Molecular analysis of cell type-specific gene expression profile during mouse spermatogenesis by laser microdissection and qRT-PCR

Laser microdissection (LMD) is a selective cell isolation technique that enables the separation of desired homogenous cell subpopulations from complex tissues such as the testes under direct microscopic visualization. The LMD accompanied by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) represents an indispensable tool in quantifying messenger RNA (mRNA) expression among defined cell populations. Gene expression is temporally and spatially regulated at 3 sequential phases of mitotic, meiotic, and postmeiotic stages of spermatogenesis. The present study demonstrates a short modified LMD protocol based upon hematoxylin and eosin (H&E) staining. Stage-specific LMD success was validated by the use of mRNA profiling of "marker genes" which are conserved across species and are known to be differentially expressed during spermatogenesis. Magea4, Hspa2, Cox6b2, Tnp1, Prm1, and Prm2 are used to differentiate among the microdissected cell populations, namely spermatogonia (group I), spermatocytes (group II), round and condensing spermatids (group III), and elongated and condensed spermatids (group IV), respectively. The LMD combined with qRT-PCR is further extended to assess the cell stage-specific distribution of selected stress response genes such as Hsp90aa1, Gpx4, Ucp2, Sod1, and Sod2. The germ cell-specific mRNA profiles are suitably complemented by Western blot of the LMD samples, immunohistochemistry, and confocal localization of the corresponding proteins. The current study suggests that LMD can successfully isolate cell subpopulations from the complex tissues of the testes; and establish cell stage-specific basal expression patterns of selected stress response genes and proteins. It is our hypothesis that the baseline expression of stress response genes will differ by cell stage to create discrete stage-specific vulnerabilities to reproductive toxicants.