Cx30 homozygous knockout-LacZ mice (Gjb6tm1Kwi/Gjb6tm1Kwi; MGI:2447863; EM:00323), hereafter abbreviated as Cx30−/−, are a model for humans in which large deletions in the DFNB1 locus lead to downregulation of both GJB2/CX26 and GJB6/CX30 and profound deafness. The gene discussed is GJB2; the disease is deafness.