Metallothionein Mto gene of Drosophila melanogaster: structure and regulation.

We report the sequence of the Mto gene, one of the two known metallothionein genes of Drosophila melanogaster, and compare its structure with that of the other metallothionein gene, Mtn. The main structural features are the presence of a small intron (61 base-pairs), the presence of four potential MREs (metal regulatory elements) and the absence of a TATA box in the promoter region. Of all metals tested, Hg2+, Cd2+ and Cu2+ are the most efficient ions for inducing an increase in Mto gene transcription. The Mto and Mtn genes are differentially regulated during normal development. Transcription of Mto is detected early in embryogenesis (0 to 3 h) and persists to the third larval instar, while Mtn expression starts later in embryogenesis (12 to 15 h) and is thereafter maintained throughout larval development and adult stages. Sequencing of the Mto protein is in good agreement with the nucleic acid data. Surprisingly, attempts to isolate and characterize the Mtn protein were unsuccessful. Several lines of evidence suggest that this metallothionein is rapidly incorporated after its synthesis into lysosomes, where it would be processed in a way that would not permit its purification. The function of the Mtn protein thus appears to be mainly related to detoxification processes. The pattern of expression of Mto suggests that this gene may be involved in the control of metal homeostasis during development.

Metallothionein genes in Drosophila melanogaster constitute a dual system.

We have selected a metallothionein (MT) cDNA clone from a cadmium-resistant Drosophila melanogaster cell line. This clone includes an open reading frame coding for a 43-amino acid protein whose characteristics are a high cysteine content (12 cysteines, 28% of all residues) and a lack of aromatic amino acids. This protein differs markedly from the Drosophila MT (Mtn gene) previously reported [Lastowski-Perry, D., Otto, E. & Maroni, G. (1985) J. Biol. Chem. 260, 1527-1530). The MT system of Drosophila thus consists of at least two distantly related genes, in sharp contrast with vertebrate MT systems, in which the different members of MT gene families display high similarity. The gene corresponding to our MT cDNA (Mto) is inducible in Drosophila cell lines and in both larval and adult flies.

Metallothioneins and resistance to cadmium poisoning in Drosophila cells.

Toxicity of cadmium on Drosophila cell lines has been studied. Maximal tolerance for cadmium chloride is 10 microM. Metallothioneins are induced in Drosophila cells following cadmium addition. A stable cadmium resistant cell line (Cd R200) has been selected starting from the haploid D clone. The Cd R200 cells are diploid and display metallothionein levels 22 times higher than cells of the original line fully induced with cadmium. The 200 microM CdCl2 tolerance upper limit in Cd R200 line is overcome if L-cysteine is supplemented to the medium. It is thus possible, in the presence of 5 mM L-cysteine, to select cells able to resist 800 microM CdCl2. These cells produce 4 times more metallothioneins than Cd R200 cells.

[Place of aspiration lipolysis in the surgical treatment of Launois-Bensaude syndrome]. / Place de la lipolyse-aspiration dans le traitement chirurgical du syndrome de Launois-Bensaude.

Modifying the mass contour with liposuction by developing numerous subcutaneous "tunnels" with subsequent homogeneous contractions of the overlying skin will add a new dimension to the treatment of the Launois-Bensaude syndrome. Successful correction of these deformities can be obtained without a large amount of surgical undermining and skin resection and with minimal scar formation.

[Kniest's disease]. / La maladie de Kniest.

A one year old child with Kniest's disease was admitted for reconstructive surgery of the bone deficit of a palatine cleft. This syndrome is recognizable at a very early age by the shortness of the limbs or the increase in size of the joints. Clinically it associates mild facial dystrophy and nanism from reduction in height of the trunk and the shortness and deviations of the limbs. Frequently associated are myopia, deafness and a palatine cleft. Radiological signs are reduced height of vertebral bodies, and a not infrequent finding is a cuneiform deformity of the first lumbar vertebrae. Epiphyseal development is anarchic, that of the knee large, while the femoral head is small, fragmented or absent. Transmission is by the dominant mode. Kniest's syndrome must be differentiated from metratropic dwarfism in which there is greater progression of spinal deformities.