Within the brush border (BB) of proximal tubule cells (PTC), the intermicrovillar area connecting the base of the microvilli constitutes a distinct microdomain characterized by the presence on the cytoplasmic side of the membrane of an extensive clathrin coat (1). Kerjaschki and Farquhar (2) and Chatelet et al. (3) have shown that a 330-kD glycoprotein (gp), initially described as the nephritogenic antigen of Heymann's nephritis, is concentrated on the luminal aspect of these areas, at variance with other BB proteins such as maltase (4), which are distributed over the entire surface of the microvilli. To our knowledge, gp330 is the only membrane gp confined to the intermicrovillar domain (IMVD) . It is also expressed in coated pits of glomerular epithelial cells, pneumocytes type II, epididymis, and epithelial cells of the visceral yolk sac (VYS) (5, 6), but its function remains unknown . This paper describes a 280-kD BB protein, defined by mAbs raised against rat renal BB, which is only found in the IMVD of the PTC and on the apical domain of epithelial cells of the VYS . When injected to pregnant rats, the mAbs induce embryonic resorption and/or fetal abnormalities, suggesting that the 280-kD protein plays a key role in endocytosis-related cell function. Materials and MethodsAntibodies. The two mAbs reported in this study (F5/75, an IgGI with a pl of 6.8-7.6, and F5/46, an IgGI with a pl of 8.1-8.5) were obtained by immunization of mice against rat BB (7) . They were analyzed in relation to mAb F1/12 and polyclonal antibodies specific for gp330 (8), and mAb F2/180 reactive with the 300-kD maltase .Characterization of the 280-kD Antigen. The antigen identified by mAb F5/75 and F5/46 on tubular BB was identified by immunoprecipitation ofradiolabeled BB membrane vesicles (BBMV) (7) and immunoadsorption techniques . Purified mAbs F5/75 and F5/46, as well as mAbs F1/12 and F2/180, were individually coupled to Sepharose 4B (Pharmacia Fine Chemicals, Velizy, France) . All steps involving antigenic preparations and immunoadsorption were carried out in the presence of 1 mM PMSF and 2 mM benzamidine . BBMV (7,8) and yolk sacs dissected at 19 d of gestation were washed extensively in PBS and solubilized in 1 % Triton X100 . 1-2 ml of each immunoabsorbent was incubated with either 20 mg of solubilized BBMV, or with the material from 10 yolk sacs.
We showed previously that 3 distal inhibitors of cholesterol synthesis are highly teratogenic in rats. AY 9944 and BM 15766 inhibit 7-dehydrocholesterol reductase, which catalyzes the last step of cholesterol synthesis, and triparanol inhibits Delta(24)-dehydrocholesterol reductase, which catalyzes the last step in another pathway. These molecules cause holoprosencephalic brain anomalies. Under certain experimental conditions, other anomalies (of the limbs and male genitalia) are also observed. Assays performed by gas chromatography-mass spectrometry (GC-MS) show hypocholesterolemia and an accumulation of precursors. These data indicate that this animal model can be considered a model of Smith-Lemli-Opitz syndrome. Smith-Lemli-Opitz syndrome is a recessive autosomal genetic disease characterized by malformations (microcephaly, corpus callosum agenesis, holoprosencephaly, and mental retardation), male pseudohermaphroditism, finger anomalies, and failure to thrive. The syndrome has been attributed to a deficit in 7-dehydrocholesterol reductase. As assayed by GC-MS, the sterol status of these patients indicates severe hypocholesterolemia and an accumulation of precursors: 7-dehydrocholesterol, 8-dehydrocholesterol, and oxidized derivatives. The presence of 7-dehydrocholesterol in the serum of patients is pathognomonic of the disease. The developmental gene Shh (sonic hedgehog) plays a key role in brain, limb, and genital development; it was shown recently that the Shh protein has to be covalently linked to cholesterol to be active. This is the first time that a posttranslational function has been attributed to cholesterol. There is an obvious relation between Shh dysfunction and the malformations observed in our experiments and in patients with Smith-Lemli-Opitz syndrome. However, the exact relation remains to be clarified. It is clear, however, that the role of cholesterol in embryonic development must be taken into account.
In order to study the role played by the fetoplacental unit in providing the human fetus with arachidonic acid, Δ5- and Δ6-desaturase activities were studied in microsomes from human fetal liver and placenta after 18 and 22 weeks of gestation. We evidenced for the first time Δ5- and Δ6-desaturase activities in fetal liver microsomes. As in adult liver, Δ6-desaturation is the rate-limiting step of arachidonic acid synthesis. No activity was found in the placenta. Arachidonic acid concentrations were higher in fetal serum than in maternal serum while the opposite was observed for linoleic acid. The fetal liver microsomal content in arachidonic acid was low. Taken together the data suggest that arachidonic acid is supplied to the fetus through a preferential transfer across the placenta.
Restrictive dermopathy is a rare, lethal autosomal recessive syndrome. We report on 3 unrelated affected stillborn infants of consanguineous parents. Clinical findings include a tight, thin, translucent, taut skin, which tears spontaneously in flexion creases, arthrogryposis multiplex congenita (including the temporomandibular joint), enlarged fontanelles, typical face and dysplasia of clavicles and long bones. Histologic abnormalities include hyperplastic, abnormally keratinized epidermis, reduced tonofilaments, thin, compact dermis with hypoplasia of the elastic fibres, and abnormal subcutaneous fat. Fifteen previous cases are reviewed.
An early case of prenatal Caffey disease is reported. Ultrasound examination performed at 20 weeks showed major angulations of long bones, but both ultrasound scan and X-rays failed to make the differential diagnosis between Caffey disease and lethal osteogenesis imperfecta. A cordocentesis allowed us to find important biological abnormalities. The pregnancy was terminated after the rapid development of hydrops fetalis. The definitive diagnosis of Caffey disease was obtained by special X-ray and pathological study.
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