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1.  Visualization and Identification of IL-7 Producing Cells in Reporter Mice 
PLoS ONE  2009;4(11):e7637.
Interleukin-7 (IL-7) is required for lymphocyte development and homeostasis although the actual sites of IL-7 production have never been clearly identified. We produced a bacterial artificial chromosome (BAC) transgenic mouse expressing ECFP in the Il7 locus. The construct lacked a signal peptide and ECFP (enhanced cyan fluorescent protein ) accumulated inside IL-7-producing stromal cells in thoracic thymus, cervical thymus and bone marrow. In thymus, an extensive reticular network of IL-7-containing processes extended from cortical and medullary epithelial cells, closely contacting thymocytes. Central memory CD8 T cells, which require IL-7 and home to bone marrow, physically associated with IL-7-producing cells as we demonstrate by intravital imaging.
doi:10.1371/journal.pone.0007637
PMCID: PMC2770321  PMID: 19907640
2.  Zfp423 Is Required for Normal Cerebellar Development†  
Molecular and Cellular Biology  2006;26(18):6913-6922.
Zinc finger protein 423 (also known as Ebf-associated zinc finger protein, Ebfaz) binds to and negatively regulates Ebf1, a basic helix-loop-helix transcription factor required for B-cell lineage commitment and olfactory epithelium development. Zfp423 also binds to Smad1/Smad4 in response to Bmp2 signaling. Zfp423 contains 30 Krüppel-like zinc fingers that are organized into discrete clusters; some zinc fingers are used to bind DNA, while others mediate Zfp423's interaction with other signaling proteins such as Ebf1 and Smad1/Smad4. Previously, we showed that Zfp423 is an oncogene whose upregulation following retroviral integration in murine B cells leads to an arrest in B-cell differentiation and the subsequent development of B-cell lymphomas. To study the biological functions of Zfp423 in vivo, we used recombineering and gene targeting to generate mice that carry conditional as well as null alleles of Zfp423. Homozygous Zfp423 null mice are runted and ataxic, the cerebellum is underdeveloped, and the vermis is severely reduced. In the remaining cerebellar structures, the Purkinje cells are poorly developed and mislocalized. In mice carrying a hypomorphic Zfp423 gene trap allele, lacZ expression in the cerebellum correlates with the Purkinje cell layer, suggesting that these phenotypes are a result of a Purkinje cell-intrinsic defect.
doi:10.1128/MCB.02255-05
PMCID: PMC1592861  PMID: 16943432
3.  Simple and highly efficient BAC recombineering using galK selection 
Nucleic Acids Research  2005;33(4):e36.
Recombineering allows DNA cloned in Escherichia coli to be modified via lambda (λ) Red-mediated homologous recombination, obviating the need for restriction enzymes and DNA ligases to modify DNA. Here, we describe the construction of three new recombineering strains (SW102, SW105 and SW106) that allow bacterial artificial chromosomes (BACs) to be modified using galK positive/negative selection. This two-step selection procedure allows DNA to be modified without introducing an unwanted selectable marker at the modification site. All three strains contain an otherwise complete galactose operon, except for a precise deletion of the galK gene, and a defective temperature-sensitive λ prophage that makes recombineering possible. SW105 and SW106 cells in addition carry l-arabinose-inducible Cre or Flp genes, respectively. The galK function can be selected both for and against. This feature greatly reduces the background seen in other negative-selection schemes, and galK selection is considerably more efficient than other related selection methods published. We also show how galK selection can be used to rapidly introduce point mutations, deletions and loxP sites into BAC DNA and thus facilitate functional studies of SNP and/or disease-causing point mutations, the identification of long-range regulatory elements and the construction of conditional targeting vectors.
doi:10.1093/nar/gni035
PMCID: PMC549575  PMID: 15731329
4.  Critical role of activation induced cytidine deaminase in Experimental Autoimmune Encephalomyelitis 
Autoimmunity  2012;46(2):157-167.
Multiple Sclerosis (MS) is a neurodegenerative autoimmune disorder caused by chronic inflammation and demyelination within the central nervous system (CNS). Clinical studies in MS patients have demonstrated efficacy with B cell targeted therapies such as anti-CD20. However, the exact role that B cells play in the disease process is unclear. Activation Induced cytidine deaminase (AID) is an essential enzyme for the processes of antibody affinity maturation and isotype switching. To evaluate the impact of affinity maturation and isotype switching, we have interrogated the effect of AID-deficiency in an animal model of MS. Here, we show that the severity of experimental autoimmune encephalomyelitis (EAE) induced by the extracellular domain of human myelin oligodendrocyte glycoprotein (MOG1-125) is significantly reduced in Aicda deficient mice, which, unlike wild-type mice, lack serum IgG to myelin associated antigens. MOG specific T cell responses are comparable between wild-type and Aicda knockout mice suggesting an active role for antigen experienced B cells. Thus affinity maturation and/or class switching are critical processes in the pathogenesis of EAE.
doi:10.3109/08916934.2012.750301
PMCID: PMC3581050  PMID: 23167594
AID; EAE; MS; affinity maturation; Isotype switching

Results 1-4 (4)