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. 2015 Oct 5;1:15018. doi: 10.1038/cddiscovery.2015.18

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Copyright © 2015 Cell Death Differentiation Association

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ERBB-family signaling molecules in rat testis cells. (a) Polypeptides in the EGF super-family signal by activating ERBB-family transmembrane receptor tyrosine kinases. ERBB1 is a receptor for ‘classical’ low molecular weight EGF-like peptides. ERBB2 is the primary transducer for ligand-bound ERBB1, ERBB3 and ERBB4. ERBB2’s extracellular domain does not bind known ligands. ERBB3 is a receptor for Neuregulin-1 (NRG1), NRG2 and Neuroglycan-C (CSPG5). Ligand bound ERBB3 displays poor kinase activity and signals most effectively as a heteromer with ERBB1, ERBB2 and/or ERBB4. ERBB4 is a receptor for NRG1, NRG2, NRG3 and NRG4 plus other EGF-like peptides*. (b) Western blotting analysis of ERBB-family proteins in fractions of testis cells from 23-day-old rats. Lysates of type A spermatogonia after proliferating for ~180 days/15 passages in culture (SgL), freshly isolated laminin-binding type A spermatogonia (Sg), laminin non-binding spermatogenic cells (Scy), tubular somatic cells (SC), interstitial somatic cells (IC), MCF7 human mammary gland cells (MCF) and COS7 monkey kidney cells (COS). Arrowheads: ERBBs 1–4 (~185 kDa), RET (~155 and 170 kDa) and TUBA1a (~55 kDa). (c) Relative abundance (qtPCR) of ERBB-family transcripts in testis cells isolated from 23-day-old rats (n=cells from three different rats; ±S.E.M.). Spermatogonia (Sg), Spermatocytes (Scy; differentiating spermatogonia/early spermatocytes), Tubular somatic cells (SC) and Interstitial somatic cells (IC) are cell types described in panel (b). (d) Testis cross-section from 26-day-old tgGCS-EGFP transgenic rats labeled with anti-ERBB2 (Red) overlaying EGFP fluorescence from germ cells (green). Note, cytoplasmic ERBB2 labeling in germ cells resembling differentiating spermatogonia (white arrows) and spermatocytes (yellow arrow). Scale, 40 μm. (e) Rat seminiferous tubule whole mount from 24-day-old wild-type rat labeled using antibodies to ERBB2 (Red) and ZBTB16 (Green). Scale, 20 μm. Note: nuclear ZBTB16 labeling is more robust in ERBB2-dim spermatogonia (cyan arrows), compared with ERBB2-bright spermatogenic cells (white arrows). (f) Rat seminiferous tubule whole mount from a 24-day-old wild-type rat labeled with antibodies to ERBB2 (Red) and phospho-Histone-3 (pH3, Green). Scale, 40 μm. Note: nuclear pH3 in large mitotic ERBB2⁺ syncytia.