GJA1 (also known and referred to here as connexin 43 and abbreviated CX43) is the predominant testicular gap junction protein, and CX43 may regulate Sertoli cell maturation and spermatogenesis. We hypothesized that lack of CX43 would inhibit Sertoli cell differentiation and extend proliferation. To test this, a Sertoli cell-specific Cx43 knockout (SC-Cx43 KO) mouse was generated using Cre-lox technology. Immunohistochemistry indicated that CX43 was not expressed in the Sertoli cells of SC-Cx43 KO mice, but was normal in organs such as the heart. Testicular weight was reduced by 41% and 76% in SC-Cx43 KO mice at 20 and 60 days, respectively, vs. wild-type (wt) mice. Seminiferous tubules of SC-Cx43 KO mice contained only Sertoli cells and actively proliferating early spermatogonia. Sertoli cells normally cease proliferation at 2 wk of age in mice and become terminally differentiated. However, proliferating Sertoli cells were present in SC-Cx43 KO but not wt mice at 20 and 60 days of age. Thyroid hormone receptor alpha (THRA) is high in proliferating Sertoli cells, then declines sharply in adulthood. Thra mRNA expression was increased in 20-day SC-Cx43 KO vs. wt mice, and it showed a trend toward an increase in 60-day mice, indicating that loss of CX43 in Sertoli cells inhibited their maturation. In conclusion, we have generated mice lacking CX43 in Sertoli cells but not other tissues. Our data indicate that CX43 in Sertoli cells is essential for spermatogenesis but not spermatogonial maintenance/proliferation. SC-Cx43 KO mice showed continued Sertoli cell proliferation and delayed maturation in adulthood, indicating that CX43 plays key roles in Sertoli cell development.

Deciphering the mechanisms of hematopoietic stem/progenitor cell (HSPC) mobilization and homing is important for the development of strategies to enhance the efficacy of HSPC transplantation and achieve the full potential of HSPC-based cellular therapy. Investigation of these mechanisms has revealed interdependence among the various molecules, pathways and cellular components involved, and underscored the complex nature of these two processes. This review summarizes recent progress in identifying the specific factors implicated in HSPC mobilization and homing, with emphasis on our own work. Particularly, we will discuss our studies on stromal cell-derived factor-1 and its interaction with its receptor CXCR4, proteases (matrix metalloproteinases and carboxypeptidase M), complement proteins (C1q, C3a, C5a, membrane attack complex), sphingosine-1-phosphate, and pharmacologic agents such as the histone deacetylase inhibitor valproic acid and hyaluronic acid.

Connexin 43 (CX43, also known as GJA1) is the predominant testicular gap-junction protein. In the seminiferous epithelium, gap junctions occur between adjacent Sertoli cells and between Sertoli and germ cells. The specific role of CX43 in Sertoli cell has been difficult to study because of the neonatal lethality of the Cx43 global knockout. Recently two laboratories have independently developed a Sertoli cell conditional Cx43 knockout using Cre-loxP methodology. These have allowed the role of CX43 in Sertoli cells to be determined while circumventing lethal abnormalities in organs such as the heart seen in Cx43 global knockouts. In this review the focus is on the insights into the role of CX43 in Sertoli cells derived from these new model systems. Results indicate that CX43 is essential for cessation of proliferation and normal maturation in Sertoli cells. In addition, CX43 in Sertoli cells is required for spermatogenesis, but not early germ cell proliferation. These model systems show that CX43 is important in Sertoli cell development, and will be useful in further studies of its role in Sertoli cell and testis biology.

The identification of CXCR7 in addition to CXCR4 as a receptor for the chemokine CXCL12/SDF-1 and recent reports that CXCR7 is expressed in many cancers including breast, lung and prostate prompted us to evaluate the role of CXCR7 in hematological malignancies. While CXCR4 is known to be involved in the progression of acute lymphoblastic leukemia (ALL) and acute myelogenous leukemia (AML), the role of CXCR7 in leukemic dissemination remains unknown. Using immunohistochemistry, we evaluated the expression patterns of CXCR7 and CXCR4 in tissue microarrays (TMAs) constructed from bone marrow biopsies obtained from patients diagnosed with pre B- and B-ALL (n=75; median age 5 yrs, range 6 mo-72 yrs), T-ALL (n=11; median age 12 yrs, range 4-29 yrs) and AML (n=140; median age 62 yrs, range 1-83 yrs). CXCR7 expression was also evaluated at the gene and protein levels in peripheral blood mononuclear cells from ALL and AML patients and in B-cell lines (Raji, NC-37, Ramos, Nalm-6, Reh), T-cell lines (Jurkat, Hut-102B, Sez-4, CEM), and myeloid cell lines (KG-1, HL-60, THP-1, U-937, K562, HEL) using RT-PCR and flow cytometry. We found that in B-and preB-ALL TMAs, CXCR7 was immunopositive in 79% of the patients, in contrast to negative immunostaining in 100% of T-ALL and AML samples. Consistently, flow cytometry showed that CXCR7 protein is expressed on the surface of preB-ALL cells, but not on T-ALL, AML or normal controls. CXCR7 surface expression in the cell lines studied showed that three (NC-37, Raji, Reh) out of five B-cell lines expressed CXCR7, but not in any of the T-cell lines, and only weakly in one (KG-1) of six myeloid cell lines studied. Analysis of the functional role of CXCR7 in leukemia revealed that CXCR7 did not mediate chemotaxis of CXCR7-positive NC-37 B-cell line and CXCR7-negative HL-60 myeloid cell line towards an SDF-1 gradient. However, CXCR7 was found to mediate the trans-endothelial migration, adhesion to HUVEC and survival of NC-37 cells, but not the adhesion to HUVEC or survival of HL-60 cells. In conclusion, the selective strong expression of CXCR7 in B-ALL but not in T-ALL or AML suggests a differential role this protein may play in various types of leukemia. As CXCR7 mediates trans-endothelial migration, adhesion and survival of B-cell line, further investigations into the functional role of CXCR7 in primary B-ALL are warranted with the aim of identifying new therapeutic targets. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 464. doi:1538-7445.AM2012-464