A sensitised mutagenesis screen in the mouse to explore the bovine genome: study of muscle characteristics

Meat yield and quality are closely related to muscle development. The muscle characteristics mainly take place during embryonic and postnatal phases. Thus, genetic control of muscle development in early stages represents a significant stake to improve product quality and production efficiency. In bovine, several programmes have been developed to detect quantitative trait loci (QTL) affecting growth, carcass composition or meat quality traits. Such strategy is incontestably very powerful yet extremely cumbersome and costly when dealing with large animals such as ruminants. Furthermore, the fine mapping of the QTL remains a real challenge. Here, we proposed an alternative approach based on chemical mutagenesis in the mouse combined with comparative genomics to identify regions or genes controlling muscle development in cattle. At present, we isolated seven independent mouse lines of high interest. Two lines exhibit a hypermuscular phenotype, and the other five show various skeletomuscular phenotypes. Detailed characterisation of these mouse mutants will give crucial input for the identification and the mapping of genes that control muscular development. Our strategy will provide the opportunity to understand the function and control of genes involved in improvement of animal physiology.     

Diminished social motivation negatively impacts reputation management: autism spectrum disorders as a case in point

Human beings are endowed with a unique motivation to be included in social interactions. This natural social motivation, in turn, is thought to encourage behaviours such as flattery or self-deprecation aimed to ease interaction and to enhance the reputation of the individual who produces them. If this is the case, diminished social interest should affect reputation management. Here, we use Autism Spectrum Disorders (ASDs)--primarily characterised by pervasive social disinterest--as a model to investigate the effect of social motivation on reputation management. Children first rated a set of pictures and were then given the opportunity to inflate their initial ratings in front of an experimenter who declared that she had drawn the picture. Contrary to the controls, children with ASD did not enhance their ratings in the drawer's presence. Moreover, participants' flattery behaviour correlated with self-reports of social enjoyment. Our findings point to a link between diminished social interest and reputation management.     

Determination of chromosome size and number of rrn loci in Lactobacillus plantarum by pulsed-field gel electrophoresis

Abstract When genomic DNA fragments from Streptomyces venezuelae ISP5230 were probed at moderate stringency with recA from Mycobacterium tuberculosis a 2.0-kb Sma I fragment was identified. The fragment was isolated by cloning a Bam HI digest of S. venezuelae DNA in pHJL400 and screening the plasmids in Escherichia coli by Southern hybridization using a sib-selection technique. Sequencing the hybridizing region located an open reading frame encoding 377 amino acids. Its deduced amino acid sequence resembled that of recA genes from other bacteria. The cloned S. venezuelae gene conferred partial resistance to ethyl methanesulfonate when expressed in E. coli from the lacZ promoter.     

Oxidative stress-alleviating strategies to improve recombinant protein production in CHO cells

Large scale biopharmaceutical production of biologics relies on the overexpression of foreign proteins by cells cultivated in stirred tank bioreactors. It is well recognized and documented fact that protein overexpression may impact host cell metabolism and that factors associated with large scale culture, such as the hydrodynamic forces and inhomogeneities within the bioreactors, may promote cellular stress. The metabolic adaptations required to support the high-level expression of recombinant proteins include increased energy production and improved secretory capacity, which, in turn, can lead to a rise of reactive oxygen species (ROS) generated through the respiration metabolism and the interaction with media components. Oxidative stress is defined as the imbalance between the production of free radicals and the antioxidant response within the cells. Accumulation of intracellular ROS can interfere with the cellular activities and exert cytotoxic effects via the alternation of cellular components. In this context, strategies aiming to alleviate oxidative stress generated during the culture have been developed to improve cell growth, productivity, and reduce product microheterogeneity. In this review, we present a summary of the different approaches used to decrease the oxidative stress in Chinese hamster ovary cells and highlight media development and cell engineering as the main pathways through which ROS levels may be kept under control.     

Studies on ATP-dependent deoxyribonuclease of Haemophilus influenzae: involvement of the enzyme in the transformation process

An ATP-dependent deoxyribonuclease deficient mutant of Haemophilus influenzae has been isolated on the basis of sensitivity to methyl methane sulfonate (mms). Furthermore, the involvement of the ATP-dependent deoxyribonuclease in the process of transformation in H. influenzae has been demonstrated. Among the 75 mms-sensitive mutants, two mutants lacking ATP-dependent deoxyribonuclease were isolated. One mutant $\text{Rd}\text{mms-s}$ 21 has no measurable ATP-dependent deoxyribonuclease activity, is almost transformation deficient and has normal DNA uptake after being submitted to competence protocole. The second ATP-dependent deoxyribonuclease deficient mutant which has abnormal DNA uptake is still under investigation. Furthermore, the enzyme deficient mutant mms-s 21 transformed back to mms-resistance, recovers the ATP-dependent deoxyribonuclease as well as the transforming ability. The involvement of the ATP-dependent deoxyribonuclease in the process of transformation in H. influenzae is therefore positively established.     

Lysobisphosphatidic acid controls endosomal cholesterol levels

Most cell types acquire cholesterol by endocytosis of circulating low density lipoprotein, but little is known about the mechanisms of intra-endosomal cholesterol transport and about the primary cause of its aberrant accumulation in the cholesterol storage disorder Niemann-Pick type C (NPC). Here we report that lysobisphosphatidic acid (LBPA), an unconventional phospholipid that is only detected in late endosomes, regulates endosomal cholesterol levels under the control of Alix/AlP1, which is an LBPA-interacting protein involved in sorting into multivesicular endosomes. We find that Alix down-expression decreases both LBPA levels and the lumenal vesicle content of late endosomes. Cellular cholesterol levels are also decreased, presumably because the storage capacity of endosomes is affected and thus cholesterol clearance accelerated. Both lumenal membranes and cholesterol can be restored in Alix knockdown cells by exogenously added LBPA. Conversely, we also find that LBPA becomes limiting upon pathological cholesterol accumulation in NPC cells, because the addition of exogenous LBPA, but not of LBPA isoforms or analogues, partially reverts the NPC phenotype. We conclude that LBPA controls the cholesterol capacity of endosomes.