Ultrastructural localization of hair keratin homologs in the claw of the lizard <i>Anolis carolinensis</i>

The study investigated the presence and localization of hair keratin homologs in the claws of the lizard Anolis carolinensis. It was found that two hair keratin homologs, hard acid keratin 1 (HA1) and hard basic keratin 1 (HB1), were expressed in the upper and precorneous layers of the claw, but absent in the basal and lower spinosus layers. Immunogold labeling and electron microscopy revealed that these keratins were loosely associated with filament structures, forming a fibrous framework similar to that of beta-keratins. This suggested a potential interaction between alpha- and beta-keratins during claw morphogenesis, drawing parallels between lizard claws and mammalian hard epidermal appendages.