Poly(A) + mRNA is preferred as a template for ... Transfer the retentates containing cDNA to fresh 0.5-ml microcentrifuge tubes, and reduce the volumes to ∼10 μl in a rotary vacuum evaporator.

We used human heart, placenta and testis total RNA (Clontech) and human brain poly(A) + RNA (Clontech) for cDNA synthesis using M-MLV reverse transcriptase (Promega) and random hexamers (Promega).