Claude Turc-Carel

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.

The Ewing Family of Tumors -- A Subgroup of Small-Round-Cell Tumors Defined by Specific Chimeric Transcripts

BACKGROUND Precise diagnosis of small-round-cell tumors is often a challenge to the pathologist and the clinical oncologist. In Ewings sarcomas and related peripheral primitive neuroectodermal tumors, a t(11;22) translocation or a (21,22) rearrangement is associated with hybrid transcripts of the EWS gene with the FLI1 or ERG gene. To investigate the diagnostic implication of this observation, we searched for these hybrid transcripts in tumors from patients with clinical and radiologic features of Ewings sarcoma or peripheral primitive neuroectodermal tumors. METHODS Samples of RNA from 114 tumors were reverse transcribed and subjected to the polymerase chain reaction with primers designed to amplify the relevant chimeric transcripts. All amplified products were sequenced. RESULTS In-frame hybrid transcripts were observed in 89 cases. A hybrid transcript was found in 83 of 87 cases (95 percent) of Ewings sarcoma or peripheral primitive neuroectodermal tumors. Samples of RNA from all of 12 tumors that had been proved to be other than Ewings sarcoma or neuroectodermal tumors had no hybrid transcript. However, 6 of 15 undifferentiated tumors whose type was ambiguous (nonsecreting, poorly differentiated neuroblastoma or undifferentiated sarcoma) contained a hybrid transcript, suggesting that they might have to be reclassified. CONCLUSIONS A subgroup of small-round-cell tumors identified as belonging to the Ewing family of tumors can be defined according to a specific molecular genetic lesion that is detectable by a rapid, reliable, and efficient method. This approach can be applied to small specimens obtained by fine-needle biopsies.

Chromosomes in Ewing's sarcoma. I. An evaluation of 85 cases and remarkable consistency of t(11;22)(q24;q12)

Since our initial reports on chromosomal studies in eight Ewings sarcomas (ES), we have carried out similar investigations on 23 additional ES specimens following short-term culture of tumor cells (16 cases), and established in vitro cell lines (three cases) and on xenografted tumors in nude mice (four cases). We demonstrated the presence of the reciprocal t(11;22)(q24;q12) in every case except one that exhibited a complex t(11;22;14)(q24;q12;q11). On the basis of results from these additional 23 cases, we confirm the consistency of the t(11;22)(q24;q12) in ES. Moreover, we reviewed 54 ES cases reported by other investigators; when added to our 31 cases, this brings the total number to 85 unrelated cases of ES available for an evaluation of the frequency of involvement of bands 11q24 and 22q12 in translocations in ES. The standard t(11;22)(q24;q12) proved to be a remarkably consistent event, present in 83% of the cases. Five percent of the cases exhibited complex translocations involving a third chromosome in addition to chromosomes #11 and #22. In 4% of the cases variant translocations involved 22q12 but with a chromosome(s) other than #11. The breakpoint on chromosome 22q12 appears to be the most consistently observed event in 92% of the cases, whereas, the breakpoint at chromosome 11q24 was observed in 88% of the cases.

Transplantation of a multipotent cell population from human adipose tissue induces dystrophin expression in the immunocompetent mdx mouse

Here, we report the isolation of a human multipotent adipose-derived stem (hMADS) cell population from adipose tissue of young donors. hMADS cells display normal karyotype; have active telomerase; proliferate >200 population doublings; and differentiate into adipocytes, osteoblasts, and myoblasts. Flow cytometry analysis indicates that hMADS cells are CD44+, CD49b+, CD105+, CD90+, CD13+, Stro-1−, CD34−, CD15−, CD117−, Flk-1−, gly-A−, CD133−, HLA-DR−, and HLA-Ilow. Transplantation of hMADS cells into the mdx mouse, an animal model of Duchenne muscular dystrophy, results in substantial expression of human dystrophin in the injected tibialis anterior and the adjacent gastrocnemius muscle. Long-term engraftment of hMADS cells takes place in nonimmunocompromised animals. Based on the small amounts of an easily available tissue source, their strong capacity for expansion ex vivo, their multipotent differentiation, and their immune-privileged behavior, our results suggest that hMADS cells will be an important tool for muscle cell–mediated therapy.

Chromosome study of Ewing's Sarcoma (ES) cell lines. Consistency of a reciprocal translocation t(11;22)(q24;q12)

A detailed banded chromosome analysis was performed in five established Ewings sarcoma (ES) cell lines originating from four unrelated patients in relapse. Of various numerical and structural abnormalities, a reciprocal translocation between chromosomes #11 and #22, t(11;22)(q24;q12), was observed in four of the lines. The t(11;22) was seen in every cell in three lines; in the fourth, it was seen in only 21% of the cells considered stemline, but the der(22) was present in the remaining 79% of cells. These results suggest that t(11;22)(q24;q12) is a chromosomal change specific to ES cells, in which the rearrangement of chromosome #22 could be the consistent karyotypic feature and the crucial step in terms of cell proliferation. Other, nonrandom chromosomal changes were found: monosomies 2p11----2pter, 10q25----10qter, and 17pter----17q11, and partial trisomies 1q21----1q31 and 8q24.1----8q24.2. The role of the therapeutic regimen received by these patients must be evaluated with regard to the formation of a wide variety of homogeneously staining regions, which were observed in every cell line, particularly on the short arm of chromosome #7, which was observed in three of the five cell lines.

Structure of the supernumerary ring and giant rod chromosomes in adipose tissue tumors

Supernumerary ring or giant rod marker chromosomes are a characteristic of well‐differentiated liposarcomas (WDLPS) and atypical lipomas (ALP) and are often observed as the sole cytogenetic abnormality, but are rare in lipomas. Using a combination of different methods, we extensively investigated the structure and composition of rings and giant rods in a series of 17 WDLPS‐ALP samples and three intra‐ or intermuscular lipomas (IMLP), revealing a unique combination of particular features strikingly related to these tumors. Although the rings and rods displayed in vitro and in vivo stability, the presence of alpha‐satellites could not be detected on these supernumerary structures. Comparative genomic hybridization analysis, in combination with fluorescence in situ hybridization, identified the chromosomal regions contributing to the formation of these chromosomes: in WDLPS‐ALP, all carried amplifications of 12q14–15 and the MDM2 gene, with variable other noncontiguous regions. In the three IMLP, the rings consistently carried amplifications of 12q15–21 and 1q21, but increased copies of MDM2 were found in only one case. Other genes located more proximal in 12q14–15 were amplified in several WDLPS‐ALP, but showed a normal copy number in IMLP. Furthermore, the immunohistochemical expression of the MDM2 protein was detected in most (12/14) WDLPS‐ALP, in 1–30% of the cells, but never in IMLP. These supernumerary chromosomes represent a peculiar kind of amplification structure, midway between double minute chromosomes and homogeneously staining regions, but the mechanisms underlying the formation of these structures remain obscure. Genes Chromosomes Cancer 24:30–41, 1999.

Cytogenetic studies of adipose tissue tumors. II. Recurrent reciprocal translocation t(12;16)(q13;p11) in myxoid liposarcomas

Detailed chromosome studies, briefly reported previously, from short-term cultures of tumor cells from myxoid liposarcomas are reported. A common reciprocal translocation, t(12;16)(q13;p11), was found in three cases and a complex t(1;12;16)(p11;q13;p11) in the fourth one. This nonrandom primary change, not described before in solid tumors, could characterize the myxoid form of liposarcoma. The involvement of a closely located breakpoint on chromosome #12 in a reciprocal t(3;12)(q28;q14) described in a lipoma in the previous article of this series, suggests a common basis in the biological process of proliferation of tumors sharing a common histogenesis.

Translocation, t(17;22)(q22;q13), in dermatofibrosarcoma protuberans: a new tumor-associated chromosome rearrangement

A translocation, t(17;22)(q22;q13), was identified in two cases of dermatofibrosarcoma protuberans (DP). They bring to four the number of DP cases characterized by an identical t(17;22)(q22;q13), which can be considered as a new tumor-associated chromosome rearrangement. To date, this translocation has been found only in DP and its juvenile form, giant-cell fibroblastoma. This finding has two major consequences. First, it casts light on the development and significance in DP of ring chromosomes which consistently harbor sequences derived from chromosomes 17 and 22. Second, the identification of this new chromosome marker, and eventually of the underlying molecular rearrangement, should help to classify DP, a soft-tissue tumor of still uncertain cell origin. In addition, it could be used to differentiate DP from truly benign or malignant entities, in order that this tumor of intermediate malignancy could be adequately managed.

Various regions within the alpha-helical domain of the COL1A1 gene are fused to the second exon of the PDGFB gene in dermatofibrosarcomas and giant-cell fibroblastomas

Dermatofibrosarcoma protuberans (DFSP) and its juvenile form, giant‐cell fibroblastoma (GCF), are uncommon infiltrative tumors of the dermis, which present unique cytogenetic features, such as the reciprocal translocation t(17;22) or, more commonly, supernumerary ring chromosomes containing sequences from chromosomes 17 and 22. We have recently shown that these aberrations are cytogenetic manifestations of gene fusions between the platelet‐derived growth factor B‐chain gene (PDGFB), the cellular equivalent of the v‐sis oncogene, and the collagen type I alpha 1 gene (COL1A1), the major protein constituent of the extracellular matrix in connective tissue of skin. We now report characterization of COL1A1/PDGFB chimeric genes at the RNA and DNA sequence levels in a series of DFSPs and GCFs. All 16 tumors studied contained the COL1A1/PDGFB gene. The location of breakpoints within COL1A1 varied greatly, but was always limited to the region encoding the alpha‐helical domain. The PDGFB segment of the chimeric transcript always starts with exon 2, placing PDGFB under the control of the COL1A1 promoter and removing all known elements negatively controlling PDGFB transcription and translation. Production of these aberrant transcripts in fibroblasts, the suspected cell of origin of DFSP/GCF, likely causes autocrine stimulation and cell proliferation. No specific function has yet been assigned to exon 2 of PDGFB, and this exon does not encode for the mature growth factor. Its retention in all chimeric COL1A1/PDGFB genes suggests that it is important for the normal processing of the PDGFB polypeptide. Genes Chromosomes Cancer 23:187–193, 1998.

The cytogenetics of solid tumors. Relation to diagnosis, classification and pathology

This overview discusses the chromosome changes in solid tumors and how recent advancements in techniques have yielded results which at least qualitatively are similar to those obtained in the leukemias, i.e., that consistent and recurrent chromosome changes characterize most tumors adequately examined and that tumor entities consist of cytogenetically defined and unique subsets. Thus, the findings point to a similar application of the chromosome changes in tumors in their classification, diagnosis and causation.