GJA1 and in situ carcinoma: It has also been noted that claudin-11, another tight junction protein, has been linked to blood-testis barrier (BTB) formation (Gow et al. 1999) and is overexpressed in men with CIS (Fink et al. 2009) and altered in arrested spermatogenesis (Chiba et al. 2012; Gerber et al. 2014; Haverfield et al. 2013; Hollenbach et al. 2018; McCabe et al. 2016; Stammler et al. 2016), concomitantly with a downregulation of Cx43 (Brehm et al. 2002; Brehm et al. 2006).