Isolation of a zinc finger gene consistently deleted in DiGeorge syndrome

DiGeorge syndrome is a human developmental disorder resulting in hypoplasia of the thymus and parathyroids, and conotruncal heart defects. We recently isolated four genes with zinc finger DNA binding motifs mapping to chromosome 22q11.2 DiGeorge critical region. We now report that one of them, ZNF74 gene, is hemizygously deleted in 23 out of 24 DiGeorge syndrome patients tested. ZNF74 mRNA transcripts are detected in human and mouse embryos but not in adult tissues. Sequence analysis of a corresponding cDNA reveals an an open reading frame encoding 12 zinc finger motifs of the Kruppel/TFIIIA type as well as N-terminal and C-terminal non-zinc finger domains. These results suggest that changes in the dosage of a putative transcription factor through ZNF74 hemizygous deletion may be critical for DiGeorge developmental anomalies.

Cloning of six new genes with zinc finger motifs mapping to short and long arms of human acrocentric chromosome 22 (p and q11.2)

Zinc finger genes encode proteins containing tandemly repeated zinc-mediated folded structures that are found in several transcriptional regulatory proteins. To identify new zinc finger genes, we have screened at low stringency human cosmid libraries enriched in chromosome 22 sequences with a probe derived from the finger region of the mouse Kruppel-like gene, mKr2. We identified 23 nonoverlapping human cosmids cross-hybridizing with the probe. All sequences obtained from cosmid subclones hybridizing with the probe revealed Kruppel-type consensus sequences. Hybridizations to somatic cell hybrid panels and to metaphase chromosomes revealed that 2 nonoverlapping zinc finger cosmids map to chromosome 22p and 4 map to 22q11.2. The 17 other nonoverlapping cosmids most likely map to other chromosomes. The short arms of acrocentric chromosomes are thought to encode only ribosomal RNA genes. Therefore, the identification of two zinc finger genes on chromosome 22p represents an unexpected finding of unknown significance. The four zinc finger genes that map to 22q11.2 are within the cat eye and DiGeorge syndrome regions and thus provide us with potential candidate genes for these developmental malformations.

Tubulin is phosphorylated at tyrosine by pp60c-src in nerve growth cone membranes

We show here that tubulin is the major in vivo substrate of the tyrosine-specific protein kinase pp60c-src in nerve growth cone membranes. Phosphotyrosine antibodies were used to demonstrate phosphotyrosyl residues in a subpopulation of alpha- and beta-tubulin that was highly enriched in a subcellular fraction of growth cone membranes from fetal rat brain. The presence of phosphotyrosine-modified isoforms of alpha- and beta-tubulin in vivo was confirmed by 32p labeling of rat cortical neurons in culture. Tubulin in growth cone membranes was phosphorylated at tyrosine in endogenous membrane phosphorylation reactions (0.068 mol phosphotyrosine/mol alpha-tubulin and 0.045 mol phosphotyrosine/mol beta-tubulin), and phosphorylation was specifically inhibited by antibodies directed against pp60c-src, which is localized in the growth cone membranes. pp60c-src was capable of directly phosphorylating tubulin as shown in immune complex kinase assays with purified brain tubulin. Phosphopeptide mapping revealed a limited number of sites of tyrosine phosphorylation in alpha- and beta-tubulin, with similar phosphopeptides observed in vivo and in vitro. These results reveal a novel posttranslational modification of tubulin that could regulate microtubule dynamics at the growth cone.

Monoclonal antibodies as probes for the transmembrane structure of neutral endopeptidase 24.11 ('enkephalinase')

The neutral endopeptidase (EC 3.4.24.11) ('enkephalinase') is a membrane-bound metalloendopeptidase that is present in large amounts in the microvilli of the kidney proximal tubules. By immunizing mice with purified rabbit kidney brush-border membranes, we have obtained four different monoclonal antibodies that recognize this enzyme in dot-blot and Western-blot assays and can be used for immunoprecipitation of neutral endopeptidase from crude kidney solubilizates. One of these monoclonal antibodies (2B12) allows the labeling of proximal tubule cells with colloidal gold particles. This monoclonal antibody also binds to native brush-border membrane vesicles (which are mostly in the right-side-out configuration) and recognizes an epitope which is destroyed after reduction and alkylation of the protein. By contrast, all three other monoclonal antibodies (21G10, 23B11 and 22E2) compete for another epitope of neutral endopeptidase that is not exposed at the extracytoplasmic surface either in intact cells or in sealed brush-border vesicles. Permeabilization of the vesicles with digitonin, however, restores the full binding activity. Binding of these antibodies is not altered by prior reduction and alkylation of the protein. Taken together, these results strongly suggest that the 2B12 monoclonal antibody binds a conformational epitope located on the ectodomain of the enzyme, whereas the three others (21G10, 23B11 and 22E2) bind to a common or to overlapping epitopes located on the cytosolic domain. These results also demonstrate unambiguously the transmembrane nature of neutral endopeptidase.

Determination of brush border membrane vesicle orientation using monoclonal antibodies recognizing extracytoplasmic and cytoplasmic domains of neutral endopeptidase-24.11

A method for determination of the orientation and integrity of brush border membrane vesicles is described. The method takes advantage of the availability of two monoclonal antibodies, 23B11 and 2B12, which recognize a cytoplasmic and an extracytoplasmic domain, respectively, of the neutral endopeptidase-24.11. Specific binding of the antibodies to intact kidney brush border vesicles or to vesicles permeabilized by digitonin is detected by fluorescence using an anti-mouse immunoglobulin G-fluorescein isothiocyanate conjugate. The method allows discrimination between right side out, inside out, and unsealed vesicles. It requires limited amounts of material and can be completed the day of the brush border vesicle preparation. Application to rabbit kidney brush border membranes freshly prepared led to values of 89, 8, and 3% for right side out, inside out, and unsealed vesicles, respectively. Storage at low temperature was associated with a marked increase in the proportion of unsealed vesicles.

Developmental regulation of protein tyrosine phosphorylation in rat brain

Proteins phosphorylated at tyrosine residues in the developing rat brain have been identified with a focus on the nerve growth cone and synaptic terminal. Endogenous protein phosphorylation in membranes from a subcellular growth cone fraction of fetal rat brain revealed prominent 55-60 kD phosphotyrosine-containing proteins. Proteins of similar size were recognized by phosphotyrosine antibodies in isolated growth cone membranes, indicating that they contained phosphotyrosine in vivo. Proteins of 55-60 kD were not highly phosphorylated in synaptosomes from adult brain, suggesting a growth cone-specific function. Generally, tyrosine phosphorylation was much lower in adult brain than in fetal brain fractions. Although some synaptosomal membrane proteins that contained phosphotyrosine corresponded in size with those in growth cone membranes (92 kD, 41 kD), others were unique to synaptosomal membranes (38 kD and 30 kD). Immunoperoxidase staining of fetal rat neocortex with phosphotyrosine antibodies at embryonic day 19 revealed immunoreactivity in presumptive migratory neuroblasts in the intermediate zone and in processes of the molecular layer. Proliferating neuroepithelial cells of the ventricular zone showed little immunoreactivity. Lower levels of phosphotyrosine immunoreactivity were seen until postnatal day 10, correlating with the period of maximal process outgrowth. These results indicate that protein tyrosine phosphorylation in the developing nervous system may be functionally significant in an aspect of neuronal differentiation such as growth cone-mediated process extension and cell migration. An analogous role in the mature brain may be related to synaptic plasticity or function.

c-src gene product in developing rat brain is enriched in nerve growth cone membranes

Differentiating rat neurons express high levels of the protooncogene product pp60c-src, a 60-kDa tyrosine kinase of unknown function encoded by c-src. pp60c-src was found to be concentrated at least 9-fold in membranes from a subcellular fraction of nerve growth cones, the motile tips of outgrowing neuronal processes. Indirect immunofluorescence staining of cultured chick retinal explants showed pp60c-src in neuronal growth cones and processes, with the antigen particularly concentrated in growth cones of long neurites. pp60c-src in growth cone membranes was an active tyrosine-specific protein kinase with elevated tyrosine-specific protein kinase activity and reduced electrophoretic mobility characteristic of the form of pp60c-src in central nervous system neurons. pp60c-src was present at lower levels in subcellular fractions from mature rat brain but synaptosomal membranes were not enriched. Preferential localization of an active form of pp60c-src in nerve growth cone membranes and persistence of pp60c-src in mature neurons suggest that this tyrosine kinase is important in growth cone-mediated neurite extension and synaptic plasticity.

The use of a monoclonal antibody for the rapid purification of kidney neutral endopeptidase ("enkephalinase") solubilized in octyl glucoside

The neutral endopeptidase ("enkephalinase") of the rabbit brush border membrane has been purified to homogeneity by a rapid immunoaffinity method using a monoclonal antibody. In contrast with other methods used so far, a complete extraction of enkephalinase from the brush border membrane can be achieved with octyl glucoside, without loss of activity. The solubilized enzyme can be selectively separated from the other proteins in a single step using an immunoaffinity column consisting of the monoclonal antibody covalently linked to Sepharose CL-4B. It is demonstrated that enkephalinase can then be recovered in an active form by elution at low pH. The purified enzyme obtained by this method is completely inhibited by thiorphan and appears as a single 94,000 dalton protein after polyacrylamide gel electrophoresis under denaturing and reducing conditions.

Homozygous hemoglobin Knossos (alpha 2 beta 227(B9) Ala----Ser): a new variety of beta (+)-thalassemia intermedia associated with delta (0)-thalassemia

Hb Knossos (beta 27 (B9) Ala----Ser) is a recently discovered hemoglobin variant endowed with beta-thalassemic properties (1,2) We present the first homozygous cases. The propositus, a 19-year-old man is originally from northeast Algeria, but is unrelated to other Algerians who have hemoglobin Knossos. He has a beta(+)-thalassemia intermedia syndrome, including microcytic, hypochromic anemia, enlargement of the spleen, and an increase in the number of reticulocytes. The reduction of beta-chain synthesis is pronounced (alpha/non alpha:2.76). Whole cells containing Hb Knossos have a dramatically low oxygen affinity (P50:38 mm Hg). The propositus also has homozygous delta(0)-thalassemia. The chromosome carrying these mutations is characterized by the DNA haplotype I.

[Comparative study on the digestion of radiolabelled vicilin, legumin and lectin of Pisum sativum in the rat]

Storage proteins, vicilin, legumin as well as the lectin, purified from pea seed proteins, were radiolabelled with [14C]- or [3H]-formaldehyde, then mixed with the pea flour which was incorporated in a liquid meal and given to rats through a gastric tubing. Radiolabelled casein (75% of the total proteins in the meal) and triolein were added to the meal and the animals were killed after 2 and 7 h. Samples were taken from the stomach and intestinal contents and from the intestinal mucosa and the liver. 2 h: gastric emptying and intestinal absorption from vicilin and legumin materials were as high as for casein. 7 h: in the colon contents an excess of labelled vicilin and legumin (2.9 and 2.6% of the radioactive dose from the meal) was observed compared to casein (1.5%). The pea lectin disappeared slowlier from the intestinal contents than did the three other radiolabelled proteins (2 h) which gave the highest radioactive materials in the livers. The lectin did not interact with the intestinal mucosa but it was less hydrolysed than the three other proteins tested and 15% of the dose reached the colon (7 h). This lectin could have been adsorbed on pancreatic enzymes such as a lipase, but radiolabelled triolein did not produce radioactive material in the colon, demonstrating that lectin or other pea proteins, in these experiments did not inhibit this lipase. Short-time experiments (2 h, 7 h) were sufficient to describe and compare the digestion of three radiolabelled pea proteins.

The production and characterization of a monoclonal antibody specific for the 94,000 dalton enkephalin-degrading peptidase from rabbit kidney brush border

We have prepared a monoclonal antibody specific for a major 94,000 dalton protein from the brush border membrane of rabbit kidney cortex. The monoclonal antibody was used for the immunoaffinity purification of this protein after solubilization of brush border membranes with octylglucoside. The 94,000 dalton protein is a peptidase capable of cleaving the Gly3-Phe4 bond of methionine-enkephalin. Identification of this peptidase as a previously described 94,000 dalton enkephalinase of kidney cortex was confirmed by its sensitivity to EDTA and inhibitors such as thiorphan and phosphoramidon.

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Een studie over de Rijselse renteniers en andere opzoekingen maken het mogelijk nu te pogen de mortaliteitscurve van de renteniers in een lange période in de xive eeuw te bepalen. Deze studie steunt op de Rijselse stadsrekeningen van die période, en op een steekproef van 385 personen (239 vrouwen en 146 mannen). Zo hebben wij verschillende sterftecurven opgesteld (mannen, vrouwen, mannen en vrouwen samen). Een aantal topjaren vallen op : het zijn 1329, 1333, 1340, 1349 en vooral 1360 en 1367.

Een poging tot verklaring volgt ; men kan alleen maar betreuren dat de stadsrekeningen van Rijsel maar weinig informatie over de doodsoorzaak geven.

Biosynthesis of a putative gonadotropin receptor component by rat leydig cells: isolation of a radiolabeled acidic protein of 79,000 molecular weight by affinity chromatography

The Leydig cells of the testis are known to possess high affinity receptors for luteinizing hormone and human chorionic gonadotropin (hCG), but no information concerning the synthesis of these receptors is available yet. In order to investigate this question, we have purified crude rat interstitial cell preparations on discontinuous Percoll gradients, and Leydig cells recovered from fractions demonstrating maximum testosterone production and hCG binding capacity were incubated for 17 h in a culture medium containing [35S]methionine. Radioactive proteins solubilized with Triton X-100 were submitted to affinity chromatography on a resin consisting of hCG covalently linked to agarose. Proteins bound to the column were analyzed by two-dimensional gel electrophoresis. Autoradiography of the gel revealed a major protein (molecular weight: 79,000; pI 4.5) whose binding to the resin could be greatly diminished by an excess of hCG. The electrophoretic properties of this protein are similar to those of previously isolated gonadotropin receptor components.

Kinetics of the inactivation of human and bovine trypsins and chymotrypsins by alpha1-proteinase inhibitor and of their reactivation by alpha2-macroglobulin

The time dependency of inactivation of human cationic trypsin and chymotrypsin II and of bovine trypsin and alpha-chymotrypsin by human serum has been investigated. Since the molar concentration of serum alpha1-proteinase inhibitor is much higher than that of other inhibitors, this time dependence could be used to calculate the rate constants kass for the association of alpha1-proteinase inhibitor with the four proteases. The association process was found to be second order, with kass ranging from 1 x10(4) s-1 (human trypsin) to 2.6 x 10(6) s-1 (bovine chymotrypsin). The human proteases react much more slowly with human alpha1-proteinase inhibitor than the bovine ones. But, whatever the species, chymotrypsin is inhibited more quickly than trypsin. Addition of alpha2-macroblobulin to the inactive complexes resulted in a time-dependent regeneration of enzymic activity due to the formation of alpha2-macroglobulin-protease complexes. The reactivation (i.e. dissociation) process was first order and extremely slow: the half-life of the alpha1-proteinase inhibitor-proteinase complexes ranged from 8 days (bovine chymotrypsin) to 9 months (human chymotrypsin). The human proteases formed the most stable complexes with alpha1-proteinase inhibitor. The pathological implications of these findings are discussed.

A kinetic study of the inhibition of human and bovine trypsins and chymotrypsins by the inter-alpha-inhibitor from human plasma

Human plasma inter-alpha-inhibitor forms 1:1 inactive complexes with human and bovine trypsins (EC 3.4.21.4) and chymotrypsins (EC 3.4.21.1). The association and dissociation rate constants as well as the equilibrium dissociation constants (Ki) of the complexes formed of inter-alpha-inhibitor and the four proteases have been measured. The most stable complexes are those formed with the bovine enzymes. For instance, Ki = 2.1-10-11 M for bovine trypsin whereas Ki = 1.2 - 10-8 M for human trypsin. Whatever the species, the complexes formed with the chymotrypsins are less stable than those formed with the trypsins.

LSD: no teratogenic action in rats, mice, and hamsters

Lysergic acid diethylamide tartrate was given to 98 pregnant rats, 67 mice, and 22 hamsters as a single dose of 5 to 500 micrograms per kilogram of body weight per day either at the beginning of gestation or during the period of organogenesis. Examination of the 1003 rat fetuses, 521 mouse fetuses, and 189 hamster fetuses obtained failed to prove any abortifacient, teratogenic, or growth-depressing effects.