Trisomy 10 mosaicism and maternal uniparental disomy 10 in a liveborn infant with severe congenital malformations

Ontogenetic and Pathogenetic Views on Somatic Chromosomal Mosaicism

Intercellular karyotypic variability has been a focus of genetic research for more than 50 years. It has been repeatedly shown that chromosome heterogeneity manifesting as chromosomal mosaicism is associated with a variety of human diseases. Due to the ability of changing dynamically throughout the ontogeny, chromosomal mosaicism may mediate genome/chromosome instability and intercellular diversity in health and disease in a bottleneck fashion. However, the ubiquity of negligibly small populations of cells with abnormal karyotypes results in difficulties of the interpretation and detection, which may be nonetheless solved by post-genomic cytogenomic technologies. In the post-genomic era, it has become possible to uncover molecular and cellular pathways to genome/chromosome instability (chromosomal mosaicism or heterogeneity) using advanced whole-genome scanning technologies and bioinformatic tools. Furthermore, the opportunities to determine the effect of chromosomal abnormalities on the cellular phenotype seem to be useful for uncovering the intrinsic consequences of chromosomal mosaicism. Accordingly, a post-genomic review of chromosomal mosaicism in the ontogenetic and pathogenetic contexts appears to be required. Here, we review chromosomal mosaicism in its widest sense and discuss further directions of cyto(post)genomic research dedicated to chromosomal heterogeneity.

Identification of paternal uniparental disomy on chromosome 22 and a de novo deletion on chromosome 18 in individuals with orofacial clefts

Background

Orofacial clefts are the most common malformations of the head and neck region. Genetic and environmental factors have been implicated in the etiology of these traits.

Methods

We recently conducted genotyping of individuals from the African population using the multiethnic genotyping array (MEGA) to identify common genetic variation associated with nonsyndromic orofacial clefts. The data cleaning of this dataset allowed for screening of annotated sex versus genetic sex, confirmation of identify by descent and identification of large chromosomal anomalies.

Results

We identified the first reported orofacial cleft case associated with paternal uniparental disomy (patUPD) on chromosome 22. We also identified a de novo deletion on chromosome 18. In addition to chromosomal anomalies, we identified cases with molecular karyotypes suggesting Klinefelter syndrome, Turner syndrome and Triple X syndrome.

Conclusion

Observations from our study support the need for genetic testing when clinically indicated in order to exclude chromosomal anomalies associated with clefting. The identification of these chromosomal anomalies and sex aneuploidies is important in genetic counseling for families that are at risk. Clinicians should share any identified genetic findings and place them in context for the families during routine clinical visits and evaluations.

Mosaicism trisomy 10 in a 14-month-old child with additional neurological abnormalities: case report and literature review

Background

Trisomy 10 is very rarely diagnosed, especially in living persons. Most reports of trisomy 10 pertain to prenatal diagnosis of trisomy 10 in the fetus. In addition, trisomy 10 has been reported as part of partial chromosomal abnormalities in some leukemic cells and tumor specimens. Only 6 cases of mosaicism trisomy 10 have been reported so far. None of these reports pertain to living children with neurological abnormalities.

Case presentation

We report the case of a 14-month-old girl who was brought for treatment of unusual facies, growth retardation, and patent ductus arteriosus. Karyotype analysis revealed a 47, XX, + 10/46, XX pattern. MRI showed characteristics of Dandy–Walker syndrome and ventricular enlargement in the brain.

Conclusions

This case is distinguished by its extreme rarity and its potential for use as a reference case of this condition in clinical settings.

Causal variants screened by whole exome sequencing in a patient with maternal uniparental isodisomy of chromosome 10 and a complicated phenotype

Uniparental disomy (UPD), which is the abnormal situation in which both copies of a chromosomal pair have been inherited from one parent, may cause clinical abnormalities by affecting genomic imprinting or causing autosomal recessive variation. Whole Exome Sequencing (WES) and chromosomal microarray analysis (CMA) are powerful technologies used to search for underlying causal variants. In the present study, WES was used to screen for candidate causal variants in the genome of a Chinese pediatric patient, who had been shown by CMA to have maternal uniparental isodisomy of chromosome 10. This was associated with numerous severe medical problems, including bilateral deafness, binocular blindness, stunted growth and leukoderma. A total of 13 rare homozygous variants of these genes were identified on chromosome 10. These included a classical splice variant in the HPS1 gene (c.398+5G>A), which causes Hermansky-Pudlak syndrome type 1 and may explain the patient's ocular and dermal disorders. In addition, six likely pathogenic genes on other chromosomes were found to be associated with the subject's ocular and aural disorders by phenotypic analysis. The results of the present study demonstrated that WES and CMA may be successfully combined in order to identify candidate causal genes. Furthermore, a connection between phenotype and genotype was established in this patient.

Prenatal diagnosis of bilateral ectrodactyly and radial agenesis associated with trisomy 10 mosaicism

Ectrodactyly or split hand and foot malformations (SHFMs) are rare malformations of the limbs, characterized by median clefts of the hands and feet, syndactyly, and aplasia and/or hypoplasia of the phalanges. They represent a clinically and genetically heterogeneous disorder, with both sporadic and familial cases. Most of the genomic rearrangements identified to date in some forms of SHFM are autosomal dominant traits, involving various chromosome regions. Bilateral radial ray defects comprise also a large heterogenous group of disorders, including trisomy 18, Fanconi anemia, and thrombocytopenia-absent-radius syndrome, not commonly associated with ectrodactyly. The present paper describes a case of ectrodactyly associated with bilateral radial ray defects, diagnosed in the first trimester of pregnancy, in a fetus affected by trisomy 10. Only four cases of sporadic and isolated ectrodactyly, diagnosed by ultrasonography between 14 and 22 weeks' gestation, have been reported. To our knowledge, the present case is the first report of mosaic trisomy 10 associated with SHFM and radial aplasia. Trisomy 10 is a rare lethal chromosomal abnormality, most frequently found in abortion products. Only six liveborn mosaic trisomy 10 infants, with severe malformations, dead in early infancy, have been reported. A severe clinical syndrome can be defined, comprising ear abnormalities, cleft lip/palate, malformations of eyes, heart, and kidneys, and deformity of hands and feet and most often associated with death neonatally or in early infancy.

Constitutional and acquired autosomal aneuploidy

Chromosomal imbalances can result from numerical or structural anomalies. Numerical chromosomal abnormalities are often referred to as aneuploid conditions. This article focuses on the occurrence of constitutional and acquired autosomal aneuploidy in humans. Topics covered include frequency, mosaicism, phenotypic findings, and etiology. The article concludes with a consideration of anticipated advances that might allow for the development of screening tests and/or lead to improvements in our understanding and management of the role that aneuploidy plays in the aging process and acquisition of age-related and constitutional conditions.

Novel mutation of the perforin gene and maternal uniparental disomy 10 in a patient with familial hemophagocytic lymphohistiocytosis

Familial hemophagocytic lymphohistiocytosis is a rare disorder characterized by lethal primary immunodeficiency associated with hypercytokinemia and a concomitant defect in natural killer cell cytotoxicity. We report a fatal case of familial hemophagocytic lymphohistiocytosis homozygous caused by a novel nonsense mutation of the perforin gene. Homozygosity was established to be the result of uniparental disomy of the maternal chromosome 10. Uniparental disomy increases the risk of autosomal recessive disease.