Paternal Uniparental Disomy Of Chromosome Research Articles

Transient Neonatal Diabetes Mellitus in an Infant with Paternal Uniparental Disomy of Chromosome 6 Including Heterodisomy for 6q24

We describe a female infant who developed transient neonatal diabetes mellitus (TNDM) (MIM 601410). At birth she presented with growth retardation and macroglossia. Diabetes was diagnosed on the fourth day of life and it resolved after two months of insulin therapy. Genetic testing revealed the presence of paternal uniparental disomy of chromosome 6 (UPD6) including heterodisomy of 6q24. This is the first documented case of uniparental heterodisomy for chromosome 6.

Segmental and full paternal isodisomy for chromosome 14 in three patients: Narrowing the critical region and implication for the clinical features

We report on segmental and full paternal isodisomy for chromosome 14 in three previously unreported Japanese patients. Patient 1 was a 5(6/12)-year-old girl, Patient 2 was a male neonate, and Patient 3 was a -year-old girl. Physical examination at birth showed various somatic features characteristic of paternal uniparental disomy for chromosome 14 (upd(14)pat) such as hairy forehead, protruding philtrum, micrognathia, small thorax, and abdominal wall defects in Patients 1-3, and the constellation of somatic features was persistently observed in Patients 1 and 3. Radiological studies at birth delineated unique bell-shaped thorax with coat-hanger appearance of the ribs in Patients 1-3, but the thoracic deformity ameliorated in Patients 1 and 3 by mid childhood. Chromosome analysis showed a 46,XX karyotype in Patients 1 and 3 and was not performed in Patient 2. Microsatellite analysis indicated full paternal isodisomy for chromosome 14 in Patients 1 and 2 and segmental paternal isodisomy for chromosome 14 distal to D14S981 at 14q23.3 in Patient 3. Methylation specific PCR assay for the differentially methylated region (DMR) of GTL2 at 14q32 yielded positive products with methylated allele specific primers and no products with unmethylated allele specific primers in Patients 1-3. Since clinical phenotype was similar between Patient 3 with segmental upd(14)pat and Patients 1 and 2 with full upd(14)pat, the results are keeping with the 14q32 localized imprinted genes as the critical components of the phenotype observed in upd(14)pat and help narrow the search for additional genes to the approximately 40 Mb region distal to D14S981. Furthermore, it is likely that the characteristic thoracic deformity ameliorates with age.

Paternal uniparental disomy of chromosome 14 and unique exchange of chromosome 7 in cases of spontaneous abortion

To investigate the involvement of uniparental disomies (UPDs) in spontaneous abortion, the polymorphic patterns of microsatellites on each chromosome were analyzed in 164 cases of abortion. Eighty-three of the 164 cases had chromosomal abnormalities. In 79 of the remaining 81 cases with normal karyotypes, the microsatellite analysis revealed that biparental patterns were present in the informative microsatellites in all chromosomes. In one of the remaining two cases, however, the polymorphic patterns of chromosome 14 appeared to be both of paternal origin. The patterns of the distal of the long arm were homozygous, and those of the remaining region were heterozygous. That is, this fetus had paternal UPD 14, originating from meiosis I nondisjunction. In the other case, the polymorphic patterns of the distal one third of the long arm of chromosome 7 were uniparental (maternal) in origin whereas those of the remaining region of this chromosome were biparental. These findings thus suggested that this chromosome might have originated from chromatid exchange between the long arms of paternal and maternal chromosome 7 at the first mitotic division. Microsatellite analysis, however, produced no evidence of duplication or deletion of any segments. The findings also suggest the possibility that some UPDs may cause spontaneous abortion.

Bisulphite sequencing of the transient neonatal diabetes mellitus DMR facilitates a novel diagnostic test but reveals no methylation anomalies in patients of unknown aetiology

Transient neonatal diabetes mellitus (TNDM) is associated with overexpression of an imprinted locus on chromosome 6q24; this locus contains a differentially methylated region (DMR) consisting of an imprinted CpG island that normally allows expression only from the paternal allele of genes under its control. Three types of abnormality involving 6q24 are known to cause TNDM: paternal uniparental disomy of chromosome 6 (pUPD6), an isolated methylation defect of the imprinted CpG island at chromosome 6q24 and a duplication of 6q24 of paternal origin. A fourth group of patients has no identifiable anomaly of 6q24. Bisulphite sequencing of the DMR has facilitated the development of a diagnostic test for TNDM based on ratiometric methylation-specific polymerase chain reaction. We have applied this method to 45 cases of TNDM, including 12 with pUPD6, 11 with an isolated methylation mutation at 6q24, 16 with a duplication of 6q24 and six of unknown aetiology, together with 29 normal controls. All were correctly assigned. The method is therefore capable of detecting all known genetic causes of TNDM at 6q24, although pUPD6 and methylation mutation cases are not distinguished from one another. In addition, we have carried out bisulphite sequencing of the DMR to compare its methylation status between six TNDM patients with a known methylation mutation, six patients with no identifiable 6q24 mutation and six normal controls. Whereas methylation mutation patients showed a near-total absence of DNA methylation at the TNDM locus, the patients with no identified molecular anomaly showed no marked methylation variation from controls.

Skeletal defects in paternal uniparental disomy for chromosome 14 are re-capitulated in the mouse model (paternal uniparental disomy 12).

Human paternal uniparental disomy for chromosome 14 (upd(14)pat) presents with skeletal abnormalities, joint contractures, dysmorphic facial features and developmental delay/mental retardation. Distal human chromosome 14 (HSA14) is homologous to distal mouse chromosome 12 (MMU12) and both regions have been shown to contain imprinted genes. In humans, consistent radiographic findings include a narrow, bell-shaped thorax with caudal bowing of the anterior ribs, cranial bowing of the posterior ribs and flaring of the iliac wings without shortening or dysplasia of the long bones. Mice with upd(12)pat have thin ribs with delayed ossification of the sternum, skull and feet. In both mice and humans, the axial skeleton is predominantly affected. We hypothesize that there is an imprinted gene or genes on HSA14/MMU12 that specifically affects rib/thorax development and the maturation of ossification centers in the sternum, feet and skull with little effect on long bone development.

Paternal uniparental disomy 14: introducing the "coat-hanger" sign.

Paternal uniparental disomy for chromosome 14 (patUPD14) is a rare condition, this being the eighth report. A male infant, born prematurely, was noted to have extremely lax skin and bilateral inguinal hernias. Skin biopsy confirmed the clinical diagnosis of congenital cutis laxa, but this did not explain the limb abnormalities. Radiographic findings (particularly the "coat-hanger" configuration of the ribs on the chest radiograph), suggested a diagnosis of patUPD14, which was confirmed following DNA analysis. The patient died after prolonged respiratory failure. This combination of patUPD14 and congenital cutis laxa has not previously been described. Radiology can play a pivotal role in guiding the geneticist's choice of investigation.

Mutations in the DNAH11 (axonemal heavy chain dynein type 11) gene cause one form of situs inversus totalis and most likely primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD; MIM 242650) is an autosomal recessive disorder of ciliary dysfunction with extensive genetic heterogeneity. PCD is characterized by bronchiectasis and upper respiratory tract infections, and half of the patients with PCD have situs inversus (Kartagener syndrome). We characterized the transcript and the genomic organization of the axonemal heavy chain dynein type 11 (DNAH11) gene, the human homologue of murine Dnah11 or lrd, which is mutated in the iv/iv mouse model with situs inversus. To assess the role of DNAH11, which maps on chromosome 7p21, we searched for mutations in the 82 exons of this gene in a patient with situs inversus totalis, and probable Kartagener syndrome associated with paternal uniparental disomy of chromosome 7 (patUPD7). We identified a homozygous nonsense mutation (R2852X) in the DNAH11 gene. This patient is remarkable because he is also homozygous for the F508del allele of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Sequence analysis of the DNAH11 gene in an additional 6 selected PCD sibships that shared DNAH11 alleles revealed polymorphic variants and an R3004Q substitution in a conserved position that might be pathogenic. We conclude that mutations in the coding region of DNAH11 account for situs inversus totalis and probably a minority of cases of PCD.

Paternal UPD14 is responsible for a distinctive malformation complex.

We present a boy and two girls with paternal uniparental disomy of chromosome 14q (patUPD14). One girl had a Robertsonian translocation, whereas two a normal karyotype. Based on the manifestations of these patients and four previously reported patients who all had translocated chromosome 14, The patUPD14 was thought to constitute a distinctive syndrome. The hallmarks included abdominal muscular defects, skeletal anomalies, and characteristic facies. The phenotype of patUPD14 was consistent with that of a previously reported mouse model, i.e., mouse embryos with paternal uniparental disomy of chromosome 12 that has a region orthologous to that of human chromosome 14. Dose effects of newly recognized imprinted genes on human chromosome 14q32, DLK1 and GTL2, could play an important role in the pathogenic mechanism of the distinctive malformation complex.

Imprinting of a Small Nucleolar RNA Gene on Mouse Chromosome 12

We have identified a novel, maternally expressed imprinted gene encoding a C/D-box small nucleolar RNA (snoRNA) called MBII-343, which may regulate RNA editing or alternative splicing of an as yet unknown target gene. This gene is closely linked to an imprinted gene, Meg3, on mouse distal chromosome 12, which is syntenic to human chromosome 14. The paternal duplication of mouse distal chromosome 12 leads to late embryonal/neonatal lethality, growth promotion, and cardiomyopathy, whereas maternal duplication leads to late embryonal lethality and growth retardation. Human paternal uniparental disomy for chromosome 14 leads to musculoskeletal problems and mental retardation, whereas maternal uniparental disomy leads to intrauterine growth retardation, motor developmental delay, premature puberty, hypotonia, joint laxity, macrocephaly, short statue, neonatal poor sucking, skill with jigsaw puzzles, skin picking, obesity, and maturity onset diabetes of the young.

Cardiomyopathy in mice with paternal uniparental disomy for chromosome 12.

Mice inheriting both copies of MMU12 either maternally or paternally demonstrate imprinting effects. Whereas maternal uniparental disomy 12 (matUPD12) fetuses are growth retarded and die perinatally, paternal UPD12 (patUPD12) fetuses die during late gestation and exhibit placentomegaly and skeletal muscle maturation defects. To examine further the developmental consequences of UPD12, we intercrossed mouse stocks heterozygous for Robertsonian translocation chromosomes (8.12) and (10.12). We report that at 13.5-14.5 dg patUPD12 hearts exhibit increased ventricular diameter, thinner, less compact myocardium, and deep intertrabecular recesses when compared to controls. These data provide evidence for cardiac failure, a lethal condition, and suggest a role for an imprinted gene(s) in normal heart development.

American College of Medical Genetics Statement on Diagnostic Testing for Uniparental Disomy

American College of Medical Genetics Statement on Diagnostic Testing for Uniparental Disomy

Maternal and Paternal Chromosomes 7 Show Differential Methylation of Many Genes in Lymphoblast DNA

Genomic imprinting, the differential expression of paternal and maternal alleles, involves many chromosomal regions and plays a role in development and growth. Differential methylation of maternal and paternal alleles is a hallmark of imprinted genes, and thus methylation assays are widely used to support the identification of novel imprinted genes. Either blood or lymphoblast DNAs are most often used in these assays, even though methylation levels may change in cell culture. We undertook a systematic survey of parent-of-origin-specific methylation of chromosome 7 genes and ESTs by comparing DNA samples from cases of maternal and paternal uniparental disomy for chromosome 7 using DNA from fresh blood and lymphoblast cell lines. Our results revealed that up to 41% of genes and ESTs show parent-of-origin-specific methylation differences in lymphoblast DNA after only a short time in culture, whereas methylation differences were not seen in blood DNA. The methylation changes occurred most commonly on paternal chromosome 7, whereas alterations on maternal chromosome 7 were more infrequent and weaker. These findings indicate that methylation patterns may change significantly during cell culture in a parent-of-origin-dependent manner and suggest that methylation is maintained differently on maternal and paternal chromosomes 7.

Chromosome abnormalities and epilepsy.

Chromosome abnormalities are often associated with central nervous system (CNS) malformations and with other neurologic dysfunctions. In particular, patients with chromosomal abnormalities can have mental retardation (MR) and have a higher risk for seizures than that found in the general population (1). Genetic tools such as karyotyping, high-resolution chromosome banding, fluorescent in situ hybridization (FISH), and other molecular genetics techniques have increased the number of chromosome abnormalities detected in subjects with MR or seizures. However, the majority of studies and reports published have usually considered sporadic cases or very small groups of patients with chromosome abnormalities. Furthermore, the characteristics of seizures and EEGs have been described in detail on very few occasions, to define the electroclinical phenotype, and eventually to classify the epilepsy. In recent years, a few identified chromosome abnormality syndromes seem to show a particular clinical and EEG picture; some of them are relatively common, such as Angelman’s syndrome, the fragile-X (fra-X) syndrome, the Miller‐Dieker syndrome; and others are more rare, such as trisomy 12p syndrome, the Wolf‐ Hirschhorn syndrome, and ring 20 syndrome. We review some clinical and neurophysiologic aspects of these syndromes that can support the neurologist in choosing the genetic analysis to be carried out, and help to identify specific genes influencing epileptogenesis. ANGELMAN’S SYNDROME

Partial Paternal Uniparental Disomy of Chromosome 6 in an Infant with Neonatal Diabetes, Macroglossia, and Craniofacial Abnormalities

Neonatal diabetes, which can be transient or permanent, is defined as hyperglycemia that presents within the first month of life and requires insulin therapy. Transient neonatal diabetes mellitus has been associated with abnormalities of the paternally inherited copy of chromosome 6, including duplications of a portion of the long arm of chromosome 6 and uniparental disomy, implicating overexpression of an imprinted gene in this disorder. To date, all patients with transient neonatal diabetes mellitus and uniparental disomy have had complete paternal isodisomy. We describe a patient with neonatal diabetes, macroglossia, and craniofacial abnormalities, with partial paternal uniparental disomy of chromosome 6 involving the distal portion of 6q, from 6q24-qter. This observation demonstrates that mitotic recombination of chromosome 6 can also give rise to uniparental disomy and neonatal diabetes, a situation similar to that observed in Beckwith-Wiedemann syndrome, another imprinted disorder. This finding has clinical implications, since somatic mosaicism for uniparental disomy of chromosome 6 should also be considered in patients with transient neonatal diabetes mellitus.

Robertsonian Translocation in an Oligozoospermic Male Carrier: Sperm FISH Study, ART Strategy and Genetic Counselling

Objective: Evaluation of a 13;14 translocation in a male patient requiring ICSI concerning 1) risk of chromosomally unbalanced sperm, 2) indication for chromosome prenatal diagnosis, 3) number of embryos to be transferred after ICSI balancing the risks of multiple pregnancies and prenatal diagnosis. Design: FISH analysis on sperm in a male carrier of a 13; 14 Robertsonian translocation before ICSI; fœtal karyotype and uniparental disomy for chromosome 14 were checked. Materials and Method: A 32 year old patient and his 27 year old wife required assisted reproduction. The spermogram showed oligozoospermia (2.1 millions per ml). The karyotypes, in both patients were 45,XY,t(13;14) and 46,XX respectively. FISH analysis on sperm used subtelomeric probes (Cytocell, amplitech°) labelled with biotin and digoxigenin for 13q and 14q and DAPI counterstained hybridized slides were observed with a fluorescent microscope equipped with FITC, Cy3 DAPI filters associated with a Perceptive Scientific International analyzing system. ICSI was performed on 15 oocytes in metaphase; 13 ovocytes were fertilized, 2 embryos were transfered, 7 embryos were frozen. This resulted in a singleton pregnancy and a chorion villi biopsy was performed for karyotype and molecular biology in order to check the parental origin of chromosomes 14. Results: 107 spermatozoa were analyzed and 86% (n=93) could be scored. 43% (n=40) showed normal FISH signals: single spot for both 13qter and 14qter (thus either balanced or normal). 57% were abnormal: 11.8% (n=11) were disomic for chromosome 13, thus potentially leading to embryos with trisomy 13. The risk is higher than expected from published results on prenatal diagnosis and chromosomal analysis of fertile sperm in this situation. 13.9% (n=13) were disomic for chromosome 14. The high proportion of abnormalities especially disomy 13 and the need for invasive prenatal diagnosis made us opt for a transfer limited to two embryos; chorion villi analysis of the resulting monofetal pregnancy revealed a normal karyotype without uniparental disomy 14. Conclusion: Evaluation of ICSI embryos for chromosomal risk by FISH analysis of sperm in a male carrier of a translocation is useful to provide adequate counselling for prenatal diagnosis after ICSI and to choose the number of embryos to be transfered. Indeed published evaluations of chromosomal risks for fertile patients with translocation may be inadequate for infertile couples requiring ICSI. This work was supported by a clinical research grant APHP CRC n°96053 Cytogenetic analysis of sperm from a male heterozygous for a 13;14 Robertsonian translocation. Martin RH, Hum Genet, 1988 Dec, 80:4, 357–61. Paternal uniparental disomy for chromosome 14. American Journal of Medical Genetics 1997, 70:74–79.

Delta-like and gtl2 are reciprocally expressed, differentially methylated linked imprinted genes on mouse chromosome 12.

The distal portion of mouse chromosome 12 is imprinted. To date, however, Gtl2 is the only imprinted gene identified on chromosome 12. Gtl2 encodes multiple alternatively spliced transcripts with no apparent open reading frame. Using conceptuses with maternal or paternal uniparental disomy for chromosome 12 (UPD12), we found that Gtl2 is expressed from the maternal allele and methylated at the 5' end of the silent paternal allele. A reciprocally imprinted gene, Delta-like (Dlk), with homology to genes involved in the Notch signalling pathway was identified 80kb upstream of Gtl2. Dlk was expressed exclusively from the paternal allele in both the embryo and placenta, but the CpG-island promoter of Dlk was completely unmethylated on both parental alleles. Rather, a paternally methylated region was identified in the last exon of the active Dlk allele. The proximity, reciprocal imprinting and methylation in this domain are reminiscent of the co-ordinately regulated Igf2-H19 imprinted domain on mouse chromosome 7. Like H19 and Igf2, Gtl2 and Dlk were found to be co-expressed in the same tissues throughout development, though not after birth. These results have implications for the regulation, function and evolution of imprinted domains.

An imprinted locus associated with transient neonatal diabetes mellitus.

Recently, we reported the localization of a gene for transient neonatal diabetes mellitus (TNDM), a rare form of childhood diabetes, to an approximately 5.4 Mb region of chromosome 6q24. We have also shown that TNDM is associated with both paternal uniparental disomy (UPD) of chromosome 6 and paternal duplications of the critical region. The sequencing of P1-derived artificial chromosome clones from within the region of interest has allowed us to further localize the gene and to investigate the methylation status of the region. The gene is now known to reside in a 300-400 kb region of 6q24 which contains several CpG islands. At one island we have demonstrated differential DNA methylation between patients with paternal UPD of chromosome 6 and normal controls. In addition, two patients with TNDM, in whom neither paternal UPD of chromosome 6 nor duplication of 6q24 have been found, show a DNA methylation pattern identical to that of patients with paternal UPD of chromosome 6. Control individuals show a hemizygous methylation pattern. These results show that TNDM can be associated with a methylation change and identify a novel methylation imprint on chromosome 6 associated with TNDM.

Paternal isodisomy 13 in a normal newborn infant after trisomy rescue evidenced by prenatal diagnosis

Maternal and paternal uniparental disomy of chromosome 13 have been associated with normal phenotypes. We report on a new case of paternal isodisomy 13 in a phenotypically normal girl. Prenatal diagnosis had shown a 46,XX,-13,der(13;13) karyotype in chorionic villi and a 45,XX,der(13;13) karyotype in amniocytes and fetal blood. Molecular studies demonstrated that the de novo der(13;13) was an isochromosome 13 of paternal origin. This observation supports the lack of imprinting effects on chromosome 13 and trisomy rescue as a mechanism leading to uniparental disomy in cases involving isochromosomes.

Significance of genetic testing for paternal uniparental disomy of chromosome 6 in neonatal diabetes mellitus

Two patients who presented at birth with neonatal diabetes mellitus (NDM) are described: one with paternal uniparental disomy for chromosome 6 and one with normal, biparental inheritance. The first child presented with low birth weight, macroglossia, hypertelorism, and club foot in addition to NDM. In this patient hyperglycemia was transient, and insulin treatment was discontinued at 4 months of age. The second child also presented with low birth weight but was normal in appearance, and insulin dependence continues after 5 years. Genetic analysis with polymorphic DNA markers for chromosome 6 indicated the presence of paternal uniparental disomy (UPD) in the first case and normal, biparental inheritance in the second case. Paternal UPD 6 has been reported in 8 previous cases of which 6 showed NDM. Three cases with paternal UPD 6 also included additional anomalies, such as macroglossia, not usually associated with NDM. Therefore the simultaneous finding of NDM and macroglossia should be a strong indicator for genetic testing. The genetic finding of paternal UPD 6 allows prediction of a transient, rather than permanent, form of diabetes mellitus and no increased recurrence risk of transient NDM in subsequent pregnancies. (J Pediatr 1999;134:42-6)

Paternal Uniparental Disomy for Chromosome 1 Revealed by Molecular Analysis of a Patient with Pycnodysostosis

Molecular analysis of a patient affected by the autosomal recessive skeletal dysplasia, pycnodysostosis (cathepsin K deficiency; MIM 265800), revealed homozygosity for a novel missense mutation (A277V). Since the A277V mutation was carried by the patient's father but not by his mother, who had two normal cathepsin K alleles, paternal uniparental disomy was suspected. Karyotyping of the patient and of both parents was normal, and high-resolution cytogenetic analyses of chromosome 1, to which cathepsin K is mapped, revealed no abnormalities. Evaluation of polymorphic DNA markers spanning chromosome 1 demonstrated that the patient had inherited two paternal chromosome 1 homologues, whereas alleles for markers from other chromosomes were inherited in a Mendelian fashion. The patient was homoallelic for informative markers mapping near the chromosome 1 centromere, but he was heteroallelic for markers near both telomeres, establishing that the paternal uniparental disomy with partial isodisomy was caused by a meiosis II nondisjunction event. Phenotypically, the patient had normal birth height and weight, had normal psychomotor development at age 7 years, and had only the usual features of pycnodysostosis. This patient represents the first case of paternal uniparental disomy of chromosome 1 and provides conclusive evidence that paternally derived genes on human chromosome 1 are not imprinted.