No abstract

Alternative splicing of the rat type 1 pituitary adenylate cyclase-activating polypeptide (PACAP) receptor (PVR1) produces variants that couple either to both adenylyl cyclase (AC) and phospholipase C (PLC) (PVR1 short, PVR1 hop, PVR1 hiphop), or to AC alone (PVR1 hip). We have previously shown that populations of clonal T3-1 gonadotrophs express PVR1 hop and PVR1 short mRNAs, whereas clonal GH 4 C 1 somatotrophs do not. Here we have used the single cell RT-PCR technique to investigate whether normal rat gonadotrophs and somatotrophs express PVR1 mRNA, whether a single cell co-expresses multiple splice variant forms, and whether differential PVR1 mRNA expression correlates with differences in PACAP-stimulated Ca 2+ signalling. We found that individual rat gonadotrophs expressed mRNA either for PVR1 hop, for PVR1 short, or co-expressed the two forms. Although we found no differences between the splice variant(s) expressed and the characteristics of PACAP-stimulated Ca 2+ responses, the expression of PVR1 mRNA is consistent with the known PACAP stimulation of the PLC system in gonadotrophs. Individual rat somatotrophs also expressed PVR1 hop or PVR1 short (but not PVR1 hip) mRNAs although these forms were never co-expressed. The expression of PVR1 mRNA in somatotrophs can explain in part the activation by PACAP of the AC system in such cells. In conclusion, the single cell RT-PCR technique was used to demonstrate expression of multiple PVR1 splice variants in single identified pituitary cells. These findings open up important questions on the role of alternative splicing in cell biology.

Non-Hodgkin B-cell lymphomas (B-NHL) mainly develop within lymph nodes (LN) as densely packed aggregates of tumor cells and their surrounding microenvironment, creating a tumor niche specific to each lymphoma subtypes. In vitro preclinical models mimicking biomechanical forces, cellular microenvironment, and 3D organization of B-cell lymphomas remain scarce, while all these parameters constitute key determinants of lymphomagenesis and drug resistance. Using a microfluidic method based on cell encapsulation inside permeable, elastic, and hollow alginate microspheres, we developed a new tunable 3D-model incorporating lymphoma B cells, extracellular matrix (ECM), and/or tonsil stromal cells (TSC). We revealed that under 3D confinement lymphoma B cells were able to form cohesive spheroids resulting from overexpression of ECM components. Moreover, lymphoma B cells and TSC dynamically formed self-organized 3D spheroids favoring spheroid growth. 3D culture induced resistance to classical chemotherapeutic agent doxorubicin, but not to BCL2 inhibitor ABT-199, identifying this approach as a relevant in vitro model to assess the activity of therapeutic agents in B-NHL. RNAseq analysis highlighted the synergy of 3D, ECM, and TSC in upregulating similar pathways in malignant B cells in vitro than those overexpressed in primary lymphoma cells in situ. Finally, our 3D model including ECM and TSC allowed long-term in vitro survival of primary follicular lymphoma B cells. In conclusion, we propose a new high throughput 3D model mimicking lymphoma tumor niche and making it possible to study the dynamic relationship between lymphoma B cells and their microenvironment and to screen new anti-cancer drugs.