AbstractHuman α2-macroglobulin is synthesized in the liver and in some extra-hepatic tissues but the physiological role of the protein remains unexplained. We initiated studies to characterize the promoter of the gene. In transient transfections 240 bp of the proximal promoter were necessary and sufficient for CAT-expression in HepG2 cells and lung fibroblasts. This promoter was silent in skin fibroblasts. In DNase I footprint analyses, five regions bound nuclear factors from expressing and non-expressing cells. FPII (−144 to −104) was most prominent with extracts from HepG2 cells and lung fibroblasts. In mobility shifts, FPII bound nuclear factors present in the order : HepG2 > lung ⪢ skin fibroblasts. This region contains a canonical TRE/RARE/ERE halfsite (TGACCT) flanked by 2 related hexamers in the combinations PR4 (palindromic repeat, spacing 4) and ER1 (everted repeat, spacing 1). The interplay of (orphan) members of the steroid receptor family could explain the tissue- and species-specific regulation of the α2M gene.
AbstractDysmorphic features, multisystem disease, and central nervous system involvement are common symptoms in congenital disorders of glycosylation, including several recently discovered Golgi-related glycosylation defects. In search for discriminative features, we assessed eleven children suspected with a Golgi-related inborn error of glycosylation. We evaluated all genetically unsolved patients, diagnosed with a type 2 transferrin isofocusing pattern in the period of 1999–2009. By combining biochemical results with characteristic clinical symptoms, we used a diagnostic flow chart to approach the underlying defect in patients with congenital disorders of glycosylation-IIx. According to specific symptoms and laboratory results, we initiated additional, targeted biochemical and genetic studies. We found a distinctive spectrum of congenital disorders of glycosylation type 2-associated anomalies including sudden hearing loss, brain malformations, wrinkled skin, and epilepsy in combination with skeletal dysplasia, dilated cardiomyopathy, sudden cardiac arrest, abnormal copper and iron metabolism, and endocrine abnormalities in our patients. One patient with severe cortical malformations and mild skin abnormalities was diagnosed with a known genetic syndrome, due to an ATP6V0A2 defect. Here, we present unique congenital disorders of glycosylation type 2-associated anomalies, including both ATPase-related and unrelated cutis laxa and sensorineural hearing loss, a recently recognized symptom of congenital disorders of glycosylation. Based on our findings, we recommend clinicians to consider congenital disorders of glycosylation in patients with cardiac rhythm disorders, spondylodysplasia and biochemical abnormalities of the copper and iron metabolism even in absence of intellectual disability.