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PubMed2005

Reproductive history of a healthy woman with mosaic duplication of chromosome 4p.

OBJECTIVES: Mosaic autosomal duplications are rare and often result in mental retardation and congenital anomalies. Phenotype is not predictable depending on the chromosomal imbalance involved and the percentage and tissues distribution of unbalanced cells. We report on a young woman carrying a mosaic duplication of chromosome 4p, evaluated because of three abortions due to IUGR and fetal malformation. METHODS: Mosaic dup(4p) was detected by standard and molecular cytogenetics. RESULTS: Unbalanced cells accounted for about 20 to 30% of nuclei in four examined tissues and did not cause any obvious phenotypic effect. CONCLUSION: It is likely that mosaic duplications are underascertained because they are not associated with obvious clinical effects in some individuals. Prenatal diagnosis is the method of choice to predict the karyotype in the offspring of subjects carrying mosaic chromosome imbalances.

Abortion, Spontaneous↗
PubMed2006

The association between preeclampsia and placental trisomy 16 mosaicism.

BACKGROUND: Prenatally diagnosed trisomy 16 mosaicism is associated with the increased risk of poor pregnancy outcome including intrauterine growth restriction, intrauterine death and fetal malformation. While maternal preeclampsia has also been reported in some cases, this has not been systematically evaluated. METHODS: To better define the risk of preeclampsia and the clinical course of preeclampsia in these pregnancies and to identify associated clinical variables, we reviewed 25 cases of prenatally diagnosed trisomy 16 mosaicism for which molecular studies were undertaken and sufficient obstetrical data were present to include/exclude the diagnosis of preeclampsia. RESULTS: Six of 25 (24%) mosaic trisomy 16 cases exhibited preeclampsia as compared to 3 of 44 (7%) matched controls. There were no differences between those mosaic trisomy 16 cases presenting with preeclampsia and those that did not, in terms of the presence/absence of UPD, IUGR, malformation, or trisomy on amniocentesis. Four of the 6 (67%) preeclampsia-associated fetuses were male, compared with only 4 of 19 (21%) (p = 0.06) nonpreeclampsia case fetuses, and three of these also had hypospadias. The levels of trisomy tended to be high in placentas associated with preeclampsia; however very high levels of placental trisomy were also often seen in the absence of preeclampsia. CONCLUSION: As it is impossible to predict which subset of cases is at highest risk, all women receiving a prenatal diagnosis of trisomy 16 mosaicism should be closely monitored for signs of preeclampsia.

Adult↗
PubMed1984

United States survey on chromosome mosaicism and pseudomosaicism in prenatal diagnosis.

The survey of the incidence of chromosome mosaicism and pseudomosaicism detected in prenatal diagnosis included data from approximately 60 000 genetic amniocenteses in the United States. There were 59 participating cytogenetic laboratories nationwide. The overall incidence of chromosome mosaicism was 0.25 per cent (range of 0-0.89 per cent). The average frequency of pseudomosaicism involving multiple cells or clones was 0.7 per cent (range of 0-11.21 per cent). The frequency of single cell or clone pseudomosaicism was 2.47 per cent (range of 0-11.49 per cent). In cases of pseudomosaicism with trisomy, the most frequently involved chromosome was number 2; occurrence rates of trisomies 7,X,9,17 and 20 were also relatively high. In cases of pseudomosaicism with structural abnormalities, this survey showed an association between relative chromosome size and the frequency of involvement in structural rearrangement. Data on a total of 185 cases of chromosome mosaicism collected in this survey as well as from other documented sources showed 89 cases involved an autosome, 73 cases a sex chromosome, and 23 a marker chromosome. The frequency of noticeable phenotypic abnormalities was highest (37.8 per cent) in the autosomal mosaics and lowest (10.5 per cent) in the sex chromosome mosaics. The average rate for cytogenetic confirmation was 70 per cent.

Chromosome Aberrations↗
PubMed1984

European collaborative study on prenatal diagnosis: mosaicism, pseudomosaicism and single abnormal cells in amniotic fluid cell cultures.

A report is given of the results of a European collaborative study on mosaicism, pseudomosaicism and single abnormal cells in amniotic fluid cell cultures. The mean frequency of cases with mosaicism was 0.10 per cent, with pseudomosaicism 0.64 per cent and with single abnormal cells 2.83 per cent in a series of 44 170 amniotic fluid samples. There was no significant difference between the colony (in situ) and the flask method with regard to the frequency of mosaicism. Pseudomosaicism and single abnormal cells were more frequent in cases studied with the flask method probably due to other factors than the method of cultivation of the cells. The frequency of maternal cell contamination was 0.17 per cent and the frequency of wrong sex assignment was 0.11 per cent. A more correct estimation is obtained if these frequencies are doubled. There was a considerable variation between laboratories with regard to the frequencies given above. One reason for this variation is that there are no sharp limits between mosaicism, pseudomosaicism and single abnormal cells. Thus the material contained cases diagnosed as having pseudomosaicism which turned out to be mosaics at birth and to have an abnormal phenotype. These cases were very rare but pose a definite problem in prenatal cytogenetic diagnosis.

Amniotic Fluid↗
PubMed1988

Prenatal diagnosis, fetal pathology, and cytogenetic analysis of mosaic trisomy 14.

While true mosaicism occurs in only 0.25 per cent of genetic amniocenteses, nearly 2.5 per cent of amniotic fluid cell cultures contain a second cell line. In the common practice of prenatal diagnosis, an aberrant cell line confined to a single colony is usually disregarded. We present a case of mosaic trisomy 14 which was not detected on initial chromosome analysis. At birth, multiple malformations were apparent. Newborn cytogenetic studies revealed mosaicism [46,XX/46,XX,-14, +i(14q)] with an isochromosome 14 in 37 per cent of lymphocytes. Additional cells from the initial amniotic fluid culture were analysed post-delivery and the isochromosome 14 identified in only one of 12 total colonies. This case illustrates two important lessons in prenatal diagnosis. First, amniotic fluid cell cultures may not accurately reflect the relative distribution of the normal and abnormal cell lines within a mosaic fetus. Second, while it is generally reasonable to disregard mosaicism confined to a single colony, this policy will, on rare occasion, result in diagnostic error. This should be taken into consideration, particularly when dealing with autosomal trisomies potentially compatible with livebirth.

Abnormalities, Multiple↗
PubMed1989

The European collaborative study on mosaicism in chorionic villus sampling: data from 1986 to 1987.

Data on a total of 11,855 diagnostic chorionic villus samples obtained in the years 1986 and 1987 were compiled from a questionnaire filled in by 36 European cytogenetic centres. Mosaicism was reported in 141 cases. The cytogenetic findings were followed by induced abortion in 24 cases. Spontaneous abortion was observed in nine mosaic pregnancies, a rate not significantly different from that observed for CVS in total. Mosaicism was found in 1.2 per cent of analyses by direct analysis/short-term culture, in contrast to the 0.6 per cent found after long-term culture. Evidence for fetal non-mosaicism was found in 99 of the 141 cases. The finding of mosaicism in first-trimester CVS should always elicit further analyses, preferably after amniocentesis, to substantiate the suspected fetal chromosome aberration.

Chorionic Villi Sampling↗
PubMed1992

Canadian multicenter randomized clinical trial of chorion villus sampling and amniocentesis. chromosome mosaicism in CVS and amniocentesis samples.

Data on 1040 chorionic villus and 969 amniotic fluid samples were collected from women studied in the Canadian Multicentre Randomized Clinical Trial of Chorion Villus Sampling and Amniocentesis. Cytogenetic results were obtained from 98.0 per cent of chorionic villus samples and from 99.9 per cent of amniotic fluid samples. Level I mosaicism (a single cell with an abnormal karyotype) occurred frequently in both chorionic villus and amniotic fluid samples and appeared to have no clinical significance. Level II mosaicism occurred in 0.9 per cent of CVS mesenchyme and 1.5 per cent of amniotic fluid cultures and in general was not perceived to be of sufficient concern to warrant cytogenetic follow-up studies. Level III mosaicism was reported in 18 CVS cases (15 cytotrophoblast, 1 mesenchyme, and 2 with both cell methods) and in one amniotic fluid case. In all cases but one (fetus with trisomy 18), level III mosaicism was confined to the placenta. Maternal cell contamination occurring with a frequency of 6.4 per cent in the mesenchyme analyses was a concern. This study supports the final report of the Canadian Multicentre Randomized Clinical Trial of Chorion Villus Sampling and Amniocentesis. Cytogenetic analysis of chorionic villus samples appears to be an acceptable alternative to the analysis of amniotic fluid samples. However, because of mosaicism and maternal cell contamination concerns, the examination of both cytotrophoblast preparations and mesenchyme cultures from chorionic villus samples is recommended.

Adult↗
PubMed2002

Prenatal diagnosis of 45,X and 45,X mosaicism: the need for thorough cytogenetic and clinical evaluations.

OBJECTIVES: Mosaicism involving a 45,X cell line is relatively common in prenatal diagnosis. In prenatally diagnosed cases, the prognosis of non-mosaic 45,X and 45,X/46,XY mosaicism are different. Therefore, accurate identification of a cell line containing Y chromosome is critical for genetic counseling and postnatal management. METHODS: We investigated the ultrasound findings and outcomes of pregnancies with a 45,X cell line identified during mid-trimester cytogenetic analysis. RESULTS: A total of 105 cases were found to have a 45,X cell line by standard cytogenetic analysis. Seventy-four cases were found to have non-mosaic 45,X at initial diagnosis. Of these 74 cases, 68 had abnormal ultrasound findings that were characteristic of Turner syndrome. Of the six cases with normal ultrasound findings, ultrasound examination was normal with male genitalia identified in three cases. Thorough cytogenetic and fluorescent in situ hybridization (FISH) analysis identified Y chromosome material in all three cases, one with a dicentric Y;14 chromosome and the other two cases with a marker chromosome containing Sex-determining Region (SRY) material in a small portion of the cells. In contrast, in 31 cases with a mosaic 45,X karyotype, ultrasound abnormality was identified only in one case. CONCLUSIONS: The present data suggest the need for follow-up ultrasound examination and thorough cytogenetic and molecular analysis for Y chromosome material in 45,X cases with normal ultrasound findings.

Adult↗
PubMed2002

Isochromosome 5p mosaicism at prenatal diagnosis: observations and outcomes in six cases at chorionic villus sampling and one at amniocentesis.

We present six cases of 47,+i(5p)/46 mosaicism diagnosed at chorionic villus sampling (CVS), this being the first prospective series to be reported. The clinical indication in each was advanced maternal age. Further prenatal studies in four (amniocentesis, plus fetal blood sampling in one) did not show the isochromosome. In one case, subsequent amniocentesis showed 1/48 in situ colonies with the isochromosome, but fetal blood was karyotypically normal. These five pregnancies resulted in phenotypically normal livebirths; further normal follow-up reports (from age 4 months through 4 years) are noted in four of these. Analysis of placental tissue in one case confirmed the presence of the i(5p) mosaicism. In the remaining case, in which 100% of CVS cultured cells had the i(5p), the pregnancy was terminated. Fetal skin fibroblasts did not show the i(5p). Thus, in none of these six cases was true fetal mosaicism detected, nor an abnormal phenotype noted. We suggest that a 47,+i(5p)/46 karyotype, detected at CVS, may frequently reflect confined placental mosaicism. In addition, we report a case of the primary diagnosis of 47,+i(5p)/46 mosaicism at amniocentesis. The infant appeared normal at birth, but a brain malformation was subsequently identified.

Adult↗
PubMed2005

Evaluating current policy for detecting mosaicism in amniotic fluid cultures: implications for current cell counting practices.

Chromosomal mosaicism is one of the most vexing problems for clinical cytogenetic laboratories and personnel time used for analysis at the microscope is one of the principle costs in cytogenetic laboratories. We use data collected from 26 cytogenetic laboratories to evaluate whether the American College of Medical Genetics guidelines for minimum number of cells to count to exclude mosaicism in amniotic fluid specimens is appropriate. An accurate estimate of the number of mosaics that are missed by current cell counting practices is an important step in this process. Thus, we present a new method for estimating the number of mosaics that are missed and we use computer simulation to evaluate this new method. Our results indicate that if the clinical significance of mosaicism is suspected to be minimal for certain cytogenetic anomalies when the percentage of abnormal cells is 15 per cent or less, then it may be sufficient to use a 15-cell counting-rule-for-detection along with a minimum total cell count of 30 regardless of whether abnormal cells or normal cells are in the minority.

Amniotic Fluid↗
PubMed1999

Heterologous sequences greatly affect foreign gene expression in tobacco mosaic virus-based vectors.

A series of tobacco mosaic virus (TMV)-based hybrid vectors for transient gene expression were constructed with similar designs but differing in the source of heterologous tobamovirus sequence: Odontoglossum ringspot virus, tobacco mild green mosaic virus variants U2 and U5, tomato mosaic virus, and sunn-hemp mosaic virus. These vectors contained a heterologous coat protein subgenomic mRNA promoter and coat protein open reading frame (ORF) and either TMV or heterologous 3' nontranslated region. The foreign ORF, from the jellyfish green fluorescent protein (GFP) gene, was transcribed from the native TMV coat protein subgenomic mRNA promoter, which extended into the coat protein ORF. The presence of an in-frame stop codon within the GFP mRNA leader and the choice of sequence of GFP ORFs substantially affected translational efficiency. However, the major regulatory component of gene expression in these vectors appeared to be transcriptional rather than translational. There was an inverse relationship between expression of GFP and the heterologous coat protein genes that was reflected in accumulation of the respective mRNAs and proteins. The most effective vector in this series (30B) contained sequences encoding the coat protein subgenomic mRNA promoter, coat protein ORF, and 3' nontranslated region from tobacco mild green mosaic virus U5. Expressed from 30B, GFP accumulated up to 10% of total soluble protein in leaves.

3' Untranslated Regions↗
PubMed1992

Molecular studies of parental origin and mosaicism in 45,X conceptuses.

The present report summarizes molecular studies of parental origin and sex chromosome mosaicism in forty-one 45,X conceptuses, consisting of 29 spontaneous abortions and 12 liveborn individuals with Turner syndrome. Our studies indicate that most 45,X conceptuses have a single, maternally derived X chromosome, regardless of whether the conceptus is liveborn or spontaneously aborted. In studies of mosaicism, our identification of X- and Y-chromosome mosaics among 45,X spontaneous abortions indicates that mosaicism does not ensure survival to term of 45,X fetuses. However, the incidence of sex chromosome mosaicism is substantially higher in liveborn than in aborted 45,X conceptuses, indicating that the presence of a second cell line increases the likelihood of survival to term.

Abortion, Spontaneous↗
PubMed1987

Confined chorionic mosaicism in prenatal diagnosis.

Confined chorionic mosaicism, detected commonly on chorionic villus sampling (CVS) and occasionally in cultured amniotic fluid cells, is described in five pregnancies that showed confined chorionic mosaicism for trisomies 12, 13, 14, 17 and a marker chromosome. Cytogenetic findings in these pregnancies support the conclusion that within chorion some chromosomal mosaicism are confined to the trophectoderm derivatives while others to the extra-embryonic mesoderm. The etiology of confined chorionic mosaicism is discussed in relation to a significant role of multiple cell lineages contributing to the early development of placenta. The need is indicated for the use of both direct and long-term cultures in CVS prenatal diagnosis, and for the confirmatory testing of fetal blood or amniotic fluid in cases where mosaicism is detected in chorionic villi.

Adult↗
PubMed2004

Short stature in children with an apparently normal male phenotype can be caused by 45,X/46,XY mosaicism and is susceptible to growth hormone treatment.

UNLABELLED: Girls with unexplained short stature are routinely screened for the presence of Ullrich-Turner syndrome by clinical examination, laboratory tests, and karyotyping. In this study, we performed chromosomal analysis in boys to explore the role of 45,X/46,XY mosaicism for short stature in males. Short-term effects of growth hormone treatment in male 45,X/46,XY individuals were compared retrospectively to those in female patients. We report six boys with a normal-appearing male phenotype and 45,X/46,XY mosaicism, four of whom were diagnosed postnatally because of short stature. Two boys were diagnosed prenatally by amniocentesis. Five boys were short and were treated with growth hormone (0.04-0.05 mg/kg per day) in analogy to girls with Ullrich-Turner syndrome and gonadal dysgenesis. With the exception of one patient in whom treatment was initiated only at the age of 14.6 years, the male patients with 45,X/46,XY mosaicism responded to short-term growth hormone treatment similarly to females with an increasing height SDS. CONCLUSION: 45,X/46,XY mosaicism remains undetected in some short boys because this group is not routinely karyotyped. We recommend chromosomal analysis of boys with otherwise unexplained short stature who are short for their families. Growth hormone treatment should be offered to short boys with 45,X/46,XY mosaicism and a predicted adult height below the mid-parental range within clinical trials.

Body Height↗
PubMed2000

Neurofibromatosis type 2 attributable to gonosomal mosaicism in a clinically normal mother, and identification of seven novel mutations in the NF2 gene.

Neurofibromatosis type 2 (NF2) is an autosomal dominant cancer syndrome that predisposes to the development of bilateral vestibular schwannomas sometimes associated with schwannomas at other locations, meningiomas, ependymomas and juvenile posterior subcapsular lenticular opacities. This disease is caused by inactivating mutations in the NF2 tumour-suppressor gene, located in 22q12. Recently, somatic mosaicism has been demonstrated in some "de novo" NF2 patients. We here report the genetic study of 33 NF2 patients from 33 unrelated Italian families. Twelve mutations were characterised, including seven newly identified mutations and five recurrent ones. Furthermore, we describe one patient with an inactivating mutation that lies in exon 13 but that is present in only a portion of the lymphocytes and, more importantly, a clinically normal individual carrying a somatic/germinal mosaicism for a nonsense mutation in exon 10 of the NF2 gene. Our results confirm the relatively high percentage of mosaicism for mutations in the NF2 gene and establish the importance of evaluating genomic DNA from several tissues, in addition to lymphocytes, so as to identify mosaicism in "de novo" NF2 patients and their relatives. In addition, the demonstration of somatic and/or gonadal mosaicism is an important tool for accurate genetic counselling in families with sporadic cases of NF2.

Adult↗
PubMed1997

Analysis of chromosomal equipment in spermatozoa of a 46,XY/47,XY/+8 male by means of multicolour fluorescent in situ hybridization: confirmation of a mosaicism and evaluation of risk for offspring.

Trisomy 8 is generally associated with chromosomal mosaicism and occurs de novo, with relatively well-defined clinical manifestations, ranging from minimal effects to severe malformations. Mosaicism is often difficult to ascertain and the confirmation of diagnosis requires several chromosomal investigations on a variety of tissues. We present a case of mosaic trisomy 8 fortuitously found in a healthy 30-year-old man during a cytogenetic investigation for several spontaneous abortions: 8% of the lymphocyte metaphases showed a 47,XY,+8 karyotype. Fluorescent in situ hybridization (FISH) with the probes pJM.128 and L1.84 was performed on decondensed interphase spermatozoa. Of the 25000 analysed cells, 398 spermatozoa (1.59%) exhibited a hybridization pattern compatible with a chromosome 8 disomy; the frequency was higher than in either sperm control populations (0.17% and 0.21%). This result is in agreement with the existence of trisomy 8 mosaicism in the gonads and germ cells. FISH on decondensed interphase spermatozoa spreads is thus an easy non-invasive procedure that can be used to complement mosaicism diagnosis in tissue other than blood. Moreover, FISH provides interesting data for characterizing the risk for offspring.

Abortion, Spontaneous↗
PubMed1997

Multicolour FISH detects frequent chromosomal mosaicism and chaotic division in normal preimplantation embryos from fertile patients.

We have used multicolour fluorescent in situ hybridisation (FISH) with DNA probes for chromosomes X, Y and l to analyse spare untransferred cleavage-stage embryos after preimplantation diagnosis to avoid X-linked disease. In total, 93 morphologically normal embryos were available from seven patients (six of proven fertility) who had undergone fourteen in vitro fertilisation (IVF) cycles. The chromosome patterns observed were classified into four groups; normal, abnormal (non-mosaic), mosaic and chaotic (uncontrolled division). Approximately half of the embryos were normal for the chromosomes tested. Two embryos only were aneuploid (non-mosaic) throughout but, after excluding those showing chaotic division, 30% were considered to be chromosomal mosaics. Of these, a minority had arisen because of mitotic non-disjunction or chromosome loss or gain, whereas the majority were ploidy mosaics, with haploidy being the most common. The occurrence of chaotically dividing embryos was strongly patient-related, i.e. some patients had 'chaotic' embryos in repeated cycles, whereas other patients were completely free of this type of anomaly. 'Chaotic' embryos are unlikely to progress beyond implantation. These findings have important implications both for routine IVF and preimplantation genetic diagnosis.

Adult↗
PubMed2004

Characterization of a distinct Johnsongrass mosaic virus strain isolated from sorghum in Nigeria.

A virus isolated from sorghum in Nigeria has been partially characterized. It was tested by enzyme-linked immunosorbent assay (ELISA) using antisera to Maize dwarf mosaic virus, Johnsongrass mosaic virus (JGMV), Sugarcane mosaic virus strain-MDB, Sorghum mosaic virus, and Zea mosaic virus. A partial host range, symptom phenotypes for selected sorghum lines, and the mass of the coat protein (CP) subunit was analyzed by sodium-dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and its amino acid (aa) sequence determined by time-of-flight mass spectrometry (TOFMS). The Nigerian isolate was positive in ELISA to only JGMV antiserum. It infected sorghum and smooth brome but not oat or johnsongrass. It caused necrosis in 12 of 13 tested sorghum lines, while the USA JGMV isolate caused necrosis in only one sorghum line. In SDS-PAGE, the mass of the Nigerian virus CP was 3,000 Da smaller than that of JGMV-MDO. Moreover, TOFMS analyses showed that, while residues 1-7 of the CP aa sequence were identical to those of JGMV (GenBank #A27631), and residues 57-293 were almost identical to residues 67-303 of JGMV, the intermediate region exhibited significant differences, including a 10 aa deletion. These data indicate that the virus should be considered a distinct isolate of JGMV (JGMV-N) and expands the known range of JGMV to Africa.

Amino Acid Sequence↗