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PubMed1994

Uniparental disomy occurs infrequently in Wilms tumor patients.

Wilms tumors commonly exhibit loss of heterozygosity for polymorphic DNA markers located on the short arm of chromosome 11 at band p15. In some instances, the deleted region does not include 11p13, the location of the WT1 gene, suggesting the existence of a second Wilms tumor gene on 11p. Both the exclusive loss of the maternally derived allele in Wilms tumors and the recent description of constitutional paternal isodisomy for this region in patients with either the Beckwith-Wiedemann syndrome (BWS) or isolated hemihypertrophy have suggested that this second locus is subject to sex-specific genomic imprinting. Given that one of these isodisomic patients had minimal congenital anomalies (hemihypertrophy), we hypothesized that a proportion of Wilms tumors which had not lost heterozygosity for 11p markers (about 60% of all cases) might have arisen consequent to 11p paternal heterodisomy and that patients constitutionally homozygous at 11p15 might harbor paternal isodisomy. We have analyzed 40 Wilms tumor cases to determine the parental origin of the child's 11p15 alleles. Paternal heterodisomy could be excluded in all 28 unilateral and 8/9 bilateral potential candidates. It is intriguing that somatic mosaicism for 11p paternal isodisomy was detected in one child with bilateral Wilms tumor and macroglossia. Isodisomy could only be excluded in one of the three possible cases. Thus, 11p paternal hetero- and isodisomy appear to be uncommon causes of non-anomaly-associated Wilms tumors but may be more frequent in Wilms tumor patients with BWS-associated anomalies.

Aneuploidy↗
PubMed1997

Role of imprinting in abnormal human development.

Parental-specific differences in the expression of certain genes (imprinting), may be implicated in the pathogenesis of anomalous gestations, but only a minority manifest themselves as malformation syndromes. Delayed or lost gestations are much more frequent sequelae, as are those disorganized to such an extent that they are usually classified as neoplastic rather than developmental processes. Expression levels from imprinted loci are dependent not only on the number of genomic alleles present and their structural integrity, but also on their specific parental origin. Anomalous expression of imprinted genes during development is sometimes caused by imbalanced representation of maternal and paternal contributions, 'uniparental disomy'. Uniparental parthenogenetic or androgenetic gestations form ovarian teratomas or complete hydatidiform moles, respectively--examples of an arrested developmental program. Uniparental disomy of individual chromosomes or portions thereof has been associated with developmental delay or gestational loss. The phenotype of hemizygous mutation or deletion of imprinted genes is modified by the parental origin of the mutant copy, with dichotomous syndromes defined by parental inheritance, as in the Prader-Willi and Angelman syndromes. Lastly, failure of the imprinting process itself, 'loss of imprinting', may quantitatively alter expression levels of normally imprinted transforming or tumor-suppressing genes, thereby increasing risk for developmental tumors such as Wilms' tumor or choriocarcinoma.

Abortion, Spontaneous↗
PubMed2006

Interactions between imprinting effects: summary and review.

Mice with uniparental disomies (uniparental duplications) for defined regions of certain chromosomes, or certain disomies, show a range of developmental abnormalities most of which affect growth. These defects can be attributed to incorrect dosages of maternal or paternal copies of imprinted genes lying within the regions involved. Combinations of certain partial disomies result in interactions between the imprinting effects that seemingly independently affect foetal and/or placental growth in different ways or modify neonatal and postnatal development. The findings are generally in accord with the 'conflict hypothesis' for the evolution of genomic imprinting but do not demonstrate common growth axes within which imprinted genes may interact. Instead, it would seem that any gene that favours embryonic/foetal development, at consequent cost to the mother, will have been subject to evolutionary selection for only paternal allele expression. Reciprocally, any gene that reduces embryonic/foetal growth to limit disadvantage to the mother will have been selected for only maternal allele expression. It is concluded that survival of the placenta is core to the evolution of imprinting.

Chromosome Mapping↗
PubMed2002

[Insulin-dependent neonatal and infant diabetes: genetics and physiopathology].

Insulin-dependent neonatal diabetes (ND) mellitus is uncommon with a frequency of 1/500,000 neonates in Europe. ND is characterised by hyperglycaemia, very low or undetectable insulin levels associated with intrauterine growth retardation and malformations. HLA haplotypes of juvenile diabetes or autoimmunity are not present in ND patients. Sporadic and familial forms are observed. ND could be persistent (PND) or transient (TND). Diabetes relapses occur in approximately 40% of TND patients. Hypothesis for ND aetiology such as pancreatic or beta pancreatic islets of Langerhans immaturity or abnormalities of pancreas organogenesis are postulated. Different genetic basis underlie transient or permanent forms though their clinical features do not allow to distinguish them. TND may in about 20-30% of the cases be associated with chromosome 6 paternal uniparental disomy. A candidate locus for an imprinted gene is mapped to 6q24. The permanent forms are less understood. Homozygous mutations of the IPF1/PDX1 (MODY4) and of the Glucokinase (GK, MODY2) genes have been reported. The association of a ND with a macroglossia should be a strong indicator for genetic testing. The genetic findings of a paternal disomy uniparental allows the prediction of a transient rather than a permanent form. Mutation in the Glucokinase gene should be sought in an infant with ND whose first degree relatives have glucose intolerance.

Chromosome Banding↗
PubMed2004

Mosaic paternal uniparental (iso)disomy for chromosome 20 associated with multiple anomalies.

Uniparental disomy for a number of human chromosomes is associated with clinical abnormalities. We report a child with a complex chromosomal rearrangement involving chromosome 20 (45,XY,psu dic (20;20)(p13;p13)) and paternal uniparental isodisomy for chromosome 20 in peripheral blood and bone marrow. This patient had multiple congenital abnormalities including microtia/anotia, micrencephaly, congenital heart disease, neuronal subependymal heterotopias, and colonic agangliosis. Molecular studies on DNA from peripheral blood demonstrated paternal uniparental inheritance of chromosome 20. However, fibroblasts demonstrated a mosaic karyotype, with one cell line having 45 chromosomes, including the pseudodicentric chromosome 20 (75% of cells), and a second cell line having 46 chromosomes, including the pseudodicentric chromosome 20, and a normal chromosome 20 (trisomy 20) (25% of cells). FISH experiments using a sub-telomeric probe that maps approximately 120 kb from the 20p telomere, showed that both copies of these sequences were present on the rearranged chromosome, consistent with deletion of a very small interval. This leads us to suggest that in addition to trisomy 20 mosaicism, paternal uniparental disomy for chromosome 20 could contribute to his clinical phenotype.

Abnormalities, Multiple↗