Increased occurrence of cleft lip in glycogen storage disease type II (GSDII): exclusion of a contiguous gene syndrome in two patients by presence of intragenic mutations including a novel nonsense mutation Gln58Stop.

Genetic deficiency of lysosomal acid alpha-glucosidase (acid maltase) results in the autosomal recessive disorder glycogen storage disease type II (GSDII) in which intralysosomal accumulation of glycogen primarily affects function of skeletal and cardiac muscle. During an earlier review we noted 3 in 100 cases of GSDII with incidental description of cleft lip. In addition, we identified 2 of 35 GSDII patients referred to us for molecular studies with co-occurence of cleft lip, considerably greater than the estimated frequency of nonsyndromic cleft lip with or without cleft palate of 1 in 700 to 1,000. Because several lines of evidence support a minor cleft lip/palate (Cl/P) locus on chromosome 17q close to the locus for GSDII, we defined the molecular basis for the GSDII in these two patients to determine if they represented a contiguous gene syndrome. Patient I (of Dutch descent) was homozygous and the parents heterozygous for an intragenic deletion of exon 18 (deltaex18), common in Dutch patients. Patient II was heterozygous for delta525T, a mutation also common in Dutch patients and a novel nonsense mutation (172 [corrected] C-->T; Gln58Stop) in exon 2, the first coding exon. The mother was heterozygous for the delta525T and the father for the 172 [corrected] C-->T; Gln58Stop. The finding that both patients carried intragenic mutations eliminates a contiguous gene syndrome. Whereas the presence of cleft lip/cleft palate in a patient with GSDII could be coincidental, these co-occurences could represent a modifying action of acid alpha-glucosidase deficiency on unlinked or linked genes that result in increased susceptibility for cleft lip.

Constitutional and mosaic large NF1 gene deletions in neurofibromatosis type 1.

A set of neurofibromatosis type 1 (NF1) patients was screened for large NF1 gene deletions by comparing patient and parent genotypes at 10 intragenic polymorphic loci. Of 67 patient/parent sets (47 new mutation patients and 20 familial cases), five (7.5%) showed loss of heterozygosity (LOH), indicative of NF1 gene deletion. These five patients did not have severe NF1 manifestations, mental retardation, or dysmorphic features, in contrast to previous reports of large NF1 deletions. All five deletions were de novo and occurred on the maternal chromosome. However, two patients showed partial LOH, consistent with somatic mosaicism for the deletion, suggesting that mosaicism may be more frequent in NF1 than previously recognised (and may have bearing on clinical severity). We suggest that large NF1 deletions (1) are not always associated with unusual clinical features, (2) tend to occur more frequently on maternal alleles, and (3) are an important mechanism for constitutional and somatic mutations in NF1 patients.

Hyperphenylalaninemia with high levels of 7-biopterin is associated with mutations in the PCBD gene encoding the bifunctional protein pterin-4a-carbinolamine dehydratase and transcriptional coactivator (DCoH).

Pterin-4a-carbinolamine dehydratase (PCD) is required for efficient tetrahydrobiopterin regeneration after phenylalanine hydroxylase activity. This catalytic function was proposed to be specifically defective in newborns with a mild form of hyperphenylalaninemia (HPA) and persistent high urinary levels of primapterin (7-biopterin). A second regulatory task of the same protein is DCoH, a coactivation of transcription by hepatocyte nuclear factor 1alpha (HNF-1alpha), a function that is apparently not impaired in these HPA individuals. It has been shown elsewhere that the human PCD/DCoH bifunctional protein is encoded by a single 4-exon-containing gene, PCBD, located on chromosome 10q22. We have now examined the PCBD gene for mutations at the genomic level in six such HPA patients from four different families. By the use of new intron-specific primers, we detected, in all six patients, single, homozygous nucleotide alterations, in exon 4, that were inherited from their parents. These homozygous alterations predicted mutant PCD/DCoH with a single amino acid exchange, in two cases (alleles T78I), or premature stop codons, in the other four patients (alleles E86X and Q97X). Recombinant expression in Escherichia coli revealed that the mutant proteins-T78I, E86X, and Q97X-are almost entirely in the insoluble fraction, in contrast to wild type, which is expressed as a soluble protein. These data support the proposal that HPA in combination with urinary primapterin may be due to autosomal recessive inheritance of mutations in the PCBD gene specifically affecting the dehydratase activity.

Methylenetetrahydrofolate reductase deficiency in a patient with phenotypic findings of Angelman syndrome.

Deficiency of methylenetetrahydrofolate reductase (MTHFR) is associated with a variable phenotype that includes mental retardation, gait abnormalities, and seizures. Many of the same clinical findings are also seen in patients with Angelman syndrome. We report on a patient with MTHFR deficiency who was initially diagnosed as having Angelman syndrome. This case illustrates that MTHFR deficiency can mimic the phenotype of Angelman syndrome and that MTHFR deficiency should be excluded in patients with manifestations of Angelman syndrome whose molecular studies of chromosome 15 are normal.

Reproductive outcome in 3 families with a satellited chromosome 4 with review of the literature.

We describe 3 families segregating for a translocation of the nucleolus organizer region (NOR) onto chromosome 4. Review of previously reported cases of translocations involving NOR and chromosome 4 shows that these translocations may be associated with variable reproductive outcomes. We provide evidence that imprinting is not the mechanism responsible for the variable reproductive outcomes in the case of satellited 4p chromosomes; this may offer indirect support for a ribosomal gene position effect. Translocated ribosomal genes may influence the expression of neighboring genes and could explain the variable phenotypes in individuals with satellited nonacrocentric chromosomes. We recommend that prenatal counseling of individuals with satellited nonacrocentric chromosomes should be cautious.

Mild mandibulofacial dysostosis in a child with a deletion of 3p.

We report on a patient with mild mandibulofacial dysostosis and a small interstitial deletion of 3p, 46,XY,del(3)(p23p24.12). Linkage of Treacher Collins syndrome, the most common of the mandibulofacial dysostoses, to the 5q31.3-->q33.3 region of chromosome 5 has been established. This is the fourth report of a patient with mandibulofacial dysostosis with a chromosome abnormality outside the 5q31.3 area. Mandibulofacial dysostosis is a heterogeneous entity, and evaluation and counseling of affected individuals should be undertaken with caution.

Analysis of DNA restriction fragments greater than 5.7 Mb in size from the centromeric region of human chromosomes.

Pulsed electrophoresis was used to study the organization of the human centromeric region. Genomic DNA was digested with rare-cutting enzymes. DNA fragments from 0.2 to greater than 5.7 Mb were separated by electrophoresis and hybridized with alphoid and simple DNA repeats. Rare-cutting enzymes (Mlu I, Nar I, Not I, Nru I, Sal I, Sfi I, Sst II) demonstrated fewer restriction sites at centromeric regions than elsewhere in the genome. The enzyme Not I had the fewest restriction sites at centromeric regions. As much as 70% of these sequences from the centromeric region are present in Not I DNA fragments greater than 5.7 and estimated to be as large as 10 Mb in size. Other repetitive sequences such as short interspersed repeated segments (SINEs), long interspersed repeated segments (LINEs), ribosomal DNA, and mini-satellite DNA that are not enriched at the centromeric region, are not enriched in Not I fragments of greater than 5.7 Mb in size.

Characterization of human centromeric regions using restriction enzyme banding, alphoid DNA and structural alterations.

Studies of banding induced by restriction enzymes may provide insight into banding mechanisms and chromosome structure. We examined whether or not the sizes of chromosome-specific alphoid DNA fragments created by digestion with various restriction enzymes relate to the presence or absence of C-like bands produced by these same enzymes. We sized alphoid DNA fragments from five different chromosomes, digested with each of six different restriction enzymes. There was no obvious correlation between the length of alphoid restriction fragments at specific human centromeric regions and the production of C-like bands. We used the enzyme AluI and traditional staining (CBG) techniques to band centromeres with conformational alterations. These included dicentric chromosomes, chromosomes from a patient with Roberts syndrome, and 5-azacytidine-treated prometaphase chromosomes. In all cases bands produced by AluI resembled CBG banding. We found that markedly decondensed portions of centromeric regions induced by 5-azacytidine did not band. Our studies demonstrate that restriction endonuclease C-like banding is not strictly related to the presence of restriction sites in alphoid DNA, and the condensed chromatin conformation at the centromeric region may play a role in banding.

Outcome of pectus excavatum in patients with Marfan syndrome and in the general population.

We reviewed the records of 28 patients with Marfan syndrome and 30 age-matched control patients with presumed isolated pectus excavatum to determine the outcome of surgical repair of the pectus deformity in Marfan syndrome. One third of the patients with Marfan syndrome underwent repair of the pectus excavatum before diagnosis. Of the 30 patients with "isolated" pectus excavatum, 17 had findings by history or physical examination, such as mitral valve prolapse, scoliosis, or a relative with pectus excavatum, suggestive of an underlying disorder of connective tissue. Pectus excavatum of more than moderate severity recurred in 11 of 28 patients with Marfan syndrome and was associated with young age at initial surgery and lack of temporary internal stabilization of the chest after surgery. Only two of the control patients had recurrence of the defect; one of these patients had findings suggestive of an underlying heritable disorder of connective tissue. We conclude that pectus excavatum may indicate the presence of an underlying heritable disorder of connective tissue such as the Marfan syndrome. In patients with Marfan syndrome, and possibly other inherited connective tissue disorders, surgical repair should be delayed if possible until skeletal maturity is nearly complete and should employ internal stabilization.

Surgical management of children and young adults with Marfan syndrome and pectus excavatum.

Significant chest wall deformities occur in two thirds of children with Marfan syndrome (MS). The symptoms, physical findings, and surgical outcome of 11 patients with MS and severe pectus excavatum who required operative repair were reviewed. The diagnosis of MS was made before the pectus repair in six patients, at the time of evaluation of pectus in two patients, and after the repair in three patients. Symptoms included dyspnea upon exertion, tachypnea, and chest pain. Physical findings included aortic root enlargement or valvular disease, mitral valve disease, ligamentous disease, congestive heart failure, and ocular disease. All patients had severe pectus deformities with a narrow anteroposterior diameter in the midline, as well as a broad chest defect that extended bilaterally to the midclavicular line. The heart was shifted into the left side of the chest in all patients. A Ravitch-type pectus repair with a stainless steel substernal strut was used in eight patients, with one patient suffering a late recurrence; in three patients no strut was used, and all three had recurrence. There were no postoperative complications. In the postoperative follow-up of seven patients, symptomatic improvement of cardiopulmonary performance was noted. Four of the patients required subsequent open heart surgery, including replacement of the aortic valve in one patient, and composite grafts of the ascending aorta in three patients. Postoperative cardiac arrest was the only major open heart complication. All four patients recovered and did well after surgery, showing significant cardiac and pulmonary functional improvement.(ABSTRACT TRUNCATED AT 250 WORDS)