They did hurt some cats. You cannot do RNA sequencing without looking at tissue samples:

https://www.sciencedirect.com/science/article/pii/S096098222...

"We first performed RNA sequencing (RNA-seq) on skin tissues obtained from the auricles of different adult calico cats (#19, #20, and #22, females, precise ages unknown)"

Auricles are the earlobes.

"We then analyzed multiple skin tissues obtained from a young calico cat that died of unknown causes (#01, female, 3 weeks old) "

"A) Expression levels of ARHGAP36 and IGSF1 in cat auricles (left) and skin tissues (right). RNA-seq data were obtained in small auricle pieces of different coat colors derived from different cats (left) and in skin samples of different coat colors derived from a single calico cat (#01) (right)."

Biological samples Domestic cat blood Inakazu Dog & Cat Kashii Hospital https://www.inakazu-vet.com/ Domestic cat ovary Cat clinics in Japan N/A Domestic cat auricular Cat clinics in Japan N/A