(A) Amino acid sequence alignment of SsAqp1ab2-WT, SsAqp1ab2_v1 and SsAqp1ab2_v2 splice forms highlighting the sequences employed for the production of the sole-specific Aqp1ab2 and Aqp1ab2_v1 antibodies (α-Aqp1ab2-Nt and α-Aqp1ab2_v1, in red and blue color, respectively). The N- and C-termini of the WT channel, the six transmembrane helices (TM1-TM6) and the two conserved NPA motifs are also indicated. (B) Immunoblots of X. laevis oocytes injected with water or expressing Aqp1ab2-WT, SsAqp1ab2_v1 or SsAqp1ab2_v2 and probed with the α-Aqp1ab2-Nt or α-Aqp1ab2_v1 antisera separately. (C) Representative photomicrographs of sole ovarian follicles at different developmental stages during oocyte growth and maturation. PG, primary growth stage; CA, cortical alveoli stage. Scale bars, 50 and 250 μm. (D) Immunoblots of Aqp1ab2-WT, Aqp1ab2_v1 and Aqp1ab2_v2 in protein extracts from previtellogenic (Pv), vitellogenic (Vt), hydrating (H) and mature (Mt) follicle-enclosed oocytes, as well as from ovulated oocytes (Ov), using the generated antisera. Alpha tubulin (Tuba) was used as loading control. Duplicated blots (right) were run in parallel and incubated with the primary antibodies preadsorbed by the antigenic peptide to test for specificity. The brackets indicate potential post-translational modifications. (E) Hoechst staining of intact vitellogenic follicles and defolliculated oocytes. Scale bar, 100 μm. (F) Immunoblots of Aqp1ab2 isoforms in total protein extracts from intact or defolliculated vitellogenic follicles (+/- follicle cells, Fc). In B, D and E, the arrowheads indicate aquaporin monomers, whereas the asterisks in D and E indicate cross-reactive polypeptides revealed with the Aqp1ab2_v1 antiserum. In all blots, molecular mass markers (kDa) are on the left.

With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S).

Peer reviewed