Efficient DNA/RNA extraction from tarsal plates by SK mill, a freeze-crush apparatus

The tarsal plate is an eyelid tissue that maintains lid structure from inside the upper/lower eyelids, and it surrounds the meibomian glands and supports their unique secretion mechanism. Sebaceous carcinoma, a malignant eyelid tumour, can sometimes develop from the meibomian glands and is usually excised together with the tarsal plate during surgery, so the tarsal plate serves as a control research tissue. However, since the plate is thick, hard and heterogeneous with few cells, obtaining enough genomic DNA and/or total RNA is often difficult. Therefore, we attempted to establish an efficient protocol to obtain DNA and RNA simultaneously by comparing the combinations of homogenization (mortar/pestle, pellet pestle or SK mill) and purification (organic solvent or spin column) methods using rabbit tarsal plates. Based on the yield, quality and hands-on time, the SK mill and spin column was found to be the most efficient combination. We then applied the established protocol to extract DNA/RNA from six human tarsal-plate samples and succeeded in generating high-quality exome and transcriptome datasets via a next-generation sequencer with sufficient coverage and meibomian gland-specific expression of representative genes, respectively. Our new findings will provide ideal reference data for future genetic and gene-expression studies of sebaceous carcinoma.