Association of Deletions of the Chromosomal Region 15q24-ter and Diaphragmatic Hernia: A New Case and Discussion of the Literature

15q26 deletion in a patient with congenital heart defect, growth restriction and intellectual disability: case report and literature review

Background

15q26 deletion is a relatively rare chromosomal disorder, and it is described only in few cases. Patients with this aberration show many signs and symptoms, particularly pre- and postnatal growth restriction, developmental delay, microcephaly, intellectual disability and various congenital malformations.

Case presentation

We report on a girl, 4 years old, of consanguineous parents, with a 15q26 deletion. Clinical manifestations included failure to thrive, developmental delay, microcephaly, dysmorphic facies with broad forehead, hypertelorism, narrowed eyelid slits and protruding columella. The patient also showed skeletal abnormalities, especially clinodactyly of the 5th finger, varus equine right foot and left club foot. Additionally, she had teething delay and divergent strabismus. Heart ultrasound displayed two atrial septal defects with left-to-right shunt, enlarging the right cavities. Routine cytogenetic analysis revealed a shortened 15q chromosome. Subsequent array analysis disclosed a terminal 9.15 Mb deletion at subband 15q26.1-q26.3. Four candidate genes associated with 15q26 deletion phenotype were within the deleted region, i.e. IGF1R, NR2F2, CHD2 and MEF2A.

Conclusion

We report on an additional case of 15q26 monosomy, characterized by array-CGH. Molecular cytogenetic analysis allowed us to identify the exact size of the deletion, and four candidate genes for genotype-phenotype correlation. 15q26 monosomy should be considered when growth retardation is associated with hearing anomalies and congenital heart defect, especially atrioventricular septal defects (AVSDs) and/or aortic arch anomaly (AAA).

Array Characterization of Prenatally Diagnosed 15q26 Microdeletion and 2q37.1 Duplication: Report of a New Case with Multicystic Kidneys and Review of the Literature

We report on a molecular cytogenetic characterization of 15q26 deletion and 2q37.1 duplication in a fetus presenting with intrauterine growth restriction (IUGR), diaphragmatic hernia, multicystic kidneys, left kidney pyelectasis, and clubfeet. A terminal 15q26 deletion and a terminal 2q duplication of at least 10 and 9 Mb, respectively, derived from a maternal translocation, were found. The 15q26 deletion represents a contiguous gene deletion syndrome mainly characterized by IUGR, congenital diaphragmatic hernia, and less frequently kidney defects. This deletion encompasses the IGF1R and COUPTF2 genes, known to lead to fetal growth retardation syndrome. However, kidney malformations are less well known in such conditions, and to the best of our knowledge, no candidate gene has been proposed to date. Here, we review the literature of the 15q26 deletion syndrome and suggest that hypoplastic and multicystic kidneys, the most commonly observed anomalies in this condition, should be considered in the prenatal diagnosis setting. Based on COUPTF2 protein function, we hypothesize that its haploinsufficiency might be responsible for the renal pathology.

Pre- and Postnatal Analysis of Chromosome 15q26.1 and 8p23.1 Deletions in Congenital Diaphragmatic Hernia

Congenital diaphragmatic hernia (CDH) is defined as a protrusion of abdominal content into the thoracic cavity through an abnormal opening in the diaphragm present at birth. It is a common birth defect with high mortality and morbidity. Submicroscopic deletions of 15q26.1 and 8p23.1 have been reported in several cases of CDH. We studied a total of 17 cases with CDH in pre- and postnatal samples using FISH probes. Deletion 15q26.1 was seen in 1/17 prenatal samples. There was no deletion for 8p23.1 in all the samples analyzed. CDH has a genetic etiology, and deletion 15q26.1 increases the risk of CDH. Deletion 15q26.1 in a fetus with CDH is a predictor of poor prognosis. This deletion is also seen in a phenotype similar to Fryns syndrome. CDH identified pre- or postnatally should be investigated further to exclude a 15q26.1 deletion and enable appropriate parental counseling.

A heterozygous mutation of the insulin-like growth factor-I receptor causes retention of the nascent protein in the endoplasmic reticulum and results in intrauterine and postnatal growth retardation

BACKGROUND

Mutations in the IGF-I receptor (IGF1R) gene can be responsible for intrauterine and postnatal growth disorders.

OBJECTIVE

Here we report on a novel mutation in the IGF1R gene in a female patient. The aim of our study was to analyze the functional impact of this mutation.

PATIENT

At birth, the girl's length was 47 cm [-1.82 sd score (SDS)], and her weight was 2250 g (-2.26 SDS). Clinical examination revealed microcephaly and retarded cognitive development. She showed no postnatal catch-up growth but had relatively high IGF-I levels (+1.83 to +2.17 SDS).

RESULTS

Denaturing HPLC screening and direct DNA sequencing disclosed a heterozygous missense mutation resulting in an amino acid exchange from valine to glutamic acid at position 599 (V599E-IGF1R). Using various cell systems, we found that the V599E-IGF1R mutant was not tyrosine phosphorylated and had an impaired downstream signaling in the presence of IGF-I. Flow cytometry and live cell confocal laser scanning microscopy revealed a lack of cell surface expression due to an extensive retention of V599E-IGF1R proteins within the endoplasmic reticulum.

CONCLUSION

The V599E-IGF1R mutation interferes with the receptor's trafficking path, thereby abrogating proreceptor processing and plasma membrane localization. Diminished cell surface receptor density solely expressed from the patient's wild-type allele is supposed to lead to insufficient IGF-I signaling. We hypothesize that this mechanism results in intrauterine and postnatal growth retardation of the affected patient. The reported retention of the nascent IGF1R in the endoplasmic reticulum presents a novel mechanism of IGF-I resistance.

Fetal skin fibroblasts: a cell model for studying the retinoid pathway in congenital diaphragmatic hernia

BACKGROUND

Although there is strong evidence that genetic factors play a pathogenic role in congenital diaphragmatic hernia (CDH), few causal genes have been identified in humans. A number of studies, essentially in animal models, have suggested that disruption of the retinoid signaling pathway plays a major role in the pathogenesis of CDH. Our hypothesis is that human fetal skin fibroblasts express some metabolic and molecular actors of the retinoid pathway and that they offer convenient cellular material for investigating the molecular retinoid pathway defects associated with CDH.

METHODS

We first established the expression of receptors, enzymes and binding proteins involved in the retinoic acid (RA) pathway in non-CDH fetal skin fibroblasts using RT-PCR and immunocytochemistry approaches. We then studied the expression of these genes in skin fibroblasts from seven fetuses with isolated and nonisolated CDH.

RESULTS

Fetal skin fibroblasts expressed enzymes involved in RA metabolism as well as nuclear receptors for signal transduction. Basal levels of retinoic acid receptor, retinaldehyde dehydrogenase 2, and CYP26 (cytochrome P450 RAI) expression were altered in two of seven fetuses. Interestingly, these genes were previously described as abnormally expressed in CDH physiopathology.

CONCLUSION

Our results suggest that human fetal skin fibroblasts could be useful for studying retinoid signaling pathway disruption in the context of CDH. Our proposal is strengthened by the fact that we identified CDH fetuses for which molecular and metabolic actors of the retinoid pathway were not detected.

Array based characterization of a terminal deletion involving chromosome subband 15q26.2: an emerging syndrome associated with growth retardation, cardiac defects and developmental delay

Background

Subtelomeric regions are gene rich and deletions in these chromosomal segments have been demonstrated to account for approximately 2.5% of patients displaying mental retardation with or without association of dysmorphic features. However, cases that report de novo terminal deletions on chromosome arm 15q are rare.

Methods

In this study we present the first example of a detailed molecular genetic mapping of a de novo deletion in involving 15q26.2-qter, caused by the formation of a dicentric chromosome 15, using metaphase FISH and tiling resolution (32 k) genome-wide array-based comparative genomic hybridization (CGH).

Results

After an initial characterization of the dicentric chromosome by metaphase FISH, array CGH analysis mapped the terminal deletion to encompass a 6.48 megabase (Mb) region, ranging from 93.86–100.34 Mb on chromosome 15.

Conclusion

In conclusion, we present an additional case to the growing family of reported cases with 15q26-deletion, thoroughly characterized at the molecular cytogenetic level. In the deleted regions, four candidate genes responsible for the phenotype of the patient could be delineated: IGFR1, MEF2A, CHSY1, and TM2D3. Further characterization of additional patients harboring similar 15q-aberrations might hopefully in the future lead to the description of a clear cut clinically recognizable syndrome.

Congenital diaphragmatic hernia (CDH) etiology as revealed by pathway genetics

Congenital diaphragmatic hernia (CDH) is a common birth defect with high mortality and morbidity. Two hundred seventy CDH patients were ascertained, carefully phenotyped, and classified as isolated (diaphragm defects alone) or complex (with additional anomalies) cases. We established different strategies to reveal CDH-critical chromosome loci and genes in humans. Candidate genes for sequencing analyses were selected from CDH animal models, genetic intervals of recurrent chromosomal aberration in humans, such as 15q26.1-q26.2 or 1q41-q42.12, as well as genes in the retinoic acid and related pathways and those known to be involved in embryonic lung development. For instance, FOG2, GATA4, and COUP-TFII are all needed for both normal diaphragm and lung development and are likely all in the same genetic and molecular pathway. Linkage analysis was applied first in a large inbred family and then in four multiplex families with Donnai-Barrow syndrome (DBS) associated with CDH. 10K SNP chip and microsatellite markers revealed a DBS locus on chromosome 2q23.3-q31.1. We applied array-based comparative genomic hybridization (aCGH) techniques to over 30, mostly complex, CDH patients and found a de novo microdeletion in a patient with Fryns syndrome related to CDH. Fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) techniques allowed us to further define the deletion interval. Our aim is to identify genetic intervals and, in those, to prioritize genes that might reveal molecular pathways, mutations in any step of which, might contribute to the same phenotype. More important, the elucidation of pathways may ultimately provide clues to treatment strategies.

Molecular characterization of a ring chromosome 15 in a fetus with intra uterine growth retardation and diaphragmatic hernia

OBJECTIVE

To improve the phenotype-genotype correlation in terminal 15q deletions and ring chromosome 15 syndrome.

METHODS

Echographic examination of fetus. R-banded chromosome and FISH analysis on cultured amniocytes. Microsatellite analysis to determine parental origin of the ring chromosome 15. Fetal autopsy.

RESULTS

We report a new case of prenatal diagnosis of congenital diaphragmatic hernia and intrauterine growth retardation in a fetus with ring chromosome 15 involving 15q26.1-qter deletion.

CONCLUSION

This case support the evidence that the region 15q26.3 is implicated in intrauterine growth retardation and suggests that the 15q critical region implicated in congenital diaphragmatic hernia is localized in 15q26.1-q26.2.

Overview of epidemiology, genetics, birth defects, and chromosome abnormalities associated with CDH

Congenital diaphragmatic hernia (CDH) is a common and well-studied birth defect. The etiology of most cases remains unknown but increasing evidence points to genetic causation. The data supporting genetic etiologies which are detailed below include the association of CDH with recurring chromosome abnormalities, the existence of CDH-multiplex families, and the co-occurrence of CDH with additional congenital malformations.

Genetic factors in congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is a relatively common birth defect associated with high mortality and morbidity. Although the exact etiology of most cases of CDH remains unknown, there is a growing body of evidence that genetic factors play an important role in the development of CDH. In this review, we examine key findings that are likely to form the basis for future research in this field. Specific topics include a short overview of normal and abnormal diaphragm development, a discussion of syndromic forms of CDH, a detailed review of chromosomal regions recurrently altered in CDH, a description of the retinoid hypothesis of CDH, and evidence of the roles of specific genes in the development of CDH.

Prenatal detection and outcome of congenital diaphragmatic hernia (CDH) associated with deletion of chromosome 15q26: Two patients and review of the literature

Congenital diaphragmatic hernia (CDH) is a severe birth defect characterized by a defect in the diaphragm with pulmonary hypoplasia and postnatal pulmonary hypertension. Approximately 50% of CDH cases are associated with other non-pulmonary congenital anomalies (so called non-isolated CDH) and in 5-10% of cases there is a chromosomal etiology. The majority of CDH cases are detected prenatally. In some cases prenatal chromosome analysis reveals a causative chromosomal anomaly, most often aneuploidy. Deletion of 15q26 is the most frequently described structural chromosomal aberration in patients with non-isolated CDH. In this paper we report on two patients with a deletion of 15q26 and phenotypes similar to other patients with CDH caused by 15q26 deletions. This phenotype consists of intra-uterine growth retardation, left-sided CDH, cardiac anomalies and characteristic facial features, similar to those seen in Fryns syndrome. We propose that when this combination of birth defects is identified, either pre- or postnatally, further investigations to confirm or exclude a deletion of 15q26 are indicated, since the diagnosis of this deletion will have major consequences for the prognosis and, therefore, can affect decision making.

Array comparative genomic hybridization in patients with congenital diaphragmatic hernia: mapping of four CDH-critical regions and sequencing of candidate genes at 15q26.1–15q26.2

Congenital diaphragmatic hernia (CDH) is a common birth defect with a high mortality and morbidity. There have been few studies that have assessed copy number changes in CDH. We present array comparative genomic hybridization data for 29 CDH patients to identify and map chromosome aberrations in this disease. Three patients with 15q26.1-15q26.2 deletions had heterogeneous breakpoints that overlapped with the critical 4 Mb region previously delineated for CDH, confirming 15q26.1-15q26.2 as a critical region for CDH. The three other most compelling CDH-critical regions for genomic deletions based on these data and a literature review are located at chromosomes 8p23.1, 4p16.3-4pter, and 1q41-1q42.1. Based on these recurrent deletions at 15q26.1-15q26.2, we hypothesized that loss-of-function mutations in a gene or genes from this region could cause CDH and sequenced six candidate genes from this region in more than 100 patients with CDH. For three of these genes (CHD2, ARRDC4, and RGMA), we identified missense changes and that were not identified in normal controls; however, none of these alterations appeared unambiguously causal with CDH. These data suggest that CDH caused by chromosome deletions at 15q26.2 may arise because of a contiguous gene deletion syndrome or may have a multifactorial etiology. In addition, there is evidence for substantial genetic heterogeneity in CDH and diaphragmatic hernias can be non-penetrant in patients who have deletions involving CDH-critical regions.

Prenatal diagnosis ofde novo deletions of 8p23.1 or 15q26.1 in two fetuses with diaphragmatic hernia and congenital heart defects

OBJECTIVE

To show the importance of using high-resolution chromosome analysis and FISH-technique for finding subtle chromosomal lesions in prenatal diagnosis specially when there are abnormal ultrasound findings.

METHODS

Ecographic examination of the fetus. GTG banded chromosome and FISH analysis using subtelomeric probes on amniocytes.

RESULTS

We report two prenatal cases with congenital diaphragmatic hernia (CDH) and congenital heart defects (CHDs) with different deletions confirmed by FISH: del(8)(p23.1p23.1) and del(15)(q26.1).

CONCLUSION

These cases support the evidence that the regions 15q26.1 and 8p23.1 may play an important role in the development of the diaphragm. A deletion 8p23.1 or 15q26.1 should be considered whenever a CDH and/or a cardiac abnormality are detected on ultrasound.

Infants with Bochdalek diaphragmatic hernia: sibling precurrence and monozygotic twin discordance in a hospital-based malformation surveillance program

Congenital diaphragmatic hernia (CDH) is a common and often devastating birth defect. In order to learn more about possible genetic causes, we reviewed and classified 203 cases of the Bochdalek hernia type identified through the Brigham and Women's Hospital (BWH) Active Malformation Surveillance Program over a 28-year period. Phenotypically, 55% of the cases had isolated CDH, and 45% had complex CDH defined as CDH in association with additional major malformations or as part of a syndrome. When classified according to likely etiology, 17% had a Recognized Genetic etiology for their CDH, while the remaining 83% had No Apparent Genetic etiology. Detailed analysis using this largest cohort of consecutively collected cases of CDH showed low precurrence among siblings. Additionally, there was no concordance for CDH among five monozygotic twin pairs. These findings, in conjunction with previous reports of de novo dominant mutations in patients with CDH, suggest that new mutations may be an important mechanism responsible for CDH. The twin data also raise the possibility that epigenetic abnormalities contribute to the development of CDH.

Congenital diaphragmatic hernia and chromosome 15q26: determination of a candidate region by use of fluorescent in situ hybridization and array-based comparative genomic hybridization

Congenital diaphragmatic hernia (CDH) has an incidence of 1 in 3,000 births and a high mortality rate (33%-58%). Multifactorial inheritance, teratogenic agents, and genetic abnormalities have all been suggested as possible etiologic factors. To define candidate regions for CDH, we analyzed cytogenetic data collected on 200 CDH cases, of which 7% and 5% showed numerical and structural abnormalities, respectively. This study focused on the most frequent structural anomaly found: a deletion on chromosome 15q. We analyzed material from three of our patients and from four previously published patients with CDH and a 15q deletion. By using array-based comparative genomic hybridization and fluorescent in situ hybridization to determine the boundaries of the deletions and by including data from two individuals with terminal 15q deletions but without CDH, we were able to exclude a substantial portion of the telomeric region from the genetic etiology of this disorder. Moreover, one patient with CDH harbored a small interstitial deletion. Together, these findings allowed us to define a minimal deletion region of approximately 5 Mb at chromosome 15q26.1-26.2. The region contains four known genes, of which two--NR2F2 and CHD2--are particularly intriguing gene candidates for CDH.