Stabilization of a terminal inversion duplication of 8p by telomere capture from 18q

Terminal inversion duplications of the short arm of chromosome 8 are one of the more common chromosome rearrangements in humans. We report an infant with multiple congenital anomalies, in whom karyotype analysis showed a terminal inversion duplication of 8p including additional material at the distal end of the derivative chromosome, shown to be of chromosome 18q origin. Terminal inversion duplications of 8p are the result of meiotic recombination between inverted olfactory gene receptor repeats in 8p. This recombination generates a dicentric intermediate that breaks during anaphase, and the broken chromosome end is stabilized by telomere healing or telomere capture. The origin of the telomeric region in the majority of constitutional chromosome deletions studied to date was shown to be from telomere healing; the de novo addition of telomeric repeats. In the proband a cytogenetically detectable piece of chromosome 18q was present on the distal end of the derivative 8, suggesting that this chromosome was stabilized by telomere capture of 18q. FISH analyses of additional cases may yield information as to whether telomere capture or telomere-healing events are the predominant mechanism of chromosome stabilization in terminal inversion duplications of 8p.     

Unbalanced translocation 8;Y (45,X,dic(Y;8)(q11.23;p23.1)): case report and review of terminal 8p deletions

A boy with a rare unbalanced de novo Y/autosome translocation is presented. Main clinical features in the boy comprised a psychomotor delay, talipes planus, a dolichocephalus, low set and retroverted ears, supraorbital fullness of subcutaneous tissue and a bulbous nasal tip. Chromosomal analysis on amniocytes showed a single X chromosome and a derivative 8p (Karyotype: 45,X,der(8)GTG). The following DAPI staining revealed the inactivated centromere of the chromosome Y located on 8p and the absence of heterochromatic material Yq. Microsatellite analysis on fetal blood DNA using markers between SRY on Yp and DYS 240 on Yq proved presence of the spermatogenetic relevant factors. A terminal deletion of 8p was confirmed by FISH postnatally. Molecular genetic reassessment revealed the monosomy 8p to be of maternal origin; the translocation can thus be proven to have occurred in the zygote. The breakpoint in 8p was localised distal to GATA4, a gene which is involved in heart development; the finding that our patient did not suffer from cardiac problems agrees with the disomic presence of GATA4. Only the application of FISH combined with microsatellite analysis allowed a precise correlation between clinical phenotype and a subtle deletion of terminal 8p; furthermore, a recurrence risk for the parents could be excluded.     

The RNA export factor Gle1p is located on the cytoplasmic fibrils of the NPC and physically interacts with the FG-nucleoporin Rip1p, the DEAD-box protein Rat8p/Dbp5p and a new protein Ymr 255p

Gle1p is an essential, nuclear pore complex (NPC)-associated RNA export factor. In a screen for high copy suppressors of a GLE1 mutant strain, we identified the FG-nucleoporin Rip1p and the DEAD-box protein Rat8p/Dbp5p, both of which have roles in RNA export; we also found Ymr255p/Gfd1p, a novel inessential protein. All three high copy suppressors interact with the C-terminal domain of Gle1p; immunoelectron microscopy localizations indicate that Gle1p, Rip1p and Rat8p/Dbp5p are present on the NPC cytoplasmic fibrils; Rip1p was also found within the nucleoplasm and on the nuclear baskets. In vivo localizations support the hypothesis that Rip1p contributes to the association of Gle1p with the pore and that Gle1p, in turn, provides a binding site for Rat8p/Dbp5p at the NPC. These data are consistent with the view that Gle1p, Rip1p, Rat8p/Dbp5p and Ymr255p/Gfd1p associate on the cytoplasmic side of the NPC to act in a terminal step of RNA export. We also describe a human functional homologue of Rip1p, called hCG1, which rescues Rip1p function in yeast, consistent with the evolutionary conservation of this NPC-associated protein.     

Delineation of the critical deletion region for congenital heart defects, on chromosome 8p23.1

Deletions in the distal region of chromosome 8p (del8p) are associated with congenital heart malformations. Other major manifestations include microcephaly, intrauterine growth retardation, mental retardation, and a characteristic hyperactive, impulsive behavior. We studied genotype-phenotype correlations in nine unrelated patients with a de novo del8p, by using the combination of classic cytogenetics, FISH, and the analysis of polymorphic DNA markers. With the exception of one large terminal deletion, all deletions were interstitial. In five patients, a commonly deleted region of approximately 6 Mb was present, with breakpoints clustering in the same regions. One patient without a heart defect or microcephaly but with mild mental retardation and characteristic behavior had a smaller deletion within this commonly deleted region. Two patients without a heart defect had a more proximal interstitial deletion that did not overlap with the commonly deleted region. Taken together, these data allowed us to define the critical deletion regions for the major features of a del8p.     

肿瘤相关应激分子p8

p8是在研究急性胰腺损伤的分子机制中首先鉴定得到的一个小分子核蛋白。胰腺、肝脏、肾脏等诸多脏器受到损伤刺激后,p8能够在短时间内迅速、高水平地上调,被认为是一个应激分子。进一步研究显示,p8在包括胰腺癌、乳腺癌、甲状腺癌及前列腺癌等多种肿瘤中存在差异表达,并通过影响细胞的生长、凋亡及转移等过程参与肿瘤的发生、发展。但关于p8在肿瘤中的作用,不同研究的结果并不一致。我们简要综述p8在肿瘤中的作用。     

Comparative mapping of mink (Mustela vison) chromosome 8p: localization of three human BAC clones

Using fluorescent in situ hybridization (FISH), three human BAC clones, localized in the terminal region of human chromosome 17p (HSA17p13; 1.44--3.68 Mp), were mapped to chromosome 8p of American mink (MVI8p). It was demonstrated that in MVI8p the region, homeologous to HSA17p13, was split into three fragments, which were detected within terminal, pericentric, and probably nucleolus-organizing regions. Using human BAC clones as heterologous markers for mapping of the gene sequences to the chromosomes of American mink, regional localization of eight sequences (PRPF8, SLC43A2, and RILP in MVI8p25; C17orf31 in MVI8p21-22; and CTNS, TAX1BP3, and P2RX5 in MVI8p11) was deduced.     

Partial monosomy 8p and partial trisomy 8p with moderate mental retardation.

A female patient with mosaicism for partial monosomy 8p and partial trisomy 8p is presented. Her karyotype is 46,XX, del(8)(p21)/46,XX, dup(8)(p21----pter). She showed minimal dysmorphic features, agenesis of the corpus callosum and moderate developmental delay. There is no previous report of mosaicism for partial monosomy and partial trisomy 8p. The clinical findings in the presently described patient are less severe than those reported in cases with only monosomy or trisomy of the distal part of chromosome 8.     

Comprehensive profiling of 8p11-12 amplification in breast cancer

In human carcinomas, especially breast cancer, chromosome arm 8p is frequently involved in complex chromosomal rearrangements that combine amplification at 8p11-12, break in the 8p12-21 region, and loss of 8p21-ter. Several studies have identified putative oncogenes in the 8p11-12 amplicon. However, discrepancies and the lack of knowledge on the structure of this amplification lead us to think that the actual identity of the oncogenes is not definitively established. We present here a comprehensive study combining genomic, expression, and chromosome break analyses of the 8p11-12 region in breast cell lines and primary breast tumors. We show the existence of four amplicons at 8p11-12 using array comparative genomic hybridization. Gene expression analysis of 123 samples using DNA microarrays identified 14 genes significantly overexpressed in relation to amplification. Using fluorescence in situ hybridization analysis on tissue microarrays, we show the existence of a cluster of breakpoints spanning a region just telomeric to and associated with the amplification. Finally, we show that 8p11-12 amplification has a pejorative effect on survival in breast cancer.     

Co-dependence of HTLV-1 p12 and p8 Functions in Virus Persistence

HTLV-1 orf-I is linked to immune evasion, viral replication and persistence. Examining the orf-I sequence of 160 HTLV-1-infected individuals; we found polymorphism of orf-I that alters the relative amounts of p12 and its cleavage product p8. Three groups were identified on the basis of p12 and p8 expression: predominantly p12, predominantly p8 and balanced expression of p12 and p8. We found a significant association between balanced expression of p12 and p8 with high viral DNA loads, a correlate of disease development. To determine the individual roles of p12 and p8 in viral persistence, we constructed infectious molecular clones expressing p12 and p8 (D26), predominantly p12 (G29S) or predominantly p8 (N26). As we previously showed, cells expressing N26 had a higher level of virus transmission in vitro. However, when inoculated into Rhesus macaques, cells producing N26 virus caused only a partial seroconversion in 3 of 4 animals and only 1 of those animals was HTLV-1 DNA positive by PCR. None of the animals exposed to G29S virus seroconverted or had detectable viral DNA. In contrast, 3 of 4 animals exposed to D26 virus seroconverted and were HTLV-1 positive by PCR. In vitro studies in THP-1 cells suggested that expression of p8 was sufficient for productive infection of monocytes. Since orf-I plays a role in T-cell activation and recognition; we compared the CTL response elicited by CD4⁺ T-cells infected with the different HTLV-1 clones. Although supernatant p19 levels and viral DNA loads for all four infected lines were similar, a significant difference in Tax-specific HLA.A2-restricted killing was observed. Cells infected with Orf-I-knockout virus (12KO), G29S or N26 were killed by CTLs, whereas cells infected with D26 virus were resistant to CTL killing. These results indicate that efficient viral persistence and spread require the combined functions of p12 and p8.     

Comparative mapping of mink (<Emphasis Type="Italic">Mustela vision</Emphasis>) chromosome 8p: Localization of three human BAC clones

Using fluorescent in situ hybridization (FISH), three human BAC clones, localized in the terminal region of human chromosome 17p (HSA17p13; 1.44–3.68 Mp), were mapped in chromosome 8p of American mink (MVI8p). It was demonstrated that in MVI8p the region, homeologous to HSA17p13, was split into three fragments, which were detected within terminal, pericentric, and probably nucleolus-organizing regions. Using human BAC clones as heterologous markers for mapping of the gene sequences to the chromosomes of American mink, regional localization of eight sequences (PRPF8, SLC43A2, and RILP in MVI8p25; C17orf31 in MVI8p21-22; and CARKL, CTNS, TAX1BP3, and P2RX5 in MVI8p11) was deduced.     

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.     

Molecular cytogenetic analysis of a familial 8p23.1 deletion associated with minimal dysmorphic features,seizures, and mild mental retardation

Summary We report a family in which three members presented with minimal phenotypic abnormalities, normal intelligence to mild mental retardation, and a cytogenetically terminal chromosome deletion at band 8p23.1 Whole chromosomal painting with a chromosome 8-specific DNA library confirmed this familial chromosome abnormality as a deletion, while fluorescence in situ hybridization with telomeric probes demonstrated the presence of telomeres at the deletion site. Coagulation studies were additionally performed to evaluate the purported location of the coagulation factor VII regulator gene at 8p23.1. A review of the clinical findings of seven cases of del(8)(p23.1) is presented.     

p8 gene is necessary for tumor establishment

We identified a new gene, called p8, which showed a strong induction during the acute phase of pancreatitis. Further experiments have shown that p8 mRNA is activated in response to several stresses and that its activation is not restricted to pancreatic cells. p8 is a nuclear protein and biochemical and biophysical studies showed that p8 was in many structural aspects very similar to the HMG (high mobility group) proteins, although sharing with them low amino acid sequence homology. Also, p8 was found overexpressed in many human cancers. Therefore, we wondered whether the p8-mediated response to cellular stress was necessary for tumor establishment. Subcutaneous or intraperitoneal injections of transformed p8-expressing fibroblasts led to tumor formation in nude mice, but no tumor was observed with transformed p8-deficient cells. Restoring p8 expression in transformed p8-deficient fibroblasts led to tumor formation demonstrating that p8 expression is necessary for tumor development and suggesting that the stress-response mechanisms governed by p8 are required for tumor establishment.     

Cell growth-dependent subcellular localization of p8

p8 is a stress-induced protein, biochemically related to the architectural factor HMG-I/Y, overexpressed in many cancers and required for tumor expansion. The molecular mechanisms by which p8 may exert its effect in aspects of growth is unknown. Using immunocytochemistry, we found that p8 presents nuclear localization in sub-confluent cells, but it localizes throughout the whole cell in high density grown cells. Cells arrested in Go/G1, either by serum deprivation or by hydroxyurea treatment, show a nucleo-cytoplasmic localization of p8, whether in the rest of the cell cycle stages of actively dividing cells the localization is nuclear. A comparison of p8 sequences from human to fly predicts a conserved bipartite nuclear localization sequence (NLS). The putative NLS has been demonstrated to be functional, since nuclear import is energy dependent (inhibited by sodium azide plus 2-deoxyglucose), and fusion proteins GFP-p8 and GFP-NLSp8 localize to the nucleus, whereas GFP-p8NLSmut in which with Lys 65, 69, 76, and 77 mutated to Ala localized to the whole cell. p8 localization does not involve the CRM1 transporter, since it is insensitive to leptomycin B. Inhibitors of MAPK pathways did not affect p8 subcellular localization. The inhibition of deacetylation with Trichostatin A promotes cytoplasmic accumulation of p8. The results suggest that p8 growth stage-dependent localization is regulated by acetylation, that p8 is not free within the cell but forming part of a complex and that it may exert a role in both subcellular localizations.     

Prenatal diagnosis of de novo unbalanced translocation 8p;21q using subtelomeric probes

We report an unbalanced translocation involving chromosomes 8 and 21 in a fetus showing ultrasonographic abnormalities in the second trimester of pregnancy. A 41-year-old pregnant woman, gravida 1 para 0, was referred to the Genetics Clinic at the 16th week of gestation because of advanced maternal age and fetal pelvicaliectasis on ultrasonographic examination. Pregnancy had occurred following ICSI treatment. After genetic counseling amniocentesis was performed. Fetal karyotype analysis revealed a 46,XY,8p+ karyotype. Ultrasonographic examination was repeated at the 20th week of gestation and showed intrauterine growth retardation, ventriculomegaly, cerebellar structural abnormality and pelvicaliectasis. Chromosomes of both parents were normal. Molecular cytogenetic studies (FISH) using chromosome-specific subtelomere probes showed a terminal deletion of 8p and trisomy of the 21q subtelomeric region. Further analysis with Down Syndrome specific region probes revealed two signals. The couple decided to terminate the pregnancy. This is the first prenatally diagnosed case of unbalanced t(8p;21q) of de novo origin.     

Asymmetrically localized Bud8p and Bud9p proteins control yeast cell polarity and development

Diploid strains of the budding yeast Saccharomyces cerevisiae change the pattern of cell division from bipolar to unipolar when switching growth from the unicellular yeast form (YF) to filamentous, pseudohyphal (PH) cells in response to nitrogen starvation. The functions of two transmembrane proteins, Bud8p and Bud9p, in regulating YF and PH cell polarity were investigated. Bud8p is highly concentrated at the distal pole of both YF and PH cells, where it directs initiation of cell division. Asymmetric localization of Bud8p is independent of the Rsr1p/Bud1p GTPase. rsr1/bud1 mutations are epistatic to bud8 mutations, placing Rsr1p/Bud1p downstream of Bud8p. In YF cells, Bud9p is also localized at the distal pole, yet deletion of BUD9 favours distal bud initiation. In PH cells, nutritional starvation for nitrogen efficiently prevents distal localization of Bud9p. Because Bud8p and Bud9p proteins associate in vivo, we propose Bud8p as a landmark for bud initiation at the distal cell pole, where Bud9p acts as inhibitor. In response to nitrogen starvation, asymmetric localization of Bud9p is averted, favouring Bud8p-mediated cell division at the distal pole.