Fine Mapping of Leishmania major Susceptibility Locus lmr2 and Evidence of a Role for Fli1 in Disease and Wound Healing

Abstract

Genetic linkage studies of the host response to Leishmania major, the causative agent of cutaneous leishmaniasis, have identified significant genetic complexity in humans and mice. In the mouse model, multiple loci have been implicated in susceptibility to infection, but to date, the genes underlying these loci have not been identified. We now describe the contribution of a novel candidate gene, Fli1, to both L. major resistance and enhanced wound healing. We have previously mapped the L. major response locus, lmr2, to proximal chromosome 9 in a genetic cross between the resistant C57BL/6 strain and the susceptible BALB/c strain. We now show that the presence of the resistant C57BL/6 lmr2 allele in susceptible BALB/c mice confers an enhanced L. major resistance and wound healing phenotype. Fine mapping of the lmr2 locus permitted the localization of the lmr2 quantitative trait locus to a 5-Mb interval comprising 21 genes, of which microarray analysis was able to identify differential expression in 1 geneFli1. Analysis of Fli1 expression in wounded and L. major-infected skin and naïve and infected lymph nodes validated the importance of Fli1 in lesion resolution and wound healing and identified 3 polymorphisms in the Fli1 promoter, among which a GA repeat element may be the important contributor.Cutaneous leishmaniasis (CL) caused by the intracellular protozoan Leishmania major is a parasitic disease transmitted by blood-sucking sandflies. Skin macrophages are infected, and a skin lesion or granuloma develops at the site of infection (31). The severity of human CL varies, with phenotypes ranging from self-healing lesions to persistent lesions lasting years and leading to systemic disease (1). The severity of disease depends on the host's ability to form protective granulomas; in their absence, the parasites spread, resulting in diffuse cutaneous leishmaniasis. Studies of CL in mice have been of immense interest because they allow extensive experimental manipulation and reproduce many of the features of the human disease. To identify factors that modulate lesion resolution in infected individuals, we conducted genetic studies on two inbred mouse strains, C57BL/6 (B6) and BALB/c (Bc), that differ in their susceptibility to L. major. Resistance to L. major, epitomized by B6 mice, is characterized by the rapid healing of skin lesions, while the susceptibility in Bc mice is characterized by lesion chronicity and progression and systemic spread of the parasites.We previously identified three loci (lmr1, lmr2, and lmr3) mediating lesion resolution during L. major infection (28, 29). Mice congenic for all three resistant lmr alleles [strain C.B6-(lmr1, lmr2)] were generated on the susceptible Bc background and were shown to be more resistant to L. major and more able to heal noninfectious wounds than Bc mice, exhibiting a statistically significant tendency toward the phenotype of the donor strain B6. Furthermore, resistance to L. major was independent of T helper cell responses (12,13,30). The conclusions from these stud...

The Abl and Arg Kinases Mediate Distinct Modes of Phagocytosis and Are Required for Maximal Leishmania Infection

“…Polymorphisms in this factor's gene govern susceptibility to cutaneous leishmaniasis (6,51), and Abl facilitates FLI-1 activation (4). However, decreased FLI-1 activity and subsequent effects on wound healing should not lower parasite burdens (51). Thus, it seems unlikely that differences in FLI-1 activation are solely responsible for the differences we see in lesion size in Abl family kinase-deficient mice.…”

Wound healing genes and susceptibility to cutaneous leishmaniasis in Brazil: Role of COL1A1

“…In the last few years we have shown that polymorphisms at genes associated with wound healing and tissue repair are important risk factors for cutaneous leishmaniasis (CL) caused by Leishmania braziliensis (Castellucci et al, 2012; Castellucci et al, 2011). Thus, the FLI1 gene, initially identified and mapped as a gene controlling susceptibility to CL caused by L. major infection in mice (Sakthianandeswaren et al, 2010; Sakthianandeswaren et al, 2005), was also associated with development of CL in humans exposed to L. braziliensis in Brazil. In addition, our data showed that polymorphisms in other wound healing genes related to FLI1 function, in particular genes ( TGFB1, TGFBR2, CTGF, SMAD2/3/7 ) encoding proteins in the transforming growth factor β (TGF-β) signaling pathway, were risk factors for CL.…”

A Two-Locus System Controls Susceptibility to Colitis-Associated Colon Cancer in Mice

“…A locus regulating differential susceptibility of BALB/c (susceptible) and B6 (resistant) mice to cutaneous leishmaniasis induced by infection with Leishmania major, and designated Lmr2, has been mapped to a ~10 Mb interval on chromosome 9 that overlaps the genetic interval defined herein for the Ccs4 locus [31]. The genetic difference at Lmr2 is expressed as a vigorous wound healing response required for lesion resolution following cutaneous infection with L. major.…”

“…A number of candidate genes have been proposed for Lmr2 including Tirap, Fli1, Il10ra, as well as members of the Mmp family, and Aplp2. Recently, a functional promotor polymorphism in the Fli1 gene has been proposed as a strong candidate for Lmr2 [31]. The possibility that the Ccs4-controlled differential susceptibility to CA-CRC may involve differential response to, and recovery from acute inflammationinduced tissue injury requires further investigation.…”