Cytoplasmic dynein function is essential in Drosophila melanogaster.

The microtubule motor cytoplasmic dynein has been implicated in a variety of intracellular transport processes. We previously identified and characterized the Drosophila gene Dhc64C, which encodes a cytoplasmic dynein heavy chain. To investigate the function of the cytoplasmic dynein motor, we initiated a mutational analysis of the Dhc64C dynein gene. A small deletion that removes the chromosomal region containing the heavy chain gene was used to isolate EMS-induced lethal mutations that define at least eight essential genes in the region. Germline transformation with a Dhc64C transgene rescued 16 mutant alleles in the single complementation group that identifies the dynein heavy chain gene. All 16 alleles were hemizygous lethal, which demonstrates that the cytoplasmic dynein heavy chain gene Dhc64C is essential for Drosophila development. Furthermore, our failure to recover somatic clones of cells homozygous for a Dhc64C mutation indicates that cytoplasmic dynein function is required for cell viability in several Drosophila tissues. The intragenic complementation of dynein alleles reveals multiple mutant phenotypes including male and/or female sterility, bristle defects, and defects in eye development.

Regulation of cytoplasmic dynein function in vivo by the Drosophila Glued complex.

The Drosophila Glued gene product shares sequence homology with the p150 component of vertebrate dynactin. Dynactin is a multiprotein complex that stimulates cytoplasmic dynein-mediated vesicle motility in vitro. In this report, we present biochemical, cytological, and genetic evidence that demonstrates a functional similarity between the Drosophila Glued complex and vertebrate dynactin. We show that, similar to the vertebrate homologues in dynactin, the Glued polypeptides are components of a 20S complex. Our biochemical studies further reveal differential expression of the Glued polypeptides, all of which copurify as microtubule-associated proteins. In our analysis of the Glued polypeptides encoded by the dominant mutation, Glued, we identify a truncated polypeptide that fails to assemble into the wild-type 20S complex, but retains the ability to copurify with microtubules. The spatial and temporal distribution of the Glued complex during oogenesis is shown by immunocytochemistry methods to be identical to the pattern previously described for cytoplasmic dynein. Significantly, the pattern of Glued distribution in oogenesis is dependent on dynein function, as well as several other gene products known to be required for proper dynein localization. In genetic complementation studies, we find that certain mutations in the cytoplasmic dynein heavy chain gene Dhc64C act as dominant suppressors or enhancers of the rough eye phenotype of the dominant Glued mutation. Furthermore, we show that a mutation that was previously isolated as a suppressor of the Glued mutation is an allele of Dhc64C. Together with the observed dependency of Glued localization on dynein function, these genetic interactions demonstrate a functional association between the Drosophila dynein motor and Glued complexes.

A family of dynein genes in Drosophila melanogaster.

We report the identification and initial characterization of seven Drosophila dynein heavy chain genes. Each gene is single copy and maps to a unique genomic location. Sequence analysis of partial clones reveals that each encodes a highly conserved portion of the putative dynein hydrolytic ATP-binding site in dyneins that includes a consensus phosphate-binding (P-loop) motif. One of the clones is derived from a Drosophila cytoplasmic dynein heavy chain gene, Dhc64C, that shows extensive amino acid identity to cytoplasmic dynein isoforms from other organisms. Two other Drosophila dynein clones are 85 and 90% identical at the amino acid level to the corresponding region of the beta heavy chain of sea urchin axonemal dynein. Probes for all seven of the dynein-related sequences hybridize to transcripts that are of the appropriate size, approximately 14 kilobases, to encode the characteristic high molecular weight dynein heavy chain polypeptides. The Dhc64C transcript is readily detected in RNA from ovaries, embryos, and testes. Transcripts from five of the six remaining genes are also detected in much lesser amounts in tissues other than testes. All but one of the dynein transcripts are expressed at comparable levels in testes suggesting their participation in flagellar axoneme assembly and motility.

A fertility region on the Y chromosome of Drosophila melanogaster encodes a dynein microtubule motor.

A clone encoding a portion of the highly conserved ATP-binding domain of a dynein heavy-chain polypeptide was mapped to a region of the Drosophila melanogaster Y chromosome. Dyneins are large multisubunit enzymes that utilize the hydrolysis of ATP to move along microtubules. They were first identified as the motors that provide the force for flagellar and ciliary bending. Seven different dynein heavy-chain genes have been identified in D. melanogaster by PCR. In the present study, we demonstrate that one of the dynein genes, Dhc-Yh3, is located in Y chromosome region h3, which is contained within kl-5, a locus required for male fertility. The PCR clone derived from Dhc-Yh3 is 85% identical to the corresponding region of the beta heavy chain of sea urchin flagellar dynein but only 53% identical to a cytoplasmic dynein heavy chain from Drosophila. In situ hybridization to Drosophila testes shows Dhc-Yh3 is expressed in wild-type males but not in males missing the kl-5 region. These results are consistent with the hypothesis that the Y chromosome is needed for male fertility because it contains conventional genes that function during spermiogenesis.

[Surgery of the aortic arch in coronary patients. 400 surgically treated patients]. / Chirurgie du carrefour aortique chez les malades coronariens. 400 malades opérés.

Out of 400 consecutive patients who underwent aorto-iliac surgery 45 (11.25 per cent) were known to have coronary disease at the time of the operation. Pre-operative coronary arteriography was carried out in the 11 patients (2.75 per cent) who had unstable or recently worsened angina. Aorto-coronary bypass was performed preventively in 7 patients (1.75 per cent of surgical patients). Mortality from preventive aorto-coronary bypass and secondary aorto-iliac surgery was nil. A study of post-operative mortality (2.75 per cent overall) showed that only one patient (0.25 per cent of surgical patients) died of myocardial infarction. The low rate of post-operative morbidity and mortality of coronary origin therefore does not incline to extend the indications for preventive aorto-coronary bypass. However, it seems desirable to improve the indications for pre-operative coronary arteriography by performing thallium 201 myocardial scintigraphy with dipyridamole infusion in all coronary patients about to undergo aorto-iliac surgery when no exercise electrocardiogram can be obtained because of intermittent claudication. This type of examination will probably broaden the indications for pre-operative coronary arteriography and preventive aorto-coronary bypass, though presumably to a very small extent. Among these 400 patients who underwent aorto-iliac surgery and were all followed up for 2 to 12 years, only a few (0.25 per cent) benefited secondarily from coronary surgery, no doubt because the physiological age of that population was often too high. In fact, these patients were mainly at risk of cancer aggravated by both alcohol and smoking, for in this study, and rather in contrast with most publications, cancer was responsible for 44 per cent of secondary deaths, i.e. more than twice the percentage (20 per cent) of secondary deaths of cardiac origin.

[Double coronary revascularization using the internal mammary arteries. Mid-term results of 74 cases]. / Doubles revascularisations coronariennes par les artères mammaires internes. Résultats à moyen terme de 74 cas.

This study reports our experience of 74 multiple coronary artery bypass, using either the two internal mammary arteries (IMA) (43 cases), or the left internal mammary artery (LIMA), alone for sequential bypass (31 cases). Comparison with a series of 200 patients operated upon in a previous period (1981-83), when the LIMA was used alone for single bypass, showed that post-operative mortality, post-operative infarction and mediastinitis were significantly more frequent with double bypass using the two IMA; similarly, the mid-term results seemed to be less satisfactory with the double IMA bypass technique. This difference was due to the fact that using the right and left IMA means longer dissection time, greater problems of haemostasis, stronger surgical trauma and prolonged exposure of the sternum, which is a source of infection. In addition, the right internal mammary artery (RIMA) being further away from the sites of coronary grafting lends itself less readily than the LIMA to this type of bypass, and it is often used for the right and marginal coronary artery which is less suitable for surgery. Using the LIMA alone for sequential bypass does not seem to produce more complications than using that vessel for single bypass. On the basis of the results obtained, we consider that the double IMA bypass should only be used when the internal saphenous vein bypass is contraindicated (past history of stripping, varices, fragile aorta forewarning of difficult grafting).(ABSTRACT TRUNCATED AT 250 WORDS)

[Left internal mammary artery. Choice graft for coronary bypass]. / L'artère mammaire interne gauche. Greffon de choix pour les pontages coronaires.

The left internal mammary artery is a vessel with relatively constant anatomical features and which in almost all subjects is congruent with their own anterior interventricular artery. In addition, atheromatous lesions of this artery are exceptional; when grafted onto the anterior interventricular artery, it adjusts itself to the diastolic coronary flow. Finally, and this is remarkable, once grafted onto the anterior interventricular artery it virtually never undergoes long-term alterations in contrast with the internal saphenous vein. For these reasons, the left internal mammary artery should be used as often as possible to revascularize the anterior intraventricular artery. Preoperative angiography of the left internal mammary artery to evaluate its quality does not seem to be necessary; what is important in the choice of a graft is the quality of the spurt after the vessel is dissected and its distal end is severed. However, the left internal maxillary artery is smaller and more friable in women, in hypotrophic subjects and in elderly people, especially when hypertensive. In these cases, it should be used with caution or not at all, particularly for bypass with a fairly wide, atheromatous and calcified anterior intraventricular artery. Accounting for these restrictions and with some experience at least 90% of anterior interventricular arteries can be revascularized by the left internal mammary artery.

[Follow-up angiography of 100 revascularizations of the anterior interventricular artery by the left internal mammary artery]. / Contrôle angiographique de 100 revascularisations de l'interventriculaire antérieure par l'artère mammaire interne gauche.

One hundred and fifty patients who underwent revascularisation of the left anterior descending artery (LAD) by the left internal mammary artery (LIMA) between 1981 and 1983 were recalled for control coronary angiography one year after surgery. One hundred patients gave consent. The patency rate in these 100 patients was 90 per cent. The presumed causes of the 10 thromboses observed were: for LAD (5 cases), technical problems (3 cases), competitive flow (2 cases). Ten per cent of the patent LIMA grafts were abnormal: moderate stenosis of the anastomosis (5 cases), small LIMA (3 cases), stenosis of the middle segment of the LIMA (1 case). In addition, we observed 7 cases of competitive flows: 3 cases with a LAD which was not sufficiently stenotic, 4 cases with a large saphenous diagonal bypass graft. If a diagonal artery bypass is necessary, it is better to revascularize by either a latero-lateral anastomosis with the LIMA or by using the right IMA. Ninety per cent of the patent grafts were quite satisfactory ar 1 year: regular, supple, and perfectly congruent with the bypassed artery which was injected massively. As a number of North American teams have shown, this good patency rate seems to be maintained at long term, which is not the case with saphenous vein bypass grafts.