Trisomy rescue mechanism: the case of concomitant mosaic trisomy 14 and maternal uniparental disomy 14 in a 15-year-old girl.
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ABSTRACT:
SUBMITTER: Balbeur S
PROVIDER: S-EPMC4771849 | biostudies-other | 2016 Mar
REPOSITORIES: biostudies-other
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Project description:Various chromosomal anomalies including small supernumerary marker chromosome (sSMC) and Uniparental disomy (UPD) have been described in association with intellectual disability and autism spectrum disorder. Based on our reported findings, we recommend that patients with sSMC(8) be evaluated for autism spectrum disorder (ASD) for early institution of therapy. In the presence of an identifiable sSMC, exploration of UPD is also recommended to further investigate the role of chromosome 8 UPD in ASD.
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Project description:The Kagami-Ogata syndrome (KOS) is a rare imprinting disorder with a distinct clinical phenotype. In KOS, polyhydramnios is associated with a small bell-shaped thorax and coat-hanger ribs. The genetic etiology of KOS includes paternal uniparental disomy 14 [upd(14)pat], epimutations, and microdeletions affecting the maternally derived imprinted region of chromosome 14q32.2. More than 77 cases of KOS have been reported; however, only one mosaic upd(14)pat case has been reported. Here we report a second mosaic upd(14)pat case. The prognosis of upd(14)pat patients is poor because of severe respiratory insufficiency. We summarized prenatal ultrasound findings of KOS to raise awareness of this condition for possible diagnosis of KOS prenatally when polyhydramnios combination with a small bell-shaped thorax and other related features are first observed. Prenatal diagnosis using methylation-specific multiplex ligation-dependent probe amplification (MLPA) or a single-nucleotide polymorphism-based microarray analysis is recommended.
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Project description:Robertsonian translocations (ROBs) are whole arm rearrangements involving the acrocentric chromosomes 13-15 and 21-22 and carriers are at increased risk for aneuploidy and thus uniparental disomy (UPD). Chromosomes 14 and 15 are imprinted with expression of genes dependent on the parental origin of the chromosome. Correction of a trisomic or monosomic conceptus for chromosomes 14 or 15 would lead to one of the established UPD 14mat/pat or UPD 15 (Prader-Willi/Angelman) syndromes (PWS/AS). In view of this, prenatal UPD testing should be considered for balanced carriers of a ROB, fetuses with a familial or de novo balanced ROB that contains chromosome 14 or 15 or with a normal karyotype when a parent is a carrier of a balanced ROB with a 14 or 15. Individuals with congenital anomalies and an abnormal phenotype and carry a ROB involving the two imprinted chromosomes should also be UPD tested.
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Project description:Maternal uniparental disomy of chromosome 14 (upd(14)mat) or Temple syndrome is an imprinting disorder associated with a relatively mild phenotype. The absence of specific congenital malformations makes this condition underdiagnosed in clinical practice. A boy with a de novo robertsonian translocation 45,XY,rob(13;14)(q10;q10) is reported; a CGH/SNP array showed a loss of heterozygosity in 14q11.2q13.1. The final diagnosis of upd(14)mat was made by microsatellite analysis, which showed a combination of heterodisomy and isodisomy for different regions of chromosome 14. Obesity after initial failure to thrive developed, while compulsive eating habits were not present, which was helpful for the clinical differential diagnosis of Prader-Willi syndrome. In addition, the boy presented with many phenotypic features associated with upd(14)mat along with hypoesthesia to pain, previously unreported in this disorder, and bilateral cryptorchidism, also rarely described. These features, as well as other clinical manifestations (i.e., truncal obesity, altered pubertal timing), may suggest a hypothalamic-pituitary involvement. A detailed cytogenetic and molecular characterization of the genomic rearrangement is presented. Early genetic diagnosis permits a specific follow-up of children with upd(14)mat in order to optimize the long-term outcome.
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Project description:BACKGROUND:Maternal uniparental disomy of chromosome 6 (upd(6)mat) is a rare finding and its clinical relevance is currently unclear. Based on clinical data from two new cases and patients from the literature, the pathogenetic significance of upd(6)mat is delineated. METHODS:Own cases were molecularly characterized for isodisomic uniparental regions on chromosome 6. For further cases with upd(6)mat, a literature search was conducted and genetic and clinical data were ascertained. RESULTS:Comparison of isodisomic regions between the new upd(6)mat cases and those from four reports did not reveal any common isodisomic region. Among the patients with available cytogenetic data, five had a normal karyotype in lymphocytes, whereas a trisomy 6 (mosaicism) was detected prenatally in four cases. A common clinical picture was not obvious in upd(6)mat, but intrauterine growth restriction (IUGR) and preterm delivery were frequent. CONCLUSION:A common upd(6)mat phenotype is not obvious, but placental dysfunction due to trisomy 6 mosaicism probably contributes to IUGR and preterm delivery. In fact, other clinical features observed in upd(6)mat patients might be caused by homozygosity of recessive mutations or by an undetected trisomy 6 cell line. Upd(6)mat itself is not associated with clinical features, and can rather be regarded as a biomarker. In case upd(6)mat is detected, the cause for the phenotype is identified indirectly, but the UPD is not the basic cause.
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Project description:Although recent studies in patients with paternal uniparental disomy 14 [upd(14)pat] and other conditions affecting the chromosome 14q32.2 imprinted region have successfully identified underlying epigenetic factors involved in the development of upd(14)pat phenotype, several matters, including regulatory mechanism(s) for RTL1 expression, imprinting status of DIO3 and placental histological characteristics, remain to be elucidated. We therefore performed molecular studies using fresh placental samples from two patients with upd(14)pat. We observed that RTL1 expression level was about five times higher in the placental samples of the two patients than in control placental samples, whereas DIO3 expression level was similar between the placental samples of the two patients and the control placental samples. We next performed histological studies using the above fresh placental samples and formalin-fixed and paraffin-embedded placental samples obtained from a patient with a maternally derived microdeletion involving DLK1, the-IG-DMR, the MEG3-DMR and MEG3. Terminal villi were associated with swollen vascular endothelial cells and hypertrophic pericytes, together with narrowed capillary lumens. DLK1, RTL1 and DIO3 proteins were specifically identified in vascular endothelial cells and pericytes, and the degree of protein staining was well correlated with the expression dosage of corresponding genes. These results suggest that RTL1as-encoded microRNA functions as a repressor of RTL1 expression, and argue against DIO3 being a paternally expressed gene. Furthermore, it is inferred that DLK1, DIO3 and, specially, RTL1 proteins, play a pivotal role in the development of vascular endothelial cells and pericytes.
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Project description:The maternal and paternal genomes possess distinct epigenetic marks that distinguish them at imprinted loci. In order to identify imprinted loci, we used a novel method, taking advantage of the fact that uniparental disomy (UPD) provides a system that allows the two parental chromosomes to be studied independently. We profiled the paternal and maternal methylation on chromosome 15 using immunoprecipitation of methylated DNA and hybridization to tiling oligonucleotide arrays. Comparison of six individuals with maternal versus paternal UPD15 revealed 12 differentially methylated regions (DMRs). Putative DMRs were validated by bisulfite sequencing, confirming the presence of parent-of-origin-specific methylation marks. We detected DMRs associated with known imprinted genes within the Prader-Willi/Angelman syndrome region, such as SNRPN and MAGEL2, validating this as a method of detecting imprinted loci. Of the 12 DMRs identified, eight were novel, some of which are associated with genes not previously thought to be imprinted. These include a site within intron 2 of IGF1R at 15q26.3, a gene that plays a fundamental role in growth, and an intergenic site upstream of GABRG3 that lies within a previously defined candidate region conferring an increased maternal risk of psychosis. These data provide a map of parent-of-origin-specific epigenetic modifications on chromosome 15, identifying DNA elements that may play a functional role in the imprinting process. Application of this methodology to other chromosomes for which UPD has been reported will allow the systematic identification of imprinted sites throughout the genome.
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Project description:In the diploid cells of most organisms, including humans, each chromosome is usually distinguishable from its partner homolog by multiple single-nucleotide polymorphisms. One common type of genetic alteration observed in tumor cells is uniparental disomy (UPD), in which a pair of homologous chromosomes are derived from a single parent, resulting in loss of heterozygosity for all single-nucleotide polymorphisms while maintaining diploidy. Somatic UPD events are usually explained as reflecting two consecutive nondisjunction events. Here we report a previously undescribed mode of chromosome segregation in Saccharomyces cerevisiae in which one cell division produces daughter cells with reciprocal UPD for the same pair of chromosomes without an aneuploid intermediate. One pair of sister chromatids is segregated into one daughter cell and the other pair is segregated into the other daughter cell, mimicking a meiotic chromosome segregation pattern. We term this process "reciprocal uniparental disomy."
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Project description:Uniparental disomy (UPD) is often considered as an event to be characterized exclusively by molecular genetic or epigenetic approaches. This review shows that at least one third of UPD cases emerge in connection with or due to a chromosomal rearrangement. Thus, additional (molecular) cytogenetic characterization of UPD cases is essential. Up to now > 1,100 UPD cases detected in clinical, non-tumor cases are reported in the literature. Recently, these cases were summarized in a regularly updated, freely available online database http://www.med.uni-jena.de/fish/sSMC/00START-UPD.htm. Based of this, here the presently known imprinting syndromes, the chromosomal contribution to UPD phenomenon, and the cytogenetic subgroups of UPD, including cases with normal, abnormal balanced or unbalanced karyotype (like e.g. small supernumerary marker chromosomes and Robertsonian translocations) and segmental UPD are reviewed. Furthermore, chromosome fragmentation as a possible mechanism of trisomic rescue is discussed, which might help to explain the observed 1:9 rate of maternal versus paternal UPD present in cases with original trisomic karyotypes. Overall, as UPD is more but an interesting rarity, the genetic background of each "UPD-patient" needs to be characterized besides by molecular methods, also by molecular cytogenetics in detail.
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