Expression analysis of alpha keratins and corneous beta-protein genes during embryonic development of Gekko japonicus

Epidermal appendages of birds and reptiles, including claws, feathers, scales, and setae, are primarily composed of alpha keratins (KRTs) and corneous beta-proteins (CBPs). A comprehensive and systematic knowledge of KRTs and CBPs in Schlegel's Japanese gecko (Gekko japonicus) is still lacking. In this study, 22 candidate Gecko japonicus keratin (GjKRT) family genes (12 type I genes, 10 type II genes) were identified in the G. japonicus genome. The majority of GjKRT genes across various subgroups had undergone a prolonged and highly conservative evolutionary process. Through a combination of morphological observation, RNA-seq analysis, and qRT-PCR assay, it was possible to discern the dynamic alterations in the expression of GjKRTs and Gecko japonicus corneous beta-proteins genes (GjCBPs). These findings strongly indicate that GjKRTs gradually accumulate to constitute an α-layer, which is subsequently succeeded by the formation of the corneous beta layer containing GjCBPs at late stages (40-42) of embryonic development. The epidermal appendages in G. japonicus may result from the joint accumulation of KRTs and CBPs, with stages 40-42 being critical for their development. These findings provide novel insights into KRTs and CBPs of G. japonicus and offer a foundation for investigating the functions of GjKRT and GjCBP gene families. Furthermore, this knowledge contributes to unraveling the molecular mechanisms underlying the formation of epidermal appendages in G. japonicus.