Fig. 1.

Dlg1 is expressed in the growth plate cartilage. (A) The growth plate cartilage contains four populations of chondrocytes that progressively differentiate along the tissue PDA: the resting (RZ), PZ, PHZ, and HZ zones. (B) Dlg1 is comprised of three PDZ domains and one SH3-GK domain. (C) Western blot probing of chondrocyte lysate with pan-MAGUK antibody showed a band at 140 kDa, which corresponds to Dlg1. n = 5 wild-type chicken humeri. (D–G) Hybridization chain reaction with anti-Dlg1 DNA was performed on frozen sections of chicken humerus and revealed that Dlg1 mRNA (D) was expressed in both cartilage (marked by Col2a1) (E) and PC/PO (marked by Col1a) (F). A merged image is shown in G. n = 7 wild-type chick humeri. (Scale bar: G, 200 μm, applies to D–G.) (H–K) To determine the expression pattern of Dlg1 protein, immunohistochemistry was performed on frozen sections of chicken humerus. Pan-MAGUK antibody, phalloidin, and Hoechst were used to label Dlg1 (H), actin (I), and nuclei (K). As illustrated in the resting zone, Dlg1 was localized on the cell membrane in most cells and was enriched in the middle between two cells. White arrows point to cell–cell contacts with concentrated Dlg1 but without an actin-enriched contractile ring. A merged image is shown in J. n = 5 wild-type chick humeri. (Scale bar: K, 15 μm, applies to H–K.)