Alternative Splicing of Spg7, a Gene Involved in Hereditary Spastic Paraplegia, Encodes a Variant of Paraplegin Targeted to the Endoplasmic Reticulum

BACKGROUND: Hereditary spastic paraplegia defines a group of genetically heterogeneous diseases characterized by weakness and spasticity of the lower limbs owing to retrograde degeneration of corticospinal axons. One autosomal recessive form of the disease is caused by mutation in the SPG7 gene. Paraplegin, the product of SPG7, is a component of the m-AAA protease, a high molecular weight complex that resides in the mitochondrial inner membrane, and performs crucial quality control and biogenesis functions in mitochondria. PRINCIPAL FINDINGS: Here we show the existence in the mouse of a novel isoform of paraplegin, which we name paraplegin-2, encoded by alternative splicing of Spg7 through usage of an alternative first exon. Paraplegin-2 lacks the mitochondrial targeting sequence, and is identical to the mature mitochondrial protein. Remarkably, paraplegin-2 is targeted to the endoplasmic reticulum. We find that paraplegin-2 exposes the catalytic domains to the lumen of the endoplasmic reticulum. Moreover, endogenous paraplegin-2 accumulates in microsomal fractions prepared from mouse brain and retina. Finally, we show that the previously generated mouse model of Spg7-linked hereditary spastic paraplegia is an isoform-specific knock-out, in which mitochondrial paraplegin is specifically ablated, while expression of paraplegin-2 is retained. CONCLUSIONS/SIGNIFICANCE: These data suggest a possible additional role of AAA proteases outside mitochondria and open the question of their implication in neurodegeneration

Multispacer typing of Rickettsia isolates from humans and ticks in Tunisia revealing new genotypes

BACKGROUND: Rickettsioses are important remerging vector born infections. In Tunisia, many species have been described in humans and vectors. Genotyping is important for tracking pathogen movement between hosts and vectors. In this study, we characterized Rickettsia species detected in patients and vectors using multispacer typing (MST), proposed by Founier et al. and based on three intergenic spacers (dksA-xerC, rmpE- tRNA(fMet), mppA-pruC) sequencing. METHODS: Our study included 25 patients hospitalized during 2009. Ticks and fleas were collected in the vicinity of confirmed cases. Serology was performed on serum samples by microimmunofluorescence using Rickettsia conorii and Rickettsia typhi antigens. To detect and identify Rickettsia species, PCR targeting ompA, ompB and gltA genes followed by sequencing was performed on 18 obtained skin biopsies and on all collected vectors. Rickettsia positive samples were further characterized using primers targeting three intergenic spacers (dksA-xerC, rmpE- tRNA(fMet) and mppA-purC). RESULTS: A rickettsial infection was confirmed in 15 cases (60%). Serology was positive in 13 cases (52%). PCR detected Rickettsia DNA in four biopsies (16%) allowing the identification of R. conorii subsp israelensis in three cases and R. conorii subsp conorii in one case. Among 380 collected ticks, nine presented positive PCR (2.4%) allowing the identification of six R. conorii subsp israelensis, two R. massiliae and one R. conorii subsp conorii. Among 322 collected fleas, only one was positive for R. felis. R. conorii subsp israelensis strains detected in humans and vectors clustered together and showed a new MST genotype. Similarly, R. conorii subsp conorii strains detected in a skin biopsy and a tick were genetically related and presented a new MST genotype. CONCLUSIONS: New Rickettsia spotted fever strain genotypes were found in Tunisia. Isolates detected in humans and vectors were genetically homogenous despite location differences in their original isolation suggesting epidemiologic circulation of these strains

Nutritional and additive uses of chitin and chitosan in the food industry

Chitin is the first polysaccharide identified by man. Chitin and its numerous oligomeric and monomeric, acetylated or deacetylated derivates have many physiological functions and applications. Chitin is found in the cuticles of arthropods and is a major constituent of cell walls from fungal, yeast and algae, from where chitin can be extracted chemically, enzymatically or by fermentation. The principal sources of chitin and chitosan are actually crustacean shells. Worldwide, more than 13.000.000 tons of crustaceans are caught from marine habitats each year, thus generating huge amounts of food waste. The unique biodegradability, biorenewability, biocompatibility, physiological inertness and hydrophilicity of chitin and chitosan make them of high interest for research and industry. In this chapter, we review the use of chitin, chitosan and their oligomers and monomers as food additives. In particular, their use in the regulation of lipid digestion and hypocholesterolemia, their functioning as an antigastritic agent and prebiotic is highlighted. Literature shows that oligomerization and the degree of deacetylation influences the development of chitin/chitosan-based nutraceuticals. The absence of chitinases and chitosanases in the human gut renders those biopolymers resistant to even partial degradation. For food applications, they are used as emulsifying, fining, thickening and stabilizing agents, antioxidants, and low calories food mimetics