B cell development requires tight regulation to allow for the generation of a diverse repertoire while preventing the development of autoreactive cells. We report, using N-ethyl-N-nitrosourea (ENU)-induced mutagenesis, the identification of a mutant mouse (chompB) with a block in early B cell development. The blockade occurs after the transitional 1 (T1) stage and leads to a decrease in mature B cell subsets and deficits in T cell-dependent antibody responses. Additionally, chompB mice have decreases in myeloid dendritic cells (DCs). The mutation was mapped to the intramembrane protease signal peptide peptidase-like 2a (Sppl2a), a gene not previously implicated in immune cell development. Proteomic analysis identified the invariant chain (CD74) as a key substrate of Sppl2a and suggests that regulated intramembrane proteolysis of CD74 by Sppl2a contributes to B cell and DC survival. Moreover, these data suggest that modulation of Sppl2a may be a useful therapeutic strategy for treatment of B cell dependent autoimmune disorders.

, 1345 (2010); 329 Science et al. Anthony E. Boitano Human Hematopoietic Stem Cells Aryl Hydrocarbon Receptor Antagonists Promote the Expansion of This copy is for your personal, non-commercial use only. clicking here. colleagues, clients, or customers by , you can order high-quality copies for your If you wish to distribute this article to others here. following the guidelines can be obtained by Permission to republish or repurpose articles or portions of articles ): November 5, 2013 www.sciencemag.org (this information is current as of The following resources related to this article are available online at http://www.sciencemag.org/content/332/6030/664.2.full.html A correction has been published for this article at: http://www.sciencemag.org/content/329/5997/1345.full.html version of this article at: including high-resolution figures, can be found in the online Updated information and services, http://www.sciencemag.org/content/suppl/2010/08/02/science.1191536.DC1.html can be found at: Supporting Online Material http://www.sciencemag.org/content/329/5997/1345.full.html#related found at: can be related to this article A list of selected additional articles on the Science Web sites http://www.sciencemag.org/content/329/5997/1345.full.html#ref-list-1 , 8 of which can be accessed free: cites 24 articles This article http://www.sciencemag.org/content/329/5997/1345.full.html#related-urls 43 articles hosted by HighWire Press; see: cited by This article has been http://www.sciencemag.org/cgi/collection/medicine Medicine, Diseases subject collections: This article appears in the following

Although practiced clinically for more than 40 years, the use of hematopoietic stem cell (HSC) transplants remains limited by the ability to expand these cells ex vivo. An unbiased screen with primary human HSCs identified a purine derivative, StemRegenin 1 (SR1), that promotes the ex vivo expansion of CD34 + cells. Culture of HSCs with SR1 led to a 50-fold increase in cells expressing CD34 and a 17-fold increase in cells that retain the ability to engraft immunodeficient mice. Mechanistic studies show that SR1 acts by antagonizing the aryl hydrocarbon receptor (AHR). The identification of SR1 and AHR modulation as a means to induce ex vivo HSC expansion should facilitate the clinical use of HSC therapy.

We combined large-scale mRNA expression analysis and gene mapping to identify genes and loci that control hematopoietic stem cell (HSC) function. We measured mRNA expression levels in purified HSCs isolated from a panel of densely genotyped recombinant inbred mouse strains. We mapped quantitative trait loci (QTLs) associated with variation in expression of thousands of transcripts. By comparing the physical transcript position with the location of the controlling QTL, we identified polymorphic cis -acting stem cell genes. We also identified multiple trans -acting control loci that modify expression of large numbers of genes. These groups of coregulated transcripts identify pathways that specify variation in stem cells. We illustrate this concept with the identification of candidate genes involved with HSC turnover. We compared expression QTLs in HSCs and brain from the same mice and identified both shared and tissue-specific QTLs. Our data are accessible through WebQTL, a web-based interface that allows custom genetic linkage analysis and identification of coregulated transcripts.

B cell development is a tightly controlled pro­ cess that promotes the survival and expansion of B cells with affinity for invading organisms while eliminating autoreactive B cells and thereby preventing autoimmunity (Browning, 2006; Allman and Pillai, 2008). The recent clinical success of B cell targeted therapies in a multi­ tude of autoimmune disorders has highlighted the potential role of B cells in disease pathology. Work in the last several decades has also revealed that B cells have alternative effector functions in addition to antibody production, and can play a role in the pathology of a multitude of human diseases and provide additional thera­ peutic intervention points (Browning, 2006; Gürcan et al., 2009). Although much has been discovered about lymphocyte development and activation through the use of traditional gene targeting approaches, it also has its limitations. These include require­ ments for a gene in embryonic development, the development of a particular cell type, or a hy­ pothesis that a gene is involved in the function of a particular cell type or pathway. Forward ge­ netic approaches have classically proven to be valuable tools in many model organisms, and work from the last 10 years has shown that it can also be a useful tool in mice (Beutler et al., 2006; Cook et al., 2006). Random mutagenesis also provides the opportunity to identify mutants with reduced or increased activity as opposed to full ablation, which can provide insight into how a particular molecule is functioning. To this end, we used a forward genetic screen using N­ethyl­N­nitrosourea (ENU)– induced mutagenesis in mice to identify novel regulators of immune function. We discovered a CORRESPONDENCE Michael Cooke: mcooke@gnf.org The intramembrane protease Sppl2a is required for B cell and DC development and survival via cleavage of the invariant chain B cell development requires tight regulation to allow for the generation of a diverse repertoire while preventing the development of autoreactive cells. We report, using N-ethyl-N-nitrosourea (ENU)–induced mutagenesis, the identification of a mutant mouse (chompB) with a block in early B cell development. The blockade occurs after the transitional 1 (T1) stage and leads to a decrease in mature B cell subsets and deficits in T cell–dependent antibody responses. Additionally, chompB mice have decreases in myeloid dendritic cells (DCs). The mutation was mapped to the intramembrane protease signal peptide peptidase-like 2a (Sppl2a), a gene not previously implicated in immune cell development. Proteomic analysis identified the invariant …