Child with mosaic variegated aneuploidy and embryonal rhabdomyosarcoma

Mosaic variegated aneuploidy syndrome with tetraploid, and predisposition to male infertility triggered by mutant CEP192

In this study, we report on mosaic variegated aneuploidy (MVA) syndrome with tetraploidy and predisposition to infertility in a family. Sequencing analysis identified that the CEP192 biallelic variants (c.1912C>T, p.His638Tyr and c.5750A>G, p.Asn1917Ser) segregated with microcephaly, short stature, limb-extremity dysplasia, and reduced testicular size, while CEP192 monoallelic variants segregated with infertility and/or reduced testicular size in the family. In 1,264 unrelated patients, variant screening for CEP192 identified a same variant (c.5750A>G, p.Asn1917Ser) and other variants significantly associated with infertility. Two lines of Cep192 mice model that are equivalent to human variants were generated. Embryos with Cep192 biallelic variants arrested at E7 because of cell apoptosis mediated by MVA/tetraploidy cell acumination. Mice with heterozygous variants replicated the predisposition to male infertility. Mouse primary embryonic fibroblasts with Cep192 biallelic variants cultured in vitro showed abnormal morphology, mitotic arresting, and disruption of spindle formation. In patient epithelial cells with biallelic variants cultured in vitro, the number of cells arrested during the prophase increased because of the failure of spindle formation. Accordingly, we present mutant CEP192, which is a link for the MVA syndrome with tetraploidy and the predisposition to male infertility.

Pathogenic correlation between mosaic variegated aneuploidy 1 (MVA1) and a novel BUB1B variant: a reappraisal of a severe syndrome

Background

The BUB 1 mitotic checkpoint serine/threonine kinase B (BUB1B) gene encodes a key protein in the mitotic spindle checkpoint, which acts as a surveillance mechanism, crucial for the maintenance of the correct chromosome number during cell deviation. Mutations of BUB1B gene are linked to mosaic variegated aneuploidy 1 (MVA1) syndrome, a rare autosomal recessive disorder characterized by widespread mosaic aneuploidies, involving different chromosomes and tissues. MVA1 is clinically characterized by intrauterine growth restriction, post-natal growth retardation, and severe neurologic impairment including microcephaly, developmental delay/intellectual disability, epileptic seizures, and generalized hypotonia. Malignancies are also serious sequelae associated with the disorder. We reported on a case of two-year-old Italian girl with MVA1 who shows severe neurologic impairment, microcephaly and epileptic seizures.

Materials and methods

Clinical data collection and genetic diagnosis of the patient were assessed. Mutational analysis covers the chromosomal microarray analysis, the gene methylation pattern studied using the methylation-specific multiplex ligation-dependent probe amplification, and the family-based Whole Exome Sequencing (WES). A literature research based on reported cases of MVA and premature chromatid separation was also included.

Results

Karyotyping has revealed 12% of mosaics in the patient who carries a novel variant in BUB1B gene (c.2679A > T, p.Arg893Ser) detected by WES. Thirty-one cases of MVA1 including the present report, and four prenatally diagnosed cases with MVA1 were selected and inspected.

Conclusion

Clinical and genetic findings reported in the girl strongly suggest a new MVA1 genotype–phenotype correlation and lead to a reappraisal of a severe syndrome. Diagnosis and in-depth follow-up provided worthwhile data.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10072-022-06247-w.

Checkpoint control in meiotic prophase: Idiosyncratic demands require unique characteristics

Chromosomal transactions such as replication, recombination and segregation are monitored by cell cycle checkpoint cascades. These checkpoints ensure the proper execution of processes that are needed for faithful genome inheritance from one cell to the next, and across generations. In meiotic prophase, a specialized checkpoint monitors defining events of meiosis: programmed DNA break formation, followed by dedicated repair through recombination based on interhomolog (IH) crossovers. This checkpoint shares molecular characteristics with canonical DNA damage checkpoints active during somatic cell cycles. However, idiosyncratic requirements of meiotic prophase have introduced unique features in this signaling cascade. In this review, we discuss the unique features of the meiotic prophase checkpoint. While being related to canonical DNA damage checkpoint cascades, the meiotic prophase checkpoint also shows similarities with the spindle assembly checkpoint (SAC) that guards chromosome segregation. We highlight these emerging similarities in the signaling logic of the checkpoints that govern meiotic prophase and chromosome segregation, and how thinking of these similarities can help us better understand meiotic prophase control. We also discuss work showing that, when aberrantly expressed, components of the meiotic prophase checkpoint might alter DNA repair fidelity and chromosome segregation in cancer cells. Considering checkpoint function in light of demands imposed by the special characteristics of meiotic prophase helps us understand checkpoint integration into the meiotic cell cycle machinery.

Biallelic BUB1 mutations cause microcephaly, developmental delay, and variable effects on cohesion and chromosome segregation

Budding uninhibited by benzimidazoles (BUB1) contributes to multiple mitotic processes. Here, we describe the first two patients with biallelic BUB1 germline mutations, who both display microcephaly, intellectual disability, and several patient-specific features. The identified mutations cause variable degrees of reduced total protein level and kinase activity, leading to distinct mitotic defects. Both patients’ cells show prolonged mitosis duration, chromosome segregation errors, and an overall functional spindle assembly checkpoint. However, while BUB1 levels mostly affect BUBR1 kinetochore recruitment, impaired kinase activity prohibits centromeric recruitment of Aurora B, SGO1, and TOP2A, correlating with anaphase bridges, aneuploidy, and defective sister chromatid cohesion. We do not observe accelerated cohesion fatigue. We hypothesize that unresolved DNA catenanes increase cohesion strength, with concomitant increase in anaphase bridges. In conclusion, BUB1 mutations cause a neurodevelopmental disorder, with clinical and cellular phenotypes that partially resemble previously described syndromes, including autosomal recessive primary microcephaly, mosaic variegated aneuploidy, and cohesinopathies.

Genes Regulating Spermatogenesis and Sperm Function Associated With Rare Disorders

Spermatogenesis is a cell differentiation process that ensures the production of fertilizing sperm, which ultimately fuse with an egg to form a zygote. Normal spermatogenesis relies on Sertoli cells, which preserve cell junctions while providing nutrients for mitosis and meiosis of male germ cells. Several genes regulate normal spermatogenesis, some of which are not exclusively expressed in the testis and control multiple physiological processes in an organism. Loss-of-function mutations in some of these genes result in spermatogenesis and sperm functionality defects, potentially leading to the insurgence of rare genetic disorders. To identify genetic intersections between spermatogenesis and rare diseases, we screened public archives of human genetic conditions available on the Genetic and Rare Diseases Information Center (GARD), the Online Mendelian Inheritance in Man (OMIM), and the Clinical Variant (ClinVar), and after an extensive literature search, we identified 22 distinct genes associated with 21 rare genetic conditions and defective spermatogenesis or sperm function. These protein-coding genes regulate Sertoli cell development and function during spermatogenesis, checkpoint signaling pathways at meiosis, cellular organization and shape definition during spermiogenesis, sperm motility, and capacitation at fertilization. A number of these genes regulate folliculogenesis and oogenesis as well. For each gene, we review the genotype–phenotype association together with associative or causative polymorphisms in humans, and provide a description of the shared molecular mechanisms that regulate gametogenesis and fertilization obtained in transgenic animal models.

Aneuploidy in health, disease, and aging

Aneuploidy, an aberrant number of chromosomes, has been recognized as a feature of human malignancies for over a century, but compelling evidence for causality was largely lacking until mouse models for chromosome number instability were used. These in vivo studies have not only uncovered important new insights into the extremely complex aneuploidy-cancer relationship but also into the molecular mechanisms underlying proper and aberrant chromosome segregation. A series of diverse mouse models for the mitotic checkpoint protein BubR1 has provided evidence for a provocative novel link between aneuploidization and the development of age-related pathologies.

The genomically mosaic brain: aneuploidy and more in neural diversity and disease

Genomically identical cells have long been assumed to comprise the human brain, with post-genomic mechanisms giving rise to its enormous diversity, complexity, and disease susceptibility. However, the identification of neural cells containing somatically generated mosaic aneuploidy - loss and/or gain of chromosomes from a euploid complement - and other genomic variations including LINE1 retrotransposons and regional patterns of DNA content variation (DCV), demonstrate that the brain is genomically heterogeneous. The precise phenotypes and functions produced by genomic mosaicism are not well understood, although the effects of constitutive aberrations, as observed in Down syndrome, implicate roles for defined mosaic genomes relevant to cellular survival, differentiation potential, stem cell biology, and brain organization. Here we discuss genomic mosaicism as a feature of the normal brain as well as a possible factor in the weak or complex genetic linkages observed for many of the most common forms of neurological and psychiatric diseases.

Reduced life- and healthspan in mice carrying a mono-allelic BubR1 MVA mutation

Mosaic Variegated Aneuploidy (MVA) syndrome is a rare autosomal recessive disorder characterized by inaccurate chromosome segregation and high rates of near-diploid aneuploidy. Children with MVA syndrome die at an early age, are cancer prone, and have progeroid features like facial dysmorphisms, short stature, and cataracts. The majority of MVA cases are linked to mutations in BUBR1, a mitotic checkpoint gene required for proper chromosome segregation. Affected patients either have bi-allelic BUBR1 mutations, with one allele harboring a missense mutation and the other a nonsense mutation, or mono-allelic BUBR1 mutations combined with allelic variants that yield low amounts of wild-type BubR1 protein. Parents of MVA patients that carry single allele mutations have mild mitotic defects, but whether they are at risk for any of the pathologies associated with MVA syndrome is unknown. To address this, we engineered a mouse model for the nonsense mutation 2211insGTTA (referred to as GTTA) found in MVA patients with bi-allelic BUBR1 mutations. Here we report that both the median and maximum lifespans of the resulting BubR1^+/GTTA mice are significantly reduced. Furthermore, BubR1^+/GTTA mice develop several aging-related phenotypes at an accelerated rate, including cataract formation, lordokyphosis, skeletal muscle wasting, impaired exercise ability, and fat loss. BubR1^+/GTTA mice develop mild aneuploidies and show enhanced growth of carcinogen-induced tumors. Collectively, these data demonstrate that the BUBR1 GTTA mutation compromises longevity and healthspan, raising the interesting possibility that mono-allelic changes in BUBR1 might contribute to differences in aging rates in the general population.

Aging is the main risk factor for the majority of chronic diseases and the leading cause of death and disability in humans. Humans age at different rates, but the molecular genetic basis underlying this phenomenon remains largely unknown. Efforts to understand how we age have focused on genetic changes that extend lifespan or underlie progeroid disorders. One potential progeroid disorder, MVA syndrome, has been associated with mutations in the mitotic regulator BUBR1. Although MVA syndrome is rare due to its recessive nature, individuals carrying heterozygous BUBR1 mutations associated with MVA would be much more prevalent. However, whether such carriers are asymptomatic or at risk of developing aspects of MVA syndrome later in life is unknown. To investigate this, we engineered mice to carry an analogous mutation to the human MVA BUBR1 nonsense mutation 2211insGTTA. We find that these mice have a reduced lifespan and develop several age-related phenotypes at an accelerated rate. These findings suggest that bi-allelic integrity of BUBR1 is a key determinant of healthspan and longevity, and provide a conceptual framework for elucidating differences in aging rates among humans.

Myogenic tumors in children and adolescents

Neoplasms of striated and smooth muscle in children are a diverse group of neoplasms that have some unique aspects in contrast to these tumors in adults. Rhabdomyosarcoma is the most common soft tissue sarcoma of infancy and childhood and is relatively common in adolescents. In contrast, smooth muscle tumors are relatively rare, and the various types of rhabdomyoma and smooth and skeletal muscle hamartomas are very uncommon. In recent years, the understanding of the pathologic and genetic aspects of rhabdomyosarcoma has been enhanced by adjunct techniques, such as immunohistochemistry and cytogenetic or molecular genetic analysis. The current classification of rhabdomyosarcoma emphasizes the histologic-prognostic correlations. This article reviews the clinicopathologic features of striated and smooth muscle tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents and the differential diagnosis.

Cell cycle activation and aneuploid neurons in Alzheimer's disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder, characterized by synaptic degeneration associated with fibrillar aggregates of the amyloid-ß peptide and the microtubule-associated protein tau. The progression of neurofibrillary degeneration throughout the brain during AD follows a predictive pattern which provides the basis for the neuropathological staging of the disease. This pattern of selective neuronal vulnerability against neurofibrillary degeneration matches the regional degree of neuronal plasticity and inversely recapitulates ontogenetic and phylogenetic brain development which links neurodegenerative cell death to neuroplasticity and brain development. Here, we summarize recent evidence for a loss of neuronal differentiation control as a critical pathogenetic event in AD, associated with a reactivation of the cell cycle and a partial or full replication of DNA giving rise to neurons with a content of DNA above the diploid level. Neurons with an aneuploid set of chromosomes are also present at a low frequency in the normal brain where they appear to be well tolerated. In AD, however, where the number of aneuploid neurons is highly increased, a rather selective cell death of neurons with this chromosomal aberrancy occurs. This finding add aneuploidy to the list of critical molecular events that are shared between neurodegeneration and oncogenesis. It defines a molecular signature for neuronal vulnerability and directs our attention to a failure of neuronal differentiation control as a critical pathogenetic event and potential therapeutic target in AD.

Cytogenetics of primary embryonal rhabdomyosarcoma of the cheek

Rhabdomyosarcoma (RMS) is the most common malignant soft tissue tumour of childhood and has two main subtypes: embryonal and alveolar. The embryonal subtype accounts for most cases in the genitourinary tract and head and neck. Oral presentations are rare, and mainly in the tongue, palate, or cheek. Cytogenetically, alveolar RMS is characterised by the translocation t(2;13)(q35;q14), which plays an important part in diagnosis, but no consistent and unique genetic alterations have been identified in embryonal RMS. It is currently not known whether oral embryonal RMS is similar to those that arise from other sites, as only one cytogenetic report has been published to date. We present the case of a 9-year-old boy with embryonal RMS of the cheek, and discuss the cytogenetic alterations in his case.

Kinetochores and disease: keeping microtubule dynamics in check!

The essential role of microtubules in cell division has long been known. Yet the mechanism by which microtubule attachment to chromosomes at kinetochores is regulated has only been recently revealed. Here, we review the role of kinetochore-microtubule (kMT) attachment dynamics in the cell cycle as well as emerging evidence linking deregulation of kMT attachments to diseases where chromosome mis-segregation and aneuploidy play a central role. Evidence indicates that the dynamic behavior of kMTs must fall within narrow permissible boundaries, which simultaneously allow a level of stability sufficient to establish and maintain chromosome-microtubule attachments and a degree of instability that permits error correction required for accurate chromosome segregation.

BUB1 and BUBR1: multifaceted kinases of the cell cycle

The multidomain protein kinases BUB1 and BUBR1 (Mad3 in yeast, worms and plants) are central components of the mitotic checkpoint for spindle assembly (SAC). This evolutionarily conserved and essential self-monitoring system of the eukaryotic cell cycle ensures the high fidelity of chromosome segregation by delaying the onset of anaphase until all chromosomes are properly bi-oriented on the mitotic spindle. Despite their amino acid sequence conservation and similar domain organization, BUB1 and BUBR1 perform different functions in the SAC. Recent structural information provides crucial molecular insights into the regulation and recognition of BUB1 and BUBR1, and a solid foundation to dissect the roles of these proteins in the control of chromosome segregation in normal and oncogenic cells.

Neuronal aneuploidy in health and disease: a cytomic approach to understand the molecular individuality of neurons

Structural variation in the human genome is likely to be an important mechanism for neuronal diversity and brain disease. A combination of multiple different forms of aneuploid cells due to loss or gain of whole chromosomes giving rise to cellular diversity at the genomic level have been described in neurons of the normal and diseased adult human brain. Here, we describe recent advances in molecular neuropathology based on the combination of slide-based cytometry with molecular biological techniques that will contribute to the understanding of genetic neuronal heterogeneity in the CNS and its potential impact on Alzheimer's disease and age-related disorders.

Clinical and genetic heterogeneity in patients with mosaic variegated aneuploidy: delineation of clinical subtypes

Mosaic variegated aneuploidy (MVA) is a rare autosomal recessive syndrome related to BUB1B gene mutations and characterized by multiple mosaic aneuploidies, cancer predisposition, and a distinct phenotype. We report on two mildly affected sibs with MVA syndrome but without BUB1B mutation. Both patients exhibited growth retardation, frontal bossing, triangular face and micrognathia but not microcephaly or cancer. Aneuploidies were assessed both in G-banded metaphases from lymphocyte cultures and in interphase nuclei from buccal cells by FISH. Screening of 23 exons and intron-exon boundaries of BUB1B was also carried out. These patients were then compared with other 19 MVA patients screened for BUB1B mutations. Around one half of the cultured lymphocytes from our patients had aneuploidies ranging from nullisomies to heptasomies; the most frequent abnormalities were trisomies (42%) and monosomies (28%). FISH results demonstrated more chromosomal losses than gains. Screening of BUB1B in our two patients failed to identify any mutation. A review of the 21/35 patients screened for BUB1B demonstrated three clinical pictures. Patients with monoallelic BUB1B mutations were severely affected with Dandy-Walker complex (7/8), cataracts (6/6), and Wilms' tumor (7/8); premature chromatid separation (PCS) was observed in 8/8 propositi and 7/7 carrier parents. Patients without BUB1B mutations were mildly affected with no evidence of cancer, Dandy-Walker malformation or cataract, and rarely (1/7) showed PCS. Finally, patients with biallelic BUB1B mutations showed a moderate phenotype. The distinct MVA clinical groups delineated here point to involvement of at least another mitotic spindle checkpoint gene in addition to the BUB1B gene.

Mosaic variegated aneuploidy without microcephaly: implications for cytogenetic diagnosis

Mosaic variegated aneuploidy (MVA) is a rare condition characterized by multiple trisomies, rarely monosomies, and a non-specific phenotype including microcephaly, growth and mental retardation, mild malformations, and an increased risk of malignancy. We describe a patient with MVA in whom trisomy 19 mosaicism was originally suspected. The patient was the product of an uncomplicated term pregnancy and delivery. Significant findings were mental retardation, obesity, mild epicanthal folds, tapering fingers, relatively small hands and feet, alternating exotropia, nasal speech limited to short phrases, and generalized hypotonia. There is no family history for birth defects, mental retardation, or consanguinity. The initial peripheral blood chromosome study showed trisomy 19 in 4 of 31 metaphase cells. Because mosaic trisomy 19 is rare, the study was extended to 100 cells, wherein two cells with trisomy 8 were identified. A second blood karyotype was obtained and found to be 47,XX,+8[3]/47,XX,+19[3]/47,XX, +18[2]/47,XX,+9[1]/46,XX[91]. Skin fibroblast chromosome studies revealed a 46,XX karyotype in 120 cells examined. There was no evidence of premature centromere separation. Mutations in the BUB1B gene that encodes a key mitotic spindle checkpoint protein have been described in MVA; however, no mutations of this gene were identified in our patient. This case illustrates the importance of considering other possibilities when confronted with an extremely rare diagnosis such as mosaic trisomy 19. In addition, it shows the importance of not simply interpreting a low percentage of multiple aneuploidies as cell culture artifact, because an additional work-up to rule out MVA may be warranted since this diagnosis is associated with an increased risk of malignancy.

Does aneuploidy cause cancer?

Aneuploidy has been recognized as a common characteristic of cancer cells for >100 years. Aneuploidy frequently results from errors of the mitotic checkpoint, the major cell cycle control mechanism that acts to prevent chromosome missegregation. The mitotic checkpoint is often compromised in human tumors, although not as a result of germline mutations in genes encoding checkpoint proteins. Less obviously, aneuploidy of whole chromosomes rapidly results from mutations in genes encoding several tumor suppressors and DNA mismatch repair proteins, suggesting cooperation between mechanisms of tumorigenesis that were previously thought to act independently. Cumulatively, the current evidence suggests that aneuploidy promotes tumorigenesis, at least at low frequency, but a definitive test has not yet been reported.

Nondisjunction, aneuploidy and tetraploidy

One simple, widely accepted mechanism for generating an aberrant chromosome number, or aneuploidy, is through nondisjunction--a chromosome distribution error that occurs during mitosis when both copies of a duplicated chromosome are deposited into one daughter cell and none into the other. Shi and King challenge this view, concluding that nondisjunction does not yield aneuploid cells directly, but instead gives rise to tetraploid cells that may subsequently become aneuploid through further division. Here we show that the direct result of chromosome nondisjunction is gain or loss of a single chromosome, which results in near-diploid aneuploidy, not tetraploidy. We suggest that chromatin trapped in the cytokinetic cleavage furrow is the more likely reason for furrow regression and tetraploidization.

Microcephaly is not mandatory for the diagnosis of mosaic variegated aneuploidy syndrome

The phenotype of mosaic variegated aneuploidy (MVA) syndrome is characterized by severe microcephaly, growth deficiency, mental retardation, and mild physical anomalies. The MVA syndrome is associated with mosaicism for several different aneuploidies involving many different chromosomes with or without premature centromere division (PCD). To date 28 cases of MVA syndrome have been reported. We report the first case of MVA syndrome without microcephaly. The clinical features in our patient included craniofacial dysmorphic features, growth retardation, and developmental delay. Cytogenetics analyses and FISH studies showed multiple aneuploidy with trisomy 18, 19, and 8, respectively in blood lymphocyte and fibroblasts without PCD. This case is compared with the other of MVA syndrome previously reported in literature. From this case report, we suggest that microcephaly is not mandatory for the diagnosis of MVA syndrome.

Constitutional aneuploidy and cancer predisposition caused by biallelic mutations in BUB1B

Mosaic variegated aneuploidy is a rare recessive condition characterized by growth retardation, microcephaly, childhood cancer and constitutional mosaicism for chromosomal gains and losses. In five families with mosaic variegated aneuploidy, including two with embryonal rhabdomyosarcoma, we identified truncating and missense mutations of BUB1B, which encodes BUBR1, a key protein in the mitotic spindle checkpoint. These data are the first to relate germline mutations in a spindle checkpoint gene with a human disorder and strongly support a causal link between aneuploidy and cancer development.

Cystic partially differentiated nephroblastoma, embryonal rhabdomyosarcoma, and multiple congenital anomalies associated with variegated mosaic aneuploidy and premature centromere division: a case report

A rare association of embryonal genitourinary tumor(s) with cerebral malformations has been reported in eight infants with variegated mosaic aneuploidy (VMA) and premature centromere division. The authors report a new case of cystic partially differentiated nephroblastoma and embryonal rhabdomyosarcoma associated with VMA, premature centromere division, microcephalus, Dandy-Walker malformation, and cataracts. Nonrandom involvement of the chromosomes was found in VMA of the lymphocytes and the skin fibroblasts. In the cultured nephroblastoma cells, hyperdiploidy involving the same group of chromosomes involved in VMA of the somatic cells was observed, suggesting their derivation from the aneuploid population of the somatic cells.

Mosaic variegated aneuploidy with growth hormone deficiency and congenital heart defects

We describe a 12-year-old boy with mosaic variegated aneuploidy (MVA), subnormal response to growth hormone (GH) stimulation testing, and short stature. In addition to features more commonly described in MVA such as microcephaly, cognitive deficits, and certain facial features, he also has features not commonly reported in MVA, including short limb segments, epidermoid cysts, ventricular septal defect, and subaortic stenosis. Chromosomal analysis revealed hyperdiploid chromosome numbers ranging from 47 to 70; modal number 50, in 24% of the metaphases. This case demonstrates that although the phenotype of MVA almost always includes growth failure, microcephaly, and mental retardation, additional features may vary greatly across individuals. His clinical features and course suggest that in addition to GH deficiency, he may have an intrinsic inability of the growth plate to respond to growth hormone.

High risk of malignancy in mosaic variegated aneuploidy syndrome

Fourteen cases of mosaic variegated aneuploidy (MVA) syndrome have been reported in the last 10 years. The phenotype of this rare condition has been quite consistent: severe microcephaly, growth deficiency, mild physical anomalies, and mental retardation. We describe here a young boy in whom MVA syndrome is associated to myelodysplasia with a monosomy 7 bone marrow clone. At the age of 3 years, myelodysplasia progressed to an acute lymphoblastic leukemia, and the patient died soon after. Several syndromes with short stature and severe microcephaly, such as the Seckel and Nijmegen syndromes, comprise hematological findings and chromosome instability. However, chromosome instability was not confirmed in our patient. MVA with hematological findings has not been reported before, but 3 patients of 14 (21%) have developed a malignancy (rhabdomyosarcoma, acute lymphoblastic leukemia, and nephroblastoma). Therefore, we propose that MVA is a condition predisposing to neoplasia.

Cancer-prone syndrome of mosaic variegated aneuploidy and total premature chromatid separation: report of five infants

Five infants (two girls and three boys) from four families all had severe pre- and postnatal growth retardation, profound developmental delay, microcephaly, hypoplasia of the brain with Dandy-Walker complex or other posterior fossa malformations, and developed uncontrollable clonic seizures. Four infants developed Wilms tumors, and one showed cystic lesions in bilateral kidneys. All five infants showed variegated mosaic aneuploidy in cultured lymphocytes. In two infants whose chromosomes were prepared by us, 48.5%-83.2% lymphocytes showed total premature chromatid separation (PCS). Their parents had 3.5%-41.7% of their lymphocytes in total PCS. The remaining three infants and their parents, whose chromosomes were prepared at outside laboratories, tended to show lower frequencies of total PCS. Another five infants reported with the disorder were reviewed together with the five infants we described. Together, their clinical and cytogenetic manifestations were similar enough to suggest a syndrome. Seven of the 10 infants developed proven or probable Wilms tumors. The age at diagnosis of the tumors was younger than usual at 2-16 months. The tumors were bilateral in four infants and unilateral in three infants, and cystic changes were present in six infants. Two infants developed botryoid rhabdomyosarcoma. The carriers of the syndrome are thus liable to tumorigenesis. The possible role of mitotic checkpoint defects, proven in two infants with the syndrome (Matsuura et al. [2000: Am J Hum Genet 69:483-486]), was discussed in connection with tumor development and progression.

Variegated aneuploidy related to premature centromere division (PCD) is expressed in vivo and is a cancer-prone disease

We present three patients with variegated aneuploidy and premature centromere division (PCD), a rare chromosomal abnormality in humans. Comparison of these three and eight other patients with variegated aneuploidy related to PCD demonstrates a phenotype comprising most frequently microcephaly, CNS anomalies (with cerebellar affection and migration defects), mental retardation, pre-and postnatal growth retardation, flat and broad nasal bridge, apparently low-set ears, eye and skin abnormalities, and ambiguous genitalia in male patients. The occurrence of Wilms tumor in three patients, rhabdomyosarcoma in two others and acute leukemia in a fifth characterizes this condition as a chromosome or genome instability disorder with a high risk of malignancy. FISH studies in uncultured blood and buccal smear cells demonstrate that the random aneuploidies are not limited to cultured cells, but also occur in vivo.