Prader-Willi syndrome with an unusually large 15q deletion due to an unbalanced translocation t(4;15)

Prader-Willi syndrome (PWS) is a neurobehavioral disorder caused by deletions in the 15q11-q13 region, by maternal uniparental disomy of chromosome 15 or by imprinting defects. Structural rearrangements of chromosome 15 have been described in about 5% of the patients with typical or atypical PWS phenotype. An 8-year-old boy with a clinical diagnosis of PWS, severe neurodevelopmental delay, absence of speech and mental retardation was studied by cytogenetic and molecular techniques, and an unbalanced de novo karyotype 45,XY,der(4)t(4;15)(q35;q14),-15 was detected after GTG-banding. The patient was diagnosed by SNURF-SNRPN exon 1 methylation assay, and the extent of the deletions on chromosomes 4 and 15 was investigated by microsatellite analysis of markers located in 4qter and 15q13-q14 regions. The deletion of chromosome 4q was distal to D4S1652, and that of chromosome 15 was located between D15S1043 and D15S1010. Our patient's severely affected phenotype could be due to the extent of the deletion, larger than usually seen in PWS patients, although the unbalance of the derivative chromosome 4 cannot be ruled out as another possible cause. The breakpoint was located in the subtelomeric region, very close to the telomere, a region that has been described as having the lowest gene concentrations in the human genome.     

Chromosomes 17 and 22 involved in marker formation in neurofibrosarcoma in von Recklinghausen disease

Summary We describe the cytogenetic findings in a recurrent neurofibrosarcoma in a patient with nonfamilial von Recklinghausen disease. The composite karyotype was: 40,Y,-X,+dic r(X;20)(:Xp22.2q26::20p13 q13:), -1, +der(1)t(1;3) (p21;p24),-3,-4,-5,+der(5) t(5;?)(q31;?),-9,-9,+der(9)t(3;9)(q21 or q13;p24 or p22), -11,+der(11)t(11;?)(q22.2;?), -17,+der(17)t(17; 22;?)(q21;q13.1;?), -20, -21, -22, -22, +der(22)t(17; 22;?)(q21;q13.1;?),t(2;10)(q37;q22). The derivative chromosomes were demonstrated at the 500 band level. Chromosomes 17 and 22 were shown to be involved in an unbalanced three-way translocation: t(17;22;?)(q21;q13.1;?). This event was confirmed by in situ hybridization, using two probes mapped to chromosome 17. Hill H is a probe derived from the novel oncogene TRE and is located at 17q12–22. The second probe, derived from the granulocyte colony-stimulating factor (G-CSF), is located at 17q11–q21. The rearrangement between chromosomes 17 and 22 showed breakpoints similar or close to the gene loci for neurofibromatosis 1 (NF-1) and NF-2. Based on our observations we recommend that genetic studies on NF-1 tumors include both gene sites (NF-1 and NF-2) rather than focus on one gene locus.     

The RING-H2 protein RNF11 is differentially expressed in breast tumours and interacts with HECT-type E3 ligases

A breast cancer-associated mRNA originally cloned as a 475-bp partial cDNA from a library enriched for tumour cDNAs [Oncogene 16 (1998) 327] is expressed at high levels in breast and prostate cancer cells. Immunohistochemical analysis indicates that the protein is expressed in primary breast tumours. We used RT-PCR to generate a full-length 2852 nt mRNA sequence that includes the hypothetical open reading frame (ORF) for human RNF11. Our analysis shows that RNF11 encodes modular domains and motifs likely to interact with other proteins involved in oncogenesis. Chief among these are the RING-H2 finger domain that could facilitate the degradation of specific substrate(s) involved in oncogenesis and the PY motif which binds to WW-domain proteins, several of which are known to be E3 ubiquitin ligases. Our GST-pulldown and immunoprecipitation results indicate that RNF11 interacts with the E3 ligase AIP4 when coexpressed with RNF11 in mammalian cells.     

Cloning and mapping of members of the MYM family.

Tandem repeats of a novel, putative, zinc-binding motif (MYM) have been described within the products of two, highly homologous genes: ZNF198/RAMP/FIM and ZNF261/DXS6673E. ZNF198, mapping to 13q11-q12, was recently shown to fuse to the fibroblast growth factor receptor 1 gene in the t(8;13)(p11;q11-q12) rearrangement associated with a stem cell leukemia/lymphoma syndrome. ZNF261 at Xq13.1 is disrupted by a t(X;13)(q13.1;q32) rearrangement in a mentally retarded patient and is a candidate gene for nonspecific X-linked mental retardation. Here we have cloned another member of this family, designated ZNF258, and mapped it to chromosome band 14q12. In addition, ZNF262/KIAA0425 was identified as a further member of the family and mapped to 1p32-p34. The predicted protein products of ZNF258 and ZNF262 maintain the repeats of the MYM motif. Isolation of these new members will facilitate the functional characterization of the MYM family and motif.     

Chromosome mapping of RNF16 and rnf16, human, mouse and rat genes coding for testis RING finger protein (terf), a member of the RING finger family

RNF16 (ring finger protein 16; alias terf), a member of the RING finger family, has been shown to be exclusively expressed in the testis. Human RNF16 is located at 1q42 based on PCR-assisted analysis of both a human/rodent mono-chromosomal hybrid cell panel and a radiation hybrid-mapping panel. On the other hand, chromosomal mapping of the RNF16 gene by fluorescence in situ hybridization reveals that mouse Rnf16 is located at 11B1.2-B1.3 and rat Rnf16 at 10q22. These results provide additional evidence that the mouse 11B region displays conserved linkage homology with the rat 10q22 region, whereas in the case of RNF16, this homology is only conserved among rodents, distinct from the 1q42 region of the human genome.     

Regional assignment of arylsulfatase A,mitochondrial aconitase and NADH-cytochrome b5 reductase by somatic cell hybridization

Summary By using somatic cell hybrids between HPRT deficient hamster cells and fibroblasts derived from a patient with a X/22 translocation t(X;22)(q13;q112), we have assigned the genes for human ARSA, DIA 1, and ACO 2 to region q112qter of human chromosome 22 and the gene for human PGK close to the breakpoint in band Xq13.     

Marked differences in unilateral isolated retinoblastomas from young and older children studied by comparative genomic hybridization

Although it is established that the loss of function of both alleles of the RB1 gene is a prerequisite for the development of retinoblastoma, little is known about the genetic events that are required for tumor progression. We used comparative genomic hybridization (CGH) to search for DNA copy number changes in isolated unilateral retinoblastomas. From a series of 66 patients with retinoblastomas with somatic mutations in both RB1 alleles, tumor samples from 13 children with the youngest (2.0-9.8 months) and 13 with the oldest (36.2-84.1 months) age at operation were studied. Loss at 13q14, the location of RB1, was demonstrated in two tumors only. Recurring chromosome imbalances included gains at 6p (11/26), 1q (10/26), 2p (4/26), and 17q (4/26), gains of the entire chromosome 19 (3/26), and losses at 16q (9/26). A commonly gained region at 1q32 was identified. Increased dosage of GAC1, a candidate oncogene located in 1q32, was found in two of four tumors by Southern blot analysis. Comparison of the CGH findings revealed that retinoblastomas from children with an older age at operation showed significantly more frequent (13/13 cases vs 4/13 cases; P = 0.0005) and more complex genetic abnormalities (median, 5 changes/abnormal tumor vs median, 1.5 changes/abnormal tumor; P = 0.003) than retinoblastomas from children with a young age at operation. Gains at 1q, 2p, 17q, of the entire chromosome 19 and losses of 16q were restricted to the older age group. Our results suggest that the progression of retinoblastomas from older patients follows mutational pathways different from those of younger patients.     

Detection of an unbalanced t(4;15) by FISH in a child with multiple congenital anomalies

Detection of an unbalanced t(4;15) by FISH in a child with multiple congenital anomalies: In this report, we present the clinical history and findings in a 6-month-old male with multiple congenital anomalies, developmental delay, and an initial male karyotype with 4q+. The origin of the additional segment on 4q was unequivocally established by fluorescence in situ hybridization (FISH). Whole chromosome probe for chromosome 4 and chromosome 15-specific a-satellite probe were used. The karyotype was demonstrated to be 46,XY,der(4), t(4;15)(q35;?),inv(9)(p13q13). To the best of our knowledge the above cytogenetic abnormalities with these clinical findings have not been described previously. This case further demonstrates the advantage of FISH in the identification of anomalous chromosome regions and breakpoints.     

Molecular cytogenetic aberrations in Tunisian patients with multiple myeloma identified by cIg-FISH in fixed bone marrow cells

Cytogenetic studies in multiple myeloma (MM) are hampered by the hypo-proliferative nature of plasma cells. In order to circumvent this problem, we have used a combination of immunolabeling of cytoplasmic Ig light chains (λ or κ) and FISH (cIg-FISH), which allowed a comprehensive detection of the most common and/or recurrent molecular cytogenetic aberrations on fixed bone marrow cells of 70 Tunisian patients. Translocations involving the chromosome 14q32 region were observed in 32 cases (45.7%), including 18 cases with a t(11;14), 8 cases with a t(4;14), and 2 cases with a t(14;16). Deletions of the 13q14 region (D13S319/RB1) were detected in 18.6%, and deletions of the 17p13 region (TP53) in 5.7% of the cases, respectively. Of all patients with a D13S319/RB1 deletion, 61.5% also carried a 14q32 translocation, whereas TP53 deletions were associated with a t(11;14) in 2 cases (50%) and a D13S319 deletion in 1 case (25%). Our results suggest that there is a correlation between the presence of 14q32 translocations and chromosome 13q14 deletions in MM patients and that cIg-FISH is more sensitive as compared to conventional karyotyping in detecting molecular cytogenetic abnormalities in this disease.     

Ring finger protein 146/Iduna is a Poly (ADP-ribose) polymer binding and PARsylation dependent E3 ubiquitin ligase

Recent findings suggest that Ring finger protein 146 (RNF146), also called Iduna, have neuroprotective property due to its inhibition of Parthanatos via binding with Poly(ADP-ribose) (PAR). The Parthanatos is a PAR dependent cell death that has been implicated in many human diseases. RNF146/Iduna acts as a PARsylation-directed E3 ubquitin ligase to mediate tankyrase-dependent degradation of axin, thereby positively regulates Wnt signaling. RNF146/Iduna can also facilitate DNA repair and protect against cell death induced by DNA damaging agents or γ-irradiation. It can translocate to the nucleus after cellular injury and promote the ubiquitination and degradation of various nuclear proteins involved in DNA damage repair. The PARsylation-directed ubquitination mediated by RNF146/Iduna is analogous to the phosphorylation-directed ubquitination catalyzed by Skp1-Cul1-F-box (SCF) E3 ubiquitin complex. RNF146/Iduna has been found to be implicated in neurodegenerative disease and cancer development. Therefore modulation of the PAR-binding and PARsylation dependent E3 ligase activity of RNF146/Iduna could have therapeutic significance for diseases, in which PAR and PAR-binding proteins play key pathophysiologic roles.Key words: E3 ubquitin ligase, ring finger protein 146, PAR-binding proteins, PARsylation, Parthanatos inhibitors, ubiquitinationRing finger proteins contain ring fingers, which are considered to be the functional module for E3 ubiquitin ligase activity.^1,2 Ring finger protein 146 (RNF146), a novel PARsylation-directed ring finger E3 ubiquitin ligase, is located at 6q22.1-q22.33 of human chromosome.³ RNF146 encodes a protein of 359 amino acids with a predicted molecular weight of 39.8 kDa.³ The molecular structure of RNF146 contains one N-terminus C₃HC₄ ring finger domain (35–77 aa) as well as one WWE domain (91–167 aa).³ The poly(ADP-ribose) (PAR) binding motif (144–167 aa) at the tail of WWE domain of RNF146 is involved in various important functions. The detailed molecular structure of RNF146 is illustrated in Figure 1. This PAR-binding protein was recently demonstrated to protect against Parthanatos and function as PARsylation-directed E3 ubquitin ligase to ubiquitinate PARsylated substrates.^3–5 Here, we provide a concise summary of these novel functions of RNF146 and discuss the potential pathophysiological and therapeutic significance of novel functions of RNF146 for human diseases.Open in a separate windowFigure 1Molecular structure of RNF146. The RNF146 is a novel ring finger E3 ubiquitin ligase with 359 amino acids. The molecular structure of RNF146 contains one N-terminus C₃HC₄ ring finger domain (35–77 aa, 7 cysteine and 1 histidine residues involved in ring finger formation is highlighted in red) as well as one WWE domain (91–167 aa, the highly conserved 2 tryptophan and 1 glutamic acid, which WWE domain is named after, are highlighted in red). The PAR binding motif (144–167 aa) is at the C-terminus tail of WWE domain of RNF146 (highlighted in blue at the end of WWE sequence).     

The gene encoding TBC1D1 with homology to the tre-2/USP6 oncogene, BUB2, and cdc16 maps to mouse chromosome 5 and human chromosome 4

TBC1D1 is the founding member of a family of related proteins with homology to tre-2/UPS6, BUB2, and cdc16 and containing the tbc box motif of 180-220 amino acids. This protein family is thought to have a role in differentiation and in regulating cell growth. We set out to map the TBC1D1 gene in mouse and human. Segregation analysis of a TBC1D1 RFLP in two independent mouse RI (recombinant inbred) lines reveals that mouse Tbc1d1 is closely linked to Pgm1 on chromosome 5. The human TBC1D1 gene was assigned to human chromosome 4p15.1-->4q21 using Southern blot analyses of genomic DNAs from rodent-human somatic cell lines. A human-specific genomic fragment was observed in the somatic cell lines containing human chromosome 4 or the 4p15.1-->4q21 region of the chromosome. TBC1D1 maps to the region containing the ortholog of mouse Pgm1 adding another locus to this long region of conserved synteny between mouse and man.     

Conserved autosomal syntenic group on mouse (MMU) chromosome 15 and human (HSA) chromosome 22: assignment of a gene for arylsulfatase A to MMU 15 and regional mapping of DIA1, ARSA, and ACO2 on HSA 22

We have utilized a panel of Chinese hamster x mouse somatic cell hybrids segregating mouse chromosomes to assign a gene for arylsulfatase A (ARSA) to mouse chromosome 15. Considering our previous assignment of a gene for diaphorase-1 (DIA1) to the same mouse chromosome, we have evidence for another syntenic relationship that has been conserved, since the homologous loci for human ARSA and DIA1 are both located on human chromosome 22. Because MMU 15 and HSA 22 are quite dissimilar in size and banding patterns, we have attempted to identify the conserved portion by regional mapping of human DIA1 and ARSA using somatic cell hybrids segregating a human chromosome translocation t(15;22)(q14;q13.31). The results assign human DIA1 and ARSA to the distal sub-band of 22q13 (region 22q13.31 leads to qter). The locus for mitochondrial aconitase (ACO2) has been separated by the breakpoint from DIA1 and ARSA and is located more proximally.     

Closely linked loci on the long arm of chromosome 13 flank a specific 2;13 translocation breakpoint in childhood rhabdomyosarcoma

A specific chromosomal translocation, t(2;13)(q35;q14), is present in tumor cells from about one-half of children with alveolar rhabdomyosarcoma, who generally have widely disseminated disease at diagnosis. Using a series of six DNA probes from five loci previously assigned to bands 13q12----q14, we have localized the translocation breakpoint on chromosome 13 by in situ hybridization. Each probe was used to examine metaphase spreads from two or more rhabdomyosarcoma cell lines that have the t(2;13), as well as from control lymphoblastoid cell metaphases. All six probes bound to chromosome 13q12----q14 in the control cell line, but showed no appreciable hybridization to other sites. With rhabdomyosarcoma metaphases, cDNA clones of the retinoblastoma susceptibility gene (RB1) and the esterase D gene (ESD), as well as the arbitrary genomic fragment 7D2 (D13S10), showed specific hybridization to the normal chromosome 13 and the der(2) marker, but not to the der(13). By contrast, the genomic fragments HU10 (D13S6) and 7F12 (D13S1) hybridized specifically to the normal chromosome 13 and the der(13), but not to the der(2). Thus, the breakpoint of this translocation lies distal to D13S6 and D13S1 and proximal to ESD, RB1, and D13S10. Our data indicate that the locus affected by the translocation breakpoint on chromosome 13, which we have termed RMS, is physically distinct from the RB1 locus and is, in fact, proximal to ESD, which others have placed at least 10(6) bp proximal to RB1. The consistent presence of the der(2) marker chromosome, coupled with occasional loss of the der(13), suggests that the RMS gene, or at least a critical component, moves to chromosome 2 in tumors with this translocation.     

An attempt to locate the gene for congenital cataracts using linkage analysis]

Analysis of linkage between the gene of autosomal dominant congenital cataract and 10 polymorphic loci localized in 1, 2, 3, 4, 6, 13, 16 chromosomes was performed. Some loci were only informative for this purpose: Mucin located in 1q21, NH24 located in the 2-nd chromosome and Pi located in 1q21 32.17. No linkage was observed for the cataract gene and the loci located in chromosomes 1 and 2. The maximum estimate of likelihood is approx. 0.2 for the cataract gene and the Pi locus located in 14q32.1, though the value of the maximal lod score was only, 0.732.     

Evidence that chromosome band 22q12 is concerned with cell proliferation in chronic myeloid leukaemia

Summary A man and two of his three children carried an abnormally short chromosome 22 resembling the Philadelphia chromosome (Ph¹). Giemsa banding showed that the abnormal chromosome resulted from a translocation t(11;22) (q25;q13). The breakpoint on chromosome 22 was at the q12/q13 band interface compared with the breakpoint of Ph¹ at the q11/q12 band interface. The absence of leukaemia or haematological disorder in members of this family suggests that the critical genetic site on chromosome 22 concerned with abnormal myeloid cell proliferation in human leukaemia is contained in the 22q12 band.     

The gene that encodes the human CD20 (B1) differentiation antigen is located on chromosome 11 near the t(11;14)(q13;q32) translocation site

The human CD20 gene (B1) encodes a B lymphocyte-specific, cell-surface molecule that is involved in B cell activation and differentiation. We report that the CD20 gene is located on human chromosome 11 at position q12-q13. The location of CD20 was determined by in situ hybridization and was further confirmed by Southern blot analysis of DNA from rodent/human hybrids that contained only portions of human chromosome 11. This localization places the CD20 gene near the site of the t(11;14)(q13;q32) translocation that is found in a subgroup of B cell-lineage malignancies. The site of this translocation has been previously identified by DNA cloning and termed bcl-1. The CD20 gene was found to lie on the centromeric side of bcl-1 on chromosome 11 and to be separated from bcl-1 by at least 50 kb of DNA. These results raise the possibility that alterations in the expression of the CD20 gene may result after the t(11;14) chromosomal alteration.     

Identification and molecular characterization of de novo translocation t(8;14)(q22.3;q13) associated with a vascular and tissue overgrowth syndrome

Klippel-Trenaunay syndrome (KTS) is a disorder primarily characterized by capillary-venous vascular malformations associated with altered limb bulk and/or length. We report the identification of a balanced translocation involving chromosomes 8q22.3 and 14q13 in a patient with a vascular and tissue overgrowth syndrome consistent with KTS. We demonstrated that translocation t(8;14)(q22.3;q13) arose de novo. These data suggest that a pathogenic gene for a vascular and tissue overgrowth syndrome (KTS) may be located at chromosome 8q22.3 or 14q13. Fluorescence in situ hybridization (FISH) analysis was used to define the breakpoint on chromosome 8q22.3 to a <5-cM interval flanked by markers AFMA082TG9 and GATA25E10, and the 14q13 breakpoint within a 1-cM region between STSs WI-6583 and D14S989. This study provides a framework for the fine-mapping and ultimate cloning of a novel vascular gene at 8q22.3 or 14q13.