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PubMed2005

Another small supernumerary marker chromosome (sSMC) derived from chromosome 2: towards a genotype/phenotype correlation.

Here we report a prenatally detected small supernumerary marker chromosome (sSMC) derived from chromosome 2 as demonstrated by cenM-FISH (centromere-specific multicolor fluorescence in situ hybridization). By application of a recently described subcentromere-specific probe set (subcenM-FISH) for chromosome 2, the presence of a small partial trisomy due to a karyotype 47,XX,+r(2)(::p11.1->q11.2::) was demonstrated. Including this case, a total of 11 patients with sSMC(2) are described throughout the literature. Based on that data, a first genotype/phenotype correlation according to the size and structure of the marker is suggested.

Chromosomes, Human, Pair 2↗
PubMed2002

Current developments in human molecular cytogenetic techniques.

In the last decade a variety of fluorescence in situ hybridization (FISH) assays have been developed. In this paper we present an overview on the currently available methods in molecular cytogenetics, highlighting their advantages and limitations, as well as their applications. Even though one has to be impressed by the total number of new techniques introduced in molecular cytogenetics, one has to be aware of the fact that it is not the brilliance of a technique that is important but the scientific question that can be addressed by it. In this review special emphasis has given in describing possible strategies for the characterization of marker and derivative chromosomes in tumor- and clinical cytogenetics.

Centromere↗
PubMed2002

[Confined placental mosaicism: definition, consequences and outcome].

Confined placental mosaicism (CPM) occurs in approximately 2 per cent of viable pregnancies studies by chorionic villus sampling. The great majority of pregnancies with confined placental mosaicism proceed uneventfully, resulting in normal liveborn infants. However, a few specific chromosomal abnormalities have been associated with fetal growth retardation. Fetal karyotype should be checked by amniocentesis and such pregnancies should have careful ultrasound follow-up.

Amniocentesis↗
PubMed2002

[Transient neonatal diabetes associated with uniparental isodisomy of chromosome 6].

A female neonate was born after a 37.4-week pregnancy to a healthy primipara. There was a family history of diabetes on the father's side. The neonate's birth weight was 1,955 g and she was 43 cm long. Physical examination showed bilateral palpebral edema, macroglossia, umbilical hernia and abdominal distension. At 29 hours of life she presented hyperglycemia without acidosis or ketosis. Insulin treatment was started and maintained intermittently until 38 days of life. The patient presented anemia from the second day of life, which required iron therapy and blood transfusion one month after birth. The karyotype was 46, XX with paternal uniparental isodisomy of chromosome 6. Paternal uniparental isodisomy of chromosome 6 has been described as the pathogenic mechanism of transient neonatal diabetes, which provides evidence for an imprinted gene exclusively of paternal expression. In paternal isodisomy (as in regional duplications) there is overexpression due to the existence of two functional copies of the gene, which is responsible for transient neonatal diabetes mellitus. Transient neonatal diabetes associated with macroglossia, umbilical hernia and anemia has been described in only a few cases.

Chromosomes, Human, Pair 6↗
PubMed2003

[Monogenic hereditary diseases].

Monogenic disorders are caused by the inheritance of single gene mutations; alternatively, a monogenic disorder arises as a consequence of a de novo mutation in either the paternal or maternal germ line. The exponential increase in our understanding of the human genome has resulted in the localisation and cloning of a vast number of disease genes which has enabled the precise characterization of the underlying molecular defect in many of these disorders. Single nucleotide substitutions and microdeletions are the major types of disease-related mutations, but more complex mutations have also been described.

Genes, Dominant↗
PubMed2003

[The frequency of heteroploidy in spermatozoa of patients with infertility].

The incidence of heteroploid spermatozoa was studied by mono- and dual-colored fluorescence in situ hybridization in semen samples from donors and patients with normal and impaired spermatogenesis. The frequency of heteroploid sperm in the ejaculate was linearly and inversely correlated with sperm parameters (sperm concentration in the ejaculate and proportion of motile and morphologically normal spermatozoa). The level of heterploidy was the most significant in the semen samples from patients with oligoasthenoteratospermia and oligoasthenospermia.

Chromosomes, Human, Pair 18↗
PubMed2005

Analysis of the characteristics of epilepsy in 37 patients with the molecular diagnosis of Angelman syndrome.

Angelman syndrome is a genetic disorder caused by defects in the maternally inherited imprinted domain located on chromosome 15q11-q13. Most patients with Angelman syndrome present with severe mental retardation, characteristic physical appearance, behavioral traits, and severe, early-onset epilepsy. We retrospectively reviewed the medical histories of 37 patients, all with the molecular diagnosis of Angelman syndrome and at least three years of follow-up in our neurology department, for further information about their epilepsy: age of onset, type of seizures initially and during follow-up, EEG recordings, treatments and response. The molecular studies showed 87% deletions de novo, 8% uniparental, paternal disomy, and 5% imprinting defects. The median age at diagnosis was 6.5 years, with 20% having begun to manifest febrile seizures at an average age of 1.9 years. Nearly all (95%) presented with epilepsy, the majority under the age of three (76%). The most frequent seizure types were myoclonic, atonic, generalized tonic-clonic and atypical absences. At onset, two patients exhibited West syndrome. EEG recordings typical of Angelman syndrome were found in 68%. Normalization of EEG appeared in 12 patients after nine years. Control of epileptic seizures improved after the age of 8.5 years. The most effective treatments were valproic acid and clonazepam. We conclude that epilepsy was present in nearly all of our cases with Angelman syndrome, and that the EEG can be a useful diagnostic tool. On comparing the severity of epilepsy with the type of genetic alteration, we did not find any statistically significant correlations.

Adolescent↗
PubMed1996

Kabuki syndrome in son and low grade mosaic 45,X/46,XX in mother.

We report on a two-year-old boy with Kabuk syndrome and a normal male karyotype whose mother is a low grade mosaic 45,X/46,XX. We hypothesized that the son's Kabuki syndrome might have been caused by gonosomal uniparental (paternal) disomy DNA analysis proved this hypothesis to be incorrect. A review of twelve patients with Kabuki syndrome or Kabuki-syndrome-like features and chromosome abnormalities is presented.

Abnormalities, Multiple↗
PubMed1998

Isolated hemihyperplasia (hemihypertrophy): report of a prospective multicenter study of the incidence of neoplasia and review.

Hemihyperplasia is characterized by asymmetric growth of cranium, face, trunk, limbs, and/or digits, with or without visceral involvement. It may be an isolated finding in an otherwise normal individual, or it may occur in several syndromes. Although isolated hemihyperplasia (IHH) is of unknown cause, it may represent one end of the clinical spectrum of the Wiedemann-Beckwith syndrome (WBS). Uniparental paternal disomy of 11p15.5 or altered expression of insulin-like growth factor 2 (IGF2) from the normally silent maternal allele have been implicated as causes of some cases of WBS. IHH and other mild manifestations of WBS may represent patchy overexpression of the IGF2 gene following defective imprinting in a mosaic fashion. The natural history of IHH varies markedly. An association among many overgrowth syndromes and a predisposition to neoplasia is well recognized. Heretofore the risk for tumor development in children with IHH was unknown. We report on the results of a prospective multicenter clinical study of the incidence and nature of neoplasia in children evaluated because of IHH. One hundred sixty-eight patients were ascertained. A total of 10 tumors developed in nine patients, for an overall incidence of 5.9%. Tumors were of embryonal origin (similar to those noted in other overgrowth disorders), including Wilms tumor, hepatoblastoma, adrenal cell carcinoma, and leiomyosarcoma of the small bowel in one case. These data support a tumor surveillance protocol for children with IHH similar to that performed in other syndromes associated with overgrowth.

Humans↗
PubMed2004

Interactions between imprinting effects in the mouse.

Mice with uniparental partial or complete disomies for any one of 11 identified chromosomes show abnormal phenotypes. The abnormalities, or imprinting effects, can be attributable to an incorrect dosage of maternal or paternal copies of imprinted gene(s) located within the regions involved. Here we show that combinations of partial disomies may result in interactions between imprinting effects that seemingly independently affect fetal and/or placental growth in different ways or modify neonatal and postnatal imprinting effects. Candidate genes within the regions have been identified. The findings are generally in accord with the "conflict hypothesis" for the evolution of genomic imprinting but do not clearly demonstrate common growth axes within which imprinted genes may interact. Instead, it would seem that any gene that represses or limits embryonic/fetal growth to the advantage of the mother--by any developmental means--will have been subject to evolutionary selection for paternal allele repression. Likewise, any gene that favors embryonic/fetal development at consequent cost to the mother--by any developmental means--will have faced selection for maternal allele repression. The classical Igf2-Igf2r axis may therefore be unique. The findings involve reinterpretation of older imprinting data and consequently revision of the mouse imprinting map.

Amidinotransferases↗
PubMed1995

Mosaicism for trisomy 12: four cases with varying outcomes.

Trisomy 12 observed in chorionic villus sampling (CVS) may reflect generalized mosaicism or indicate mosaicism confined to only the placenta. In this report, four cases of trisomy 12 observed in CVS or cultured placental biopsies with varying outcomes are presented. Seven dinucleotide repeat polymorphisms for chromosome 12 were used to determine the chromosome 12 origins in the fetus or child and to delineate the mechanism(s) that gave rise to the trisomy. In two cases (cases A and C), the mosaicism was confined to the placenta, resulting in normal liveborns. Although, in one case, the molecular results suggested an apparent duplication of one paternal chromosome 12 in the placenta, normal biparental inheritance was found in the diploid fetal cell line in both cases. In two other cases (cases B and D), trisomy 12 was observed in both extraembryonic and fetal tissues. In one of these pregnancies, a child was born by Caesarean section at 37 weeks because of intrauterine growth retardation and oligohydramnios, and resulted in neonatal death. Molecular markers and fluorescence in situ hybridization (FISH) revealed low-level trisomy 12 mosaicism in the spleen. In the fourth case, fetal abnormalities were detected on ultrasound and low-level trisomy 12 mosaicism was observed in amniotic fluid cells using conventional cytogenetics and FISH. Molecular markers revealed a maternal meiosis I non-disjunction of chromosome 12 in DNA from a cultured placental biopsy. Although predicting the outcomes of pregnancies involving confined placental mosaicism remains difficult, molecular techniques are valuable tools for distinguishing uniparental from biparental disomy and mechanisms of mosaicism.

Adult↗
PubMed2003

Postzygotic diploidization of triploids as a source of unusual cases of mosaicism, chimerism and twinning.

Triploidy is one of the most frequent chromosomal errors responsible for reproduction failure. This paper encompasses, in one conceptual frame, four recent findings in reproduction biology: predominant dispermic origin of triploids, paternal centrosome inheritance, eccentric cleavage divisions of dispermic triploid zygotes and certain intricate cases of mosaicism/chimerism. It is argued that dispermic zygotes, in contrast to digynic ones, are characterized by cytogenetic phenomenon described here as postzygotic diploidization of triploids (PDT). PDT embraces three main developmental scenarios: (i) the maintenance of the triploid state accompanied by regular segregation of 2n cells and the 2n/3n mixoploid populations; (ii) immediate diploidization with elimination of an odd haploid set of chromosomes and regular appearance of 1n/2n, 2n/3n and other mixoploids and (iii) tripolar spindle formation leading to gross aneuploidy, cell death with occasional survival of 2n+1 or 2n+1+1 trisomics and uniparental disomics. According to the PDT concept, a trisomy and disomy might occur due to generalized karyotype instability of dispermic triploids. PDT may provide a natural explanation for the regular appearance of 2n homozygous androgenic moles, various 2n/3n, 2n/2n molar/twin complexes without necessitating the concept of the 'empty' oocyte fertilization. Convincing evidence for a reservoir of anuclear oocytes does not exist. Peculiar implications are expected in the case of two rounds of diploidizations or involvement of triploid cell derivatives in the twinning process. Cryptic mosaic/chimeras and unusual twins intermediate between monozygotic (MZ) and dizygotic (DZ) are expected. Thus, PDT could have an explanation for the broad spectrum of odd reproductive cytogenetic events and might provide additional alternatives and definite predictions.

Chimera↗
PubMed2004

Analysis of imprinting in mice with uniparental duplication of proximal chromosomes 7 and 15 by use of a custom oligonucleotide microarray.

We have developed an imprinting assay combining the use of mice carrying maternal or paternal duplication of chromosomal regions of interest with custom oligonucleotide microarrays. As a model system, we analyzed RNA from CNS tissue of neonatal mice carrying the reciprocal translocation T(7;15)9H and uniparental duplication of proximal Chr 7 and 15. The duplicated region includes the locus on proximal Chr 7 corresponding to the human Prader-Willi/Angelman Syndrome. The microarray contained 322 oligonucleotides, including probes to detect major genes involved in neural excitability and synaptic transmission, as well as known imprinted genes mapping to proximal Chr 7: Ndn, Snrpn, Mkrn3, Magel2, Peg3, and Ube3a. Imprinting of these genes in neonatal cortex and cerebellum was first confirmed by quantitative RT-PCR. Their inclusion on the microarray thus provided positive controls for evaluating the effect of background on the sensitivity of the assay, and for establishing the minimum level of expression required to detect imprinting. Our analysis extended previous work by revealing bi-allelic expression in CNS tissue of those queried genes mapping to proximal Chr 7 or 15, including the Gabrb3 gene, for which there have been conflicting reports. Microarray analysis also revealed no effect of the maternal or paternal disomy on expression levels of the unlinked genes detected, including those potentially implicated in the Prader-Willi or Angelman Syndrome. In addition, quantitative RT-PCR revealed a gene dosage effect in both cerebellum and cortex for all of the known imprinted genes assayed, except for Ube3a in cerebellum.

Animals↗