Translational control in early adipogenesis

In obesity, adipose tissue expands by increasing the volume of existing adipocytes (hypertrophy), increasing the number of small adipocytes (hyperplasia) or both. Much is known about transcriptional control during adipogenesis, including early events. However, translational control plays a pivotal role in many dynamic processes and we presume that it is also important for the control of adipogenesis, especially in the first hours after hormonal induction. By use of ribosome profiling we identified 43 genes that are up-regulated and 2 genes that are down-regulated during the first six hours of adipogenesis in 3T3-L1 cells. Interestingly, we found Ghrelin to be down-regulated. Up-regulated genes comprise factors that are nucleic acid binding (Cdkn1c, eIF4b, Hsf1, Irf6, Myc, Plekhn1, Polr2a, Rpl18, Rpl27a, Rpl6, Rpl7a, Rps18, Rpsa, Sema3g, Tbc1d22a, Tsc22d3), form part of ribosomes (L6, L7a, L18, L27a, Sa, S18, S15a pseudogene), act on the regulation of translation (eIF4b) or transcription (Hsf1, Irf6, Myc, Tsc22d3). Others act as chaperones (Bag3, Hspa8/Hsc70, Hsp90ab1) or in other metabolic or signals transducing processes. We conclude that a moderate reorganisation of the functionality of the ribosomal machinery is a very important step for the growth and expression control at the beginning of adipogenesis. 12 samples: 4 (0h, non-polysomal fraction; 0h, polysomal fraction; 6h, non-polysomal fraction; 6h, polysomal fraction) x3 replicates