Biomedical subjects

Fernando Martin

Publications and source records attributed to Fernando Martin.

9 recordsLinked to original sources

PubMed2024

Neutralizing IFN-γ autoantibodies are rare and pathogenic in HLA-DRB1*15:02 or 16:02 individuals.

BACKGROUNDWeakly virulent environmental mycobacteria (EM) can cause severe disease in HLA-DRB1*15:02 or 16:02 adults harboring neutralizing anti-IFN-γ autoantibodies (nAIGAs). The overall prevalence of nAIGAs in the general population is unknown, as are the penetrance of nAIGAs in HLA-DRB1*15:02 or 16:02 individuals and the proportion of patients with unexplained, adult-onset EM infections carrying nAIGAs.METHODSThis study analyzed the detection and neutralization of anti-IFN-γ autoantibodies (auto-Abs) from 8,430 healthy individuals of the general population, 257 HLA-DRB1*15:02 or 16:02 carriers, 1,063 patients with autoimmune disease, and 497 patients with unexplained severe disease due to EM.RESULTSWe found that anti-IFN-γ auto-Abs detected in 4,148 of 8,430 healthy individuals (49.2%) from the general population of an unknown HLA-DRB1 genotype were not neutralizing. Moreover, we did not find nAIGAs in 257 individuals carrying HLA-DRB1* 15:02 or 16:02. Additionally, nAIGAs were absent in 1,063 patients with an autoimmune disease. Finally, 7 of 497 patients (1.4%) with unexplained severe disease due to EM harbored nAIGAs.CONCLUSIONThese findings suggest that nAIGAs are isolated and that their penetrance in HLA-DRB1*15:02 or 16:02 individuals is low, implying that they may be triggered by rare germline or somatic variants. In contrast, the risk of mycobacterial disease in patients with nAIGAs is high, confirming that these nAIGAs are the cause of EM disease.FUNDINGThe Laboratory of Human Genetics of Infectious Diseases is supported by the Howard Hughes Medical Institute, the Rockefeller University, the St. Giles Foundation, the National Institutes of Health (NIH) (R01AI095983 and U19AIN1625568), the National Center for Advancing Translational Sciences (NCATS), the NIH Clinical and Translational Science Award (CTSA) program (UL1 TR001866), the French National Research Agency (ANR) under the "Investments for the Future" program (ANR-10-IAHU-01), the Integrative Biology of Emerging Infectious Diseases Laboratory of Excellence (ANR-10-LABX-62-IBEID), ANR-GENMSMD (ANR-16-CE17-0005-01), ANR-MAFMACRO (ANR-22-CE92-0008), ANRSECTZ170784, the French Foundation for Medical Research (FRM) (EQU201903007798), the ANRS-COV05, ANR GENVIR (ANR-20-CE93-003), and ANR AI2D (ANR-22-CE15-0046) projects, the ANR-RHU program (ANR-21-RHUS-08-COVIFERON), the European Union's Horizon 2020 research and innovation program under grant agreement no. 824110 (EASI-genomics), the Square Foundation, Grandir - Fonds de solidarité pour l'enfance, the Fondation du Souffle, the SCOR Corporate Foundation for Science, the Battersea & Bowery Advisory Group, William E. Ford, General Atlantic's Chairman and Chief Executive Officer, Gabriel Caillaux, General Atlantic's Co-President, Managing Director, and Head of business in EMEA, and the General Atlantic Foundation, Institut National de la Santé et de la Recherche Médicale (INSERM) and of Paris Cité University. JR was supported by the INSERM PhD program for doctors of pharmacy (poste d'accueil INSERM). JR and TLV were supported by the Bettencourt-Schueller Foundation and the MD-PhD program of the Imagine Institute. MO was supported by the David Rockefeller Graduate Program, the Funai Foundation for Information Technology (FFIT), the Honjo International Scholarship Foundation (HISF), and the New York Hideyo Noguchi Memorial Society (HNMS).

Adult↗

PubMed2006

The Inositol 1,4,5-triphosphate kinase1 gene affects olfactory reception in Drosophila melanogaster.

The Inositol 1,4,5-triphosphate (IP3) route is one of the two main transduction cascades that mediate olfactory reception in Drosophila melanogaster. The activity of IP3 kinase1 reduces the levels of this substrate by phosphorylation into inositol 1,3,4,5-tetrakiphosphate (IP4). We show here that the gene is expressed in olfactory sensory organs as well as in the rest of the head. To evaluate in vivo the olfactory functional effects of up-regulating IP3K1, individuals with directed genetic changes at the reception level only were generated using the UAS/Gal4 method. In this report, we described the consequences in olfactory perception of overexpressing the IP3Kinase1 gene at eight different olfactory receptor-neuron subsets. Six out of the eight studied Gal-4/UAS-IP3K1 hybrids displayed abnormal behavioral responses to ethyl acetate, acetone, ethanol or propionaldehyde. Specific behavioral defects corresponded to the particular neuronal olfactory profile. These data confirm the role of the IP3kinase1 gene, and consequently the IP3 transduction cascade, in mediating olfactory information at the reception level.

Animals↗

PubMed2005

Formation of multicellular epithelial structures.

The kidney is primarily comprised of highly polarized epithelial cells. Much has been learned recently about the mechanisms of epithelial polarization. However, in most experimental systems the orientation of this polarity is determined by external cues, such as growth of epithelial cells on a filter support. When Madin-Darby canine kidney (MDCK) cells are grown instead in a three-dimensional (3D) collagen gel, the cells form hollow cysts lined by a monolayer of epithelial cells, with their apical surfaces all facing the central lumen. We have found that expression of a dominant-negative (DN) form of the small GTPase Rac1 causes an inversion of epithelial polarity, such that the apical surface of the cells instead faces the periphery of the cyst. This indicates that the establishment of polarity and the orientation of polarity can be experimentally separated by growing cells in a 3D collagen gel, where there is no filter support to provide an external cue for orientation. DN Rac1 causes a defect in the assembly of laminin into its normal basement membrane network, and addition of a high concentration of exogenous laminin rescues the inversion of polarity caused by DN Rac1.

Animals↗

PubMed2004

The structure of (3R)-hydroxyacyl-acyl carrier protein dehydratase (FabZ) from Pseudomonas aeruginosa.

Type II fatty acid biosynthesis systems are essential for membrane formation in bacteria, making the constituent proteins of this pathway attractive targets for antibacterial drug discovery. The third step in the elongation cycle of the type II fatty acid biosynthesis is catalyzed by beta-hydroxyacyl-(acyl carrier protein) (ACP) dehydratase. There are two isoforms. FabZ, which catalyzes the dehydration of (3R)-hydroxyacyl-ACP to trans-2-acyl-ACP, is a universally expressed component of the bacterial type II system. FabA, the second isoform, as has more limited distribution in nature and, in addition to dehydration, also carries out the isomerization of trans-2- to cis-3-decenoyl-ACP as an essential step in unsaturated fatty acid biosynthesis. We report the structure of FabZ from the important human pathogen Pseudomonas aeruginosa at 2.5 A of resolution. PaFabZ is a hexamer (trimer of dimers) with the His/Glu catalytic dyad located within a deep, narrow tunnel formed at the dimer interface. Site-directed mutagenesis experiments showed that the obvious differences in the active site residues that distinguish the FabA and FabZ subfamilies of dehydratases do not account for the unique ability of FabA to catalyze isomerization. Because the catalytic machinery of the two enzymes is practically indistinguishable, the structural differences observed in the shape of the substrate binding channels of FabA and FabZ lead us to hypothesize that the different shapes of the tunnels control the conformation and positioning of the bound substrate, allowing FabA, but not FabZ, to catalyze the isomerization reaction.

Amino Acid Sequence↗

PubMed2004

In vivo light-induced and basal phospholipase C activity in Drosophila photoreceptors measured with genetically targeted phosphatidylinositol 4,5-bisphosphate-sensitive ion channels (Kir2.1).

The phosphatidylinositol 4,5-bisphosphate (PIP(2))-sensitive inward rectifier channel Kir2.1 was expressed in Drosophila photoreceptors and used to monitor in vivo PIP(2) levels. Since the wild-type (WT) Kir2.1 channel appeared to be saturated by the prevailing PIP(2) concentration, we made a single amino acid substitution (R228Q), which reduced the effective affinity for PIP(2) and yielded channels generating currents proportional to the PIP(2) levels relevant for phototransduction. To isolate Kir2.1 currents, recordings were made from mutants lacking both classes of light-sensitive transient receptor potential channels (TRP and TRPL). Light resulted in the effective depletion of PIP(2) by phospholipase C (PLC) in approximately three or four microvilli per absorbed photon at rates exceeding approximately 150% of total microvillar phosphoinositides per second. PIP(2) was resynthesized with a half-time of approximately 50 s. When PIP(2) resynthesis was prevented by depriving the cell of ATP, the Kir current spontaneously decayed at maximal rates representing a loss of approximately 40% loss of total PIP(2) per minute. This loss was attributed primarily to basal PLC activity, because it was greatly decreased in norpA mutants lacking PLC. We tried to confirm this by using the PLC inhibitor U73122; however, this was found to act as a novel inhibitor of the Kir2.1 channel. PIP(2) levels were reduced approximately 5-fold in the diacylglycerol kinase mutant (rdgA), but basal PLC activity was still pronounced, consistent with the suggestion that raised diacylglycerol levels are responsible for the constitutive TRP channel activity characteristic of this mutant.

Animals↗

PubMed2004

The cAMP transduction cascade mediates olfactory reception in Drosophila melanogaster.

Two main second messenger systems depending on IP3 and cAMP have been related to olfaction in vertebrates as well as invertebrates. In Drosophila melanogaster, the availability of mutations affecting one or the other pathway (rdgB and norpA or rut and dnc, respectively) allowed showing of abnormal olfactory behavior phenotypes associated with olfactory transduction in complete living animals. However, because rut and dnc genes showed ubiquitous expression at olfactory receptor organs and some brain locations, the mutant behavior cannot be assigned exclusively to olfactory reception. In this report, overexpression of the dnc gene directed specifically to different olfactory receptor neuron subsets was used to produce dominant mutants. Abnormal olfactory behavior was found in 62.5% of the 8 lines studied in response to some odorants, depending on the affected neuronal subset. These results suggest that even for a small number of tested odorants (5), cAMP cascade is involved in olfactory reception to an important extent.

Animals↗

PubMed2003

Rescue of light responses in the Drosophila "null" phospholipase C mutant, norpAP24, by the diacylglycerol kinase mutant, rdgA, and by metabolic inhibition.

Light responses in Drosophila are reportedly abolished in severe mutants of the phospholipase C (PLC) gene, norpA. However, on establishing the whole-cell recording configuration in photoreceptors of the supposedly null allele, norpAP24, we detected a small ( approximately 15 pA) inward current that represented spontaneous light channel activity. The current decayed during approximately 20 min, after which tiny residual responses (<2 pA) were elicited by intense flashes. Both spontaneous currents and light responses appeared to be mediated by residual PLC activity, because they were enhanced by impairing diacylglycerol (DAG) kinase function by mutation (rdgA) or by restricting ATP but were reduced or abolished by a mutation of the PLC-specific Gq alpha subunit. It was reported recently that metabolic inhibition activated the light-sensitive transient receptor potential and transient receptor potential-like channels, even in norpAP24, leading to the conclusion that this action was independent of PLC (Agam, K., von Campenhausen, M., Levy, S., Ben-Ami, H. C., Cook, B., Kirschfeld, K., and Minke, B. (2000) J. Neurosci. 20, 5748-5755). However, we found that channel activation by metabolic inhibitors in norpAP24 was strictly dependent on the residual PLC activity underlying the spontaneous current, because the inhibitors failed to activate any channels after the spontaneous current had decayed. By contrast, polyunsaturated fatty acids invariably activated the channels independently of PLC. The results strongly support the obligatory requirement for PLC and DAG in Drosophila phototransduction, suggest that activation by metabolic inhibition is primarily because of the failure of diacylglycerol kinase, and are consistent with the proposal that polyunsaturated fatty acids, which are potential DAG metabolites, act directly on the channels.

2,4-Dinitrophenol↗

PubMed2002

Factor analysis of olfactory responses in Drosophila melanogaster enhancer-trap lines as a method for ascertaining common reception components for different odorants.

Olfactory information is transmitted to the brain using combinatorial receptor codes; consequently, a single reception element can be activated by different odorants. Several methods have been applied to describe from a functional point of view those odorants sharing olfactory reception components. A genetic approach in Drosophila melanogaster used correlation between behavioral responses to different odorants for deducing common olfactory pathway-genes. A factor analysis applied to behavioral responses to five odorants of 27 antennal enhancer-trap lines revealed three components, explaining 82.1% of the total observed variance. A first factor affects simultaneously the response to ethyl acetate, propionaldehyde, and acetone. A second factor was related to responses to ethyl acetate, ethyl alcohol, and acetone, and, finally, the third factor associates responses to acetic acid and ethyl acetate. They contribute by 35.1%, 36.9%, and 28%, respectively, to the explained variance.

Animals↗

PubMedDate not supplied

High efficiency of a double-screening method on single P-element insertion lines to identify quantitative trait mutants in Drosophila melanogaster.

Enhancer trap P-element insertion has become a common method for generating new mutations in Drosophila melanogaster. When this method is used to isolate mutants for quantitative traits, an appropriate control must be established to define normal and mutant phenotypes. Considering that enhancer-trap lines are generated by crossing several strains, usually with no homogeneous genetic background, no clear control strain can be selected. Previous reports tried to overcome this problem by homogenizing the genetic background of the original lines. However, this is not the most common scenario, especially when functional phenotypes are studied in previously generated lines. Without such caution, is it possible to identify functional mutants among P-element insertion lines? We tested this for olfactory preference, a quantitative trait. Using as control measurement the average phenotype of 30 simultaneously generated P-element insertion lines with preferential reporter-gene expression in olfactory reception organs, we found that 25 of the lines exhibited mutant phenotypes in response to one or several of 5 tested odorants. Additional tests showed that the efficiency of the method for detecting olfactory mutations exceeded 60% even for such a small number of tested odorants. According to these results this approach greatly facilitates the identification of putative abnormal phenotypes, which must be extensively confirmed afterwards.

Animals↗