BackgroundThe mouse inbred line C57BL/6J is widely used in mouse genetics and its genome has been incorporated into many genetic reference populations. More recently large initiatives such as the International Knockout Mouse Consortium (IKMC) are using the C57BL/6N mouse strain to generate null alleles for all mouse genes. Hence both strains are now widely used in mouse genetics studies. Here we perform a comprehensive genomic and phenotypic analysis of the two strains to identify differences that may influence their underlying genetic mechanisms.ResultsWe undertake genome sequence comparisons of C57BL/6J and C57BL/6N to identify SNPs, indels and structural variants, with a focus on identifying all coding variants. We annotate 34 SNPs and 2 indels that distinguish C57BL/6J and C57BL/6N coding sequences, as well as 15 structural variants that overlap a gene. In parallel we assess the comparative phenotypes of the two inbred lines utilizing the EMPReSSslim phenotyping pipeline, a broad based assessment encompassing diverse biological systems. We perform additional secondary phenotyping assessments to explore other phenotype domains and to elaborate phenotype differences identified in the primary assessment. We uncover significant phenotypic differences between the two lines, replicated across multiple centers, in a number of physiological, biochemical and behavioral systems.ConclusionsComparison of C57BL/6J and C57BL/6N demonstrates a range of phenotypic differences that have the potential to impact upon penetrance and expressivity of mutational effects in these strains. Moreover, the sequence variants we identify provide a set of candidate genes for the phenotypic differences observed between the two strains.

Three chicken Sox (SRY-like box) genes have been identified that show an interactive pattern of expression in the developing embryonic nervous system. cSox2 and cSox3 code for related proteins and both are predominantly expressed in the immature neural epithelium of the entire CNS of HH stage 10 to 34 embryos. cSox11 is related to cSox2 and cSox3 only by virtue of containing an SRY-like HMG-box sequence but shows extensive homology with Sox-4 at its C-terminus. cSox11 is expressed in the neural epithelium but is transiently upregulated in maturing neurons after they leave the neural epithelium. These patterns of expression suggest that Sox genes play a role in neural development and that the developmental programme from immature to mature neurons may involve switching of Sox gene expression. cSox11 also exhibits a lineage restricted pattern of expression in the peripheral nervous system.

Calcium and Ca 2؉ -dependent signals play a crucial role in sperm motility and mammalian fertilization, but the molecules and mechanisms underlying these Ca 2؉ -dependent pathways are incompletely understood. Here we show that homozygous male mice with a targeted gene deletion of isoform 4 of the plasma membrane calcium/ calmodulin-dependent calcium ATPase (PMCA), which is highly enriched in the sperm tail, are infertile due to severely impaired sperm motility. Furthermore, the PMCA inhibitor 5-(and-6)-carboxyeosin diacetate succinimidyl ester reduced sperm motility in wild-type animals, thus mimicking the effects of PMCA4 deficiency on sperm motility and supporting the hypothesis of a pivotal role of the PMCA4 on the regulation of sperm function and intracellular Ca 2؉ levels.Successful fertilization requires the sperm to travel long distances and undergo capacitation prior to reaching the female egg. After reaching their target, the sperm must interact with the extracellular matrix of the egg, including proteins of the zona pellucida, and release acrosomal material. Calcium is considered to exert a function on most, if not all, of these processes. In this field, most of the work on Ca 2ϩ signaling has focused on Ca 2ϩ entry mechanisms, especially on the role of Ca 2ϩ channels (1-4). For example, gene ablation of the cation channel of sperm (CatSper) leads to impaired sperm motility and male infertility (5), and mice lacking the mitochondrial voltage-dependent anion channel type 3 (VDAC3) are also infertile due to immotile sperm (6). These results show that tight regulation of ion entry by ion channels is critical to sperm function. Although there is little doubt as to the importance of calcium homeostasis in sperm motility and fertilization (7-12), the function of the plasma membrane Ca 2ϩ /calmodulin-dependent Ca 2ϩ ATPase (PMCA) 1 during this process remained enigmatic.PMCA represents a family of enzymes that extrude calcium from the cytosol across the plasma membrane of eukaryotic cells. Since their initial identification in erythrocytes (13), four different isoforms have been identified, and multiple splice forms of these isoforms have been described. The well defined tissue-specific expression pattern of different isoforms and splice variants of the pump in various mammalian tissues (14) and the regulated expression pattern during mouse development (15) strongly suggest a specific physiological function for each isoform and splice variant (reviewed in Strehler and Zacharias (16)). The identification of physical and functional interaction partners of the Ca 2ϩ pump has given insights into the putative functions of PMCAs as regulators of Ca 2ϩ -dependent signal transduction processes (17-21). Interaction of PMCA2 and -4 "b" splice variants was shown to be mediated by the PDZ-(PSD-95/Dlg/ZO-1) domain of the corresponding interaction partner and the C termini of the PMCA isoform (which harbors a typical PDZ domain binding motif (17)). Both modes of interaction with PDZ domain-containing proteins, specific and...

Given that cardiovascular safety liabilities remain a major cause of drug attrition during preclinical and clinical development, adverse drug reactions, and post‐approval withdrawal of medicines, the Medical Research Council Centre for Drug Safety Science hosted a workshop to discuss current challenges in determining, understanding and addressing ‘Cardiovascular Toxicity of Medicines’. This article summarizes the key discussions from the workshop that aimed to address three major questions: (i) what are the key cardiovascular safety liabilities in drug discovery, drug development and clinical practice? (ii) how good are preclinical and clinical strategies for detecting cardiovascular liabilities? and (iii) do we have a mechanistic understanding of these liabilities? It was concluded that in order to understand, address and ultimately reduce cardiovascular safety liabilities of new therapeutic agents there is an urgent need to: Fully characterize the incidence, prevalence and impact of drug‐induced cardiovascular issues at all stages of the drug development process. Ascertain the predictive value of existing non‐clinical models and assays towards the clinical outcome. Understand the mechanistic basis of cardiovascular liabilities; by addressing areas where it is currently not possible to predict clinical outcome based on preclinical safety data. Provide scientists in all disciplines with additional skills to enable them to better integrate preclinical and clinical data and to better understand the biological and clinical significance of observed changes. Develop more appropriate, highly relevant and predictive tools and assays to identify and wherever feasible to eliminate cardiovascular safety liabilities from molecules and wherever appropriate to develop clinically relevant and reliable safety biomarkers.