome, using FISH and four DNA polymorphisms.

Williams syndrome (WS) is associated with a submicroscopic deletion of the elastin gene (ELN) at 7q11.23. The deletion encompasses closely linked DNA markers.

Identification of point mutations in 41 unrelated patients affected with Menkes disease.

Genomic DNA of 41 unrelated patients affected with the classical severe form of Menkes disease was investigated for point mutations in the ATP7A gene (previously designated as the "MNK" gene). Using SSCP analysis and direct sequencing of the exons amplified by PCR, we identified 41 different mutations, including 19 insertions/deletions, 10 nonsense mutations, 4 missense mutations, and 8 splice-site alterations. Approximately 90% of the mutations were predicted to result in the truncation of the protein (ATP7A).

Etiology and pathogenesis of attention-deficit hyperactivity disorder (ADHD): significance of prematurity and perinatal hypoxic-haemodynamic encephalopathy.

Attention-deficit Hyperactivity Disorder (ADHD), defined as a disorder of awareness with impulsivity, has lately been characterized as a dysfunction of the striatum (neostriatum = globus pallidus + putamen). This structure is in a unique position of contextual analysis and samples information samples information from almost the entire cortex through its spiny neurons. The etiology is heterogeneous, with genetic as well as lesional factors.

Chromosome 22q11 deletion and other chromosome aberrations in cases with cleft palate, congenital heart defects and/or mental disability. A survey based on the Danish Facial Cleft Register.

Velo-cardio-facial syndrome (VCFS) is a syndrome associated with haplo-insufficiency of genes at chromosome 22q11. The syndrome has a broad phenotypic spectrum including multiple anomalies, of which cleft palate (CP), congenital heart defects (CHD), and mental disabilities are among the most common. Hence, a high prevalence of 22q11 deletions should be expected among cases with a combination of CP and CHD or/and mental disability.

The influence of mutations of enzyme activity and phenylalanine tolerance in phenylalanine hydroxylase deficiency.

The phenylalanine hydroxylase (PAH) deficiency trait is heterogeneous with a continuum of metabolic phenotypes ranging from classical phenylketonuria (PKU) to mild hyperphenylalaninaemia (MHP). More than 200 mutations in the PAH gene are associated with PAH deficiency. From theoretical considerations or in vitro expression studies each mutation has a particular influence on enzyme activity, which explains the variation in dietary tolerance for phenylalanine (Phe).

Phenylalanine hydroxylase gene mutations in the United States: report from the Maternal PKU Collaborative Study.

The major cause of hyperphenylalaninemia is mutations in the gene encoding phenylalanine hydroxylase (PAH). The known mutations have been identified primarily in European patients. The purpose of this study was to determine the spectrum of mutations responsible for PAH deficiency in the United States.

Menkes disease: recent advances and new insights into copper metabolism.

Copper is a trace element necessary for the normal function of several important enzymes but copper homeostasis is still poorly understood. In recent years remarkable progress has been made in this field following the isolation of the gene defective in Menkes disease. Menkes disease and occipital horn syndrome are X-linked recessive disorders, demonstrating the vital importance of copper, which is also highly toxic in excessive amounts.

Exclusion of SNRPN as a major determinant of Prader-Willi syndrome by a translocation breakpoint.

The predominant genetic defects in Prader-Willi syndrome (PWS) are 15q11-q13 deletions of paternal origin and maternal chromosome 15 uniparental disomy (UPD). In contrast, maternal deletions and paternal chromosome 15 UPD are associated with a different neurogenetic disorder, Angelman syndrome (AS). In both disorders, these mutations are associated with parent-of-origin specific methylation at several 15q11-q13 loci.

Three prevalent mutations in a patient with phenylalanine hydroxylase deficiency: implications for diagnosis and genetic counselling.

Mutation analysis in a patient with mild hyperphenylalaninaemia showed three distinct base substitutions in exon 12 of the phenylalanine hydroxylase (PAH) gene. All three mutations, R413P, Y414C, and D415N, have previously been described as being independently associated with PAH deficiency. Family studies and independent analysis of the PAH alleles of the patient showed cosegregation of the R413P and Y414C mutations.