D8S7 is consistently deleted in inverted duplications of the short arm of chromosome 8 (inv dup 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.

46,XY,r(8)/45,XY,-8 Mosaicism as a Possible Mechanism of the Imprinted Birk-Barel Syndrome: A Case Study

Ring chromosome 8 (r(8)) is one of the least frequent ring chromosomes. Usually, maternal chromosome 8 forms a ring, which can be lost from cells due to mitotic instability. The 8q24 region contains the imprinted KCNK9 gene, which is expressed from the maternal allele. Heterozygous KCNK9 mutations are associated with the imprinting disorder Birk-Barel syndrome. Here, we report a 2.5-year-old boy with developmental delay, microcephaly, dysmorphic features, diffuse muscle hypotonia, feeding problems, motor alalia and noncoarse neurogenic type of disturbance of muscle electrogenesis, partially overlapping with Birk-Barel syndrome phenotype. Cytogenetic analysis of lymphocytes revealed his karyotype to be 46,XY,r(8)(p23q24.3)[27]/45,XY,−8[3]. A de novo 7.9 Mb terminal 8p23.3p23.1 deletion, a 27.1 Mb 8p23.1p11.22 duplication, and a 4.4 Mb intact segment with a normal copy number located between them, as well as a 154-kb maternal LINGO2 gene deletion (9p21.2) with unknown clinical significance were identified by aCGH + SNP array. These aberrations were confirmed by real-time PCR. According to FISH analysis, the 8p23.1-p11.22 duplication was inverted. The ring chromosome originated from maternal chromosome 8. Targeted massive parallel sequencing did not reveal the KCNK9 mutations associated with Birk-Barel syndrome. Our data allow to assume that autosomal monosomy with inactive allele of imprinted gene arising from the loss of a ring chromosome in some somatic cells may be an etiological mechanism of mosaic imprinting disorders, presumably with less severe phenotype.

Genotype-phenotype association studies of chromosome 8p inverted duplication deletion syndrome

Individuals diagnosed with chromosome 8p inverted duplication deletion (invdupdel(8p)) manifest a wide range of clinical features and cognitive impairment. The purpose of this study is to employ array CGH technology to define more precisely the cytogenetic breakpoints and regions of copy number variation found in several individuals with invdupdel(8p), and compare these results with their neuropsychological characteristics. We examined the cognitive-behavioral features of two male and two female children, ages 3-15 years, with invdupdel(8p). We noted cognitive deficits that ranged from mild to severe, and adaptive behavior composites that ranged from significantly to substantially lower than adequate levels. CARS scores, a measure of autistic behavior, identified three children with autism or autistic-like features. Three of the four children exhibited attention deficits and hyperactivity consistent with a DSM-IV-TR diagnosis of ADHD. One child showed extreme emotional lability. Interestingly, intellectual disability was not correlated with deletion size, nor was the deletion location associated with the autistic phenotype. On the other hand, the duplication length in 8p21.1/8p22 was associated with cognitive deficit. In addition, a small locus of over-expression in 8p21.3 was common for all three participants diagnosed as autistic. A limitation of the study is its small sample size. Further analyses of the deleted and over-expressed regions are needed to ascertain the genes involved in cognitive function and, possibly, autism.

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.

Inverted duplications deletions: underdiagnosed rearrangements??

Molecular techniques led to the discovery that several chromosome rearrangements interpreted as terminal duplications were in fact inverted duplications contiguous to terminal deletions. Inv dup del rearrangements originate through a symmetric dicentric chromosome that, after asymmetric breakage, generates an inv dup del and a deleted chromosome. In recurrent inverted duplications the dicentric chromosome is formed at meiosis through non-allelic homologous recombination. In non-recurrent inv dup del cases, dicentric intermediates are formed by non-homologous end joining or intrastrand annealing. Some authors hypothesized that in these cases the dicentric may have been formed directly in the zygote. Healing of the broken dicentric chromosomes can occur not only in a telomerase-dependent way but also through telomere capture and circularization thus creating translocated or ring inv dup del chromosomes. In all the cases reported up to now, the duplicated region was always longer than the deleted one, but we can safely assume that there is another group of rearrangements where the deleted region is longer than the duplicated portion. In general, in these cases, the cytogeneticist will suspect the presence of a deletion and confirm it by FISH with a subtelomeric probe, but he/she will almost certainly miss the duplication. It is likely that the conventional analysis techniques used until now have led to a substantial underestimate of the frequency of inv dup del rearrangements and that the widespread use of array-CGH in routine analysis will allow a more realistic estimate. Obviously, the concomitant presence of deletion and duplication has important consequences in genotype/phenotype correlations.

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.

Inverted duplication with terminal deletion of 5p and no cat-like cry

We report on a 6-year-old boy referred for cytogenetics study. A few non-specific features were observed in the newborn: hypotonia, failure to thrive, seizures, pre-auricular skin tags. Cat-like cry was not identified. No remarkable facial dysmorphism, gastrointestinal, respiratory or cardiac abnormalities were identified. At age 4 years, speech and motor skill delays were apparent. Karyotyping and FISH analysis revealed a de novo rearranged chromosome 5p, with subtelomeric deletion of 5p and a duplication of the cri-du-chat critical region. Array CGH using sub-megabase resolution tiling-set (SMRT) array followed by FISH analysis with labeled BACs showed a deletion of 5pter to 5p15.31 (0-6.9 Mb) and an inverted duplication of the greater part of 5p15.31 to the distal end of 5p14.3 (6.9-19.9 Mb). Although very rare, inverted duplications with terminal deletion (inv dup del) have been reported at different chromosomal ends. Our finding adds a second patient of inv dup del 5p to this growing list, and the potential causative mechanisms for this rearrangement are discussed. Review of the mapping information of cri-du-chat patients and the comparison with a previously reported patient suggested that the critical region for cat-like cry is located within a 0.6 Mb region.

Prenatal detection of ade novo terminal inverted duplication 4p in a fetus with the Wolf-Hirschhorn syndrome phenotype

OBJECTIVES

To present the prenatal diagnosis of a de novo terminal inversion duplication of the short arm of chromosome 4 and a review of the literature.

CASE

An amniocentesis for chromosome analysis was performed at 33 weeks' gestation because ultrasound examination showed a female fetus with multiple abnormalities consisting of severe intrauterine growth retardation, microcephaly, a cleft lip and renal hypoplasia.

RESULTS

Cytogenetic analysis and FISH studies of the cultured amniocytes revealed a de novo terminal inversion duplication of the short arm of chromosome 4 characterized by a duplication of 4p14-p16.1 chromosome region concomitant with a terminal deletion 4p16.1-pter. The karyotype was thus: 46,XX, inv dup del (4)(:p14-->p16.1::p16.1-->qter). The parents opted to terminate the pregnancy. Fetopathological examination showed dysmorphic features and abnormalities consistent with a Wolf-Hirschhorn syndrome (WHS) diagnosis, clinical manifestations of partial 4p trisomy being mild.

CONCLUSION

Although relatively rare, inverted duplications have been reported repeatedly in an increasing number of chromosomes. Only two previous cases with de novo inv dup del (4p) and one with tandem dup 4p have been reported, all of them associated with a 4pter deletion. We report the first case diagnosed prenatally. Breakpoints are variable, resulting in different abnormal phenotype. In our case, clinical manifestations resulted in a WHS phenotype.

Duplication 8 [inv dup(8)(p12p23)] with macrocephaly

A 10-month old female is described with inv dup(8)(p12p23) who had macrocephaly with subtle changes in facial appearance and no structural birth defects. Her findings, together with those of 37 reported cases with inv dup (8), define a syndrome that emphasizes the importance of genes on the 8p region for brain development.

Loss of subtelomeric sequence associated with a terminal inversion duplication of the short arm of chromosome 4

We report on a 4(1/2)-year-old girl, who presented with multiple minor anomalies consistent with trisomy for 4p. GTG-banding identified a de novo terminal inversion duplication of distal 4p, dup(4)(p16.3p15.3). Fluorescence in situ hybridization (FISH) with a wcp4 probe confirmed the chromosome 4 origin of the additional material. FISH with a 4p subtelomere probe, D4F26, showed no signal on the dup(4) chromosome identifying a deletion of this region. Molecular analysis of 4p STS loci confirmed the subtelomeric deletion and showed loss of the paternal allele in this region. The paternal origin of the deleted region and homozygosity for one of the two paternal alleles within the region of the duplication suggests that a sister chromatid rearrangement on the paternal chromosome 4 was involved in the formation of the dup(4) chromosome. To date, the best characterized mechanisms of formation of chromosome duplications are terminal inversion duplications of 8p, which were shown to be derived from rearrangements at maternal meiosis-I. Our data show that mechanisms other than a maternal meiosis-I rearrangement can lead to the formation of terminal inversion duplications. FISH analysis with the appropriate subtelomeric probes is warranted in terminal inversion duplications to check for associated deletions.

Familial dup(8)(p12p21.1): mild phenotypic effect and review of partial 8p duplications

We describe a family with direct transmission of a duplication of 8p12-->8p21.1. The phenotype of affected relatives included mild mental retardation but no minor anomalies. The duplication was identified by means of GTG-banding and fluorescence in situ hybridization with a probe specific for 8p12 generated by microdissection and degenerate oligonucleotide primed-polymerase chain reaction. Assay of glutathione reductase, which has been localised to 8p21.1, was significantly increased when compared with controls with normal chromosomal constitution. To the best of our knowledge, a proximal direct duplication of 8p restricted to subbands p12-->p21.1 has not been reported so far. The reported aberration is compared with other partial duplications of 8p, in particular to inversion duplications 8p and to small direct distal duplications involving 8p23.1. Am. J. Med. Genet. 94:306-310, 2000.

Prenatal diagnosis of inverted duplicated 8p

The phenotype of inverted duplicated 8p, region 8p11.2-p23, reported in children and adults, includes: severe mental retardation, minor facial anomalies, agenesis of corpus callosum, and other malformations including those of heart and kidneys. We report on the prenatal diagnosis of 2 cases of inverted duplication 8p. Both cases were ascertained by abnormal level 2 ultrasound findings. Case 1 presented at 16.5 weeks of gestation with massive distention of the fetal bladder, bilateral hydronephrosis, abnormality of the lower lumbar spine, absence of the sacral spine and a Dandy-Walker variant (interhemispheric cyst and enlarged third ventricle). Case 2 presented at 30 weeks of gestation with agenesis of corpus callosum, slightly enlarged lateral ventricles, interhemispheric cyst and enlarged third ventricle, and possible coarctation of the aorta. The intracranial and cardiac anomalies were confirmed and further defined after delivery. Cytogenetic analysis in both cases showed additional material on 8p. In both cases, fluorescence in situ hybridization (FISH) defined the abnormal chromosome, as a pseudodicentric chromosome with duplication of the short arm from centromere to p23 and deletion from p23 to pter. Our findings support those of prior reports of the inverted duplicated 8p chromosome with multiple anomalies and add prenatal findings to our knowledge.

Cloning, sequencing, and analysis of inv8 chromosome breakpoints associated with recombinant 8 syndrome

Rec8 syndrome (also known as "recombinant 8 syndrome" and "San Luis Valley syndrome") is a chromosomal disorder found in individuals of Hispanic descent with ancestry from the San Luis Valley of southern Colorado and northern New Mexico. Affected individuals typically have mental retardation, congenital heart defects, seizures, a characteristic facial appearance, and other manifestations. The recombinant chromosome is rec(8)dup(8q)inv(8)(p23.1q22.1), and is derived from a parental pericentric inversion, inv(8)(p23.1q22.1). Here we report on the cloning, sequencing, and characterization of the 8p23.1 and 8q22 breakpoints from the inversion 8 chromosome associated with Rec8 syndrome. Analysis of the breakpoint regions indicates that they are highly repetitive. Of 6 kb surrounding the 8p23.1 breakpoint, 75% consists of repetitive gene family members-including Alu, LINE, and LTR elements-and the inversion took place in a small single-copy region flanked by repetitive elements. Analysis of 3.7 kb surrounding the 8q22 breakpoint region reveals that it is 99% repetitive and contains multiple LTR elements, and that the 8q inversion site is within one of the LTR elements.

Complex congenital heart malformations in mosaic tetrasomy 8p: case report and review of the literature

We describe a 5-month-old boy with complex congenital heart defects (dTGA, DORV, VSD, ASD, and PDA), minor facial and ear anomalies, deep palmar creases, multiple vertebral anomalies, agenesis of the corpus callosum, and mosaic tetrasomy 8p (47,XY,+i(8)(p10)[88%]/46,XY[12%] in blood with normal chromosomes in cultured skin fibroblasts. This infant represents the eleventh reported case of mosaic tetrasomy 8p since its first description by Kristofferson et al. [1988: Clin Genet 34:201-203]. The pattern of heart malformations and discordance of blood and fibroblast karyotypes make our case unique. Our report and review suggest that an important distinction between mosaic tetrasomy 8p and other chromosome 8 aneuploidies involves the increased incidence and complexity of congenital heart malformations.

Familial partial trisomy 8p without dysmorphic features and only mild mental retardation

We report on a mother and her two sons who had a direct duplication of chromosome region 8p22-8p23.1 without dysmorphic features and only mild mental retardation. The patients have been studied using G banding, chromosome painting, and FISH using cosmid probes specific for the region 8p23.1-8pter. Comparison of the phenotypes of our patients and of published patients with an inversion duplication of the short arm of chromosome 8 indicates that trisomy for chromosome band 8p21 causes the more severe clinical picture in the latter.

Clinical and cytogenetic findings in seven cases of inverted duplication of 8p with evidence of a telomeric deletion using fluorescence in situ hybridization

We report on the clinical and cytogenetic findings in 7 cases of inverted duplication of region 8p11.2p23. The phenotype of inv dup (8p) compiled from this series and the literature (N = 29) consists of severe mental retardation (100%), minor facial alterations (97%), agenesis of the corpus callosum (80%), hypotonia (66%), orthopedic abnormalities (58%), scoliosis/kyphosis (40%), and congenital heart defect (26%). A telomeric deletion of region 8p23.3-pter was confirmed in 3 of our cases studied using fluorescent in situ hybridization with a telomeric probe for 8p. Thus, these karyotypes are inv dup del(8) (qter-->p23.1::p23.1-->p11.2:). Our findings suggest that most cases of inv dup(8p) probably have a telomeric deletion.

Protelomeric sequences are deleted in cases of short arm inverted duplication of chromosome 8

We present a patient with a de novo inverted duplication of the short arm of chromosome 8. Molecular analysis confirmed the cytogenetic suspicion of a simultaneous deletion of the tip of the short arm and indicated the maternal origin of the abnormality. This deletion made no detectable contribution to the phenotype of the patient which was comparable to that of previous cases of 8p duplication. Similar investigations of inverted duplications involving other chromosomes may reveal unexpected deletions with significant phenotypic consequences.

Trisomy 8 syndrome owing to isodicentric 8p chromosomes: regional assignment of a presumptive gene involved in corpus callosum development

Two patients with trisomy 8 syndrome owing to an isodicentric 8p;8p chromosome are described. Case 1 had a 46,XX/46,XX,-8,+idic(8)(p23) karyotype while case 2, a male, had the same abnormal karyotype without evidence of mosaicism. In situ hybridisation, performed in case 1, showed that the isochromosome was asymmetrical. Agenesis of the corpus callosum (ACC), which is a feature of trisomy 8 syndrome, was found in both patients. Although ACC is associated with aneuploidies for different chromosomes, a review of published reports indicates that, when associated with chromosome 8, this defect is the result of duplication of a gene located within 8p21-pter. Molecular analysis in one of our patients led us to exclude the distal 23 Mb of 8p from this ACC region.