Josiane Grosgeorge

Nuclear gene OPA1 , encoding a mitochondrial dynamin-related protein, is mutated in dominant optic atrophy

Optic atrophy type 1 (OPA1, MIM 165500) is a dominantly inherited optic neuropathy occurring in 1 in 50,000 individuals that features progressive loss in visual acuity leading, in many cases, to legal blindness. Phenotypic variations and loss of retinal ganglion cells, as found in Leber hereditary optic neuropathy (LHON), have suggested possible mitochondrial impairment. The OPA1 gene has been localized to 3q28–q29 (refs 13–19). We describe here a nuclear gene, OPA1, that maps within the candidate region and encodes a dynamin-related protein localized to mitochondria. We found four different OPA1 mutations, including frameshift and missense mutations, to segregate with the disease, demonstrating a role for mitochondria in retinal ganglion cell pathophysiology.

Detailed map of a region commonly amplified at 11q13→q14 in human breast carcinoma

Amplification of loci present on band q13 of human chromosome 11 is a feature of a subset of estrogen receptor positive breast carcinomas prone to metastasis. As many as five distinct amplification units have been described on 11q13. They include particularly a genomic area encompassing the GARP gene at 11q13.5-->q14.1. We have reassessed our current knowledge of this region, located telomeric to CCND1 and EMS1, which is amplified in 7-10% of mammary tumors. The loose definition of the driving forces of these amplification events led us to map accurately the boundaries of the amplifiable region, and thus to contribute a physical and transcriptional map of a 3-Mb region of chromosome 11. Four new genes were placed on the regional map, namely CBP2, CLNS1A, UVRAG, and PAK1. We have narrowed the core of the 11q13-->q14 amplicon to a 350-kb area encompassing D11S533, mostly on its telomeric side. The map reported here represents an indispensable step toward sequencing the entire region, and thus toward uncovering gene(s) which play(s) a critical role in breast cancer progression.

Comparative Genomic Hybridization Reveals Novel Chromosome Deletions in 90 Primary Soft Tissue Tumors

Comparative genomic hybridization (CGH) was used to detect chromosomal gains and losses in a series of 90 frozen soft tissue primary tumors (STTs), all untreated. The material consisted of 69 malignant sarcomas, including 20 malignant fibrous histiocytomas (MFH), 23 liposarcomas (LPS), 6 leiomyosarcomas (LMS), 4 synovial sarcomas, 4 primitive neuroectodermal tumors (PNETs), and various others subtypes, in addition to 21 benign tumors. Within the benign tumors, only 2 of the 3 schwannomas showed genetic changes. In malignant sarcomas, genetic changes were detected in 64 of the 69 samples analyzed (92%), with a mean of 4.5 per sample (range 0-10). Gains and losses on chromosome 13 were observed in 32% of the sarcomas with genomic imbalance. Recurring low-level copy number increases were found at new sites on chromosomes 7 (6 MFH samples, 30%) and 8 (10 LPS samples, 43%), the minimal common regions being 7p15-pter and 8q24. No new recurring high-level amplifications were found. Surprisingly, losses of DNA sequences were more frequent than gains; particularly, losses were the main feature in LMS, with highly recurrent common minimal losses at 11q14-qter and 13q21-q22 (4 samples, 66%, and 5 samples, 83%, respectively). Losses of chromosome 2 sequences (minimal common regions at 2p24-pter and 2q32-qter) were observed in 50% of the MFH analyzed. New recurrent losses of whole or part of chromosome 14 were found in 57% of the pleomorphic LPS (PLPS) analyzed. This study uncovers new clues for the diagnosis of malignant STTs and shows the importance of deletions as events in the early steps involved in the tumorigenesis of STTs.

Structural analysis, expression, and chromosomal localization of the mouse ikba gene.

Abstract The pleiotropic transcription factor NF-κB is localized in the cytoplasm bound to its inhibitory subunit IκB. The predominant form of NF-κB is a p50/p65 heterodimer which can be released from IκB-α and migrate to the nucleus. Previous studies have shown that IκB-α–/– mice die 8 to 10 days postnatally, showing runting and a severe dermatitis. However, the organ distribution of mouse IκB-α, the exon-intron structure, and the chromosomal localization of ikba have not been determined so far. A mouse Sv129 genomic DNA library was screened with a human IκB-α/MAD-3 cDNA probe. One clone (P1) was isolated, spanning the complete ikba gene and the promoter/enhancer region. We show that the exon-intron structure between mouse and pig ikba is completely conserved. In contrast to human ikba, the ankyrin repeat 5 is not interrupted by an intron. Furthermore, the mouse ikba promoter contains 6 putative NF-κB binding sequences, which are conserved in mouse, pig, and human, underlining the importance of NF-κB as a key regulator of ikba transcription. The deduced amino acid sequence shows >90% similarity between mouse, pig, and human ikba. Chromosome mapping localized the mouse ikba gene to chromosome 12. Northern blot analysis demonstrated predominant expression in lymphoid tissue (lymph node and thymus). However, IκB-α mRNA was detected as well in liver tissue, the gastrointestinal tract, and the reproductive tract. The cloning and determination of the structure are a prerequisite for the construction of vectors for conditional gene targeting experiments.

Human gp130 transducer chain gene (IL6ST) is localized to chromosome band 5q11 and possesses a pseudogene on chromosome band 17p11

Human gp130 (IL6ST) is one of the most widely used chains of the cytokine receptor family. Indeed, it is involved in signal transduction of interleukin-6, interleukin-11, leukemia inhibitory factor, oncostatin M, and ciliary neurotrophic factor. In a previous report, IL6ST was assigned to chromosomes 5 and 17. Here we specify the chromosomal sublocalization of IL6ST and show that the sequence detected on 17p11 corresponds, in fact, to a nontranscribed pseudogene, whereas the active gene is located at chromosome band 5q11.

Localization of 11q13 loci with respect to regional chromosomal breakpoints

We have employed two strategies to map 13 markers located at 11q13. First, we used pulsed-field gel electrophoresis of DNA fragments obtained with methylation-sensitive restriction enzymes. The markers used in this study were scattered over 8.4 Mb and, for most of them, could not be linked one to another. A second mapping strategy employed hybridization to either DNA of somatic hybrids containing various parts of the long arm of chromosome 11 or metaphase chromosomes of a B-cell line containing the t(11;14)(q13;q32) translocation. We were able to sort out the centromeric from the telomeric probes with respect to translocation breakpoints taken as reference chromosomal landmarks by this approach. BCL1, which corresponds to the region where the t(11;14)(q13;q32) translocation breakpoints are clustered, appears as a boundary between two areas of human/mouse homology present in conserved syntenic regions on mouse chromosomes 7 and 19.

Mapping FRA11A, a folate-sensitive fragile site in human chromosome band 11q13.3

FRA11A, a rare folate-sensitive fragile site assigned to 11q13.3, lies in an area of genomic instability associated with several diseases and amplification events. To map FRA11A, we used fluorescence in situ hybridization with yeast artificial chromosome and cosmid probes on metaphase chromosomes of patients expressing the fragile site. FRA11A was found situated centromeric to ACTN3 and telomeric to D11S913, these markers being within an interval of approximately 1 Mb in the 11q13.3 region.

Description of a 700-kb yeast artificial chromosome contig containing the BCL1 translocation breakpoint region at 11q13

We screened two human yeast artificial chromosome (YAC) libraries by polymerase chain reaction (PCR) with oligonucleotides specific to the BCL1 major translocation breakpoint cluster region at 11q13. Five YACs were isolated. Two of them were chimeric. One of these and remaining three YACs were characterized by hybridization with various known 11q13 probes, Alu-PCR fingerprinting, in situ hybridization, and isolation of YAC ends. A map of this ca 700-kb YAC contig was obtained. This map was consistent with maps established from total human genomic DNA. Every YAC in this region was found unstable and gave rise to reproducibly deleted lineages. Analysis in detail of these deletions over many generations showed that more than a single sequence might be involved. The availability of cloned material will facilitate the search for the still elusive genetic elements responsible for amplifications, deletions and translocations observed at 11q13 in malignancies.

Distinct MDM2 and P14ARF expression and centrosome amplification in well-differentiated liposarcomas.

Well‐differentiated liposarcomas (WDLs) are common soft‐tissue tumors in adults. They are characterized by large marker chromosomes and/or ring chromosomes containing 12q‐derived sequences in which MDM2 is consistently amplified. WDLs are subdivided into two subtypes according to their karyotype. Type D cells exhibit a near‐diploid karyotype, with very few or no chromosome changes. Type H cells exhibit a near‐tetraploid karyotype and many structural changes. Expression of P14ARF, MDM2, and TP53 proteins was assayed in the two WDL subtypes to establish whether distinct expression profiles correlated with cell ploidy. Although a transcriptionally functional TP53 was present in most tumors independent of their karyotype, type H cells were characterized by high levels of P14ARF and MDM2 proteins. Although amplified within similar chromosome markers in type D tumors, MDM2 did not appear to be overexpressed. In addition, it was present as a C‐terminal truncated protein, indicative of alternatively spliced variants of MDM2 mRNA. As the existence of karyotypically distinct tumors could result from alterations of the mitotic machinery, we investigated the centrosome behavior in the two WDL subtypes. Centrosome amplification occurred in WDL tumors types H and D independent of their ploidy status. Moreover, no functional centrosome difference was found between the two tumor subtypes.