Abundant expression of SPARC, birc2 and boca mRNAs in goldfish scale

Abstract

The existence of scales in teleost is related to the protective functions of the vertebrate integument and each scale is considered to be a counterpart of hair and/or nail. However, the scales can contain about 20% of the total body Ca so that they also appear to represent an internal Ca reservoir. Thus, in order to confirm whether scales are available for calcified tissue research or keratinized tissue research, characteristics of cells in the scale were examined by identifying differentially expressed genes. Subtraction cloning was subjected to scale ‐ gill (SG) and gill ‐ scale (GS). Six clones from SG and 4 from GS were isolated. Among them, SG1, SG2, and SG3 showed the high homology to SPARC, baculoviral IAP repeat containing 2 (birc2), and bcl2‐related ovarian killer a (boka), respectively. In situ hybridization confirmed birc2 and boca expression in flat cells along the ridge. Birc2 also expressed in large cells between the ridges. SPARC expressed in flat and small cells between the ridges. Although all the cells in the scale were designated as scleroblasts, there were several types of cells with different gene expression. Co‐expression of birc2 and boka along the ridge suggested that anti‐apoptotic mechanism worked to maintain the ridges. Since the cells did not always express SPARC, Ca homeostasis and/or osteocytic manifestation seemed to be maintained by the limited number of the cells.