Assessment of PAX6 alleles in 66 families with aniridia.

We report on PAX6 alleles associated with a clinical diagnosis of classical aniridia in 81 affected individuals representing 66 families. Allelic variants expected to affect PAX6 function were identified in 61 families (76 individuals). Ten cases of sporadic aniridia (10 families) had complete (8 cases) or partial (2 cases) deletion of the PAX6 gene. Sequence changes that introduced a premature termination codon into the open reading frame of PAX6 occurred in 47 families (62 individuals). Three individuals with sporadic aniridia (three families) had sequence changes (one deletion, two run-on mutations) expected to result in a C-terminal extension. An intronic deletion of unknown functional significance was detected in one case of sporadic aniridia (one family), but not in unaffected relatives. Within these 61 families, single nucleotide substitutions accounted for 30/61 (49%), indels for 23/61 (38%), and complete deletion of the PAX6 locus for 8/61 (13%). In five cases of sporadic aniridia (five families), no disease-causing mutation in the coding region was detected. In total, 23 unique variants were identified that have not been reported in the Leiden Open Variation Database (LOVD) database. Within the group assessed, 92% had sequence changes expected to reduce PAX6 function, confirming the primacy of PAX6 haploinsufficiency as causal for aniridia.

Space plasma physics: space experiments with particle accelerators.

Electron and plasma beams and neutral gas plumes were injected into the space environment by instruments on Spacelab 1, and various diagnostic measurements including television camera observations were performed. The results yield information on vehicle charging and neutralization, beam-plasma interactions, and ionization enhancement by neutral beam injection.

Transcription factor IIIA gene expression in Xenopus oocytes utilizes a transcription factor similar to the major late transcription factor.

Xenopus transcription factor IIIA (TFIIIA) gene expression is stringently regulated during development. The steady-state level of TFIIIA mRNA in a somatic cell is approximately 10(6) times less than in an immature oocyte. We have undertaken studies designed to identify differences in how the TFIIIA gene is transcribed in oocytes and somatic cells. In this regard, we have localized an upstream transcriptional control element in the TFIIIA promoter that stimulates transcription from the TFIIIA promoter approximately threefold in microinjected oocytes. The upstream element, in cis. does not stimulate transcription from the TFIIIA promoter in somatic cells. Thus, the element appears to be oocyte specific in the context of the TFIIIA promoter. However, both oocytes and somatic cells contain a protein (or a related protein) that binds the upstream element. We have termed this protein from oocytes the TFIIIA distal element factor. The sequence of the upstream element is similar to the sequence of the upstream element found in the adenovirus major late promoter that is a binding site for the major late transcription factor. By gel shift analysis, chemical footprinting, methylation intereference, and point mutation analysis, we demonstrate that the TFIIIA distal element factor and major late transcription factor have similar DNA-binding properties.

Xenopus TFIIIA gene transcription is dependent on cis-element positioning and chromatin structure.

The Xenopus TFIIIA gene is transcribed very efficiently in oocytes. In addition to a TATA element at -30, we show that from -425 to +7 the TFIIIA gene contains only two positive cis elements centered at -267 (element 1) and -230 (element 2). This arrangement of the cis elements in the TFIIIA gene is striking because these two elements are positioned very close to each other yet separated from the TATA element by approximately 190 nucleotides. We show that the 190-nucleotide spacing between the TATA element and the upstream cis elements (elements 1 and 2) is critical for efficient transcription of the gene in oocytes and that a nucleosome is positioned in this intervening region. This nucleosome may act positively on TFIIIA transcription in oocytes by placing transcription factors bound at elements 1 and 2 in a favorable position relative to the transcription complex at the TATA element.

The inhibition of thyrotropin-releasing hormone deamidation in porcine hypothalamic tissues.

Frozen porcine hypothalamic fragments afford an enzymic fraction that forms exclusively pyroGlu-His-Pro by enzymatic degradation of thyroliberin. Ten compounds have been examined as inhibitors of this reaction and the results indicate that the enzyme(s) responsible for this conversion have an absolute sulfhydryl requirement. Concentrations of thyroliberin have also recently been reported in areas of the brain in addition to the hypothalamus. Each of these areas actively degrade thyroliberin with the hypothalamus being most active.

Vg1 RBP intracellular distribution and evolutionarily conserved expression at multiple stages during development.

We have analyzed the expression and intracellular distribution, during oogenesis and embryogenesis, of Vg1 RBP, a protein implicated in the intracellular localization of Vg1 mRNA to the vegetal cortex of Xenopus oocytes. Vg1 RBP (protein) colocalizes with Vg1 RNA at all stages of oogenesis. Vg1 RBP RNA, however, localizes to the animal pole during late oogenesis, and remains in the animal blastomeres and ectodermal precursors until its zygotic transcription is activated, around stage 12. Vg1 RBP mRNA then becomes expressed throughout the neural epithelium. Vg1 RBP mRNA expression is also detected in what appears to be neural crest cells undergoing delamination and lateral migration. By tailbud stages, Vg1 RBP expression is present in the branchial arches, otic vesicle, pronephros, and along the neural tube. To examine the expression pattern in different species, we cloned the zebrafish homolog of Vg1 RBP by using a highly homologous EST clone to screen an embryonic cDNA library. In situ hybridization reveals that Vg1 RBP RNA localizes early in oogenesis to the animal pole. Although Vg1 RBP RNA is detected in all blastomeres of the early embryo, the expression pattern in the one day old zebrafish embryo is almost identical to that of the equivalent stage Xenopus embryo. These results indicate that the zygotic expression pattern is similar in frogs and fish, and that there is a conserved zygotic expression of Vg1 RBP distinct from its expression in the oocyte.

In familial hyperaldosteronism type I, hybrid gene-induced aldosterone production dominates that induced by wild-type genes.

We compared the aldosterone-producing potency of the angiotensin II-sensitive wild-type aldosterone synthase genes and the ACTH-sensitive hybrid 11 beta-hydroxylase/aldosterone synthase gene by examining aldosterone, PRA, and cortisol day-curves (2-hourly levels over 24 h) in patients with familial hyperaldosteronism type I, before and during long-term (0.8-13.5 yr) glucocorticoid treatment. In 8 untreated patients, PRA levels were usually suppressed, and aldosterone correlated strongly with cortisol (r = 0.69-0.99). Fourteen studies were performed on 10 patients receiving glucocorticoid treatment that corrected hypertension, hypokalemia, and PRA suppression in all. ACTH was markedly and continuously suppressed in 6 studies, 3 of which demonstrated strong correlations between aldosterone and PRA (r = 0.77-0.92). ACTH was only partially suppressed in the remaining 8 studies; aldosterone correlated strongly: 1) with cortisol alone in 5 (r = 0.71-0.98); 2) with cortisol (r = 0.90) and PRA (r = 0.74) in one; 3) with PRA only in one (r = 0.80); and 4) with neither PRA nor cortisol in one. Unless ACTH is markedly and continuously suppressed, aldosterone is more responsive to ACTH than to renin/angiotensin II, despite the latter being unsuppressed. This is consistent with the hybrid gene being more powerfully expressed than the wild-type aldosterone synthase genes in familial hyperaldosteronism type I.

Evidence for persistent dysfunction of wild-type aldosterone synthase gene in glucocorticoid-treated familial hyperaldosteronism type I.

BACKGROUND: In familial hyperaldosteronism type I (FH-I), glucocorticoid treatment suppresses adrenocorticotrophic hormone-regulated hybrid gene expression and corrects hyperaldosteronism. OBJECTIVE: To determine whether the wild-type aldosterone synthase genes, thereby released from chronic suppression, are capable of functioning normally. METHODS: We compared mid-morning levels of plasma potassium, plasma aldosterone, plasma renin activity (PRA) and aldosterone: PRA ratios, measured with patients in an upright position, and responsiveness of aldosterone levels to infusion of angiotensin II (AII), for 11 patients with FH-I before and during long-term (0.8-14.3 years) treatment with 0.25-0.75 mg/day dexamethasone or 2.5-10 mg/day prednisolone. RESULTS: During glucocorticoid treatment, hypertension was corrected in all. Potassium levels, which had been low (< 3.5 mmol/l) in two patients before treatment, were normal in all during treatment (mean 4.0+/-0.1 mmol/l, range 3.5-4.6). Aldosterone levels during treatment [13.2+/-2.1 ng/100 ml (mean+/-SEM)] were lower than those before treatment (20.1+/-2.5 ng/100 ml, P< 0.05). PRA levels, which had been suppressed before treatment (0.5+/-0.2 ng/ml per h), were unsuppressed during treatment (5.1+/-1.5 ng/ml per h, P< 0.01) and elevated (> 4 ng/ml per h) in six patients. Aldosterone: PRA ratios, which had been elevated (> 30) before treatment (101.1+/-25.9), were much lower during treatment (4.1+/-1.0, P< 0.005) and below normal (< 5) in eight patients. Surprisingly, aldosterone level, which had not been responsive (< 50% rise) to infusion of AII for all 11 patients before treatment, remained unresponsive for 10 during treatment. CONCLUSIONS: Apparently regardless of duration of glucocorticoid treatment in FH-I, aldosterone level remains poorly responsive to AII, with a higher than normal PRA and a low aldosterone: PRA ratio. This is consistent with there being a persistent defect in functioning of wild-type aldosterone synthase gene.

Isolation and characterization of the Xenopus laevis cDNA and genomic homologs of neuropeptide Y.

We have isolated Xenopus laevis cDNA and genomic clones encoding the neuropeptide Y (NPY) mRNA and gene using a probe from the human NPY gene. The longest open reading frame in the cDNA encodes a peptide 76% identical to human prepro-NPY and 73% identical to rat prepro-NPY. The putative mature Xenopus NPY (XNPY) peptide is 94% identical to both human and rat peptides. A genomic clone containing 422 base pairs of 5'-flanking sequences and the 5'-end of the mRNA was also isolated. Primer extension analysis was used to map the transcription initiation site of the Xenopus NPY gene. Comparison of the 5'-flanking sequences of the Xenopus laevis, human, and rat NPY genes resulted in areas of high conservation, including the TATA box and the CT box previously shown to interact with Sp1-like proteins. Distribution of the Xenopus NPY message was analyzed by Northern analysis and RNAse protection. XNPY transcripts were not detected in whole developing embryo RNA, but were detected in adult frog brain RNA. We have also conducted preliminary studies of the XNPY promoter, utilizing an XNPY/chloramphenicol acetyl-transferase fusion construct. This study has demonstrated that Xenopus NPY shares a high degree of identity to its human and rat counterparts and that this homology extends to the gene, which contains similar cis-elements positioned near the transcription start site.

Transcription factor-green fluorescent protein chimeric fusion proteins and their use in studies of DNA affinity chromatography.

A new plasmid, pJ22, was produced by introducing the enhanced green fluorescent protein (GFP) coding sequence into the pET28 plasmid while retaining much of the multiple cloning site. This new plasmid was then used to produce a chimeric fusion protein containing the DNA-binding region of the rat liver CAAT enhancer binding protein (C/EBP) fused to the COOH-terminus of GFP. This new GFP-C/EBP fusion protein also contains (His)6 to facilitate purification by Ni(2+)-agarose and several other useful features. The plasmid and protein were developed to allow us to more rapidly investigate the DNA-Sepharose affinity chromatography of transcription factors. The GFP-C/EBP protein is virtually identical in its DNA-binding properties to a well-characterized, bacterially expressed protein called C/EBP 62 which has been shown to mimic rat wild-type C/EBP DNA-binding. GFP-C/EBP also binds to DNA-Sepharose which contains the CAAT element and is eluted by a salt gradient. Salt-dependent elution was highly temperature-dependent over the range of 4-19 degrees C. Since temperature-dependent DNA-binding has also been reported for other DNA-binding proteins, this may also occur with other transcription factors. DNA-affinity chromatography gave higher purity than that obtained by Ni(2+)-agarose chromatography and chromatography on the same DNA-Sepharose column at two different temperatures resulted in the greatest purification, to near homogeneity. This temperature-dependent affinity chromatography provides an important new approach to transcription factor purification.

Bi-column method for purification of transcription factors.

A novel bi-column method for purifying transcription factors, using two different columns and two different elution strategies is described. Lac repressor elutes at lower heparin concentrations from a lower affinity lactose operatorl (Op1)-Sepharose column than from a higher affinity column containing the same sequence with a T18:A18 tail (Op1T18). A bi-column method was developed in which lac repressor fusion protein is eluted from the Op1-Sepharose with a low heparin concentration and trapped on a Op1T18-Sepharose column because of its higher affinity for the lac repressor protein. Elution of the latter column with buffer containing a high salt concentration gives significantly purer transcription factor than the conventionally used single column methods and removes residual heparin. Highly pure CAAT enhancer binding protein and the B3 transcription factor are also obtained by using variants of this bi-column method.

Comparative studies on discrete and concatemeric DNA-sepharose columns for purification of transcription factors.

Concatemers, tandem copies of DNA elements ligated together, are widely used for the DNA affinity chromatography of transcription factors. Purification of different transcription factors using discrete, concatemeric and T18:A18 tailed DNA affinity columns was studied. Columns having a discrete DNA sequence bound by cytidylic-adenylic-adenylic-thymidylic oligonucleotide (CAAT) enhancer binding protein (C/EBP) yields significantly more green fluorescent protein-C/EBP (GFP-C/EBP) fusion protein than a concatemeric DNA column made from five tandem repeats of the same DNA sequence. For lac repressor protein, the concatemeric and T18:A18 tailed columns show greater retention times than a discrete, untailed DNA affinity column. It was observed that the T18:A18 tailed column gives better resolution than either the discrete or concatemeric columns, of mixtures containing both lac repressor and GFP-C/EBP. Discrete concatemeric and T18:A18 tail columns all bound the Sp1 transcription factor and showed similar retention. The T18:A18 tailed column gives higher yield for Sp1 than the other columns. Our study shows concatemeric columns do not have any distinct advantage for the three different transcription factors we studied including Sp1, the original justification for the concatemeric approach.

Gene expression in accumbens GABA neurons from inbred rats with different drug-taking behavior.

Inbred Lewis and Fisher 344 rat strains differ greatly in drug self-administration; Lewis rats operantly self-administer drugs of abuse including nicotine, whereas Fisher self-administer poorly. As shown herein, operant food self-administration is similar. On the basis of their pivotal role in drug reward, we hypothesized that differences in basal gene expression in GABAergic neurons projecting from nucleus accumbens (NAcc) to ventral pallidum (VP) play a role in vulnerability to drug-taking behavior. The transcriptomes of NAcc shell-VP GABAergic neurons from these two strains were analyzed in adolescents, using a multidisciplinary approach that combined stereotaxic ionotophoretic brain microinjections, laser-capture microdissection (LCM) and microarray measurement of transcripts. Laser-capture microdissection enriched the gene transcripts detected in gamma-aminobutyric acid (GABA) neurons compared to the residual NAcc tissue: a ratio of neuron/residual >1 and false discovery rate (FDR) <5% yielded 6623 transcripts, whereas a ratio of >3 yielded 3514. Strain-dependent differences in gene expression within GABA neurons were identified; 322 vs. 60 transcripts showed 1.5-fold vs. 2-fold differences in expression (FDR < 5%). Classification by gene ontology showed that these 322 transcripts were widely distributed, without categorical enrichment. This is most consistent with a global change in GABA neuron function. Literature mining by Chilibot found 38 genes related to synaptic plasticity, signaling and gene transcription, all of which determine drug abuse; 33 genes have no known association with addiction or nicotine. In Lewis rats, upregulation of Mint-1, Cask, CamkII , Ncam1, Vsnl1, Hpcal1 and Car8 indicates that these transcripts likely contribute to altered signaling and synaptic function in NAcc GABA projection neurons to VP.

Characterization of a Xenopus oocyte factor that binds to a developmentally regulated cis-element in the TFIIIA gene.

TFIIIA mRNA expression is developmentally regulated during Xenopus oogenesis. We have identified a positive-acting cis-element in the TFIIIA gene located between -671 and -629 with respect to the mRNA initiation site, termed element 3. Element 3 contributes to the efficient transcription of the TFIIIA gene in stage III oocytes, but is inactive in the normal context of the TFIIIA gene in stage VI oocytes. A trans-acting factor, termed B3, in immature ovary extracts binds to a region within element 3 containing four repeats of the consensus nucleotide sequence 5' (T/A)GGTTACT. We discuss how the developmental regulation of B3-element 3 function could be achieved in the context of the TFIIIA gene during oogenesis.

Purification and characterization of a thyrotropin-releasing hormone deamidase from rat brain.

This report describes the purification of a rat brain thyrotropin-releasing hormone (TRH) deamidating enzyme to apparent homogeneity. Criteria for purity include sodium dodecyl sulfate and disc gel electrophoresis, as well as isoelectric focusing (pI = 4.5). Enzyme purification was facilitated by development of a rapid and sensitive continuous assay using the substrate L-pyroglutamyl-Nim-benzylhistidyl-L-prolyl-beta-naphthylamide, which, upon hydrolysis of the naphthylamide, results in the appearance of the fluorescent product, beta-naphthylamine (beta NA). With this substrate the homogeneous enzyme had a specific activity of 14.5 mumol of beta NA min-1 mg-1. The only peptide product formed was shown to be L-pyroglutamyl-Nim-benzylhistidyl-L-proline. Hydrolysis of [L-prolyl-2,3-3H]TRH was shown to yield L-pyro-glutamyl-L-histidyl-L-proline as the only radiolabeled product. Characterization of the brain deamidase by gel filtration chromatography and sodium dodecyl sulfate gel electrophoresis indicated that the enzyme consists of a single polypeptide chain having molecular weights of 70,000 and 73,500, respectively. Rat brain TRH deamidase has an apparent Km of 34 micron, and a pH optimum between 7 and 8 using L-pyroglutamyl-Nim-benzylhistidyl-L-prolyl-beta-naphthylamide as a substrate. With this substrate, TRH was shown to be a competitive inhibitor with an apparent Ki of 120 +/- 20 micron.

pOEV: a Xenopus oocyte protein expression vector.

We have constructed a Xenopus laevis oocyte expression vector, pOEV, which allows cloned DNA to be transcribed and translated directly in the oocyte. Since proteins translated in oocytes are post-translationally modified according to conserved eukaryotic signals, these cells offer a convenient system for performing structural and functional analyses of cloned genes. pOEV can be used for direct analysis of proteins encoded by cloned cDNAs without preparing mRNA in vitro, simplifying existing protocols for translating proteins in oocytes with a very high translational yield. Transcription of the vector in oocytes is driven by the promoter for the TFIIIA gene, which can generate 1-2 ng (per oocyte within 2 days) of stable mRNA template for translation. The vector also contains SP6 and T7 promoters for in vitro transcription to make mRNA and hybridization probes. DNA clones encoding chloramphenicol acetyltransferase (CAT) were injected into oocyte germinal vesicles and CAT protein accumulated in the cell over a 2- to 4-day period. We found that the concentration of DNA injected affected protein yields; surprisingly relatively low concentrations in the range 25-50 pg DNA per oocyte gave maximum yields of CAT protein. When as little as 5 pg of pOEV DNA is injected we typically expressed 40 fmol of CAT protein per oocyte, after 4-day incubations. In addition, we have shown that this system is amenable to the expression of nuclear and membrane proteins.

Regulation of the Xenopus laevis transcription factor IIIA gene during oogenesis and early embryogenesis: negative elements repress the O-TFIIIA promoter in embryonic cells.

Expression of the Xenopus laevis transcription factor IIIA (TFIIIA) gene is developmentally regulated. In this study we have used defined nucleotide mutations to map cis-elements involved in transcriptional regulation of the promoter for oocyte-TFIIIA (O-TFIIIA) in stage II-IV oocytes, stage VI oocytes, and tail bud embryos. During oogenesis O-TFIIIA mRNA levels decline 5- to 10-fold, and during early embryogenesis O-TFIIIA mRNA levels decline approximately 10(6)-fold per cell. In stage II-IV oocytes we find evidence for at least three distinct positive-acting cis-elements that contribute to the efficient expression of O-TFIIIA. These elements are located between -1800 to -425, -280 to -235, and -235 to -220. The most distal cis-element(s) appears to be developmentally regulated during oogenesis, since deletion of nucleotide sequences from -1800 to -425 does not reduce O-TFIIIA expression in stage VI oocytes. However, the two cis-elements located between -280 to -235 and -235 to -220 are required for the efficient expression of O-TFIIIA in stage VI oocytes. In tail bud embryos we find evidence for several developmentally regulated positive and negative cis-elements involved in O-TFIIIA expression. The positive-acting cis-elements are located between -159 to -110 and -110 to -58. The negative-acting cis-elements are found at positions -425 to -350 and -200 to -159. In addition to the developmentally regulated elements controlling O-TFIIIA gene expression in tail bud embryos, the positive-acting cis-elements active during oogenesis (located between -280 to -235 and -235 to -220) are also active during early embryogenesis. Thus, transcription from the O-TFIIIA promoter appears to be regulated by a combination of constitutive positive factors and developmentally regulated positive and negative factors during oogenesis and early embryogenesis.

Studies of the regulatory mechanism of Ca2+/calmodulin-dependent protein kinase II. Mutation of threonine 286 to alanine and aspartate.

A cDNA clone for the alpha subunit of mouse brain Ca2+/CaM-dependent protein kinase II (CaM-kinase II) was transcribed in vitro and translated in a rabbit reticulocyte lysate system. Inclusion of [35S]methionine in the translation system yielded a single 35S-polypeptide of about 50 kDa. When the translation system was assayed for CaM-kinase II activity, there was a 5-10-fold enrichment of kinase activity which was totally dependent on Ca2+/calmodulin (CaM). Both the 50-kDa 35S-polypeptide and the Ca2+/CaM-dependent protein kinase activity were quantitatively immunoprecipitated by rat brain CaM-kinase II antibody. When the translated wild-type kinase was subjected to autophosphorylation conditions in the presence of Ca2+, CaM, Mg2+, and ATP, the Ca2+-independent activity (assayed in the presence of [ethylenebis(oxyethylenenitrilo)]tetraacetic acid) increased from 5.8 +/- 0.7 to 26.5 +/- 2.1% of total activity (assayed in the presence of Ca2+/CaM). These properties confirm the identity of the kinase translated in vitro as CaM-kinase II. The role of Thr-286 autophosphorylation in formation of the Ca2+-independent activity was investigated by site-directed mutation of Thr-286 to Ala (Ala-286 kinase) and to Asp (Asp-286 kinase). The Ala-286 kinase was completely dependent on Ca2+/CaM for activity prior and subsequent to autophosphorylation. The Asp-286 kinase exhibited 21.9 +/- 0.8% Ca2+-independent activity, and this was not increased by autophosphorylation. These results establish that introduction of negative charge(s) at residue 286, either by autophosphorylation of Thr or by mutation to Asp, is sufficient and necessary to generate the partially Ca2+-independent form of CaM-kinase II.

Nucleotide and amino acid sequence comparisons of preprosomatostatins.

The amino acid and nucleotide sequences have been aligned for five preprosomatostatins: two from catfish, two from anglerfish, and one from rat. The physical characteristics of the aligned residues as well as substitutions in the nucleotide sequences suggest considerable mutability in one of the catfish and anglerfish precursors while three of the preprohormones which give rise to somatostatins-14 are closely related. Although there is a considerable number of amino acid substitutions within the aligned somatostatin-14 precursors, there is a high degree of structural relatedness among them. These results suggest that additional physiological roles for the amino acid sequences outside of the hormone region are likely. The predicted secondary structures of the three somatostatin-14 precursors are dominated by helical and turn configurations which are correlated with observed co- and post-translational processing of the preprohormones.

Success of surgery for primary aldosteronism judged by residual autonomous aldosterone production.

Since February 1996 we have prospectively assessed residual adrenal autonomy by the fludrocortisone suppression test (FST) in 23 patients 3 months after unilateral adrenalectomy for Conn syndrome and in 45 patients after a longer interval. In regard to blood pressure, 36 (53%) patients were cured of hypertension and the remaining 32 (47%) patients had improved hypertension control at the time of their latest postoperative clinical assessment. In regard to the outcome of surgery, patients who achieved normal suppressibility of aldosterone were regarded as cured, and those who had greater suppressibility after surgery were considered improved. Time since surgery for the whole group averaged 26 months. By these biochemical criteria, 42 patients (62%) were cured by surgery, and the rest improved; 16 (76%) of 21 women were cured, and 26 (55%) of 47 men. The women (mean +/- SD age 47 +/- 11 years) were significantly (p < 0.05) younger than the men (52 +/- 9 years). Preoperative aldosterone levels before and after FST were similar in the cured and improved groups and fell significantly (p < 0.01) in both groups following surgery. After surgical reduction of autonomous aldosterone production, mean plasma renin activity levels increased sixfold in the cured group and threefold in the improved group. Surgical mortality in this group of 68 patients with Conn syndrome was zero.