BMC Genomics 2009, 10:150 http://www.biomedcentral.com/1471-2164/10/150 14 DDbbpp 3 1 12 Nr1d2 Tef isson 11 CPPloeecrr12k e r xEp 10 RPoerr1a Rora 9 Cry2 8 Per3 Per3 7 Arntl Expression of Circadian Rhythm Genes Bhlhb2 Csnk1e Csnk1e Nr1d1 Csnk1d Strain C57BL/6J C57.YA CX Sham Treatment liPFinsritgoeubrdaercienetix5otphnreegKsesnEioeGsnGdpeapstactterhirbwneadfyoarmscmciriucrc0aad4di7ai1ann0gcieninrcteahsde(iaelinittehrrheayrttuhgrmeen)oesr Probe expression pattern for circadian genes (either genes listed in the KEGG pathway mmu04710 circa- dian rhythm or interaction genes described as circa- dian in the literature). Each line connects average expression of a given gene between CX and sham operated mice. Strain of mice is denoted by a solid line, for C57BL/6J and a dashed line for C57.YA. The vertical scale corresponds to log2 (hybridization intensity value). For the 8 genes listed in the left part of the figure (with a different color for each symbol and corresponding lines), the difference between the slopes of the lines reflects the interaction effects. For 4 addi- tional genes (listed in the right part of the figure, with sym- bols and corresponding lines formatted in gray), there is no significant interaction effect. C57BL/6J vs. CX C57.YA. Finally, an active Akt pathway may stimulate the androgen pathway in part via phospho- rylation of the androgen receptor [25]. If all these strain- dependent differences in gene expression in CX animals translate into changes at the protein level, the balance between co-repressors and co-activators would tip towards the latter in CX male C57BL/6J mice (Figure 7). Of note, some degree of constitutive activation of the AR in CX male C57BL/6J might explain why fewer genes respond to post-pubertal T in this strain than in C57.YA mice, and why there are fewer differences in gene expres- sion in intact C57BL6/J and C57.YA than in their CX counterparts. Likewise, increased sensitivity of the AR might explain why plasma testosterone is lower in intact C67BL6/J than in C57.YA mice, as measured by ourselves (data not shown) and in agreement with a previous report [13]. Expression of Cdkn1a is increased ~5-fold in the hearts of intact vs. CX C57.YA (see Additional file 1), which is in t6DFiJaiigallguynrdreaexmCp65rs7eu.smYseAmdmairincizehinegarctisrcfardoimaninctloactk sgheanmes-otpheartaatreeddCif5fe7rBeLn/- Diagram summarizing circadian clock genes that are differentially expressed in hearts from intact sham- operated C57BL/6J and C57.YA mice. Boxes are in red or green when gene expression is higher in intact male C57.YA or C57BL/6J mice, respectively. Lines terminating with an arrowhead indicate positive regulation; those termi- nating with a bar indicate negative regulation. The values rep- resent the ratio of mRNA abundance in intact (sham- operated) male C57.YA vs. C57BL/6J hearts. keeping with previous reports showing that this gene is an important target of activated androgen receptors [26]. However, there was also striking strain-selectivity in the response, as there are no changes in expression between intact and CX C57BL/6J mice. Interestingly, Cdkn1a (which encodes for a well-known regulator of cell growth) has been shown to escape from androgen-dependence in some types of prostate cancers, and this phenomenon has been implicated as one of the possible factors leading to an increase in the growth properties of these cells [27-29]. Although cardiac cells are post-mitotic, p21 may act on these cells as a negative regulator of hypertrophy [24,30]. The lack of response of Cdkn1a to post-pubertal testoster- one in C57BL/6J might thus provide an explanation for why pubertal androgens increase the size of cardiomyo- cytes in this strain, but not in C57.YA. Thirteen genes have been reported on the male-specific portion of mouse chrY. The short arm of mouse chrY (Yp, ~2.5 Mb) contains the best characterized sequences to date, i.e. Sry and the 9 following genes: Ube1y1, Zfy1, Zfy2, Jarid1d, Eif2s3y, Uty, Ddx3y, Usp9y and Rbmy1a1 [31]. Three other genes, i.e. Ssty1, Ssty2 and Sly, are present on Page 6 of 11 (page number not for citation purposes)