To further investigate the reasons underlying the reduced EP and deafness in the Spns2 tm1a/tm1a mice, we analysed expression of some key proteins involved in normal EP formation and maintenance by immunofluorescence labelling, including Kir4.1 (Kcnj10), Kv7.1 (Kcnq1), Cx26 (Gjb2), Cx30 (Gjb6), Na+, K+-ATPase (Atp1a1), NKCC1 (Slc12a2) and ZO-1 (Tjp1). This evidence concerns the gene GJB2 and deafness.