transLEISHion · A targeted knockout screen for identification of Leishmania membrane transporters required for infection of macrophages

A targeted knockout screen for identification of Leishmania membrane transporters required for infection of macrophages

Leishmania parasites cause a disease in humans known as Leishmaniasis. Widespread in 98 countries, leishmaniasis constitutes a risk for 1 billion people worldwide with an incidence of over 1 million cases per year. Leishmaniasis clinical manifestations range from cutaneous lesions to fatal visceral forms estimated to cause 20,000-40,000 deaths/year. Clinical manifestations and course of the infection depend on factors such as parasite species and the immune system of the infected individual. When a female sandfly bites a mammalian host and feeds on its blood, it injects infective forms of Leishmania parasites called metacyclic promastigotes, which are rapidly taken up by white blood cells, called macrophages, then it differentiates into aflagellated forms called amastigotes. Uniquely among organisms of the same family, Leishmania parasites are adapted to survival inside macrophages, a niche in which only few pathogens thrive. This poses specific challenges to the parasite, and it mandates the activation of mechanisms for parasite survival such as acquisition of nutrients and tolerance to acidic conditions. As there are no human vaccines available, there is a critical need for safe, non-toxic and cost-effective new drugs to treat leishmaniasis. Some transporter proteins have been implicated in parasite survival, defence from host immune attack as well as uptake of drug formulations. However significant gaps exist with regards to the importance of transporter proteins in the biology of Leishmania parasites. The Gluenz lab recently discovered several uncharacterized transporter proteins, among a number of transcripts upregulated in amastigote forms when compared to promastigote forms. These discoveries called for follow-up studies on the biological functions and relative importance of these amastigote-upregulated gene products. Due to unique genomic features, the functional study of different genes of Leishmania parasites lagged in comparison to other protozoan parasites. Taking advantage of the revolution in genome editing brought about by the discovery of the CRISPR-Cas9 system and its adaptation for biotechnology, the Gluenz lab developed a novel high-throughput genome editing method for Leishmania parasites, which allows the rapid generation of gene knockout mutants enabling for the first-time large-scale loss-of-function screens to discover genes essential for Leishmania survival. Taking advantage of these resources the main aim of transLEISHion, was (1) to generate a library of Leishmania mexicana knockout mutants for 48 genes, whose transcripts in amastigotes were observed upregulated; (2) identify membrane transporters required for the viability of vector stage promastigotes and (3) identify membrane transporters required for the viability of amastigotes.

Data: CORDIS, © European Union