Figure 7. Heterozygous loss of svep1 exacerbates the PL phenotype in tie1 mutants, indicating genetic interaction between svep1 and tie1.

(A–G) Confocal images of blood and lymphatic vasculature in the trunk of 2-dpf-old embryos derived from svep1; tie1 double heterozygous fish, showing severely reduced PL numbers in svep1; tie1 double mutants and significant decrease of PL cell numbers in svep1+/−; tie1−/− compared to svep1+/+; tie1−/− (**p = 0.0012). (H) Quantification of PL cell numbers at 2 dpf using Mann–Whitney test (siblings: n = 45; svep1+/−; tie1+/−: n = 45; svep1−/−; tie1+/+: n = 13; svep1+/+; tie1−/−: n = 15; svep1−/−; tie1+/−: n = 20; svep1+/−; tie1−/−: n = 21; svep1−/−; tie1−/−: n = 11). Scale bar = 100 µm. Values are presented as means ± standard deviation (SD), ****p < 0.0001, ***p = 0.007, *p = 0.0163, ns = not significant. dpf, days post-fertilization; PL, parachordal lymphangioblast.

Figure 7—figure supplement 1. svep1; tie1 double heterozygouse embryos show normal BLECs and facial lymphatics.

flt4:mCitrine; flt1:tdTomato positive dorsal head vasculature in (A) siblings and (B) svep1+/−; tie1+/− embryos at 3 dpf (dorsal view). svep1+/−; tie1+/− embryos (n = 9) show normal amount of BLECs. Scale bar = 100 µm. Facial lymphatics at 3 dpf in flt4:mCitrine positive (D) svep1+/−; tie1+/− embryos (n = 6) and in (C) siblings (n = 7) (lateral view). Arrowheads point to BLECs in (A, B) and to FCLV in (C, D). Scale bar = 100 µm. BLEC, brain lymphatic endothelial cell; dpf, days post-fertilization; FCLV, facial collecting lymphatic vessel.

Figure 7—figure supplement 2. tie1 expression is not altered in svep1 mutants.

In situ hybridization of tie1 in sibling (n = 14) (A, B) and svep1 mutants (n = 6) (C, D) at 24 hpf. Images have been assembled from individual pictures to ensure proper focus of all areas. (B and D) are magnifications of boxed area in (A and C), respectively. Scale bar = 100 µm. hpf, hours post-fertilization.