The Transcriptome Response to Retinoic Acid in the Adult Vitamin A Deficient Mouse Testis.

Vitamin A is essential for the normal progression of mammalian spermatogenesis. Vitamin A deficiency (VAD), results in a testis devoid of differentiated germ cells and early markers of meiotic initiation, including STRA8, are absent. Supplementing the VAD testis with vitamin A, in the form of retinoic acid (RA), reinitiates spermatogenesis in a synchronous fashion. VAD male mice were injected with 0.5 mg RA. After 8 and 24 hours, Affymetrix microarray technology was used to examine changes in gene expression. Quantitative real time PCR was used to confirm expression of select genes. Ontology analysis revealed clusters of RA-regulated genes, several exhibiting time dependency. Gene clusters that emerged were associated with: 1) retinol metabolism, 2) chemotaxis, 3) cell cycle control, 4) regulation of transcription, 5) meiosis, and 6) regulation of steroidogenesis. RA-regulated genes were found to be expressed in both germ and somatic cells by utilizing a cell-specific microarray database. Stage specificity of RA-regulated genes was examined by dissecting whole tubules from a vitamin A sufficient adult mouse testis and isolating stage clusters using transillumination. Expression of RA-regulated genes was found in all stages, with subsets of these genes found to be enriched in cluster 2 (stages II-VI), cluster 3 (stages VII-VIII), or cluster 4 (stages IX-XI). This study revealed valuable information on gene regulation by RA and its role in initiating spermatogenesis and begins to reveal the timing of these processes. Future research will focus on specific genes and networks to determine their role in spermatogenesis. This work was supported by NIH Grants HD 10808 and U54 42454 to MDG. (poster)