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PubMed1999

Molecular characterization and interviral relationships of a flexuous filamentous virus causing mosaic disease of sugarcane (Saccharum officinarum L.) in India.

A virus isolate causing mosaic disease of commercial sugarcane was purified to homogeneity. Electron microscopy revealed flexuous filamentous virus particles of ca 890 x 15 nm. The virus isolate reacted positively with heterologous antiserum to narcissus latent virus form UK, but failed to react with potyvirus group specific antiserum. N-terminal sequencing of the intact coat protein (CP) and the tryptic peptides indicated that the virus was probably a potyvirus but distinct from several reported potyviruses. Comparison of the 3'-terminal 1084 nucleotide sequence of the RNA genome of this virus revealed 93.6% sequence identity in the coat protein coding region with the recently described sugarcane streak mosaic virus (Pakistani isolate). The molecular weight of the coat protein (40 kDa) was higher than that deduced from the amino acid sequence (34 kDa). The apparent increase in size was shown to be due to glycosylation of the coat protein which has not been reported thus far in the family, Potyviridae. This is the first report on the molecular characterization of a virus causing mosaic disease of sugarcane in India and the results demonstrate that the virus is a strain of sugarcane streak mosaic virus, a member of the Tritimovirus genus of the Potyviridae. We have named it sugarcane streak mosaic virus--Andhra Pradesh isolate (SCSMV-AP).

Amino Acid Sequence↗
PubMed2006

Uncovering the post-embryonic role of embryo essential genes in Arabidopsis using the controlled induction of visibly marked genetic mosaics: EMB506, an illustration.

The embryo essential gene EMB506 plays a crucial role in the transition of the Arabidopsis embryo from radial symmetry to bilateral symmetry just prior to the early heart stage of development. In addition to influencing embryo development EMB506 also affects chloroplast biogenesis. To further investigate the role of EMB506 gene expression in Arabidopsis we have generated green fluorescent protein (GFP) marked emb506 mosaic sectors at temporally defined stages during embryogenesis and additionally during various stages of vegetative growth, in otherwise phenotypically wild-type plants. We confirm the essential requirement for EMB506 gene expression in chloroplast biogenesis as reflected by the decreased chlorophyll content in emb506 mosaic sectors. We also show that the influence of EMB506 gene expression as it impinges on chloroplast biogenesis is first relevant at an intermediate stage in embryogenesis and that the role of EMB506 gene expression in chloroplast biogenesis is distinct from the essential role of EMB506 gene expression during early embryo development. By inducing emb506 mosaicism after the essential requirement for EMB506 gene expression in embryogenesis and also during vegetative growth we reveal that EMB506 gene expression additionally is required for correct cotyledon-, true leaf- and cauline leaf margin development. The strategy that we describe can be tailored to the mosaic analysis of any cloned EMB gene for which a corresponding mutant exists and can be applied to the mosaic analysis of mutant lethal genes in general.

Arabidopsis↗
PubMed1977

Production of mosaic lethals in different germ cell stages of drosophila by N-methyl-N'-nitro-N-nitrosoguanidine.

The delayed effect of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in Drosophila melanogaster by the proportion of mosaic progeny produced after this treatment. Following injection of the chemical into wild type males, complete and mosaic sex-linked recessive lethals were scored by the Muller-5 method, in five successive broods representing the different stages of spermatogenesis. All broods showed significant increase over the control in the frequencies of complete lethals with gradual decrease in mutation rate from the post-meiotic stages to the pre-meiotic ones. In the case of mosaic lethals, too, the post-meiotic stages were generally more sensitive; but the increase over the control was significant only for the mature spermatozoa. The extension of the experiment to F4 generation showed that a mosaic F1 female may produce further mosaic progeny. The production of lethal mutations in successive generations after treatment with MNNG supports the view that chemically induced instabilities can be transmitted as such over several generations.

Animals↗
PubMed1990

The frequency of dominant cataract and recessive specific-locus mutations and mutation mosaics in F1 mice derived from post-spermatogonial treatment with ethylnitrosourea.

The frequency of dominant cataract and recessive specific-locus mutations and mutation mosaics was determined in F1 mice derived from post-spermatogonial germ-cell stage treatment with 2 X 80, 160 or 250 mg/kg ethylnitrosourea. A total of 5 dominant cataract mutations, 3 dominant cataract mutation mosaics, 1 specific-locus mutation and 9 specific-locus mutation mosaics were recovered in 15,542 screened F1 offspring. Results indicate that ethylnitrosourea treatment increases the mutation rate of dominant cataract and recessive specific-locus alleles in post-spermatogonial germ-cell stages of the mouse and that the mutations occur mainly as mosaics. Genetic confirmation of newly induced mutations occurring as mosaics is more problematical for induced recessive alleles than for induced dominant alleles and should be considered when evaluating such mutagenicity results.

Alleles↗
PubMed1987

The study of mammalian organogenesis by mosaic pattern analysis.

Chimeras are animals derived from more than one zygote and composed of two cell lineages which are distinguishable in some way at the cellular level. Spontaneous mosaic animals are also composed of distinguishable cell lineages but are monozygotic. The tissues of both mono- and multizygotic animals of this type are mosaic arrays in which aggregates of like cells form patches, the size and distribution of which can be useful in the analysis of diverse problems in developmental biology. Both biochemical and in situ methods have been applied to the elucidation of mosaic pattern. Both forms of mosaicism have proven useful in establishing theoretic constructs of the formation and maintenance of mammalian organs. A number of these constructs are discussed: cell fusion as related to myotube formation; mechanisms of coat pigmentation and the cellular origin of melanocytes; and pattern analyses of the retinal pigmented epithelium, the intestine, liver, adrenal cortex and thymus. Pathologic alterations in such animals have also been studied utilizing mosaic pattern analysis. In particular, neoplastic tumors and their associated preneoplastic lesions have been shown to be clonal.

Animals↗
PubMed1990

Comparison of epidermal patch size in X-chromosome-linked mosaic and dizygotic chimeric mice.

Mosaic animals can be made by aggregating embryonic tissues of distinguishable strains or they will occur spontaneously in eutherian mammals as a result of X-chromosome inactivation. Tissues of mosaic animals comprise aggregates of cells of similar lineage called 'patches'. The patch size of isolated epidermis from chimeras and X-chromosome-linked mosaics was compared in a quantitative fashion. Patch size was determined in the isolated epidermis of skin from aggregation chimeras between BALB/c and C3H/He strains of mice variant at the Gpi-1 locus and from the skin of X-chromosome-linked mosaic female BALB/c x C3H/He a mice heterozygous at the Pgk-1 locus. Patch size in this isolated tissue was not significantly different in these two types of mosaic animals. The results suggest that mechanisms in patch formation are primarily mechanical, dependent on cell division patterns.

Animals↗
PubMed2006

More severe epilepsy and cognitive impairment in the offspring of a mother with mosaicism for the ring 20 chromosome.

PURPOSE: Ring chromosome 20 [r(20)] syndrome is a rare chromosomal disorder. Cases tend to be sporadic. We elucidate the characteristics of an inherited r(20) mosaicism by describing the clinical features of three family members: a mother and her two children. RESULTS: The mosaicism rate of the mother was 10% and that of the children 40%. The mother experienced her first epileptic seizures at 24 years of age. Epilepsy was diagnosed two years later. After an unstable period lasting 3 years, she has been seizure-free for 13 years on a combination of valproate and lamotrigine. She has normal intelligence with full working capacity. The daughter exhibited her first epileptic seizures at the age of 7 years and she continues to have seizures weekly. The first epileptic seizures in the son were observed at 5 years of age. The son's epilepsy has been drug resistant from the onset, and a vagal nerve stimulator (VNS) has been ineffective. Psychomotor development was normal in both children up to the onset of epilepsy. Learning difficulties increased throughout school age and both children needed special educational programs. Neuropsychological evaluations have shown deterioration of cognitive levels. Both children had behavioural problems during school age but no longer in adolescence. All three subjects are nondysmophic, normocephalic and of normal growth. CONCLUSION: In this family the phenotype of r(20) mosaicism seems to be more severe in the successive generation along with a greater level of mosaicism. The aggravated clinical picture in inherited r(20) mosaicism concerned the onset of epilepsy, drug responsiveness, the cognitive level and behavioural features.

Adolescent↗
PubMed2005

Chromosome 21 mosaic human preimplantation embryos predominantly arise from diploid conceptions.

OBJECTIVE: High rates of chromosomal mosaicism in human IVF embryos question the accuracy of preimplantation genetic diagnosis, and, with the majority of embryo transfers still resulting in no pregnancy, chromosomal mosaicism is likely to be a contributing factor to human IVF failure. The aim of this study was to investigate the origin and nature of chromosome 21 (Ch21) cell division errors in human IVF embryos. DESIGN: Perform single cell Ch21 allelic profiling on human IVF embryos. SETTING: Academic research environment. PATIENT(S): Women of advanced maternal age (> 35 yrs) (n = 65) undergoing infertility treatment; and amniocytes/chorionic cells from trisomy 21 pregnancies (n = 28). INTERVENTION(S): Cells were analyzed by single cell allelic profiling, MAIN OUTCOME MEASURE(S): The origin and nature of cell division errors. RESULT(S): The vast majority of Ch21 mosaic embryos (approximately 80%) originated from diploid conceptions. In contrast, all fetal trisomy 21 originated from aneuploid conceptions. Increasing maternal age was significantly associated with aneuploid conceptions, meiotic cell division error, and adverse pregnancy outcome (P < .05). The mean daily FSH dose that produced embryos with normal Ch21 cell division was significantly lower than the mean daily FSH dose that produced embryos with mitotic Ch21 cell division errors (P < .01) and embryos with meiotic cell division errors (P < .05). CONCLUSION(S): Chromosomal mosaicism of Ch21 in human IVF embryos predominantly originate from diploid conceptions. Further understanding of chromosomal mosaicism with respect to IVF parameters, such as daily FSH dose, may eventually lead to improvements in IVF outcomes.

Adult↗
PubMed2006

Use of superparamagnetic beads for the isolation of a peptide with specificity to cymbidium mosaic virus.

A modified method for the rapid isolation of specific ligands to whole virus particles is described. Biopanning against cymbidium mosaic virus was carried out with a commercial 12-mer random peptide display library. A solution phase panning method was devised using streptavidin-coated superparamagnetic beads. The solution based panning method was more efficient than conventional immobilized target panning when using whole viral particles of cymbidium mosaic virus as a target. Enzyme-linked immunosorbent assay of cymbidium mosaic virus-binding peptides isolated from the library identified seven peptides with affinity for cymbidium mosaic virus and one peptide which was specific to cymbidium mosaic virus and had no significant binding to odontoglossum ringspot virus. This method should have broad application for the screening of whole viral particles towards the rapid development of diagnostic reagents without the requirement for cloning and expression of single antigens.

Ligands↗
PubMed2005

Cell-to-cell movement of Alfalfa mosaic virus can be mediated by the movement proteins of Ilar-, bromo-, cucumo-, tobamo- and comoviruses and does not require virion formation.

RNA 3 of Alfalfa mosaic virus (AMV) encodes the movement protein (MP) and coat protein (CP). Chimeric RNA 3 with the AMV MP gene replaced by the corresponding MP gene of Prunus necrotic ringspot virus, Brome mosaic virus, Cucumber mosaic virus or Cowpea mosaic virus efficiently moved from cell-to-cell only when the expressed MP was extended at its C-terminus with the C-terminal 44 amino acids of AMV MP. MP of Tobacco mosaic virus supported the movement of the chimeric RNA 3 whether or not the MP was extended with the C-terminal AMV MP sequence. The replacement of the CP gene in RNA 3 by a mutant gene encoding a CP defective in virion formation did not affect cell-to-cell transport of the chimera's with a functional MP. A GST pull-down technique was used to demonstrate for the first time that the C-terminal 44 amino acids of the MP of a virus belonging to the family Bromoviridae interact specifically with AMV virus particles. Together, these results demonstrate that AMV RNA 3 can be transported from cell-to-cell by both tubule-forming and non-tubule-forming MPs if a specific MP-CP interaction occurs.

Alfalfa mosaic virus↗
PubMed2005

The fate of mosaic aneuploid embryos during mouse development.

More than any other species, humans have difficulty reproducing. As recent studies show that human infertility is ever increasing, much efforts are needed towards the understanding of our low fecundity. While aneuploidy is the leading cause of spontaneous pregnancy loss in humans, we still know surprisingly little about the developmental consequences of chromosomal abnormalities. We have here used a mouse model that spontaneously incites chromosomal primary aneuploidy in female haploid oocytes and find that after fertilization, these primary aneuploid cells become cytological unstable, generating diverse karyotypic mosaic embryos. The mosaic aneuploid embryos can develop and implant into the female uterine tissue and initiate the gastrulation process (E6.5) but quickly degrade and succumb by E8.0. We find that loss of embryo viability due to chromosomal mosaicism is caused by the activation of a spatially and temporally controlled p53-independent apoptotic mechanism and does not result from a failure to progress through mitosis. We conclude that an initial state of primary aneuploidy within an embryo results in a rapid evolution of mosaicism and early embryonic death. This gestational loss due to aneuploid mosaicism could account for the large proportion of human pregnancy loss prior to clinical recognition.

Aneuploidy↗
PubMed1990

Pigmentary abnormalities and mosaicism for chromosomal aberration: association with clinical features similar to hypomelanosis of Ito.

Thirteen patients with hypopigmentation of the skin characteristic of hypomelanosis of Ito, and with developmental disabilities or structural malformations, or both, were examined at our center. Eight were found to have abnormal karyotypes in lymphocytes, fibroblasts, or both. No single clinical feature was predictive of chromosome imbalance in this group of patients. Cytogenetic findings included a balanced de novo X-autosome translocation; ring 10; 45,X/46,X,+ring; mosaic del 13q11 (fibroblasts); mosaic triploidy (fibroblasts); mosaic tetrasomy 12p (fibroblasts); mosaic apparently balanced 15;22 translocation (peripheral blood); and mosaic trisomy 18 (peripheral blood). Hypomelanosis of Ito is characterized by swirly hypopigmentation or depigmentation of the skin with or without other malformations. Autosomal dominant, autosomal recessive, and X-linked dominant inheritance have been suggested but not confirmed. Chromosomal aneuploidy has also been reported. We believe that hypomelanosis of Ito is an etiologically heterogeneous physical finding, and recommend karyotyping of multiple tissues of all patients with abnormal cutaneous pigmentation associated with developmental delay or structural malformations.

Adolescent↗
PubMed2003

Somatic mosaicism and cancer: inference based on a conditional Luria-Delbrück distribution.

Somatic mosaicism for mutations in disease-causing genes has been reported in several recent studies. Examples include hemophilia A, many skin disorders, and several cancers such as retinoblastoma and familial adenomatous polyposis. Many of these disorders require multiple mutations in order to express the disease phenotype. For example, two recessive mutations to the retinoblastoma locus are required to initiate retinoblastomal tumors. I develop a mathematical framework for somatic mosaicism in which two recessive mutations cause disease. With my framework, I analyse the following question: Given an observed frequency of cells with two mutations and an easily scored aberrant phenotype, what is the conditional frequency distribution of cells carrying one mutation and therefore susceptible to transformation by a second mutation? This question is important because a high frequency of carrier cells can cause genetic counselors to misdiagnose a mosaic as an inherited heterozygote carrier and because widespread mosaicism can lead to some germline transmission. As more data accumulate, the observed distribution of mosaics can be compared against my predicted distribution. These sorts of studies will contribute to a broader understanding of the distribution of somatic mutations, a central topic in the study of cancer.

Gene Frequency↗
PubMed1997

Hyperlipidemia and presence of thyroid autoantibodies in girls with Turner's syndrome or mosaic variance.

OBJECTIVE: The investigation of differences in the medical status between girls with Turner's syndrome or mosaic variance and healthy girls of the same age. In addition, the existence of differences between those persons with full Turner's syndrome and those with mosaic variance were examined. The influence of the treatment was also of concern because a number of the subjects in the study group were being treated with hormones (estrogen and progestin). Investigation concerned cardiovascular abnormalities, bone age, and lipid and hormonal profiles of the participating persons. PARTICIPANTS: Girls came to the hospital with problems in their menstrual cycles. Genetic control (karyotyping) took place. Each patient with symptoms of Turner's syndrome or mosaic variance was included in the study group. Every third patient with no symptoms of the syndromes and near the same age were included in the control group. METHODS: Stratification was made according to the body mass index of the participating persons. Nonparametric tests were used for the analysis. RESULTS: Differences were detected in the levels of cholesterol, low-density lipoproteins (LDLs), high-density lipoproteins (HDLs), and triglycerides, and were increased in the study group. Presence of thyroid autoantibodies, antithyreo-globulin-antibodies (AASTs) and antimicrosomatic antibodies (AASMs), was observed in the study group. In addition, differences were observed in HDL levels between persons with full Turner's syndrome and those with mosaic variance. Finally, significant difference was observed in the level of triglycerides and in the presence of AASTs and AASMs in treated and untreated persons with mosaic variance. CONCLUSIONS: Metabolic, genetic, eating or autoimmune mechanisms are suspected.

Adult↗
PubMed1994

Genotypically unbalanced diploid<==>diploid foetal mouse chimaeras: possible relevance to human confined mosaicism.

Two series of mouse chimaeras were produced by aggregating pairs of eight-cell embryos that differed at the Gpi-1s locus, encoding glucose phosphate isomerase (GPI-1); the paired embryos were respectively homozygous Gpi-1sa/Gpi-1sa and Gpi-1sb/Gpi-1sb. Chimaeric blastocysts were transferred to pseudopregnant females, that were homozygous Gpi-1sc/Gpi-1sc and produced only GPI-1C enzyme. Quantitative electrophoresis of GPI-1 was used to estimate the contribution of each embryo (GPI-1A and GPI-1B enzyme activity) to the foetus, placenta and other extraembryonic tissues of 12 1/2 day chimaeric conceptuses. For both series of chimaeras, the distributions of %GPI-1A in different tissues were classified as (1) balanced and typical, (2) balanced but atypical or (3) unbalanced. One series of chimaeras was clearly unbalanced, so that the cells derived from the (C57BL x CBA/Ca)F2 embryo (Gpi-1sb/Gpi-1sb) predominated over those derived from the BALB/c inbred strain (Gpi-1sa/Gpi-1sa) in most foetuses. Two significant observations were made concerning this unbalanced series. Firstly, the mean composition of the placenta and other extraembryonic tissues was similar to that in the foetus, i.e. also unbalanced with (C57BL x CBA/Ca)F2 (abbreviated to BF2) cells predominating. Secondly, despite this generalized deficiency of BALB/c cells, there were differences in the frequency of non-chimaeric tissues between different developmental lineages. In 20/38 [corrected] chimaeric conceptuses in the unbalanced series only BF2 cells were detected in the foetus, whereas both BF2 and BALB/c cells were present in at least one of the extraembryonic tissues. This group of chimaeras, therefore, shows some similarities to human confined mosaicism. Although chimaerism occurred more often in the primitive endoderm (hypoblast) lineage (yolk sac endoderm and parietal endoderm) than in the placenta, this may also be the case in human mosaics. The mosaic status of the human yolk sac endoderm is usually unknown so it is possible that mosaicism often occurs in the yolk sac endoderm as well as the trophectoderm in human 'confined placental mosaicism'. The uniformly unbalanced phenotype seen in the mouse chimaeras may be a result of generalized cell selection against BALB/c cells in all tissues. As an alternative explanation, we propose that most of the BALB/c cells in the blastocyst are allocated to the mural trophectoderm, which has a limited mitotic potential and so contributes little to the mid-gestation conceptus. Further work is required to test these possibilities.

Albinism, Ocular↗
PubMed2000

An association between skewed X-chromosome inactivation and abnormal outcome in mosaic trisomy 16 confined predominantly to the placenta.

Skewed X-chromosome inactivation (XCI) is frequently found in the diploid fetal tissues of individuals with mosaic trisomy that originated from a 'trisomic zygote rescue' event. This may result from a high number of trisomic cells in the embryonic cell pool at the time of XCI, which are subsequently eliminated by selection. We hypothesize that extremely skewed XCI in these mosaic cases will be associated with a poor fetal outcome due to failure to completely eliminate the trisomy from all fetal tissues. To test this hypothesis, XCI status was evaluated in 17 cases of prenatally detected trisomy 16 mosaicism. Ten of the 15 informative cases showed extreme XCI skewing ( > or = 90% inactivation of one allele) in blood or other diploid fetal tissues compared to six of the 111 controls (p < 0.001). Among these 10 'skewed' cases, 6 showed an abnormal outcome, defined as developmental abnormalities and/or intrauterine or neonatal death. In contrast, of the 5 cases without extreme skewing, none showed abnormal outcome, although outcome information was incomplete in 1 case. An additional 6 cases analyzed, involving trisomy mosaicism for other chromosomes, showed similar results. Further studies are warranted to determine if XCI status adds useful information to the prediction of pregnancy outcome in prenatally detected mosaic trisomy.

Adolescent↗
PubMed1978

Normal blood cells of anemic genotype in teratocarcinoma-derived mosaic mice.

In allophenic (mosaic) mice produced from blastocysts injected with teratocarcinoma stem cells of the OTT 6050 transplant line, an unexpected coat phenotype led to the discovery that the tumor-lineage cells carried the steel gene (Sl(J)/+). Because steel also causes a macrocytic anemia, mosaics comprising both genetically anemic and normal (+/+) cells fortuitously provided a unique opportunity to examine in vivo the etiology of this anemia in light of previous results indicating that the lesion is extrinsic to the erythroid cells. The experiment differs from previous ones, which involved postnatal grafting, in that here hematopoietic stem cells of anemic and normal genotypes coexist throughout all developmental stages, confronted by tissues of the hematopoietic microenvironment that consist partly or solely of genetically normal cells. Therefore, the possibility exists that the anemia might be completely prevented rather than secondarily ameliorated. Moreover, variation in proportion of normal-strain cells in the hematopoietic supporting tissues could serve to "titrate" minimal requirements to promote normal erythropoiesis. Mice with mixed populations of steel- and normal-genotype cells in blood and other tissues were identified by means of independent markers specific for tumor vs. blastocyst strains of origin. The clinical blood picture of these mosaics proved to be indistinguishable from that of normal controls, even when only a small minority of cells in all tissues of one of the animals were genetically normal. Phenotypic blood normalcy was shown, by occurrence of the typical steel anemia among F(1) germ-line progeny of mosaics, not to be due to any change in the capacity of the mutant gene to elicit the anemia. The results from the mosaics thus demonstrate that the primary expression of the steel lesion is indeed in the hematopoietic microenvironment. However, they also reveal that a surprisingly small complement of normal cells there appears to be adequate to prevent this anemia permanently. The hypothesis is advanced that relatively short-range diffusible substances, produced by cells in the microenvironment and required for normal erythropoiesis, may account for the inductive effectiveness of small cell numbers.

Anemia, Macrocytic↗
PubMed2003

Antenatal detection of mosaic trisomy 9 by ultrasound: a case report and literature review.

This paper presents a fetus with mosaic trisomy 9 diagnosed by chorionic villus sampling and confirmed by cordocentesis, and compares this case with published cases in order better to define the ultrasound markers confined to trisomy 9 syndrome. Detailed fetal ultrasound examination was carried out, revealing shortened femur, placental cysts and oligohydramnios. All published trisomy 9 cases with abnormal ultrasound findings were extracted from the MEDLINE database in the period from 1973 to 2002. We found 12 non-mosaic and 13 mosaic cases, including our case. The most frequent ultrasound abnormalities included characteristic cardiac, skeletal, craniofacial and central nervous system malformations. Intrauterine growth restriction and single umbilical artery were prevalent non-specific findings in both non-mosaic and mosaic groups. Parental chromosomal variations, as in our case, were not uncommon findings. When a fetus shows structural anomalies suggesting the presence of trisomy 9, karyotyping should be performed on both chorionic villi or amniocytes and fetal blood lymphocytes to enable a correct diagnosis to be made.

Adult↗