Cytogenetic findings in a prospective series of patients with DiGeorge anomaly.

High-resolution cytogenetics analysis of peripheral blood lymphocytes was done prospectively on 27 of 28 patients with features of DiGeorge anomaly. Twenty-two patients (81%) had normal chromosome studies with no detectable deletion in chromosome 22. Five patients (18%) had demonstrable chromosome abnormalities. Three patients had monosomy 22q11, one due to a 4q;22q translocation, one due to a 20q;22q translocation, and one due to an interstitial deletion of 22q11. One patient had monosomy 10p13, and one patient had monosomy 18q21.33, although the latter had subsequent resolution of T-cell defects. These findings are consistent with the heterogeneity of DiGeorge anomaly but confirm the association with monosomy 22q11 in some cases. However, monosomy 10p13 may also lead to this phenotype. Because of these associated chromosome findings, cytogenetic analyses should be done on patients with suspected DiGeorge anomaly. This is particularly important since many of the abnormalities involving chromosome 22 are translocations that can be familial with a higher recurrence risk. Since only one subtle, interstitial deletion of chromosome 22 was observed, it is not clear whether high-resolution cytogenetic analysis is cost beneficial for all such patients.     

Single-cell PCR performed with neurofibroma Schwann cells reveals the presence of both alleles of the neurofibromatosis type 1 (NF1) gene

It is commonly held that Schwann cells (SC) are the progenitor cells of benign neurofibromas. To test for loss of heterozygosity (LOH) at the neurofibromatosis 1 (NF1) gene locus, three intragenic polymorphic markers were analyzed after polymerase chain reaction amplification, starting from 98 single SC isolated from primary cultures of neurofibromas of five informative NF1 patients. The patterns obtained did not provide evidence for LOH at the NF1 gene. LOH by nondisjunction, large deletions, or somatic recombination in SC seems not to be the mechanism of generation of neurofibromas.     

X chromosome monosomy: a common mechanism for autoimmune diseases

The majority of human autoimmune diseases are characterized by female predominance. Although sex hormone influences have been suggested to explain this phenomenon, the mechanism remains unclear. In contrast to the role of hormones, it has been suggested, based on pilot data in primary biliary cirrhosis, that there is an elevation of monosomy X in autoimmune disease. Using peripheral white blood cells from women with systemic sclerosis (SSc), autoimmune thyroid disease (AITD), or healthy age-matched control women, we studied the presence of monosomy X rates using fluorescence in situ hybridization. We also performed dual-color fluorescence in situ hybridization analysis with a chromosome Y alpha-satellite probe to determine the presence of the Y chromosome in the monosomic cells. In subsets of patients and controls, we determined X monosomy rates in white blood cell subpopulations. The rates of monosomy X increased with age in all three populations. However, the rate of monosomy X was significantly higher in patients with SSc and AITD when compared with healthy women (6.2 +/- 0.3% and 4.3 +/- 0.3%, respectively, vs 2.9 +/- 0.2% in healthy women, p < 0.0001 in both comparisons). Importantly, X monosomy rate was more frequent in peripheral T and B lymphocytes than in the other blood cell populations, and there was no evidence for the presence of male fetal microchimerism. These data highlight the thesis that chromosome instability is common to women with SSc and AITD and that haploinsufficiency for X-linked genes may be a critical factor for the female predominance of autoimmune diseases.     

Cell culture studies on neurofibromatosis (von Recklinghausen). II. Occurrence of glial cells in primary cultures of peripheral neurofibromas

The occurrence of glial cells in primary cultures established from peripheral neurofibromas of 18 patients with neurofibromatosis (von Recklinghausen) is described. The spindle-shaped cells can be distinguished from fibroblasts on the basis of morphological and ultrastructural criteria. As demonstrated by immunocytochemical analysis, the spindle cells express S-100 protein. Neither glial fibrillar acidic protein nor myelin basic protein can be detected in these cells. In many respects the spindle cells resemble immature Schwann cells in culture.     

Detection of Aneuploidy in Spontaneous Abortions Using Comparative Genomic Hybridization

Comparative genomic hybridization (CGH) technique was used to examine a set of ten spontaneous abortions whose cell cultures were characterized by the lack of proliferation in vitro, and thereby, were not available for the analysis by means of routine cytogenetic methods. Five abortions (50%) had aneuploidy of autosomes, including trisomy 10, 14, 18, and 21, and monosomy 22. The latter variant of unbalanced chromosomal abnormalities is rarely detected in spontaneous abortions by use of conventional cytogenetic methods. The results were validated by using fluorescent in situ hybridization (FISH) analysis with centromere-specific DNA probes. Embryos with trisomy 10 and monosomy 22 displayed mosaicism with the frequencies of abnormal cell clones constituting 68 and 33% respectively. The advantages and limitations of the applying of CGH technique for detection of genomic abnormalities in both nonmosaic and mosaic forms are discussed.     

Detection of aneuploidy in spontaneous abortions using the comparative hybridization method

Comparative genomic hybridization (CGH) technique was used to examine a set of ten spontaneous abortions whose cell cultures were characterized by the lack of proliferation in vitro, and thereby, were not available for the analysis by means of routine cytogenetic methods. Five abortions (50%) had aneuploidy of autosomes, including trisomy 10, 14, 18, and 21, and monosomy 22. The latter variant of unbalanced chromosomal abnormalities is rarely detected in spontaneous abortions by use of conventional cytogenetic methods. The results were validated by using fluorescent in situ hybridization (FISH) analysis with centromere-specific DNA probes. Embryos with trisomy 10 and monosomy 22 displayed mosaicism with the frequencies of abnormal cell clones constituting 68 and 33% respectively. The advantages and limitations of the applying of CGH technique for detection of genomic abnormalities in both nonmosaic and mosaic forms are discussed.     

Reciprocal syndromes caused by deficiency duplication resulting from maternal t(10;18)(p12;q22) translocation

The detection of a familial translocation, t(10;18)(p12;q22), has made possible the observation in type and countertype of two related persons with opposite chromosomal imbalance: trisomy 18q22----18qter with monosomy 10p12----10pter in one of the two and monosomy 18q22----10pter in the other. In each case the abnormalities attributable to monosomy overrule those attributable to monosomy overrule those attributable to the associated trisomy.     

A cytogenetic study directly from chorionic villi of 140 spontaneous abortions

Summary Spontaneous abortions were studied by analyzing chromosomes directly from chorionic villi. The frequency and the type of anomalies detected among 140 abortuses are in good agreement with those observed by others using conventional tissue cultures. Abnormal karyotypes were found in 48.6% of the cases. Trisomy predominated (66.2%), followed by polyploidy (22.1%), monosomy X (7.4%), and structural anomalies (4.4%). Among the trisomies, the most prevalent were of chromosome 22 (22.2%), 16(22.2%), and 13 (9.5%). The relative frequencies of trisomies, monosomy X, and the different chromosomes involved in trisomies seem to differ between our study and those in which tissue cultures were analyzed. Our low frequency of 45,XO karyotypes and the shift to trisomies of chromosomes whose involvement increases steeply with maternal age are considered due to the approximately 3 year higher mean maternal age in our sample. The sex ratio (male to female) in chromosomally abnormal abortuses was 1.28, which is nearly identical to the 1.2 found in earlier studies. Surprisingly, in chromosomally normal abortions males were significantly outnumbered by females (sex ratio 0.76). Since maternal cell contamination cannot have influenced the sex ratio in our study, we consider it worthwhile to investigate whether failures associated with X inactivation are responsible for pregnancy wastage of some euploid female conceptuses. Knowledge of the karyotypes may serve as a prerequisite for the investigation of non-chromosomal genetic causes of pregnancy wastage.     

Clinical characteristics predicting internal neurofibromas in 357 children with neurofibromatosis-1: results from a cross-selectional study

ABSTRACT: OBJECTIVE: To identify clinical characteristics associated with internal neurofibromas in children with NF1, as a means of ensuring the early identification of patients at high risk for malignant peripheral nerve-sheath tumors developed from preexisting internal neurofibromas.Patients and methodsWe used data from two NF1 populations, in France and North America, respectively. The French database comprised 1083 patients meeting NIH diagnostic criteria for NF1 and the Neurofibromatosis Institute Database of North America comprised 703 patients. Patients younger than 17 years of age were eligible for our study if they had been evaluated for internal neurofibromas using computed tomography and/or magnetic resonance imaging. Clinical characteristics associated with internal neurofibromas by univariate analysis (P [LESS-THAN OR EQUAL TO] 0.15) were entered into a multiple logistic regression model after checking for potential interactions and confounding. Multiple imputation was used for missing values. RESULTS: Among the 746 children in the two databases, 357 (48%) met our inclusion criteria. Their mean age was 7.7 [PLUS-MINUS SIGN] 5.0 years and there were 192 (53.8%) males. Internal neurofibromas were present in 35 (9.8%) patients. Internal neurofibromas developed earlier in females than in males and their prevalence increased during adolescence. Factors independently associated with internal neurofibromas were age (OR = 1.16 [1.07-1.27]), xanthogranulomas (OR = 5.85 [2.18-15.89]) and presence of both subcutaneous and plexiform neurofibromas (OR = 6.80 [1.52-30.44]). CONCLUSIONS: Several easily recognizable clinical characteristics indicate a high risk of internal neurofibromas in children with NF1 and, therefore, a need for very close monitoring.     

Digeorge anomaly associated with partial deletion of chromosome 22. Report of a case with X/22 translocation and review of the literature

Partial monosomy of 22q, resulting from a de novo unbalanced translocation t(X;22)(q28;q11) was detected in a newborn female with manifestations of the DiGeorge anomaly including multiple anomalies, type I truncus arteriosus, T-cell abnormalities, thymic aplasia and parathyroid hypoplasia noted on postmortem examination. Although DiGeorge anomaly is causally heterogeneous, our patient, together with 18 previously known cases, confirm that partial monosomy of the proximal long arm of chromosome 22 is the single most common cause of this polytopic developmental field defect.     

High rate of detection of 13q14 deletion mosaicism among retinoblastoma patients (using more extensive methods)

Summary Using a cell population with a high proportion of early mitotic cells and by examining more cells derived from peripheral lymphocytes, we found three cases with a 13q14 deletion mosaicism among fifteen retinoblastoma patients; one with a de novo 13/18 balanced translocation, and another with a monosomy 13(q13»q21.2 or 21.3). The three patients with a 13q14 deletion mosaicism had sporadic retinoblastoma (two had bilateral and one unilateral retinoblastoma). The results indicate that 13q14 deletion mosaicism plays a major role in the etiology of this tumor.     

Familial translocation t(10;21)(q22;q22)

Summary A family is described with a translocation t(10;21)(q22;q22) transmitted through three generations. This family was studied for the apparition of several miscarriages and two sisters with multiple malformations. Both children had a probably partial trisomy of chromosome 10 and a monosomy of chromosome 21 due to a maternal adjacent-2 meiotic segregation.     

Complete monosomy mosaic of chromosome 21: Case report and review of literature

Complete monosomy mosaic of chromosome 21 is a rare disorder. The syndromic features are highly variable. This study describes a girl of Mexican origin with complete monosomy 21 in mosaicism with novel findings, including cortical atrophy, macrostomia, pectum excavatum and immune deficiencies. Parental karyotypes were normal. FISH analysis with probes from 21q22.1–q22.2 region and centromere of X DNA probe was performed on peripheral blood lymphocytes whereas 21q22.1–q22.2 and 21q, 4p, 4q subtelomeric DNA probes were tested in fibroblasts. We propose that the monosomy 21 mosaicism is the cause of the survival of children with more than 4 months of age.     

A retrospective study of preimplantation embryos diagnosed with monosomy by fluorescence in situ hybridization (FISH)

This report is a retrospective study of preimplantation embryos diagnosed with monosomy for chromosomes 13, 15, 16, 18, 21, 22, X and Y on day 3 to determine the rate of true positives, false positives and/or mosaicism and to assess if these embryos are suitable for in vitro fertilization (IVF) transfer. In a one year period, 80 patients went through preimplantation genetic diagnosis for aneuploidy screening (PGD-AS). Monosomy was diagnosed in 51 embryos. Fluorescence in situ hybridization (FISH) was then performed on the blastomeres at day 5-7 with commercially available probes using the same probe set that initially identified monosomy for chromosomes 13, 16, 21 and 22 or chromosomes 15, 18, X and Y. Based on FISH analysis, the monosomy diagnosed during routine PGD-AS analysis was confirmed in 17 of the 51 embryos. A euploid result for the specific chromosomes tested was observed in 16 of the 51 embryos while mosaicism was found in the remaining 18 embryos. This results in an estimated false positive rate of 3.8% for a diagnosis of monosomy. Reanalysis of these embryos demonstrates that the majority of monosomy diagnoses represents true monosomy or mosaicism and should be excluded for transfer in IVF. Furthermore, improved understanding from recent emerging data regarding the fate of oocytes in women with advanced maternal age undergoing IVF to the development of early embryos may provide a valuable insight into the mechanism of chromosome mosaicism.     

Microphthalmia with linear skin defects syndrome in a mosaic female infant with monosomy for the Xp22 region: molecular analysis of the Xp22 breakpoint and the X-inactivation pattern

This paper describes a female infant with microphthalmia with linear skin defects syndrome (MLS) and monosomy for the Xp22 region. Her clinical features included right microphthalmia and sclerocornea, left corneal opacity, linear red rash and scar-like skin lesion on the nose and cheeks, and absence of the corpus callosum. Cytogenetic studies revealed a 45,X[18]/46,X,r(X)(p22q21) [24]/46,X,del(X)(p22)[58] karyotype. Fluorescence in situ hybridization analysis showed that the ring X chromosome was positive for DXZ1 and XIST and negative for the Xp and Xq telomeric regions, whereas the deleted X chromosome was positive for DXZ1, XIST, and the Xq telomeric region and negative for the Xp telomeric region. Microsatellite analysis for 19 loci at the X-differential region of Xp22 disclosed monosomy for Xp22 involving the critical region for the MLS gene, with the breakpoint between DXS1053 and DXS418. X-inactivation analysis for the methylation status of the PGK gene indicated the presence of inactive normal X chromosomes. The Xp22 deletion of our patient is the largest in MLS patients with molecularly defined Xp22 monosomy. Nevertheless, the result of X-inactivation analysis implies that the normal X chromosomes in the 46,X,del(X)(p22) cell lineage were more or less subject to X-inactivation, because normal X chromosomes in the 45,X and 46,X,r(X)(p22q21) cell lineages are unlikely to undergo X-inactivation. This supports the notion that functional absence of the MLS gene caused by inactivation of the normal X chromosome plays a pivotal role in the development of MLS in patients with Xp22 monosomy. Received: 16 December 1997 / Accepted: 25 February 1998     

Localization of 27 DNA markers to the region of human chromosome 22q11-pter deleted in patients with the DiGeorge syndrome and duplicated in the der22 syndrome

DiGeorge syndrome is a human developmental field defect with the pathological features of an abnormality of embryogenesis at 4 to 6 weeks of gestation. Cytogenetic analyses of patients have revealed a number of instances of monosomy 22q11-pter in this condition. We have analyzed 52 DNA markers that map to 22q11-pter and have found 27 that are deleted in DiGeorge syndrome patients with known monosomy for part of this region and that are duplicated in patients with the der22 syndrome. The set of clones mapping to the DiGeorge region was further assigned to a proximal or a distal location within the deletion.     

A severely mental and motor retarded boy with monosomy 9pter-->p22 trisomy 10q26-->qter due to paternal reciprocal translocation 46,XY,t(9;10)(p23;q26)

We report on a twenty-two months old male patient with hypotonia, mental and motor retardation and trigonocephaly. Standard GTG banding chromosomal analysis (from metaphyses of a periferal blood lymphocyte culture) showed 46,XY, der(9) monosomy 9pter-->p22, trisomy 10q26--> qter karyotype. This unbalanced translocation resulted from the father's t(9,10) (p22;p26) karyotype. Deletions of the terminal part of 9p and partial trisomy of chromosome 10q are rare chromosomal disorders. To our knowledge, this is the first case report in the literature of a deletion of 9pter-->p22.3 and a duplication of 10q26-->qter. We assume that the clinical anomalies are due to der(9) monosomy 9pter-->p22, trisomy 10q-->26qter.     

Different Patterns of Mast Cells Distinguish Diffuse from Encapsulated Neurofibromas in Patients with Neurofibromatosis 1

Multiple neurofibromas are cardinal features of neurofibromatosis 1 (NF1). Several different types of NF1-associated neurofibromas occur, each distinct in terms of pathological details, clinical presentation, and natural history. Mast cells are present in most neurofibromas and have been shown to be critical to the origin and progression of neurofibromas in both human NF1 and relevant mouse models. In this investigation, the authors determined whether mast cell involvement is the same for all types of NF1-associated neurofibromas. They examined the density and distribution of mast cells within 49 NF1-associated neurofibromas classified histopathologically as diffuse or encapsulated on the basis of the presence or absence of the perineurium or its constituent cells. They made two observations: (1) Diffuse neurofibromas had significantly higher densities of mast cells than did encapsulated neurofibromas, and (2) mast cells were evenly distributed throughout diffuse neurofibromas but were primarily restricted to the periphery of encapsulated neurofibromas. The differences in mast cell density and distribution differentiate the two basic types of NF1-associated neurofibromas, suggesting that the pathogenesis of diffuse and encapsulated neurofibromas may be significantly different.     

Familial DiGeorge syndrome and associated partial monosomy of chromosome 22

Summary Partial monosomy of 22q due to an unbalanced 4;22 translocation was seen in a 2-month-old male with Type I truncus arterious, dysmorphic features, and T-cell abnormalities. The family history revealed a previous sib with Type I truncus arteriosus, thymic aplasia, and parathyroid hypoplasia noted on postmortem examination, consistent with DiGeorge syndrome. Evaluation of the asymptomatic mother of these two patients revealed partial T-cell deficiency and the same unbalanced translocation with deletion of proximal 22qll. These findings provide further evidence that some cases of complete or partial DiGeorge syndrome are associated with monosomy of the proximal long arm of chromosome 22, and they may explain many, if not all, familial cases of the syndrome.Supported in part by National Foundation-March of Dimes Grant No. 2-161/C-331. Funds from the Texas Department of Health through PL94-278 National Genetic Diseases Act, from the Robert J. Kleberg, Jr. Center for Human Genetics, and USPHS Grant No. RR-05425.