Paternal uniparental isodisomy for chromosome 14 in a patient with a normal 46,XY karyotype

First prenatal case of Kagami-Ogata syndrome associated with a small supernumerary marker chromosome derived from chromosome 15

OBJECTIVE

Uniparental disomy (UPD) is one of the common causes of imprinting disorders, which can have an impact on gene expression according to the origin of the parental chromosome. Paternal UPD14 leads to Kagami-Ogata syndrome (KOS), which has a more severe phenotype than maternal UPD14, also called Temple syndrome. Small supernumerary marker chromosomes (SSMCs) are defined as structural chromosomal abnormalities that may be inherited or come from micronucleus-mediated chromothripsis. The association of UPD and SSMC is very rare but not fortuitous and several mechanisms can explain this phenomenon.

CASE REPORT

We report the first prenatal case of paternal isodisomy for chromosome 14 associated with a de novo SSMC originating from chromosome 15 and revealed by KOS. The mechanism could be a chromothripsis mediated by trisomy rescue.

CONCLUSION

Regarding this case, in relation to a de novo SSMC, it could be important to extend the research of UPD to other acrocentric chromosomes if ultrasound signs are evocative.

A revised model for mitochondrial dysfunction in Duchenne muscular dystrophy

We recently identified a signaling pathway that links the upregulation of miR-379 with a mitochondrial response in dystrophic muscle. In the present commentary, we explain the significance that this pathway may have in mitochondrial dysfunction in Duchenne muscular dystrophy (DMD). We identified the upregulation of miR-379 in the serum and muscles of DMD animal models and patients. We found that miR-379 is one of very few miRNAs whose expression was normalized in DMD patients treated with glucocorticoid. We identified EIF4G2 as a miR-379 target, which may promote mitochondrial oxidative phosphorylation (OxPhos) in the skeletal muscle. We found enriched EIF4G2 expression in oxidative fibers, and identified the mitochondrial ATP synthase subunit DAPIT as a translational target of EIF4G2. The identified signaling cascade, which comprises miR-379, EIF4G2 and DAPIT, may link the glucocorticoid treatment in DMD to a recovered mitochondrial ATP synthesis rate. We propose an updated model of mitochondrial dysfunction in DMD.

Kagami-Ogata Syndrome: Case Series and Review of Literature

Kagami-Ogata syndrome (KOS) (OMIM #608149) is a genetic imprinting disorder affecting chromosome 14 that results in a characteristic phenotype consisting of typical facial features, skeletal abnormalities including rib abnormalities described as "coat hanger ribs," respiratory distress, abdominal wall defects, polyhydramnios, and developmental delay. First identified by Wang et al in 1991, over 80 cases of KOS have been reported in the literature. KOS, however, continues to remain a rare and potentially underdiagnosed disorder. In this report, we describe two unrelated male infants with differing initial presentations who were both found to have the characteristic "coat hanger" rib appearance on chest X-ray, raising suspicion for KOS. Molecular testing confirmed KOS in each case. In addition to these new cases, we reviewed the existing cases reported in literature. Presence of polyhydramnios, small thorax, curved ribs, and abdominal wall defects must alert the perinatologist toward the possibility of KOS to facilitate appropriate molecular testing. The overall prognosis of KOS remains poor. Early diagnosis allows for counseling by a multidisciplinary team and enables parents to make informed decisions regarding both pregnancy management and postnatal care.

Reviewing the Limitations of Adult Mammalian Cardiac Regeneration: Noncoding RNAs as Regulators of Cardiomyogenesis

The adult mammalian heart is incapable of regeneration following cardiac injury, leading to a decline in function and eventually heart failure. One of the most evident barriers limiting cardiac regeneration is the inability of cardiomyocytes to divide. It has recently become clear that the mammalian heart undergoes limited cardiomyocyte self-renewal throughout life and is even capable of modest regeneration early after birth. These exciting findings have awakened the goal to promote cardiomyogenesis of the human heart to repair cardiac injury or treat heart failure. We are still far from understanding why adult mammalian cardiomyocytes possess only a limited capacity to proliferate. Identifying the key regulators may help to progress towards such revolutionary therapy. Specific noncoding RNAs control cardiomyocyte division, including well explored microRNAs and more recently emerged long noncoding RNAs. Elucidating their function and molecular mechanisms during cardiomyogenesis is a prerequisite to advance towards therapeutic options for cardiac regeneration. In this review, we present an overview of the molecular basis of cardiac regeneration and describe current evidence implicating microRNAs and long noncoding RNAs in this process. Current limitations and future opportunities regarding how these regulatory mechanisms can be harnessed to study myocardial regeneration will be addressed.

Paternal uniparental disomy for chromosome 14: prenatal management

We present a case of a 34-year-old multiparous woman who had been diagnosed with a 14 weeks' gestation showing an abdominal wall bulge possibly representing an omphalocele, containing liver and intestinal loops, at her first-trimester ultrasound scan. At 16 weeks' gestation, an amniocentesis was performed and karyotype analysis revealed a balanced Robertsonian translocation between chromosomes 13 and 14 in a female fetus (45,XX,der(13;14)(q10;q10)). Given this result and ultrasound findings, karyotype and molecular study of the couple were suggested. The results pointed out the absence of maternal contribution to the analysed regions by paternal uniparental disomy for chromosome 14 (isodisomy), which is associated with a severe phenotype. The correlation between ultrasound findings and the genetic study is primordial to guide the diagnostic assessment and to establish the prognosis of the fetal pathology.

Prenatal diagnosis of paternal uniparental disomy for chromosome 14 using a single-nucleotide-polymorphism-based microarray analysis: A case report

Paternal uniparental disomy 14 (UDP(14)pat) is a rare imprinting disorder with a set of unique neonatal clinical features documented, including craniofacial abnormalities, thoracic and abdominal wall defects, and polyhydraminos. To date, no studies focus on prenatal diagnosis of uniparental disomy have been published. We report a case of a fetus with abnormal ultrasound features at 18 weeks of gestation and normal karyotype result. Subsequent Single nucleotide polymorphism (SNP)-based Affymetrix 750K Microarray analysis revealed the complete loss of heterozygosity for chromosome 14, identifying a case of uniparental disomy. Postmortem examination of the aborted fetus at 21 weeks, coupled with further Affymetrix 750K microarray analysis on the parents, confirmed the diagnosis of parental uniparental disomy for chromosome 14.

A Hearty Dose of Noncoding RNAs: The Imprinted DLK1-DIO3 Locus in Cardiac Development and Disease

The imprinted Dlk1-Dio3 genomic region harbors a noncoding RNA cluster encoding over fifty microRNAs (miRNAs), three long noncoding RNAs (lncRNAs), and a small nucleolar RNA (snoRNA) gene array. These distinct noncoding RNAs (ncRNAs) are thought to arise from a single polycistronic transcript that is subsequently processed into individual ncRNAs, each with important roles in diverse cellular contexts. Considering these ncRNAs are derived from a polycistron, it is possible that some coordinately regulate discrete biological processes in the heart. Here, we provide a comprehensive summary of Dlk1-Dio3 miRNAs and lncRNAs, as they are currently understood in the cellular and organ-level context of the cardiovascular system. Highlighted are expression profiles, mechanistic contributions, and functional roles of these ncRNAs in heart development and disease. Notably, a number of these ncRNAs are implicated in processes often perturbed in heart disease, including proliferation, differentiation, cell death, and fibrosis. However, most literature falls short of characterizing precise mechanisms for many of these ncRNAs, warranting further investigation. Taken together, the Dlk1-Dio3 locus represents a largely unexplored noncoding regulator of cardiac homeostasis, harboring numerous ncRNAs that may serve as therapeutic targets for cardiovascular disease.

Temple syndrome: A patient with maternal hetero-UPD14, mixed iso- and hetero-disomy detected by SNP microarray typing of patient-father duos

Temple syndrome (TS, MIM 616222) is an imprinting disorder involving genes within the imprinted region of chromosome 14q32. TS is a genetically complex disorder, which is associated with maternal uniparental disomy of chromosome 14 (UPD14), paternal deletions on chromosome 14, or loss of methylation at the intergenic differentially methylated region (IG-DMR). Here, we describe the case of a patient with maternal hetero-UPD14, mixed iso-/hetero-disomy mechanism identified by a single nucleotide polymorphism (SNP) array analysis of patient-father duos study. The phenotype of our case is similarities to Prader-Willi syndrome (PWS) during infancy and to Russell-Silver syndrome (RSS) during childhood. This SNP array appears to be an effective initial screening tool for patients with nonspecific clinical features suggestive of chromosomal disorders.

The first de novo non-mosaic 14q11.2q13.1 tetrasomy of paternal origin

Tetrasomy 14q11q13 is a very rare chromosome aberration. So far, only five patients with such an imbalance were described. All these patients had a de novo marker chromosome idic(14)(q13) leading to a partial tetrasomy of chromosome 14. We report on the first case of a de novo non-mosaic partial tetrasomy 14q resulted not from a marker chromosome, but from an inverted triplication on paternal chromosome 14, characterized by using FISH and SNP array. Our patient showed some anomalies described in tetrasomy 14q11q13 with striking presence of paternal UPD(14) features (blepharophimosis, small thorax, and joint contractures, developmental delay). This unique patient supports the hypothesis that 14q11q13 may contain imprinted gene(s) that contribute to the paternal UPD(14) features of joint contractures and/or blepharophimosis. This patient demonstrates the utility of parent of origin testing in patients with de novo chromosome 14 aberrations. Overdosage of 14q11.1q13.1 may cause some features related to UPD(14) phenotype.

Paternal uniparental disomy chromosome 14-like syndrome due a maternal de novo 160 kb deletion at the 14q32.2 region not encompassing the IG- and the MEG3-DMRs: Patient report and genotype-phenotype correlation

The human chromosome 14q32 carries a cluster of imprinted genes which include the paternally expressed genes (PEGs) DLK1 and RTL1, as well as the maternally expressed genes (MEGs) MEG3, RTL1as, and MEG8. PEGs and MEGs expression at the 14q32.2-imprinted region are regulated by two differentially methylated regions (DMRs): the IG-DMR and the MEG3-DMR, which are respectively methylated on the paternal and unmethylated on the maternal chromosome 14 in most cells. Genetic and epigenetic abnormalities affecting these imprinted gene clusters result in two different phenotypes currently known as maternal upd(14) syndrome and paternal upd(14) syndrome. However, only few patients carrying a maternal deletion at the 14q32.2-imprinted critical region have been reported so far. Here we report on the first patient with a maternal de novo deletion of 160 kb at the 14q32.2 chromosome that does not involves the IG-DMR or the MEG3-DMR but elicits a full upd(14)pat syndrome's phenotype encompassing the three mentioned MEGs. By the analysis of this unique genotype-phenotype correlation, we further widen the spectrum of the congenital anomalies associated to this rare disorder and we propose that the paternally expressed imprinted RTL1 gene, as well as its maternally expressed RTL1as antisense transcript, may play a prominent causative role.

ICR noncoding RNA expression controls imprinting and DNA replication at the Dlk1-Dio3 domain

Imprinted genes play essential roles in development, and their allelic expression is mediated by imprinting control regions (ICRs). The Dlk1-Dio3 locus is among the few imprinted domains controlled by a paternally methylated ICR. The unmethylated maternal copy activates imprinted expression early in development through an unknown mechanism. We find that in mouse embryonic stem cells (ESCs) and in blastocysts, this function is linked to maternal, bidirectional expression of noncoding RNAs (ncRNAs) from the ICR. Disruption of ICR ncRNA expression in ESCs affected gene expression in cis, led to acquisition of aberrant histone and DNA methylation, delayed replication timing along the domain on the maternal chromosome, and changed its subnuclear localization. The epigenetic alterations persisted during differentiation and affected the neurogenic potential of the stem cells. Our data indicate that monoallelic expression at an ICR of enhancer RNA-like ncRNAs controls imprinted gene expression, epigenetic maintenance processes, and DNA replication in embryonic cells.

Complete paternal uniparental isodisomy for Chromosome 2 revealed in a parentage testing case

BACKGROUND

Uniparental disomy (UPD) is a rare cytogenetic event that has previously been reported mostly via genetic analysis of patients with phenotypes of recessive diseases. The incidence of UPD of any chromosome is estimated to be approximately1:3500 live births.

CASE REPORT

In a case of disputed paternity involving a phenotypically normal male child, mother-child exclusions were observed at five short tandem repeat markers, which were all located on Chromosome 2. Ten additional dinucleotide repeat markers spanning both arms of Chromosome 2 were investigated. The results revealed that the child was homozygous for all markers tested with all alleles originating from a single paternal Chromosome 2, which was consistent with paternal UPD for Chromosome 2.

CONCLUSION

This case and other previous reports demonstrate that UPD poses a high risk for false exclusion and incorrect expert opinion. Furthermore, this case highlights that a conclusion of exclusion of paternity or maternity should not be postulated if multiple genetic incompatibilities are located on the same chromosome because of the occurrence of UPD.

Segmental paternal uniparental disomy (patUPD) of 14q32 with abnormal methylation elicits the characteristic features of complete patUPD14

Uniparental disomy (UPD) for chromosome 14 is associated with well-recognized phenotypes, depending on the parent of origin. Studies in mouse models and human patients have implicated the involvement of the distal region of the long arm of chromosome 14 in the distinctive phenotypes. This involvement is supported by the identification of an imprinting cluster at chromosome 14q32, encompassing the differentially methylated regions (DMRs), IG-DMR and MEG3-DMR, as well as the maternally expressed genes GTL2, DIO3, and RTL1 and the paternally expressed genes DLK1, RTL1as, and MEG8. Here we report on a preterm female infant with distal segmental paternal UPD14 (upd(14)pat) of 14q32-14q32.33, which resulted in thoracic deformity secondary to rib abnormalities ("coat-hanger" rib sign), polyhydramnios, and other congenital abnormalities characteristically described in cases of complete upd(14)pat. Microsatellite investigation demonstrated UPD of markers D14S250 and D14S1010, encompassing a approximately 3.5 Mb region of distal 14q and involving the imprinting cluster. This case provided insight into the etiology of the phenotypic effects of upd(14)pat, prompting methylation analysis of the GTL2 promoter and the DMR between GTL2 and DLK1. We compare the physical findings seen in this case with those of patients with other causes of abnormal methylation of 14q32, which consistently result in certain distinct clinical features, regardless of the cytogenetic and molecular etiology.

Mosaic trisomy r(14) associated with epilepsy and mental retardation

We report a patient with moderate mental retardation, benign clinical course of epilepsy, and type 2 diabetes mellitus. The patient has a mosaic karyotype with 2 cell lines: 1 with a ring chromosome 14 [r(14)], and 1 with an apparently duplicated r(14) chromosome.

Paternal uniparental isodisomy for chromosome 14 with mosaicism for a supernumerary marker chromosome 14

Uniparental disomy (UPD) describes the inheritance of two homologous chromosomes from a single parent. Disease phenotypes associated with UPD and chromosomal imprinting, rather than with mutations, include Beckwith-Wiedemann syndrome (paternal UPD11p), Angelman syndrome (paternal UPD15), Prader-Willi syndrome (maternal UPD15), and transient neonatal diabetes (paternal UPD6). Here we report on the first case of paternal uniparental isodisomy of chromosome 14 with a mosaicism for a supernumerary marker chromosome 14. The patient demonstrated a small thorax with a 'coat hanger' shape of the ribs, kyphoscoliosis, hypoplasia of the maxilla and mandible, a broad nasal bridge with anteverted nares, contractures of the wrists with ulnar deviation bilaterally, diastasis recti, and marked muscle hypotonia. Vertical skin creases under the chin and stippled epiphyses of the humeri were features not previously described in patients with paternal UPD14. This case illustrates that as with the finding of an isochromosome, a supernumerary marker chromosome can be an important clue to the presence of UPD14.

Cerebral palsy due to chromosomal anomalies and continuous gene syndromes

When cerebral palsy is defined as a disorder of movement and posture that is due to nonprogressive disturbances that occur in the developing fetal and infant brain, a significant proportion-up to 10%--is the consequence of chromosomal anomalies and continuous gene syndromes. Abnormalities of chromosomes are constitutional or acquired. Acquired chromosomal abnormalities develop postnatally, affect only one clone of cells, and are implicated in the evolution of neoplasia. Constitutional abnormalities develop during gametogenesis or early embryogenesis and affect a significant portion of the subject's cells.

Prenatal diagnostic indicators of paternal uniparental disomy 14

OBJECTIVES

To present clinical findings of a child with paternal uniparental isodisomy 14 (pat UPD14) focusing on relevant prenatal characteristics.

METHODS/RESULTS

Ultrasonography at 23 weeks of gestation of a 37-year-old multigravid woman revealed a fetus with polyhydramnios, small thorax, and short, distinctively angled ribs. Fetal karyotype was 46,XY. The child was born spontaneously at 35 weeks with poor neonatal adaptation. From birth, he presented with severe respiratory insufficiency due to severe thoracic malformation. Clinical examination revealed a small, bell-shaped thorax, redundant lax skin, mild contractures of the fingers and dysmorphic facial features. Chest X rays showed short, abnormally curved ribs that suggested the possibility of pat UPD14, which was confirmed by molecular analysis.

CONCLUSION

Pat UPD14 is associated with a distinct clinical phenotype. Prognosis is poor because of severe respiratory insufficiency and neurodevelopmental retardation. Our report confirms salient postnatal signs of previous descriptions, especially the characteristic radiological abnormalities with ribs showing a 'coat-hanger' configuration. Retrospective fetal ultrasound of our case allowed the identification of this pathognomonic feature prenatally, which makes it possible to consider pat UPD14 at routine prenatal sonography, in particular in combination with a small bell-shaped thorax and polyhydramnios.

BEGAIN: a novel imprinted gene that generates paternally expressed transcripts in a tissue- and promoter-specific manner in sheep

In this article we describe the organization of the ovine BEGAIN gene, located 138 kb proximally from the imprinted DLK1 gene and 203 kb from the CLPG mutation that causes the callipyge phenotype. We have shown that in sheep BEGAIN is ubiquitously expressed, including in skeletal muscle, throughout development. We have identified four major BEGAIN transcripts resulting from a combination of alternate promoter usage and alternative splicing. In ovine brain, kidney, liver, and skeletal muscle, these four BEGAIN transcripts exhibited paternal or biallelic expression in a tissue- and promoter-specific manner. Our results indicate that the CLPG mutation does not alter transcript levels of BEGAIN, contrary to its effect on a core cluster of genes in the DLK1-GTL2 domain. Thus, although the BEGAIN gene represents another paternally expressed gene in the ovine DLK1-GTL2 imprinted domain, its expression is not governed by the long-range regulatory element that contains the CLPG mutation.

Uniparental disomy (UPD) other than 15: Phenotypes and bibliography updated

Uniparental disomy (UPD) describes the inheritance of a pair of chromosomes from only one parent. The concept was introduced in Medical Genetics by Engel (1980); Am J Med Genet 6:137-143. Aside UPD 15, which is the most frequent one, up to now (February 2005) 197 cases with whole chromosome maternal UPD other than 15 (124 X heterodisomy, 59 X isodisomy, and 14 cases without information of the mode of UPD) and 68 cases with whole chromosome paternal UPD other than 15 (13 X heterdisomy, 53 X isodisomy, and 2 cases without information of the mode of UPD) have been reported. In this review we discuss briefly the problems associated with UPD and provide a comprehensive clinical summary with a bibliography for each UPD other than 15 as a guide for genetic counseling.

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.