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PubMed1990

Confined placental mosaicism and intrauterine development.

Confined placental chromosomal mosaicism can be detected in 1-2% of pregnancies studied by chorionic villus sampling at 9-12 weeks of gestation. It is more commonly found in the cytotrophoblast than in placental connective tissue. Aneuploid conceptions are more likely to have confined chromosomal mosaicism than euploid ones. Although intrauterine survival of chromosomally abnormal embryos and fetuses appears to be significantly enhanced by placental mosaicism, the effect of placental mosaicism on chromosomally normal fetuses is variable and, at the present time, still unpredictable.

Abortion, Missed↗
PubMed1976

[Mutagenic effect of radiation on mice, subjected to gamma-irradiation during the embryonic period. III. Frequency of coat color mosaics among mice, heterozygous for recessive mutations, subjected to irradiation during the early periods of embryogenesis].

The frequency of coat colour and coat length mosaics was investigated among heterozygous for 7 or 6 recessive mutations mice, that were gamma-irradiated at doses of 100 or 200 r at different stages of embryogenesis. Only 4 mosaics with gray coat spots were found among 1399 animals that developed from embryos irradiated at doses of 100--200 r within 4,5--13,5 days of embryogenesis. 3 of these mosaics were found among 756 animals irradiated at the dose of 100 r at the 10,5 day of embryogenesis (0,35%). This frequency is considerably lower that the frequency of coat colour mosaics obtained by other authors in similar experiments.

Animals↗
PubMed1999

[Somatic mosaicism of expanded CAG trinucleotide repeat in the neural and nonneural tissues of Machado-Joseph disease (MJD)].

The tissue-specific pattern of somatic mosaicism in Machado-Joseph disease (MJD) was reviewed. In the MJD central nervous system (CNS) tissues, the pattern of CAG repeat mosaicism in the mutant allele was similar among various portions except cerebellar cortex which had slightly smaller CAG repeat tracts. Among nonneural tissues, the muscle exhibited a lesser degree of CAG instability, while the liver, kidney and colon displayed a greater diversity of extra bands and more extended major band compared to CNS. Thus, mitotic turnover may contribute largely to the tissue-specific pattern of mosaicism in MJD, but other unknown cell specific factors should be taken into consideration for the understanding the mechanism of somatic mosaicism in CAG repeat diseases.

Animals↗
PubMed1999

[Somatic mosaicism of CAG repeats size in the nervous system of dentatorubral-pallidoluysian atrophy (DRPLA)].

The somatic mosaicism of CAG repeat expansion in the neural tissues of a dentatorubral-pallidoluysian atrophy (DRPLA) was reviewed. The size of the major bands of the expanded allele was significantly smaller in the cerebellar cortex, however no significant difference was recognized in other regions of neuronal tissues. This showed that severity of neuropathological involvement in DRPLA is not parallel to the size of the expanded allele, indicating somatic mosaicism doesn't explain the selective neurodegeneration in DRPLA. The mechanism underlying the somatic mosaicism remains unknown. However, somatic CAG instability, cell division and some tissue specific factors may closely relate to the occurrence of the somatic mosaicism.

Anticipation, Genetic↗
PubMed1999

Trisomy/tetrasomy 21 mosaicism in CVS: interpretation of cytogenetic discrepancies between placental and fetal chromosome complements.

Trisomy/tetrasomy 21 mosaicism was found in chorionic villi (semidirect preparation) obtained from a 40 year old pregnant woman. Since both cell lines were abnormal, the couple elected for pregnancy termination. Placenta and fetal tissue samples were obtained for cytogenetic study. Long term cultured villi showed a non-mosaic trisomy 21 karyotype, while other tissues showed either a normal karyotype or normal/trisomy21 mosaicism. These discrepancies could be explained by a modified "bottle neck" embryogenic model with a trisomic zygote and a non-disjunction event taking place in one of the first divisions. Our case emphasises the need for confirmatory studies in other tissues when mosaicism is encountered in chorionic villi, even if all cell lines are abnormal.

Adult↗
PubMed1999

Mosaicism for a full mutation and a normal size allele in two fragile X males.

Confirmation of the clinical diagnosis of fragile X syndrome by molecular tests is based on both the presence of a full mutation and methylation of the promotor region of the FMR1 gene. The mechanism leading to mosaic alleles of repeat number and the role of methylation in this process is still under discussion. We report two cases of males who show mosaic patterns for both number of CGG repeats and methylation status. In the first patient, a mosaic pattern of a normal allele of 34+/-1 CGGs, a borderline premutation/full mutation, and a full mutation was observed. The mother exhibited alleles of 30+/-1 and approximately 100 CGGs. The second patient was mosaic for a normal allele of 47+/-1 CGGs and a full mutation. His mother carried alleles of 40+/-1 and approximately 100 CGGs. Chromosomal analysis in the patients showed normal male karyotypes with no evidence that they had inherited both maternal X chromosomes. Furthermore, haplotyping excluded disomy of the repeat flanking region in these patients. So far, it is not clear whether the normal alleles in the patients, leukocytes of 34 and 47 CGGs, respectively, may be caused by the contraction of the maternal premutations of 100 CGGs or be caused by the deletion from the full mutation alleles.

Blotting, Southern↗
PubMed1999

Direct androgenic regulation of calcitonin gene-related peptide expression in motoneurons of rats with mosaic androgen insensitivity.

The spinal nucleus of the bulbocavernosus (SNB) and its target muscles, bulbocavernosus and levator ani (BC/LA), form a sexually dimorphic neuromuscular circuit whose development and maintenance are androgen-dependent. The mechanisms whereby androgen regulates gene expression in the SNB of adult rats are largely unknown, although a retrograde influence from the BC/LA muscles has been suggested to underlie the suppression of calcitonin gene-related peptide (CGRP) expression observed in SNB motoneurons after systemic androgen treatment. A mosaic paradigm was used to determine the site of action of androgen in the regulation of CGRP expression in SNB motoneurons. As a consequence of random X chromosome inactivation, androgenized female rats heterozygous for the tfm androgen receptor (AR) mutation (XwtXtfm-mosaics) express a mosaic of androgen-sensitive and androgen-insensitive motoneurons in the SNB, whereas the BC/LA target musculature appears to be uniformly sensitive to androgens. In adult mosaics, testosterone administration resulted in a reduction in the proportion of androgen-sensitive cells expressing CGRP, whereas no such reduction was observed in the androgen-insensitive population, indicating that neuronal AR plays an essential role in the neuromuscular regulation of CGRP expression in these motoneurons. This provides the first in vivo demonstration of AR regulation of gene expression unambiguously localized to a neuronal population.

Androgen-Insensitivity Syndrome↗
PubMed1999

Variable levels of mosaicism for trisomy 21 in a non-immune hydropic infant with chylothorax.

We report the first case of mosaic trisomy 21 with non-immune hydrops fetalis and bilateral chylothoraces. Prenatal fetal blood karyotype analysis of 15 fetal cells revealed a 46,XX karyotype. Aggressive prenatal management, including fetal thoracocentesis and pleuro-amniotic shunt, was performed. A clinical phenotype of Down syndrome was apparent after the gross oedema had subsided. Subsequent chromosome study of neonatal blood lymphocytes showed mosaic trisomy 21 with 23 per cent trisomic cells. Review of the initial fetal blood sample identified trisomy in 5 per cent of 134 cells. Follow-up study at five months showed no trisomy 21 in 100 cells. This case illustrates the variable levels of mosaicism manifest in the peripheral blood of an infant with obvious Down syndrome phenotype, and the limitation of cytogenetic analysis of peripheral lymphocytes alone in prenatal and postnatal detection of low levels of mosaicism.

Adult↗
PubMed1999

[Detection of mosaicism in women with Turner's syndrome using fluorescence in situ hybridization].

BACKGROUND: According to the literature approximately 50% of patients with Turner's syndrome have karyotype 45,X in every cell, the rest have two or more cell lines with mosaics of sex chromosomes. New methods have shown that the mosaicism is probably more frequent than expected from classical cytogenetics examinations. The aim of this study was to detect numerical changes of sex chromosomes in mitoses and interphase nuclei of cultivated peripheral lymphocytes of patients with Turner's syndrome by means of FISH, to compare the sensitivity of classical and molecular-cytogenetic methods and to estimate the values obtained in 10 control healthy females with karyotype 46,XX. METHODS AND RESULTS: 18 females with Turner's syndrome were examined. Karyotype 45,X was found by classical cytogenetics in all cells of 9 females. The 9 remaining patients had sex chromosome mosaicism of two or more clones. In all patients FISH confirmed the results of classical cytogenetic methods and in 6 patients (30%) it revealed other clones previously not detected. CONCLUSIONS: Higher sensitivity of FISH enables more precise detection of mosaicism of cell lines than classical cytogenetics and this technique is more suitable for examinations of patients with Turner' syndrome.

Adult↗
PubMed2000

[Position effect variegation of the mosaic type, arising as a result of transposition AR4-24P[white, rosy] in the Drosophila melanogaster genome].

A line with the mosaic expression of the white+ transgene was obtained by inducing transposition of the AR4-24P[white, rosy] transposon and was used for the second round of induction. As a result, 57 lines with the mosaic eye pigmentation were obtained. In situ hybridization and Southern blotting showed that genomic DNA fragments flanking AR4-24 were, in some cases, transposed together with the transposon. A spontaneous loss of these fragments resulted in reversion to the wild-type phenotype. The mosaic eye pigmentation in a line that carried the AR4-24 transposon flanked with the same fragments in region 24D1-2 was not affected by the Su(var)3-6 gene modifying position effect variegation (PEV). Other PEV modifiers, Su(var)3-9 and Su(var)2-5, had only a slight effect on PEV; Su(var)3-7 restored the wild-type phenotype. The genomic fragments captured by the transposon may contain DNA sequences that autonomously induce mosaic PEV of the white gene.

Animals↗
PubMed2000

Blaschkolinear skin pigmentary variation due to trisomy 7 mosaicism.

Mosaic trisomy 7 is a rare condition that can be seen in individuals with Blaschkolinear skin pigmentary variation, somatic asymmetry, and variable other clinical anomalies. In any patient presenting with Blaschkolinear skin pigmentary variation, varying degrees of asymmetrical growth disturbance, developmental delay, and a normal lymphocytic karyotype, chromosomal mosaicism may be present. To rule out tissue-specific or occult chromosomal mosaicism, it is recommended to culture and karyotype skin fibroblasts, since lymphocyte cell lines may not demonstrate the abnormal cell line. Early diagnosis is of paramount importance, since early physical, occupational, and speech/language therapy can greatly improve the developmental outcome of these patients. We report on a fourth patient with trisomy 7 mosaicism in whom early diagnosis and developmental therapy contributed to an improved developmental outcome when compared with patients in previous reports. Early intervention can greatly benefit patients with this diagnosis, especially in minimizing the aggressive behavior associated with communication difficulties. Our patient has milder manifestations than the previously reported patients with no seizure activity or asymmetry and fewer cells with trisomy 7.

Adult↗
PubMed2001

Neuronal size in the spinal nucleus of the bulbocavernosus: direct modulation by androgen in rats with mosaic androgen insensitivity.

The motoneurons of the spinal nucleus of the bulbocavernosus (SNB) and its target muscles, the bulbocavernosus and levator ani, form a sexually dimorphic circuit that is developmentally dependent on androgen exposure and exhibits numerous structural and functional changes in response to androgen exposure in adulthood. Castration of male adult rats causes shrinkage of SNB somata, and testosterone replacement reverses this effect, but the site at which androgen is acting to cause this change is undetermined. We exploited the X-chromosome residency of the androgen receptor (AR) gene to generate androgenized female rats that were heterozygous for the testicular feminization mutant (tfm) AR mutation and that, as a consequence of ontogenetic random X-inactivation, expressed a blend of androgen-sensitive wild-type cells and tfm-affected androgen-insensitive cells in the SNB. Chronic testosterone treatment of adult mosaics increased soma sizes only in androgen-competent wild-type SNB cells. The size of tfm-affected SNB somata in the same animals did not differ from the size of either the wild-type or tfm-affected SNB neurons in control mosaics that did not receive androgen treatment in adulthood. Because the muscle targets of the SNB are known to be uniformly androgen-sensitive in tfm mosaics, this mosaic analysis provides unambiguous evidence that androgenic effects on motoneuron soma size are mediated locally in the SNB. It is possible that the neuronal AR plays a permissive role in coordinating the actions of androgen.

Androgen-Insensitivity Syndrome↗
PubMed1999

[Dual color fluorescent in-situ hybridization detects sex chromosome mosaicism in human embryos].

OBJECTIVE: Using dual color fluorescent in-situ hybridization (FISH) to detect sex chromosome mosaicism in human embryos and perform preimplantation gender diagnosis. METHODS: Three abnormal fertilized embryos and 18 normal fertilized embryos which were not suitable for embryo transfer and cryopreservation were analyzed by dual color fluorescent in-situ hybridization. RESULTS: Mosaicism analysis was performed on 14 normal fertilized embryos, which had more than two cells. Nine embryos had sex chromosome mosaicism. XO in male and female embryos cells were 12% and 14% respectively. CONCLUSION: Identification of sex by FISH analysis of a single cleavage cell is accurate, and sex chromosome mosaicism will not affect preimplantation gender diagnosis.

Embryo Transfer↗
PubMedDate not supplied

Sectorial mosaics in the domestic pigeion: 25 more years.

The hypothesis of bipaternity--incorporation of tissue derived from supernumerary sperms into an embryo--to explain the origin of sectorial mosaicism in pigeons was advanced in 1949. Since then, 182 additional examples have come to my attention. Only one was reported to be a gynandromorph; sex ratios generally have been near 1 : 1. No environmental variable has shown significant relation to the origin of the mosaics, and only a slight familial tendency has been indicated. At least 15 color and pattern mutants have been involved, usually contrasting only two alleles. The frequency and its use in crosses. Complex mosaics, involving two or more loci in the contrasts numbered at least 38 cases, of which 11 are examined in more detail, and 6 shown in photographs. Several instances of germinal as well as somatic mosaicism were demonstrated by progeny tests. The bipaternity hypothesis has not been ruled out by evidence in any case.

Alleles↗
PubMed2002

An unusual human mosaic for skin pigmentation.

Patterned pigmentary disturbances are seen in a large variety of human genetic disorders. Cytogenetic studies have provided evidence that such skin lesions often reflect chromosomal mosaicism. In addition to the well-known pattern of Blaschko's lines a classification of several distinct types was proposed by Happle. This report add the case of a boy with an unusual mosaic-like distribution of skin pigmentation and a further chromosomal anomaly which has not been described in pigmentary mosaicism previously. The proband was born after an uneventful pregnancy and delivery. Developmental milestones were delayed. A generalised hirsutism was noted with a facial dysmorphia: coarse facies. short philtrum, synophris, and large low set years. Hyperpigmentation followed a checkerboard pattern: alternating squares of pigmentary anomalies with a sharp midline separation. Cytogenetic findings Included a normal karyotype (peripheral blood) and a mosaicism 12q;14q translocation (70% of fibroblasts). The present case stresses the importance of careful chromosomal analysis of different tissues in patients with pigmentary anomalies.

Child, Preschool↗
PubMed2002

[Chromosomal mosaicism in the placenta].

Chromosomal mosaicism is when two (or more) cell lines with different chromosomal complements are found within one individual. Mosaicism can be found in all tissues but may also be confined to a specific tissue. During pregnancy the aberrant cell line, often with a trisomy, may be confined to the placenta. In prenatal diagnosis, more specifically in chorionic villus sampling, this can interfere with the results and may necessitate follow-up investigation with amniotic fluid cell culture. Confined placental mosaicism can have no visible effect whatsoever on foetal development, but can also lead to serious foetal problems, depending on the chromosome involved. Uniparental disomy in the diploid cell line of the mosaicism may also have a negative effect on the foetal phenotype. In the case of the reverse situation, where the normal diploid cell line is confined to the placenta and the foetus has trisomy 13 or 18, it has been suggested that the diploid cell line might play a role in intrauterine survival; a recent study by the present authors could not confirm this view.

Chorionic Villi Sampling↗
PubMed2003

Low level of mosaicism in atypical Prader Willi syndrome: detection using fluorescent in situ hybridization.

Prader Willi syndrome (PWS) most commonly is due to paternal micro-deletion of 15q11-q13. Although PWS is not a rare condition, mosaic micro-deletion cases are reported rarely. FISH using PWS micro-deletion probe is the most useful method to detect deletion including mosaicism. In this report we describe a female child with clinical features of atypical PWS and FISH analysis showing mosaicism for deletion in the PWS critical region. This is first mosaic deletion case of PWS from Indian subcontinent.

Child↗
PubMed2004

[Prospects and applications of innovated quantitative fluorescent PCR (IQF PCR) in analyses of genetic mosaics using gonosomal sequences].

BACKGROUND: Quantification of fluorescence labelled PCR products on capillary electrophoresis (QF PCR) has limits primarily in the possibility of more sensitive analyses to detect minority cell lines and small time related variations. PCR efficiency and human factor affect measuring error and reproducibility of results in these cases. The aim of this work was to assess and optimise of innovated (I)QF PCR in quantification of Y sequences in gonosomal mosaics. METHODS AND RESULTS: Artificially prepared Y/X mosaics were tested and quantified by IQF PCR, which replaces real-time PCR. Comparison of relative fluorescence to PCR cycles in different Y/X dilutions was plotted on the graphs. Calibration curve for Y sequences quantification was set by the analyses of ratio of Y/X fluorescent signals. An empirical formula was created for the rare mosaic calculation. CONCLUSIONS: QF PCR refined by manual real-time PCR eliminates limits of QF PCR and specifies quantitative analyses based on PCR. The outstanding feature of IQF PCR is its high sensitivity and accuracy in quantification of Y/X gonosomal mosaics.

Cell Line↗