Prenatal diagnosis of inverted duplicated 8p

Neurodevelopmental phenotype in 36 new patients with 8p inverted duplication-deletion: Genotype-phenotype correlation for anomalies of the corpus callosum

Inverted duplication deletion 8p [invdupdel(8p)] is a complex and rare chromosomal rearrangement that combines a distal deletion and an inverted interstitial duplication of the short arm of chromosome 8. Carrier patients usually have developmental delay and intellectual disability (ID), associated with various cerebral and extra-cerebral malformations. Invdupdel(8p) is the most common recurrent chromosomal rearrangement in ID patients with anomalies of the corpus callosum (AnCC). Only a minority of invdupdel(8p) cases reported in the literature to date had both brain cerebral imaging and chromosomal microarray (CMA) with precise breakpoints of the rearrangements, making genotype-phenotype correlation studies for AnCC difficult. In this study, we report the clinical, radiological, and molecular data from 36 new invdupdel(8p) cases including three fetuses and five individuals from the same family, with breakpoints characterized by CMA. Among those, 97% (n = 32/33) of patients presented with mild to severe developmental delay/ID and 34% had seizures with mean age of onset of 3.9 years (2 months-9 years). Moreover, out of the 24 patients with brain MRI and 3 fetuses with neuropathology analysis, 63% (n = 17/27) had AnCC. We review additional data from 99 previously published patients with invdupdel(8p) and compare data of 17 patients from the literature with both CMA analysis and brain imaging to refine genotype-phenotype correlations for AnCC. This led us to refine a region of 5.1 Mb common to duplications of patients with AnCC and discuss potential candidate genes within this region.

Structural abnormalities of chromosome 8 and fetoplacental discrepancy: A second case report and review of fetal phenotype of 8p inverted duplication deletion syndrome

We described a new second case of fetoplacental discrepancy involving first trimester prenatal detection of mosaic isochromosome i (8) (q10). A 32-year-old woman underwent chorionic villous sampling because of increased fetal nuchal translucency. Analysis of direct chromosome preparations was performed by R-banding and FISH using subtelomeric, centromeric and whole chromosome painting probes for chromosome 8 showing the presence of an isochromosome 8q with a complex, female mosaic karyotype: mos 46,XX,i (8) (q10)[13]/46,XX,del (8) (p23)[10]. Cytogenetic analysis of cultured CVS showed an interstitial duplication with concomitant terminal deletion of the short arm of chromosome 8: 46,XX,der (8)del (8) (p23)dup (8) (p?)[18]. Array-CGH analysis from cultured trophoblasts and fetal tissues revealed a 6.69 Mb terminal deletion in 8p23.3p23.1 associated with a 31.49 Mb duplication in 8p23.1p11.1. FISH analysis confirmed the 8p inverted duplication deletion syndrome. Moreover, polymorphic DNA marker analysis demonstrated that the derivative chromosome 8 was of maternal origin. FISH analysis of cultured peripheral blood lymphocytes showed that the mother also carried a cryptic paracentric inversion inv (8) (p23). Our report contributes to expand the fetal phenotype of 8p inverted duplication deletion syndrome and also provides further insight into the underlying mechanism of this rare genomic disorder.

Prenatal diagnosis of inverted duplication deletion 8p syndrome mimicking trisomy 18

Inverted duplication deletion of 8p (invdupdel[8p]) is a well-described and uncommon chromosomal rearrangement. The majority of the reported cases have revealed no life-threatening malformations. Although the invdupdel[8p] syndrome in children with central nervous system abnormalities has been reported before, we present the first prenatal microarray diagnosis of invdupdel[8p] syndrome mimicking trisomy 18 due to similar sonographic features. Contrary to reported cases with invdupdel[8p] syndrome, the present case had severe polyvalvular dysplasia and the infant deceased at day 12 of life. In this case, we also emphasize the diagnostic power of microarray analysis in detecting the underlying genetic causes for fetuses with multiple congenital anomalies. © 2017 Wiley Periodicals, Inc.

Understanding the Limitations of Circulating Cell Free Fetal DNA: An Example of Two Unique Cases

Circulating cell free fetal DNA (cffDNA) is an effective screening modality for fetal aneuploidy. We report two cases of false positive results. The first case involves a female, with self-reported Down syndrome. CffDNA returned positive for trisomy 18 leading to a maternal diagnosis of mosaicism chromosome 18 with normal fetal karyotype. The second case involves a patient with an anomalous fetal ultrasound and cffDNA positive for trisomy 13. Amniocentesis demonstrated a chromosome 8p duplication/deletion. False positive cffDNA may arise in clinical scenarios where diagnostic testing is clearly indicated. Practitioners should recognize the limitations of cffDNA.

Genomic profile of copy number variants on the short arm of human chromosome 8

We evaluated 966 consecutive pediatric patients with various developmental disorders by high-resolution microarray-based comparative genomic hybridization and found 10 individuals with pathogenic copy number variants (CNVs) on the short arm of chromosome 8 (8p), representing approximately 1% of the patients analyzed. Two patients with 8p terminal deletion associated with interstitial inverted duplication (inv dup del(8p)) had different mechanisms leading to the formation of a dicentric intermediate during meiosis. Three probands carried an identical ∼5.0 Mb interstitial duplication of chromosome 8p23.1. Four possible hotspots within 8p were observed at nucleotide coordinates of ∼10.45, 24.32-24.82, 32.19-32.77, and 38.94-39.72 Mb involving the formation of recurrent genomic rearrangements. Other CNVs with deletion- or duplication-specific start or stop coordinates on the 8p provide useful information for exploring the basic mechanisms of complex structural rearrangements in the human genome.

Chromosome 8p23.1 deletions as a cause of complex congenital heart defects and diaphragmatic hernia

Recurrent interstitial deletion of a region of 8p23.1 flanked by the low copy repeats 8p-OR-REPD and 8p-OR-REPP is associated with a spectrum of anomalies that can include congenital heart malformations and congenital diaphragmatic hernia (CDH). Haploinsufficiency of GATA4 is thought to play a critical role in the development of these birth defects. We describe two individuals and a monozygotic twin pair discordant for anterior CDH all of whom have complex congenital heart defects caused by this recurrent interstitial deletion as demonstrated by array comparative genomic hybridization. To better define the genotype/phenotype relationships associated with alterations of genes on 8p23.1, we review the spectrum of congenital heart and diaphragmatic defects that have been reported in individuals with isolated GATA4 mutations and interstitial, terminal, and complex chromosomal rearrangements involving the 8p23.1 region. Our findings allow us to clearly define the CDH minimal deleted region on chromosome 8p23.1 and suggest that haploinsufficiency of other genes, in addition to GATA4, may play a role in the severe cardiac and diaphragmatic defects associated with 8p23.1 deletions. These findings also underscore the importance of conducting a careful cytogenetic/molecular analysis of the 8p23.1 region in all prenatal and postnatal cases involving congenital defects of the heart and/or diaphragm.

The application of region-specific probes for the resolution of duplication 8p: a case report and a review of the literature

The structural rearrangement in the short arm of a chromosome 8 in a clinically affected patient has been reinvestigated by FISH using whole chromosome painting and region specific YAC probes. An inverted duplication of the segment p22-->p11.2 and a deletion of the subtelomeric region were demonstrated. By this approach, a more detailed resolution of the duplication/deletion 8p was possible. With the application of molecular cytogenetic methods the existence of different duplication segments within the clinical entity of duplication/deficiency 8p can be shown.

Fetoplacental discrepancy involving structural abnormalities of chromosome 8 detected by prenatal diagnosis

We describe the finding of three cell lines involving different structural abnormalities of chromosome 8 detected in a prenatal diagnosis. Chorionic villi sampling (CVS) was performed on a pregnant woman because of advanced maternal age. Semidirect cytogenetic analysis showed a mos46,XX,i(8q)/46,XX,del(8)(p11.2) karyotype, confirmed by fluorescence in situ hybridization (FISH). Amniocentesis was subsequently performed, and the karyotype obtained was 46,XX,dup(8)(p23p11.2). The pregnancy was terminated; pathologic findings included clubfeet, clenched left hand, subcutaneous edema and bilateral hydrocephalus. Molecular studies using chromosome 8 microsatellites performed on parents' blood and fetal tissues revealed a maternal meiotic origin of the inv dup(8p) with deletion of the distal p23 region and duplication of the remaining 8p. We propose a model to explain the cytogenetic findings, which includes a first maternal meiotic error giving rise to a large dicentric isochromosome 8 present in the ovum, a second error in one of the first zygote divisions with misdivision of the dicentric 8 giving rise to a cell line with del(8p) confined to the trophoblast and another cell line with inv dup(8p) confined to the fetal tissue and a third error in the trophoblast giving rise to a further cell line with isochromosome 8q.

Mosaic inv dup(8p) marker chromosome with stable neocentromere suggests neocentromerization is a post-zygotic event

Marker chromosomes containing active human neocentromeres have been described in individuals where the chromosomes are non-mosaic, suggesting that they are mitotically stable, but also in individuals where there is mosaicism, raising the possibility of neocentromere instability. We report two independently ascertained individuals who are mosaic for a supernumerary marker chromosome, shown by reverse chromosome painting to have an 8p origin, resulting in mosaicism for tetrasomy 8p23.1-->pter in the patient. The markers have a primary constriction but show no detectable centromeric alpha-satellite DNA. The marker in Patient 1 demonstrated no centromere protein CENP-B binding, but associated with nine different functionally critical centromere proteins. Investigation of peripheral blood lymphocytes from this patient on five separate occasions over a 13-year period showed 23-46% mosaicism for the marker chromosome with no decrease in incidence. In vitro investigation of primary and secondary sub-clones of a lymphoblast cell line derived from the patient demonstrated 100% stability of the marker chromosome indicating that neocentromere instability is unlikely to be responsible for the mosaicism in the patient. This and other available data support a general model of neocentromerization as a post-zygotic event, irrespective of whether the supernumerary chromosome fragment has arisen during meiosis or post-fertilization at mitosis.