Spatio-temporal expression patterns of glycine-rich beta proteins and cysteine-rich beta proteins in setae development of Gekko japonicus.

Background: Setae on the pad lamellae of the Japanese gecko Gekko japonicus (Schlegel, 1836), a vital epidermal derivative, are primarily composed of cornified beta-proteins (CBPs) and play a pivotal role in adhesion and climbing. The amino acid composition of CBPs might be a determining factor influencing their functional properties. However, the molecular mechanisms governed by CBP genes with diverse amino acid compositions in setae development remain unexplored.

Results: Based on RNA-seq analyses, this study confirmed that all G. japonicus CBPs (GjCBPs) are involved in setae formation. Cysteine-rich CBPs encoding genes (ge-cprp-17 to ge-cprp-26) and glycine-rich CBPs encoding genes (ge-gprp-17 to ge-gprp-22) were haphazardly selected, with quantitative real-time PCR revealing their expression patterns in embryonic pad lamellae and dorsal epidermis. It is inferred that glycine-rich CBPs are integral to the formation of both dorsal scales and lamellar setae, cysteine-rich CBPs are primarily associated with setae development. Additionally, fluorescence in situ hybridization revealed spatiotemporal differences in the expression of a glycine-rich CBP encoding gene (ge-gprp-19) and a cysteine-rich CBP encoding gene (ge-cprp-17) during dorsal scales and/or lamellar development.

Conclusions: All 66 CBPs are involved in the formation of setae. Glycine-rich CBPs hold a significant role in the development of dorsal scales and lamellar setae, whereas most cysteine-rich CBPs appear to be essential components of G. japonicus setae. Even GjCBPs with similar amino acid compositions may play diverse functions. The clear spatio-temporal expression differences between the glycine-rich and cysteine-rich CBP encoding genes during epidermal scale and/or setae formation were observed. Embryonic developmental stages 39 to 42 emerged as crucial phases for setae development. These findings lay the groundwork for deeper investigation into the function of GjCBPs in the development of G. japonicus setae.