Ataxia with isolated vitamin E deficiency (AVED) is an autosomal recessive neurodegenerative disease which maps to chromosome 8q13. AVED patients have an impaired ability to incorporate alpha-tocopherol into lipoproteins secreted by the liver, a function putatively attributable to the alpha-tocopherol transfer protein (alpha-TTP). Here we report the identification of three frame-shift mutations in the alpha TTP gene. A 744delA mutation accounts for 68% of the mutant alleles in the 17 families analysed and appears to have spread in North Africa and Italy. This mutation correlates with a severe phenotype but alters only the C-terminal tenth of the protein. Two other mutations were found in single families. The finding of alpha TTP gene mutations in AVED patients substantiates the therapeutic role of vitamin E as a protective agent against neurological damage in this disease.
"One of the first signs of vitamin E deficiency is erythrocyte fragility closely followed by anaemia, ascites, xerophthalmia, poor growth, poor food conversion, epicarditis, and ceroid deposits in spleen and liver (Halver, 2002). Symptoms of low vitamin E levels include ataxia, anemia caused by the breakdown of red blood cells and peripheral neuropathy (Ouahchi et al., 1995). Non-specific forms of degenerative conditions have been described in several species of fish fed large quantities of polyunsaturated fatty acids with inadequate tocopherol in the ration. "
[Show abstract][Hide abstract] ABSTRACT: A quick and direct method based on RP-HPLC techniques with fluorescence detector for measuring tocopherols (α, β + γ and δ) was adapted. Validation of the Rapid RP-HPLC and RP-HPLC were also assessed. To ascertain the dietary needs for tocopherols in diets used in aquaculture, the ingredients were analyzed. Vegetable oils are probably the major dietary source of tocopherols with a variable isomer profile according to the oil identity. Application of techniques for boosting tocopherols in diet in form of Dl-α-tocopheryl acetate enabled supplementation up 100-200 mg kg-1 in commercial feed. Meanwhile, Common carp, Cyprinus carpio L. was seen to have the highest requirement for tocopherols (200-300 mg kg-1). Good performance, survival, high immune response and protection against oxidative damage to fish tissues were some of the positive functions of tocopherols in growers while high fecundity is associated with tocopherols in broodfish. Hypervitaminosis E resulted in poor growth, toxic liver reaction, and death. African catfish (Clarias gariepinus) fed high α-tocopheryl acetate dose (500 mg/kg dry feed) were observed to have significantly lower hematocrit than fish fed the basal diet. One of the first signs of vitamin E deficiency is erythrocyte fragility closely followed by anaemia, ascites, xerophthalmia, poor growth, poor food conversion, epicarditis, and ceroid deposits in spleen and liver. Dietary polyunsaturated fatty acid (PUFA) content is one of the most important effective factors on dietary vitamin E requirements in fish, which means the elevation of unsaturated fatty acids can result in increased requirements for tocopherols as intracellular antioxidants to protect the cells.
"Founder mutations observed in Tunisia were also reported in populations from the Middle East such as the splice site mutation in the CA II gene responsible for carbonic anhydrase II deficiency in the Arabic peninsula  and the p.Q357R molecular defect in the UGT1A1 gene of the Crigler-Najjar type I syndrome in the Kuwaiti population . In other cases, founder mutations are dispersed around the Mediterranean basin as illustrated by the c.744delA mutation in the TTPA gene of ataxia with isolated vitamin E deficiency  and the splice site defects in megaloblastic anemia 1  and triple-A syndrome . In other examples, the founder haplotypes are shared with populations from Europe and America, as for the Parkinson disease . "
[Show abstract][Hide abstract] ABSTRACT: Background
Tunisia is a North African country of 10 million inhabitants. The native background population is Berber. However, throughout its history, Tunisia has been the site of invasions and migratory waves of allogenic populations and ethnic groups such as Phoenicians, Romans, Vandals, Arabs, Ottomans and French. Like neighbouring and Middle Eastern countries, the Tunisian population shows a relatively high rate of consanguinity and endogamy that favor expression of recessive genetic disorders at relatively high rates. Many factors could contribute to the recurrence of monogenic morbid trait expression. Among them, founder mutations that arise in one ancestral individual and diffuse through generations in isolated communities.
We report here on founder mutations in the Tunisian population by a systematic review of all available data from PubMed, other sources of the scientific literature as well as unpublished data from our research laboratory.
We identified two different classes of founder mutations. The first includes founder mutations so far reported only among Tunisians that are responsible for 30 genetic diseases. The second group represents founder haplotypes described in 51 inherited conditions that occur among Tunisians and are also shared with other North African and Middle Eastern countries. Several heavily disabilitating diseases are caused by recessive founder mutations. They include, among others, neuromuscular diseases such as congenital muscular dystrophy and spastic paraglegia and also severe genodermatoses such as dystrophic epidermolysis bullosa and xeroderma pigmentosa.
This report provides informations on founder mutations for 73 genetic diseases either specific to Tunisians or shared by other populations. Taking into account the relatively high number and frequency of genetic diseases in the region and the limited resources, screening for these founder mutations should provide a rapid and cost effective tool for molecular diagnosis. Indeed, our report should help designing appropriate measures for carrier screening, better evaluation of diseases burden and setting up of preventive measures at the regional level.
"Another conserved residue in BCH domains is Lys271 (HsBNIP-2 BCH numbering), which corresponds to K239 in yeast Sec14p and R221 in αTTP. A missense mutation at K239 in Sec14p has been reported to abolish PtIns transfer activity ,  and a R221 mutation in αTTP is associated with a hereditary disorder known as AVED (ataxia with vitamin E deficiency) , , . Being a part of a ‘hinge unit’, K239 might also contribute to controlling the movements of the helical gate . "
[Show abstract][Hide abstract] ABSTRACT: The CRAL_TRIO protein domain, which is unique to the Sec14 protein superfamily, binds to a diverse set of small lipophilic ligands. Similar domains are found in a range of different proteins including neurofibromatosis type-1, a Ras GTPase-activating Protein (RasGAP) and Rho guanine nucleotide exchange factors (RhoGEFs). Proteins containing this structural protein domain exhibit a low sequence similarity and ligand specificity while maintaining an overall characteristic three-dimensional structure. We have previously demonstrated that the BNIP-2 and Cdc42GAP Homology (BCH) protein domain, which shares a low sequence homology with the CRAL_TRIO domain, can serve as a regulatory scaffold that binds to Rho, RhoGEFs and RhoGAPs to control various cell signalling processes. In this work, we investigate 175 BCH domain-containing proteins from a wide range of different organisms. A phylogenetic analysis with ~100 CRAL_TRIO and similar domains from eight representative species indicates a clear distinction of BCH-containing proteins as a novel subclass within the CRAL_TRIO/Sec14 superfamily. BCH-containing proteins contain a hallmark sequence motif R(R/K)h(R/K)(R/K)NL(R/K)xhhhhHPs ('h' is large and hydrophobic residue and 's' is small and weekly polar residue) and can be further subdivided into three unique subtypes associated with BNIP-2-N, macro- and RhoGAP-type protein domains. A previously unknown group of genes encoding 'BCH-only' domains is also identified in plants and arthropod species. Based on an analysis of their gene-structure and their protein domain context we hypothesize that BCH domain-containing genes evolved through gene duplication, intron insertions and domain swapping events. Furthermore, we explore the point of divergence between BCH and CRAL-TRIO proteins in relation to their ability to bind small GTPases, GAPs and GEFs and lipid ligands. Our study suggests a need for a more extensive analysis of previously uncharacterized BCH, 'BCH-like' and CRAL_TRIO-containing proteins and their significance in regulating signaling events involving small GTPases.
PLoS ONE 03/2012; 7(3):e33863. DOI:10.1371/journal.pone.0033863 · 3.23 Impact Factor
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