(A) The mouse sterile alpha motif domain 14 (Samd14) locus contains an E-box-GATA composite element (Samd14-Enh sequence highlighted) in intron 1 (Hewitt et al., 2015). The G1E wild type (WT) sequence and enhancer knockout G1E-derived cell clone sequence following TALEN directed enhancer knockout (G1E-ΔEnh) are shown. (B) Western blot of Samd14 and β-actin expression in G1E, WT clone #4 and G1E-ΔEnh clone. (C) Western blot of WT G1E cell lysates following pulldown with anti-Samd14 or anti-rabbit IgG control antibody. Input corresponds to 5% of immunoprecipitation (IP) lysate. (D) Western blot of G1E-ΔEnh cell lysates expressing empty vector (EV), hemagglutinin (HA)-Samd14 or HA-Samd14 Δ SAM following anti-HA pulldown. Blots were stained with anti-Samd14, anti-Capzα1, -Capzα2, -Capzβ, and β-actin antibodies. Input corresponds to 5% of IP lysate. (E) STRING plot depicting known interactions between capping protein (CP) complex subunits CAPZA1, CAPZA2, and CAPZB (https://string-db.org/). (F) Western blot and semi-quantitative densitometry analysis of human CD34+ cell lysates at 4, 8, 12, 14, and 17 days of differentiation stained with anti-Capzβ and anti-Hsc70 antibodies. (G) Quantitation of Capzb, Capza1, and Capza2 mRNA transcript levels in fluorescence-activated cell sorting (FACS) purified mouse bone marrow-derived hematopoietic cells. . Data from RNA-sequencing in Lara-Astiaso et al., 2014. (H) Quantitation of CAPZB, CAPZA1, CAPZA2, and α-adducin (ADD1) protein copies per cell (Gautier et al., 2016). Relative levels measured by quantitative mass spectrometry to determine absolute protein levels in human erythroid progenitors throughout differentiation stages. Prog1-Band3-CD71medGPA-, Prog2- Band3-CD71highGPA-, ProE- Band3-CD71highGPAlow, Baso1- Band3lowCD71highGPAmed, Baso2- Band3medCD71highGPAhighCD49dhigh, Poly- Band3medCD71highGPAhighCD49dmed, and Ortho-Band3highCD71medGPAhigh. MEP: megakaryocyte erythroid progenitor; EryA: Ter119+CD71+FSChigh; EryB: Ter119+CD71+FSClow.