Molecular characterization and gene content of breakpoint boundaries in patients with neurofibromatosis type 1 with 17q11.2 microdeletions

Homologous recombination between poorly characterized regions flanking the NF1 locus causes the constitutional loss of approximately 1.5 Mb from 17q11.2 covering > or =11 genes in 5%-20% of patients with neurofibromatosis type 1 (NF1). To elucidate the extent of microheterogeneity at the deletion boundaries, we used single-copy DNA fragments from the extreme ends of the deleted segment to perform FISH on metaphase chromosomes from eight patients with NF1 who had large deletions. In six patients, these probes were deleted, suggesting that breakage and fusions occurred within the adjacent highly homologous sequences. Reexamination of the deleted region revealed two novel functional genes FLJ12735 (AK022797) and KIAA0653-related (WI-12393 and AJ314647), the latter of which is located closest to the distal boundary and is partially duplicated. We defined the complete reading frames for these genes and two expressed-sequence tag (EST) clusters that were reported elsewhere and are associated with the markers SHGC-2390 and WI-9521. Hybrid cell lines carrying only the deleted chromosome 17 were generated from two patients and used to identify the fusion sequences by junction-specific PCRs. The proximal breakpoints were found between positions 125279 and 125479 in one patient and within 4 kb of position 143000 on BAC R-271K11 (AC005562) in three patients, and the distal breakpoints were found at the precise homologous position on R-640N20 (AC023278). The interstitial 17q11.2 microdeletion arises from unequal crossover between two highly homologous WI-12393-derived 60-kb duplicons separated by approximately 1.5 Mb. Since patients with the NF1 large-deletion syndrome have a significantly increased risk of neurofibroma development and mental retardation, hemizygosity for genes from the deleted region around the neurofibromin locus (CYTOR4, FLJ12735, FLJ22729, HSA272195 (centaurin-alpha2), NF1, OMGP, EVI2A, EVI2B, WI-9521, HSA272196, HCA66, KIAA0160, and WI-12393) may contribute to the severe phenotype of these patients.     

Decreased theophylline half-life in cigarette smokers.

In a group of 19 hospitalized patients, most of whom smoked, the half-life of theophylline following an I.V. aminophylline bolus was 3.6 ± 1.5 hours. When the young male control group was broken down by smoking history, 10 smokers had a theophylline half-life of 4.1 ± 1.2 hours, and 14 non-smokers a theophylline half-life of 7.2 ± 1.8 hours. The prolongation of half-life in the non-smokers was very significant (p<0.0001). These findings are consistent with observations that polycyclic hydrocarbons are strong inducers of microsomal enzymes involved in drug metabolism, and may help explain the individual variations of theophylline half-life.     

The use of spinning-disk confocal microscopy for the intravital analysis of platelet dynamics in response to systemic and local inflammation

Platelets are central players in inflammation and are an important component of the innate immune response. The ability to visualize platelets within the live host is essential to understanding their role in these processes. Past approaches have involved adoptive transfer of labelled platelets, non-specific dyes, or the use of fluorescent antibodies to tag platelets in vivo. Often, these techniques result in either the activation of the platelet, or blockade of specific platelet receptors. In this report, we describe two new methods for intravital visualization of platelet biology, intravenous administration of labelled anti-CD49b, which labels all platelets, and CD41-YFP transgenic mice, in which a percentage of platelets express YFP. Both approaches label endogenous platelets and allow for their visualization using spinning-disk confocal fluorescent microscopy. Following LPS-induced inflammation, we were able to measure a significant increase in both the number and size of platelet aggregates observed within the vasculature of a number of different tissues. Real-time observation of these platelet aggregates reveals them to be large, dynamic structures that are continually expanding and sloughing-off into circulation. Using these techniques, we describe for the first time, platelet recruitment to, and behaviour within numerous tissues of the mouse, both under control conditions and following LPS induced inflammation.     

A common set of at least 11 functional genes is lost in the majority of NF1 patients with gross deletions

Large deletions of the NF1 locus occur in 5 to 10% of patients with neurofibromatosis and are commonly associated with specific additional abnormalities characterized by mental retardation, dysmorphic features, and intellectual impairment. To characterize the extent of codeleted genes we constructed a long-range physical BAC/PAC map around the NF1 locus between D17S117 and D17S57 and determined the deletion boundaries in seven unrelated patients. Surprisingly, the proximal and distal breakpoints in five of seven patients fall at almost identical positions, resulting in the loss of at least 11 functional genes. Five of six patients investigated showed a de novo deletion on the maternally derived chromosome. Since D17S117 and D17S57 were previously reported as the outer limits for the great majority of NF1 deletions, we suggest that most NF1 patients with deletion of the entire NF1 gene are hemizygous for the same set of at least 10 additional genes, including SHGC-37343, SHGC-2390, SHGC-34232, OMG, EVI2B, EVI2A, WI-9521, WI-6742, SHGC-34334, and KIAA0160, and thus present with a relatively uniform clinical phenotype.     

Semi-synthetic DNA shuffling of aveC leads to improved industrial scale production of doramectin by Streptomyces avermitilis

The avermectin analog doramectin (CHC-B1), sold commercially as Dectomax, is biosynthesized by Streptomyces avermitilis. aveC, a gene encoding an unknown mechanistic function, plays an essential role in the production of doramectin (avermectin CHC-B1), modulating the production ratio of CHC-B1 to other avermectins, most notably the undesirable analog CHC-B2. To improve the production ratio for doramectin, the aveC gene was subjected to iterative rounds of semi-synthetic DNA shuffling. Libraries of shuffled aveC gene variants were transformed into S. avermitilis, screened using a miniaturized 96-well growth and production format, and analyzed by high throughput mass spectrometry to determine CHC-B2:CHC-B1 ratios. Several improved aveC variants were identified; the best shuffled gene encoded 10 amino acid mutations, and conferred a final CHC-B2:CHC-B1 ratio of 0.07:1, a 23-fold improvement over the starting gene (aveC wild type). Chromosomal insertion of an improved aveC shuffled gene into a high titer S. avermitilis strain yielded an improved doramectin production strain. This strain is under development to be used commercially, and is expected to provide considerable cost savings in large-scale manufacture, as well as significantly reducing by-product levels of CHC-B2 requiring disposal.     

Androgen resistance in squirrel monkeys (Saimiri spp.)

The goal of this study was to understand the basis for high androgen levels in squirrel monkeys (Saimiri spp.). Mass spectrometry was used to analyze serum testosterone, androstenedione, and dihydrotestosterone of male squirrel monkeys during the nonbreeding (n = 7) and breeding (n = 10) seasons. All hormone levels were elevated compared with those of humans, even during the nonbreeding season; the highest levels occurred during the breeding season. The ratio of testosterone to dihydrotestosterone in squirrel monkeys is high during the breeding season compared to man. Squirrel monkeys may have high testosterone to compensate for inefficient metabolism to dihydrotestosterone. We also investigated whether squirrel monkeys have high androgens to compensate for low-activity androgen receptors (AR). The response to dihydrotestosterone in squirrel monkey cells transfected with AR and AR-responsive reporter plasmids was 4-fold, compared with 28-fold in human cells. This result was not due to overexpression of cellular FKBP51, which causes glucocorticoid and progestin resistance in squirrel monkeys, because overexpression of FKBP51 had no effect on dihydrotestosterone-stimulated reporter activity in a human fibroblast cell line. To test whether the inherently low levels of FKBP52 in squirrel monkeys contribute to androgen insensitivity, squirrel monkey cells were transfected with an AR expression plasmid, an AR-responsive reporter plasmid, and a plasmid expressing FKBP52. Expression of FKBP52 decreased the EC50 or increased the maximal response to dihydrotestosterone. Therefore, the high androgen levels in squirrel monkeys likely compensate for their relatively low 5 alpha-reductase activity during the breeding season and AR insensitivity resulting from low cellular levels of FKBP52.     

Homology of placental protein 11 and pea seed albumin 2 with vitronectin.

Vitronectin (complement S-protein), a plasma and tissue glycoprotein of 75 kDa, shares the amino-terminal somatomedin B domain with the membrane glycoprotein PC1 of plasma cells and several hemopexin-type repeats with hemopexin and the non-catalytic carboxy-terminal domain of collagenases. It serves as a ligand for certain integrin receptors, binds to distinct members of the serpin family and inhibits the pore-forming cytolytic reaction of the terminal complement pathway. Computer-assisted data base searches revealed the presence of a single somatomedin B domain in the recently cloned placental protein 11, and four hemopexin-type repeats in the cytosolic plant protein PA2, the major albumin of pea seeds, whose function is unknown. Our finding shows that hemopexin-type repeats are present in extracellular as well as in cytosolic proteins and most likely originated before the divergence of the animal and plant kindoms.     

Molecular cloning of S-protein, a link between complement, coagulation and cell-substrate adhesion.

cDNA clones coding for human S-protein have been isolated using monoclonal antibodies to screen a cDNA library in pEX. These clones are shown to be authentic S-protein clones on the basis of sequence, composition and immunological criteria. The complete open reading frame sequence for S-protein has been determined and shows it to be a single polypeptide chain of 459 amino acids preceded by a cleaved leader peptide of 19 residues. No evidence was found for polymorphism of S-protein suggesting that different molecular weight forms arise by proteolytic degradation. Of the first 44 amino-terminal residues 42 are identical with the so-called somatomedin B peptide suggesting that S-protein is the somatomedin B precursor. Striking homology is found in the rest of the sequence with the serum spreading factor, vitronectin, which has also been shown to contain somatomedin B sequences at its amino terminus. We conclude that S-protein and vitronectin are identical and discuss the relevance of this finding to the coagulation and complement pathways.     

Proteomic analysis of serum cytokine levels in response to highly active antiretroviral therapy (HAART)

A 30-cytokine protein microarray was used to screen for cytokine profile changes in HIV-infected patients in response to highly active antiretroviral therapy (HAART). Serum cytokines showing significant changes were confirmed by enzyme immunoassay. Monokine induced by gamma-interferon (MIG) and interferon-inducible protein-10 (IP-10) levels significantly decreased after 24 weeks of HAART. Protein microarrays are useful for initial screening of novel cytokine expression. Further studies are needed to elucidate the role of MIG and IP-10 in response to HAART.     

Cortisol metabolism in the Bolivian squirrel monkey (Saimiri boliviensis boliviensis)

New World squirrel monkeys (Saimiri spp.) have high circulating cortisol levels but normal electrolytes and blood pressures. The goal of the present study was to gain insight into adaptive mechanisms used by Bolivian squirrel monkeys to minimize the effects of high cortisol on mineralocorticoid receptor (MR) activity and electrolyte and water balance. Aldosterone levels in serum from 10 squirrel monkeys were 17.7 +/- 3.4 ng/dl (normal range in humans, 4 to 31 ng/dl), suggesting that squirrel monkeys do not exhibit a compensatory increase in aldosterone. The squirrel monkey MR was cloned and expressed in COS-7 cells and found to have similar responsiveness to cortisol and aldosterone as human MR, suggesting that squirrel monkey MR is not inherently less responsive to cortisol. To determine whether altered metabolism of cortisol might contribute to MR protection in squirrel monkeys, serum and urinary cortisol and cortisone were measured, and a comprehensive urinary corticosteroid metabolite profile was performed in samples from anesthetized and awake squirrel monkeys. The levels of cortisone exceeded those of cortisol in serum and urine, suggesting increased peripheral 11beta-hydroxysteroid dehydrogenase 2 activity in squirrel monkeys. In addition, a significant fraction (approximately 20%) of total corticosteroids excreted in the urine of squirrel monkeys appeared as 6beta-hydroxycortisol, compared with that in man (1%). Therefore, changes in cortisol metabolism likely contribute to adaptive mechanisms used by Bolivian squirrel monkeys to minimize effects of high cortisol.