Genetic diversity of natural Tunisian Lavandula multifida L. (Lamiaceae) populations assessed by allozymes and random amplification of polymorphic DNA (RAPD)

We compared the genetic diversity estimated from allozymes and from random amplified polymorphic DNA (RAPDs) in a sample of seven Lavandula multifida L. populations from three bioclimates in Tunisia. Seven isozymes coding for 14 putative loci and 97 RAPD markers, amplified by seven decamer random primers, were used. A high genetic diversity within populations was detected both by isozymes (P = 73.8%; Ap = 2.0 and He = 0.231) and RAPDs (61.86 < P < 80.41% and 0.308 < H < 0.459). The populations from the lower semi-arid bioclimate showed relatively higher polymorphism. A high genetic differentiation among all populations and a limited gene flow at all space scales were detected as a result of habitat fragmentation, low size of populations and genetic drift. However, the level of differentiation among populations revealed by RAPDs (ФST = 0.370; GST = 0.372) was higher than that of allozymes (FST = 0.244). The unweighted pair group method with arithmetic mean (UPGMA) dendrograms based on matrices of FST and ФST were not concordant, and there is no significant correlation between the two data sets. The cluster from allozymes revealed higher separation among most populations. The dendrogram from RAPDs separated populations into three distinct subclusters. The groupings of populations in both dendrograms did not reflect spatial geographic or bioclimatic patterns, indicating particular adaptation of populations to local environments. The dendrogram, based on combined data had led to similar population groupings to that probed by RAPDs. The high differentiation among all populations implies that collection of seeds for ex situ conservation should be done from all populations from all bioclimatic zones even at a low geographic distance.Keywords: Lavandula multifida, genetic diversity, population structure, isozymes, random amplified polymorphic DNA (RAPDs)African Journal of Biotechnology Vol. 12(7), pp. 648-65

Genetic diversity and chemical polymorphism of Tunisian Lavandula multifida L. (Lamiaceae) populations

Eleven Tunisian natural populations of Lavandula multifida L., from different geographic regions and bioclimates, were assessed for their variability using six polymorphic loci and 35 terpenoids. Isozymes were revealed by 13% gel electrophoresis. Volatiles were analysed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). A high genetic diversity within populations and within ecological groups was revealed by allozymes as a result of both of the outbreeding system of the species and the large size of populations before fragmentation. Cluster constructed using Nei’s genetic distances showed high differentiation between populations. Those belonging to the same bioclimatic zone were not strictly grouped together. Essential oil composition varied among populations. Carvacrol (21.14 to 47.02%), acrylic acid dodecanyl ester (8.96 to 14.06%) and β-Bisabolene (12.96 to 19%) were the main components. Chemical population’s structure, at the ecological group level, based on terpenoids was concordant with that of isozymes. Matrices of Wright’s FST and Euclidean distances were also correlated. Population differentiation performed on combined data yielded similar to that shown using each marker separately. Conservation strategies should take into account the levels of genetic diversity and chemical variation in relation to population and bioclimate.Keywords: Lavandula multifida, Tunisia, natural populations, Isozymes, essential oil, bioclimat

Effet du type de pâturage sur la qualité de la viande des agneaux élevés en mode biologique

La réglementation de l’élevage ovin en mode biologique (MB) limite l’incorporation du concentré à un maximum de 40% avec un accès obligatoire au parcours. En Tunisie, la viande d’agneau de race Barbarine élevé sur parcours est reconnue par une meilleure qualité nutritionnelle (MajdoubMathlouthi et al., 2010). Néanmoins, la qualité du parcours est très dépendante de la pluviométrie, et il parait bien impératif de trouver d’autres types de pâturage pour réussir l’élevage en MB. L’objectif de cette étude était d’évaluer la qualité de la viande d’agneaux élevés sur deux types de pâturage: le parcours naturel et une prairie d’orge en vert

Progressive Structural Defects in Canine Centronuclear Myopathy Indicate a Role for HACD1 in Maintaining Skeletal Muscle Membrane Systems

Mutations in HACD1/PTPLA cause recessive congenital myopathies in humans and dogs. Hydroxyacyl-coA dehydratases are required for elongation of very long chain fatty acids, and HACD1 has a role in early myogenesis, but the functions of this striated muscle-specific enzyme in more differentiated skeletal muscle remain unknown. Canine HACD1 deficiency is histopathologically classified as a centronuclear myopathy (CNM). We investigated the hypothesis that muscle from HACD1-deficient dogs has membrane abnormalities in common with CNMs with different genetic causes. We found progressive changes in tubuloreticular and sarcolemmal membranes and mislocalized triads and mitochondria in skeletal muscle from animals deficient in HACD1. Furthermore, comparable membranous abnormalities in cultured HACD1-deficient myotubes provide additional evidence that these defects are a primary consequence of altered HACD1 expression. Our novel findings, including T-tubule dilatation and disorganization, associated with defects in this additional CNM-associated gene provide a definitive pathophysiologic link with these disorders, confirm that dogs deficient in HACD1 are relevant models, and strengthen the evidence for a unifying pathogenesis in CNMs via defective membrane trafficking and excitation-contraction coupling in muscle. These results build on previous work by determining further functional roles of HACD1 in muscle and provide new insight into the pathology and pathogenetic mechanisms of HACD1 CNM. Consequently, alterations in membrane properties associated with HACD1 mutations should be investigated in humans with related phenotypes

Loss of Catalytically Inactive Lipid Phosphatase Myotubularin-related Protein 12 Impairs Myotubularin Stability and Promotes Centronuclear Myopathy in Zebrafish

X-linked myotubular myopathy (XLMTM) is a congenital disorder caused by mutations of the myotubularin gene, MTM1. Myotubularin belongs to a large family of conserved lipid phosphatases that include both catalytically active and inactive myotubularin-related proteins (i.e., “MTMRs”). Biochemically, catalytically inactive MTMRs have been shown to form heteroligomers with active members within the myotubularin family through protein-protein interactions. However, the pathophysiological significance of catalytically inactive MTMRs remains unknown in muscle. By in vitro as well as in vivo studies, we have identified that catalytically inactive myotubularin-related protein 12 (MTMR12) binds to myotubularin in skeletal muscle. Knockdown of the mtmr12 gene in zebrafish resulted in skeletal muscle defects and impaired motor function. Analysis of mtmr12 morphant fish showed pathological changes with central nucleation, disorganized Triads, myofiber hypotrophy and whorled membrane structures similar to those seen in X-linked myotubular myopathy. Biochemical studies showed that deficiency of MTMR12 results in reduced levels of myotubularin protein in zebrafish and mammalian C2C12 cells. Loss of myotubularin also resulted in reduction of MTMR12 protein in C2C12 cells, mice and humans. Moreover, XLMTM mutations within the myotubularin interaction domain disrupted binding to MTMR12 in cell culture. Analysis of human XLMTM patient myotubes showed that mutations that disrupt the interaction between myotubularin and MTMR12 proteins result in reduction of both myotubularin and MTMR12. These studies strongly support the concept that interactions between myotubularin and MTMR12 are required for the stability of their functional protein complex in normal skeletal muscles. This work highlights an important physiological function of catalytically inactive phosphatases in the pathophysiology of myotubular myopathy and suggests a novel therapeutic approach through identification of drugs that could stabilize the myotubularin-MTMR12 complex and hence ameliorate this disorder

Effect of beta-Dystroglycan Processing on Utrophin / DP116 Anchorage in Normal and MDX Mouse Schwann Cell Membrane

In the peripheral nervous system, utrophin and the short dystrophin isoform (Dp116) are co-localized at the outermost layer of the myelin sheath of nerve fibers; together with the dystroglycan complex. In peripheral nerve, matrix metalloproteinase (MMP) creates a 30 kDa fragment of beta-dystroglycan, leading to a disruption of the link between the extracellular matrix and the cell membrane. Here we asked if the processing of the beta-dystroglycan could influence the anchorage of Dp116 or/and utrophin in normal and mdx Schwann cell membrane. We showed that MMP-9 was more activated in mdx nerve than in wild-type one. This activation leads to an accumulation of the 30 kDa beta-dystroglycan isoform and have an impact on the anchorage of Dp116 and utrophin isoforms in mdx Schwann cells membrane. Our results showed that Dp116 had greater affinity to the full length form of beta-dystroglycan than the 30 kDa form. Moreover, we showed for the first time that the short isoform of utrophin (Up71) was over-expressed in mdx Schwann cells compared to wild-type. In addition, this utrophin isoform (Up71) seems to have greater affinity to the 30 kDa beta-dystroglycan which could explain a more stabilization of this 30 kDa at the membrane compartment. Our results highlight the potential participation of the short utrophin isoform and the cleaved form of beta-dystroglycan in mdx Schwann cell membrane architecture

Skeletal Muscle NADPH Oxidase Is Increased and Triggers Stretch-Induced Damage in the mdx Mouse

Recent studies have shown that oxidative stress contributes to the pathogenesis of muscle damage in dystrophic (mdx) mice. In this study we have investigated the role of NADPH oxidase as a source of the oxidative stress in these mice. The NADPH oxidase subunits gp91phox, p67phox and rac 1 were increased 2–3 fold in tibilais anterior muscles from mdx mice compared to wild type. Importantly, this increase occurred in 19 day old mice, before the onset of muscle necrosis and inflammation, suggesting that NADPH oxidase is an important source of oxidative stress in mdx muscle. In muscles from 9 week old mdx mice, gp91phox and p67phox were increased 3–4 fold and NADPH oxidase superoxide production was 2 times greater than wild type. In single fibers from mdx muscle NADPH oxidase subunits were all located on or near the sarcolemma, except for p67phox,which was expressed in the cytosol. Pharmacological inhibition of NADPH oxidase significantly reduced the intracellular Ca2+ rise following stretched contractions in mdx single fibers, and also attenuated the loss of muscle force. These results suggest that NADPH oxidase is a major source of reactive oxygen species in dystrophic muscle and its enhanced activity has a stimulatory effect on stretch-induced Ca2+ entry, a key mechanism for muscle damage and functional impairment

Defective Membrane Remodeling in Neuromuscular Diseases: Insights from Animal Models

Proteins involved in membrane remodeling play an essential role in a plethora of cell functions including endocytosis and intracellular transport. Defects in several of them lead to human diseases. Myotubularins, amphiphysins, and dynamins are all proteins implicated in membrane trafficking and/or remodeling. Mutations in myotubularin, amphiphysin 2 (BIN1), and dynamin 2 lead to different forms of centronuclear myopathy, while mutations in myotubularin-related proteins cause Charcot-Marie-Tooth neuropathies. In addition to centronuclear myopathy, dynamin 2 is also mutated in a dominant form of Charcot-Marie-Tooth neuropathy. While several proteins from these different families are implicated in similar diseases, mutations in close homologues or in the same protein in the case of dynamin 2 lead to diseases affecting different tissues. This suggests (1) a common molecular pathway underlying these different neuromuscular diseases, and (2) tissue-specific regulation of these proteins. This review discusses the pathophysiology of the related neuromuscular diseases on the basis of animal models developed for proteins of the myotubularin, amphiphysin, and dynamin families. A better understanding of the common mechanisms between these neuromuscular disorders will lead to more specific health care and therapeutic approaches