Mazin B. Qumsiyeh

Karyotype–phenotype insights from 11q14.1-q23.2 interstitial deletions: FZD4 haploinsufficiency and exudative vitreoretinopathy in a patient with a complex chromosome rearrangement†

We detected a unique de novo complex chromosome rearrangement (CCR) in a patient with multiple abnormalities including growth retardation, facial anomalies, exudative vitreoretinopathy (EVR), cleft palate, and minor digital anomalies. Cytogenetic analysis, fluorescent in situ hybridization, and microsatellite genotyping showed a reciprocal translocation between chromosomes 5 and 8, and a complex translocation‐deletion‐inversion process in the formation of derivative chromosomes 11 and 16. High‐density whole‐genome oligonucleotide array comparative genomic hybridization (oaCGH) defined a 35‐megabase interstitial deletion of 11q14.1‐q23.2 and a 1 megabase deletion of 16q22.3‐q23.1. The Frizzled‐4 (FZD4) gene is located within this 11q deletion. Parental studies and sequencing analysis confirmed that the patient was hemizygous for FZD4 due to the loss of a paternal allele on the derivative chromosome 11. Mutations in FZD4 are known to cause autosomal dominant exudative vitreoretinopathy (EVR1). Our patients findings suggest that haploinsufficiency of the FZD4 gene product can also be a disease‐causing mechanism for EVR1. We reviewed the clinical manifestations of 23 cases with 11q14‐q23 interstitial deletions, with particular scrutiny of the present case and four reported cases characterized by molecular cytogenetics. These findings were used to construct a regional deletion map consisting of a haplosufficient segment at 11q14.3, a flanking centromeric segment at 11q14.1‐q14.2, and a flanking telomeric segment at 11q21‐q23.3. We propose that deletions of the FZD4 gene located within the centromeric segment cause retinal dysgenesis, while deletions within the telomeric segment account for dysmorphic craniofacial features, growth and mental retardation, and mild digital anomalies. These results provide insight into karyotype–phenotype correlations and prompt a rational analytic approach to cases with interstitial deletions of the 11q14‐q23 region.

FOXC1 gene deletion is associated with eye anomalies in ring chromosome 6

We report a case of ring chromosome 6 presenting with growth and mental retardation, cerebral dysgenesis, eye malformations, mixed hearing loss, and abnormal physical features. Fluorescent in situ hybridization (FISH) and microsatellite genotyping demonstrated segmental deletions of less than 6 Mb on 6p and 1–2 Mb on 6q. The primary karyotype is designated as 46,XY,r(6)(p25q27).ish r(6)(p25.1q27)(D6S344−, FOXC1−, D6S1574+, D6S281−, D6S297+). Secondary structural and numerical variants of the ring 6 were observed in 16% of the cells analyzed. Intragenic genotyping revealed deletion of the paternal FOXC1 gene, haploinsufficiency of which has been reported to cause eye anterior chamber developmental defects. Accordingly, we propose that our patients ophthalmologic abnormalities result from haploinsufficiency of the transcription factor FOXC1. We present clinical and cytogenetic summaries on 23 reported cases of ring 6 and categorize them into mild, moderate, and severely affected groups. Further phenotype comparisons between cases with ring 6 and cases with only 6p or 6q terminal deletions suggest that genes important for hearing, vision, and central nervous system development remain to be identified in chromosome 6 terminal regions. Molecular definition of the fusion points and tissue mosaicism studies are necessary to better understand the genotype–phenotype correlation of ring 6. We recommend ophthalmology, audiology, cardiology, and central nervous system examinations be part of the routine evaluation for children with a ring chromosome 6.

Telomerase Prolongs the Lifespan of Normal Human Ovarian Surface Epithelial Cells Without Inducing Neoplastic Phenotype

Objective: The aim of this study was to determine the effects of exogenous expression of the catalytic subunit of telomerase (hTERT) on the lifespan, growth characteristics, and tumorigenicity of normal human ovarian surface epithelial (OSE) cells. Methods: Low-passage primary clutures of normal human OSE cells were transfected with hTERT and the resulting cell lines were characterized. Results: The ectopic expression of hTERT stabilized the telomeres of the OSE cultures above 8 kb. The hERT-transfected OSE cell lines grew beyond the normal lifespan seen in OSE cells and propagated in culture for more than 40 passages before senescing. Moreover, the hTERT-transfected cells demonstrated extensive proliferative capacity as evidenced by their ability to continuously grow even when seeded at low dilutions. The morphologic features and normal differentiation patterns seen in normal OSE cells were likewise retained by the hTERT-transfected cells. In addition, the cultures remained responsive to physiologic concentrations of epidermal growth factor and transforming growth factor-beta. Changes associated with neoplastic transformation like anchorage-independent growth, tumorigencity and karyotypic instability were not observed. Conclusions: We were able to show that the ectopic expression of hTERT in normal human OSE: 1) resulted in cultures with greater growth potential and longer lifespan and 2) did not induce a transformed phenotype previously seen in viral oncogene-transfected OSE cells. The established cell lines would not only provide sufficient material for comprehensive studies to investigate the normal physiology of OSE cells, but could also help in the understanding of the early steps of ovarian carcinogenesis.

Double supernumerary isodicentric chromosomes derived from 15 resulting in partial hexasomy

We report two unrelated patients each with two supernumerary marker chromosomes (SMCs) derived from chromosome 15, and thus resulting in partial hexasomy. Hexasomy in the one case (family 1) was diagnosed at prenatal diagnosis and did not include the Prader–Willi/Angelman critical region (PWACR). The double SMCs were also found in the mother, the pregnancy continued to term, and an apparently phenotypically normal child was born. This represents the first report of transmission of double SMCs from mother to child. In the second case (family 2), the hexasomy did include the PWACR and was de novo in origin. This patient manifested severe psychomotor retardation, clefting of the soft palate, hypotonia, seizure‐like episodes, and other phenotypic features. The aberrant phenotype is attributable to the hexasomy for the PWACR gene loci. The normal homologs of chromosome 15 proved to be biparental in origin while the two SMCs appeared maternal.

Rapid array-based genomic characterization of a subtle structural abnormality: A patient with psychosis and der(18)t(5;18)(p14.1;p11.23)

Array‐based copy number analysis has recently emerged as a rapid means of mapping complex and/or subtle chromosomal abnormalities. We have compared two such techniques, using bacterial artificial chromosome (BAC) and single nucleotide polymorphism (SNP) arrays in the evaluation of a 45‐year‐old woman with dysmorphic features, mental retardation, psychosis, and an unbalanced derivative chromosome 18, (46,XX, der(18)t(18;?)(p12;?)). Both array‐based methods demonstrated that the additional material on chromosome 18 was of 5p origin. The 5p duplication mapped telomeric to 25.320 Mb (BAC array) and 25.607 Mb (SNP array), corresponding to the band 5p14.1. Both BAC and SNP arrays also showed a deletion involving chromosome 18p extending telomeric from 8.437 Mb (BAC array) and 8.352 Mb (SNP array), corresponding to the band 18p11.23. Molecular cytogenetic mapping using fluorescence in situ hybridization (FISH) supported the array findings and further refined the breakpoint regions, confirming that the BAC and SNP chips were both useful in this regard. Both case reports and linkage analyses have implicated these chromosomal intervals in psychosis. The array‐based experiments were completed over the course of several days. While these methods do not eliminate the requirement for traditional fine‐mapping, they provide an efficient approach to identifying the origin and extent of deleted and duplicated material in chromosomal rearrangements.

Natural killer cell lymphoma/leukemia with homozygous loss of p27/kip1

We describe a case of natural killer (NK) cell lymphoma/leukemia with only an interstitial deletion in the short arm of chromosome 12 as the primary event. Fluorescence in situ hybridization revealed that the ETV6 locus (12p13) and subtelomeric sequences are not deleted in the process. The p27/kip1 locus (12p12-13), a candidate tumor suppressor gene, was deleted on the abnormal chromosome. Sequence analysis detected an adenine nucleotide deletion in the third codon of exon 1 leading to frameshift and premature termination at codon 41 of the retained copy of p27/kip1. To the best of our knowledge, this is the first report in literature on a NK cell lymphoma/leukemia with complete loss of p27/kip1.