Association of a mosaic chromosomal 22q11 deletion with hypoplastic left heart syndrome.

The atypical presentation of CATCH 22 raises several important concerns. First, in this patient, as in others, the heart defects were found in association with subtle facial abnormalities but with few of the other criteria normally seen in CATCH 22. This association alone may be sufficient to raise suspicion that an interstitial 22q11 deletion may be present. Second, the incidence of chromosome 22 deletions in parents of children with a 22q11 deletion (25%) suggests that siblings or subsequent fetuses may also be at risk. Parents with subtle or unusual manifestations of CATCH 22 may be unaware of their potential carrier status. Finally, the recognition of chromosomal mosaicism in this patient may have been fortuitous, as cytogenetic studies of leukocytes from other individuals with a mosaic karyotype may sometimes fail to reveal a 22q11 deletion that is present in cardiac tissues. Molecular cytogenetic analysis of cardiac specimens that are removed during routine surgical procedures may be warranted in appropriate clinical situations.

Distinct 15q genotypes in Russell-Silver and ring 15 syndromes.

Individuals with a ring 15 chromosome [r(15)] and those with Russell-Silver syndrome have short stature, developmental delay, triangular face, and clinodactyly. To assess whether the apparent phenotypic overlap of these conditions reflects a common genetic cause, the extent of deletions in chromosome 15q was determined in 5 patients with r(15), 1 patient with del 15q26.1-qter, and 5 patients with Russell-Silver syndrome. All patients with Russell-Silver syndrome were diploid for genetic markers in distal 15q, indicating that Russell-Silver syndrome in these individuals was unlikely to be related to the expression of single alleles at these or linked genetic loci. At least 3 distinct sites of chromosome breakage close to the telomere were found in the r(15) and del 15q25.1-qter patients, with 1 r(15) patient having both a terminal and an interstitial deletion. Although the patient with del 15q25.1-qter exhibited the largest deletion and the most profound growth retardation, the degree of growth impairment among the r(15) patients was not correlated with the size of the deleted interval. Rather, the parental origin of the ring chromosome in several patients was associated with phenotypes that are also seen in patients with either Prader-Willi (PWS) or Angelman (AS) syndromes, conditions that result from uniparental expression of genes on chromosome 15. In fact, unequal representation of chromosome 15 alleles in 1 patient with r(15) suggests the possibility that a mosaic karyotype composed of the constitutional cell line and cell line(s) possibly deficient in the ring chromosome might be present. The PWS-like or AS-like phenotypes could be explained by postzygotic loss of the ring chromosome, leading to uniparental inheritance of the intact chromosome in some tissues of r(15) patients.

Duplication and loss of chromosome 21 in two children with Down syndrome and acute leukemia.

Acute leukemia in Down syndrome (DS) is often associated with additional changes in the number or structure of chromosome 21. We present two DS patients whose leukemic karyotypes were associated with changes in chromosome 21 ploidy. Patient 1 developed acute lymphocytic leukemia (type L1); disomy for chromosome 21 was evident in all blast cells examined. Loss of the paternal chromosome in the leukemic clone produced maternal uniparental disomy with isodisomy over a 25-cM interval. The second patient had acute monoblastic leukemia (type M5) with tetrasomy 21 in all leukemic cells. DNA polymorphism analysis showed duplicate paternal chromosomes in the constitutional genotype. The maternal chromosome was subsequently duplicated in the leukemic clone. The distinct inheritance patterns of chromosome 21 in the blast cells of these patients would appear to indicate that leukemogenesis occurred by different genetic mechanisms in each individual.

Relationship of sleep abnormalities to patient genotypes in Prader-Willi syndrome.

To assess whether sleep abnormalities are related to the genetic abnormalities in Prader-Willi Syndrome (PWS), we performed polysomnographic studies (nighttime and daytime) and determined the chromosome 15 genotypes in eight patients with PWS. Four patients demonstrated sleep onset REM periods (SOREM), and five met the objective polysomnographic criteria for severe or moderate excessive daytime sleepiness (EDS). Three of the four patients with SOREM displayed a paternally derived deletion of chromosome 15q11-q13, whereas the fourth exhibited maternal uniparental heterodisomy in this chromosomal region (UPD). Two of the four patients that did not display SOREM carried paternally derived deletions; the remaining two demonstrated UPD. Four of the five patients with EDS displayed paternal deletions, and the fifth exhibited UPD. One of three patients without evidence of EDS demonstrated paternal deletion; the remaining two showed UPD. Although neither EDS nor SOREM was not consistently associated with a specific genetic abnormality, these phenotypes may be more common in patients with paternal deletions than in those UPD. Sleep abnormalities in PWS cannot be explained by a single genetic model.

Clinical spectrum and molecular diagnosis of Angelman and Prader-Willi syndrome patients with an imprinting mutation.

Recent studies have identified a new class of Prader-Willi syndrome (PWS) and Angelman syndrome (AS) patients who have biparental inheritance, but neither the typical deletion nor uniparental disomy (UPD) or translocation. However, these patients have uniparental DNA methylation throughout 15q11-q13, and thus appear to have a mutation in the imprinting process for this region. Here we describe detailed clinical findings of five AS imprinting mutation patients (three families) and two PWS imprinting mutation patients (one new family). All these patients have essentially the classical clinical phenotype for the respective syndrome, except that the incidence of microcephaly is lower in imprinting mutation AS patients than in deletion AS patients. Furthermore, imprinting mutation AS and PWS patients do not typically have hypopigmentation, which is commonly found in patients with the usual large deletion. Molecular diagnosis of these cases is initially achieved by DNA methylation analyses of the DN34/ZNF127, PW71 (D15S63), and SNRPN loci. The latter two probes have clear advantages in the simple molecular diagnostic analysis of PWS and AS patients with an imprinting mutation, as has been found for typical deletion or UPD PWS and AS cases. With the recent finding of inherited microdeletions in PWS and AS imprinting mutation families, our studies define a new class of these two syndromes. The clinical and molecular identification of these PWS and AS patients has important genetic counseling consequences.

Optimization of accessible catalase activity in polyacrylamide gel-immobilized Saccharomyces cerevisiae.

The permeabilization of Saccharomyces cerevisiae (baker's yeast), either before or after immobilization in polyacrylamide gel (PAG), has been examined as a means to increase the catalase activity of PAG-immobilized yeast cells. Prior permeabilization of the cells resulted in large losses of catalase activity during immobilization, but permeabilization after immobilization produced increases in the catalase activity of yeast/PAG particles. A dependence of the accessible catalase activity on the concentration of polyacrylamide in permeabilized yeast/PAG particles, and on the method of permeabilization of the immobilized cells, was observed. Optimal levels of stable catalase activity (1000-2000 IU/g PAG particles; ca. 5%-10% of total available activity) were obtained by immobilizing yeast cells (0.5 g wet cells/mL gel) in 10% (w/v) PAG, followed by permeabilization of the entrapped cells with either cetyltrimethylammonium bromide, Triton X-100 and one freeze-thaw, or five freeze-thaw cycles.

Behavioral changes in autistic individuals as a result of wearing ambient transitional prism lenses.

A double-blind crossover design was used to assess the efficacy of wearing ambient lenses to reduce the behavioral symptoms of autism. Eighteen autistic individuals, ranging in age from 7 to 18 years, participated in the study. Behavior, attention, and orientation were evaluated at 1 1/2 months, 2 months, 3 months, and 4 months. Compared to the placebo condition, the results showed a decrease in behavior problems at the 1 1/2 and 2 month assessment periods and a slight loss of these benefits at the 3 and 4 month assessment periods. These findings support the prediction that ambient lenses, worn without engaging in visual-motor exercises, have positive effects on autistic individuals.

Glyoxylic acid production using immobilized glycolate oxidase and catalase.

A variety of methods for the immobilization of glycolate oxidase have been examined for the preparation of a catalyst for the oxidation of glycolic acid to glyoxylic acid. The co-immobilization of glycolate oxidase and catalase on oxirane acrylic beads produced a catalyst which was stable to the reaction conditions used for the oxidation, where glycolic acid and oxygen are reacted in aqueous solution in the presence of the immobilized enzyme catalyst and ethylenediamine. Under optimum reaction conditions, 99% yields of glyoxylic acid were obtained at greater than 99% conversion of glycolic acid, and the recovery and reuse of the co-immobilized enzyme catalyst was demonstrated.

Relaxation of imprinting in Prader-Willi syndrome.

We describe two Prader-Willi syndrome (PWS) patients who exhibit maternal uniparental disomy (UPD) of chromosome 15 and unusual patterns of gene expression and DNA replication. Both were diagnosed during infancy as having PWS; however, their growth and development were atypical compared with others with this condition. Weight was below normal in the first patient, and height and development were within normal limits in the second individual. Hyperphagia and polyphagia were not evident in either patient. Genotypes at multiple genomic loci, allele-specific methylation, gene expression, and DNA replication were analyzed at D15S9 [ZNF127], D15S63 [PW71], SNRPN, PAR5, IPW, and D15S10 in these patients. The maternal imprint (based on the absence of gene expression, synchronous replication, and methylation of both alleles) was retained at SNRPN in these patients, as is the case in others with UPD. By contrast, cells from the first individual expressed PAR5 and ZNF127, whereas the second expressed a single IPW allele. Asynchronous DNA replication was observed in both patients at all loci, except SNRPN. These findings show that a subset of imprinted genes can be transcribed in some PWS patients with maternal UPD and that asynchronous DNA replication is coordinated with this pattern of gene expression. Relaxed imprinting in these patients is consistent with their milder phenotype.

Bloom syndrome and maternal uniparental disomy for chromosome 15.

Bloom syndrome (BS) is an autosomal recessive disorder characterized by increases in the frequency of sister-chromatid exchange and in the incidence of malignancy. Chromosome-transfer studies have shown the BS locus to map to chromosome 15q. This report describes a subject with features of both BS and Prader-Willi syndrome (PWS). Molecular analysis showed maternal uniparental disomy for chromosome 15. Meiotic recombination between the two disomic chromosomes 15 has resulted in heterodisomy for proximal 15q and isodisomy for distal 15q. In this individual BS is probably due to homozygosity for a gene that is telomeric to D15S95 (15q25), rather than to genetic imprinting, the mechanism responsible for the development of PWS. This report represents the first application of disomy analysis to the regional localization of a disease gene. This strategy promises to be useful in the genetic mapping of other uncommon autosomal recessive conditions.