Exosomes as Hedgehog carriers in cytoneme-mediated transport and secretion

The Hedgehog signalling pathway is crucial for development, adult stem cell maintenance, cell migration and axon guidance in a wide range of organisms. During development, the Hh morphogen directs tissue patterning according to a concentration gradient. Lipid modifications on Hh are needed to achieve graded distribution, leading to debate about how Hh is transported to target cells despite being membrane-tethered. Cytonemes in the region of Hh signalling have been shown to be essential for gradient formation, but the carrier of the morphogen is yet to be defined. Here we show that Hh and its co-receptor Ihog are in exovesicles transported via cytonemes. These exovesicles present protein markers and other features of exosomes. Moreover, the cell machinery for exosome formation is necessary for normal Hh secretion and graded signalling. We propose Hh transport via exosomes along cytonemes as a significant mechanism for the restricted distribution of a lipid-modified morphogen.PostprintPeer reviewe

Caracterização de gene de quitinase de Lutzomyia longipalpis: descrição de processamento alternativo e busca por seqüência promotora

Submitted by Tatiana Silva ([email protected]) on 2012-12-26T18:25:25Z No. of bitstreams: 1 joao_r_o_farias_ioc_bcm_0004_2009.pdf: 3748757 bytes, checksum: 6590fd1d1afea051ff70fc2fba034b09 (MD5)Made available in DSpace on 2012-12-26T18:25:25Z (GMT). No. of bitstreams: 1 joao_r_o_farias_ioc_bcm_0004_2009.pdf: 3748757 bytes, checksum: 6590fd1d1afea051ff70fc2fba034b09 (MD5) Previous issue date: 2009Fundação Oswaldo Cruz.Instituto Oswaldo Cruz. Rio de janeiro, RJ, BrasilAs leishmanioses são doenças causadas por protozoários do gênero Leishmania transmitidos pela picada de flebotomíneos infectados. Os atuais métodos de combate a estas moléstias têm se mostrado ineficazes e maiores conhecimentos sobre a interação Leishmania-flebotomíneos são necessários para o desenvolvimento de novas formas de controle. Com o emprego da técnica de amostragem diferencial por RT-PCR (DDRT-PCR), foi encontrado anteriormente em nosso laboratório um cDNA codificante para uma quitinase intestino-específica de Lutzomyia longipalpis, nomeada LlChit1A. Foi visto que este produto do gene LlChit1 possui altos níveis de transcrição em fêmeas adultas 3 dias após a alimentação sangüínea, indicando um possível papel na degradação da matriz peritrófica (MP). Neste trabalho, um fragmento do LlChit1A foi usado para sondar uma biblioteca genômica de L. longipalpis, possibilitando o isolamento de um clone contendo o gene codificador desta enzima, que recebeu o nome LlChit1G. A amplificação por PCR e seqüenciamento deste gene revelaram a presença de 4 introns que interrompem a seqüência codificante para a LlChit1A. Foi visto por RT-PCR que o gene LlChit1 também está ativo em larvas, transcrevendo mais duas novas formas de splicing, nomeadas LlChit1B e LlChit1C. Estes dois novos transcritos possuem códons de parada, introduzidos a partir do quarto íntron, que interrompem a tradução do domínio de ligação à quitina codificado pelo último éxon. As possíveis novas enzimas codificadas devem atuar na digestão de alimentos ricos em quitina de maneira similar ao proposto para outras quitinases de inseto sem este domínio funcional. A região flanqueadora 5’ (RF5’) do clone genômico também foi amplificada por PCR e seqüenciada, evidenciando um possível promotor mínimo. Curiosamente, um gene ortólogo de Phlebotomus papatasi contém o começo da seqüência UTR 5` idêntica ao começo do RNAm da quitinase de L. longipalpis. Isso pode ser um indício de um possível sistema promotor conservado em flebotomíneos e com possível atuação na regulação da espessura da MP. Através da técnica de PCR invertido foi amplificada e seqüenciada uma região a montante do gene, não presente no LlChit1G. Análises de bioinformática indicaram a presença de um possível envolvimento de ecdisona no controle deste promotor. Através da anotação de ESTs codificantes para a seqüência completa ou parcial de proteínas similares a quitinases de L. longipalpis e P. papatasi foi possível identificar possíveis ortólogos de glicosideohidrolases da família 18. As seqüências primárias correspondentes ao domínio catalítilico encontrado nesta família foram comparadas por filogenia a seqüências já publicadas.Leishmaniasis is a disease caused by Leishmania protozoa transmitted by the bite of infected sand flies. Current methods used to combat this illness have been shown to be inefficient, and better knowledge of aspects related to Leishmania-sand fly interaction are necessary for the development of new controlling methods. A cDNA codifying for a midgut-specific chitinase of Lutzomyia longipalpis, nominated LlChit1A, was previously identified in our laboratory using differential display RT-PCR (DDRT-PCR). It was found that the LlChit1 gene had high transcription levels 3 days after blood meal, which indicated a putative role on peritrophic matrix (PM) degradation. A LlChit1A fragment, was used for screening a L. longipalpis genomic library, which led to the isolation of a clone called LlChit1G, containing the chitinase gene. The PCR amplification and sequencing of this gene revealed 4 introns which interrupt the LlChit1A cDNA sequence. RT-PCR showed that the LlChit1 gene is also expressed in larvae where it transcribed two new forms of splicing, called LlChit1B and LlChit1C. These two transcripts possess early stop codons in the last intron, interrupting the translation of the chitin binding domain (CBD) codified by the last exon. These putative enzymes possibly act in the digestion of chitin rich food, as previously observed for others insect chitinases without this functional domain. The flanking region 5’ (FR5’) present in the genomic clone was also sequenced, evidencing a possible minimum promoter. Curiously, the initial part of this 5’ UTR sequence was identical to the initial part of a Phlebotomus papatasi orthologous gene. This may be an indication of a promoter system conserved among sandflies, with possible performance in the control of PM thickness, which seems to occur exactly at the moment and place of Leishmania attachment to the epithelium of the midgut. The use of inverted PCR allowed the sequencing of a region upstream the chitinase gene, which is not present in the genomic clone. Bioinformatics analyzes suggested the participation of ecdysone on the expression control of this gene. The annotation for ESTs codifying complete and partial chitinase like proteins from L. longipalpis and P. papatasi provided the identification of 4 new genes from the first specie and 5 new genes from the later. These genes codify for protein conserved domains with high similarity to the catalytic domain of family 18 glycosylhydrolases. Phylogenetic trees were also constructed

Alternative splicing originates different domain structure organization of Lutzomyia longipalpis chitinases

BACKGROUND The insect chitinase gene family is composed by more than 10 paralogs, which can codify proteins with different domain structures. In Lutzomyia longipalpis, the main vector of visceral leishmaniasis in Brazil, a chitinase cDNA from adult female insects was previously characterized. The predicted protein contains one catalytic domain and one chitin-binding domain (CBD). The expression of this gene coincided with the end of blood digestion indicating a putative role in peritrophic matrix degradation. OBJECTIVES To determine the occurrence of alternative splicing in chitinases of L. longipalpis. METHODS We sequenced the LlChit1 gene from a genomic clone and the three spliced forms obtained by reverse transcription polymerase chain reaction (RT-PCR) using larvae cDNA. FINDINGS We showed that LlChit1 from L. longipalpis immature forms undergoes alternative splicing. The spliced form corresponding to the adult cDNA was named LlChit1A and the two larvae specific transcripts were named LlChit1B and LlChit1C. The B and C forms possess stop codons interrupting the translation of the CBD. The A form is present in adult females post blood meal, L4 larvae and pre-pupae, while the other two forms are present only in L4 larvae and disappear just before pupation. Two bands of the expected size were identified by Western blot only in L4 larvae. MAIN CONCLUSIONS We show for the first time alternative splicing generating chitinases with different domain structures increasing our understanding on the finely regulated digestion physiology and shedding light on a potential target for controlling L. longipalpis larval development

Alternative splicing originates different domain structure organization of Lutzomyia longipalpis chitinases

<div><p> BACKGROUND The insect chitinase gene family is composed by more than 10 paralogs, which can codify proteins with different domain structures. In Lutzomyia longipalpis, the main vector of visceral leishmaniasis in Brazil, a chitinase cDNA from adult female insects was previously characterized. The predicted protein contains one catalytic domain and one chitin-binding domain (CBD). The expression of this gene coincided with the end of blood digestion indicating a putative role in peritrophic matrix degradation. OBJECTIVES To determine the occurrence of alternative splicing in chitinases of L. longipalpis. METHODS We sequenced the LlChit1 gene from a genomic clone and the three spliced forms obtained by reverse transcription polymerase chain reaction (RT-PCR) using larvae cDNA. FINDINGS We showed that LlChit1 from L. longipalpis immature forms undergoes alternative splicing. The spliced form corresponding to the adult cDNA was named LlChit1A and the two larvae specific transcripts were named LlChit1B and LlChit1C. The B and C forms possess stop codons interrupting the translation of the CBD. The A form is present in adult females post blood meal, L4 larvae and pre-pupae, while the other two forms are present only in L4 larvae and disappear just before pupation. Two bands of the expected size were identified by Western blot only in L4 larvae. MAIN CONCLUSIONS We show for the first time alternative splicing generating chitinases with different domain structures increasing our understanding on the finely regulated digestion physiology and shedding light on a potential target for controlling L. longipalpis larval development.</p></div

Exosomes as Hedgehog carriers in cytoneme-mediated transport and secretion

The Hedgehog signalling pathway is crucial for development, adult stem cell maintenance, cell migration and axon guidance in a wide range of organisms. During development, the Hh morphogen directs tissue patterning according to a concentration gradient. Lipid modifications on Hh are needed to achieve graded distribution, leading to debate about how Hh is transported to target cells despite being membrane-tethered. Cytonemes in the region of Hh signalling have been shown to be essential for gradient formation, but the carrier of the morphogen is yet to be defined. Here we show that Hh and its co-receptor Ihog are in exovesicles transported via cytonemes. These exovesicles present protein markers and other features of exosomes. Moreover, the cell machinery for exosome formation is necessary for normal Hh secretion and graded signalling. We propose Hh transport via exosomes along cytonemes as a significant mechanism for the restricted distribution of a lipid-modified morphogen

Genomic analysis of two phlebotomine sand fly vectors of Leishmania from the New and Old World.

Phlebotomine sand flies are of global significance as important vectors of human disease, transmitting bacterial, viral, and protozoan pathogens, including the kinetoplastid parasites of the genus Leishmania, the causative agents of devastating diseases collectively termed leishmaniasis. More than 40 pathogenic Leishmania species are transmitted to humans by approximately 35 sand fly species in 98 countries with hundreds of millions of people at risk around the world. No approved efficacious vaccine exists for leishmaniasis and available therapeutic drugs are either toxic and/or expensive, or the parasites are becoming resistant to the more recently developed drugs. Therefore, sand fly and/or reservoir control are currently the most effective strategies to break transmission. To better understand the biology of sand flies, including the mechanisms involved in their vectorial capacity, insecticide resistance, and population structures we sequenced the genomes of two geographically widespread and important sand fly vector species: Phlebotomus papatasi, a vector of Leishmania parasites that cause cutaneous leishmaniasis, (distributed in Europe, the Middle East and North Africa) and Lutzomyia longipalpis, a vector of Leishmania parasites that cause visceral leishmaniasis (distributed across Central and South America). We categorized and curated genes involved in processes important to their roles as disease vectors, including chemosensation, blood feeding, circadian rhythm, immunity, and detoxification, as well as mobile genetic elements. We also defined gene orthology and observed micro-synteny among the genomes. Finally, we present the genetic diversity and population structure of these species in their respective geographical areas. These genomes will be a foundation on which to base future efforts to prevent vector-borne transmission of Leishmania parasites

Glycosidase Hydrolase family 13 annotation.

Phlebotomine sand flies are of global significance as important vectors of human disease, transmitting bacterial, viral, and protozoan pathogens, including the kinetoplastid parasites of the genus Leishmania, the causative agents of devastating diseases collectively termed leishmaniasis. More than 40 pathogenic Leishmania species are transmitted to humans by approximately 35 sand fly species in 98 countries with hundreds of millions of people at risk around the world. No approved efficacious vaccine exists for leishmaniasis and available therapeutic drugs are either toxic and/or expensive, or the parasites are becoming resistant to the more recently developed drugs. Therefore, sand fly and/or reservoir control are currently the most effective strategies to break transmission. To better understand the biology of sand flies, including the mechanisms involved in their vectorial capacity, insecticide resistance, and population structures we sequenced the genomes of two geographically widespread and important sand fly vector species: Phlebotomus papatasi, a vector of Leishmania parasites that cause cutaneous leishmaniasis, (distributed in Europe, the Middle East and North Africa) and Lutzomyia longipalpis, a vector of Leishmania parasites that cause visceral leishmaniasis (distributed across Central and South America). We categorized and curated genes involved in processes important to their roles as disease vectors, including chemosensation, blood feeding, circadian rhythm, immunity, and detoxification, as well as mobile genetic elements. We also defined gene orthology and observed micro-synteny among the genomes. Finally, we present the genetic diversity and population structure of these species in their respective geographical areas. These genomes will be a foundation on which to base future efforts to prevent vector-borne transmission of Leishmania parasites.</div

Conflicting phylogenetic signals.

Analysis of the gene phylogenies of individual orthologous groups identified three major topologies with sand fly-mosquito (41%), sand fly-fly (37%), or mosquito-fly (22%) sister clades. Comparisons of average branch lengths for each topology suggest that, although substitution rates in flies are always higher, orthologs that support the sand fly-mosquito topology show the lowest substitution rates in flies and the smallest differences in substitution rates among the fly, sand fly, and mosquito clades. In contrast, the sand fly-fly and mosquito-fly topologies show much higher substitution rates in flies and much greater differences in substitution rates among the three clades. (TIF)</p