A 50-year-old woman presented with right shoulder pain after lifting a heavy container. Over the next several months she was unable to work because of the pain. Her past medical history was significant only for a hysterectomy and breast reduction surgery. On physical examination the patient had mild tenderness over the right biceps tendon and a slightly reduced range of motion at the right shoulder. She had no systemic symptoms and no lymphadenopathy. Radiographs of the right shoulder were obtained and are shown in Figure 1. A bone scan showed increased tracer uptake at the right humeral neck. Mammograms and an abdominal and pelvic computed tomography (CT) scan were normal. Magnetic resonance imaging (MRI) of the right shoulder is shown in Figure 2. A CT-guided biopsy of the right humeral neck was performed (Figure 3).
Competing interests: None declared.
Accepted for publication July 13, 2006
Correspondence to: Dr. Adel Assaf, Assistant Professor, McGill University Health Centre–Montreal General Hospital, Department of Radiology, Rm C5-118, Montreal QC H3G 1A4; fax 514 934-8263; ac.lligcm.chum@fassa.leda
The Drosophila kep1 gene encodes an RNA binding protein related to the murine QUAKING apoptotic inducer. We have previously shown that kep1 can induce apoptosis when transfected into different cell lines. To better define the role of Kep1 in apoptosis, we generated kep1 null flies. These flies were viable, but females displayed reduced fertility, with approximately half of the eggs laid from kep1 − homozygotes failing to hatch. In addition, loss of kep1 suppressed GMR-rpr -mediated apoptosis in the Drosophila eye, and kep1 mutant flies had increased susceptibility to Escherichia coli infection. We found that Kep1 bound dredd RNA in vitro , and that extracts prepared from kep1 mutant ovaries had markedly reduced proteolytic cleavage activity toward the caspase-8 target substrate IETD-7-amino-4-trifluoromethyl coumarin. We observed increased levels of the β isoform of dredd mRNA in kep1 mutants as compared with wild-type. Taken together, our results suggest that Kep1 regulates apoptosis by influencing the processing of dredd RNA.
