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Fig. 5 lamb1a mutants exhibit aberrant turbulent flow sensing. (A-F) mRNA in situ hybridisation analysis of lamb1b expression at 30 hpf in sibling (A-C) and lamb1aΔ25 mutant embryos (D-F), either uninjected (A,D), injected with a tp53 MO (B,E) or injected with a tp53 MO+tnnt2a MO (C,F). lamb1b is expressed predominantly in the ventricle/arterial pole of the heart tube endocardium in sibling uninjected (n=39/45) and control tp53 MO-injected embryos (n=43/46) at 30 hpf (arrowheads in A,B), but is lost in embryos injected with tnnt2a MO (C; n=35/40). lamb1b expression is upregulated throughout the endocardium in uninjected (n=23/23) and control tp53 MO-injected lamb1aΔ25 mutants (n=24/28) at 30 hpf (black lines; D,E) compared with sibling controls (arrowheads in A,B). Endocardial lamb1b expression is reduced in lamb1aΔ25 mutants injected with tnnt2a MO (F; n=24/28) compared with control lamb1aΔ25 mutants (D,E). (G-L) mRNA in situ hybridisation analysis of klf2a expression at 30 hpf in siblings (G-I) and lamb1aΔ25 mutants (J-L), either uninjected (G,J), injected with a tp53 MO (H,I) or with a tp53 MO+tnnt2a MO (I,L). klf2a is expressed at low levels throughout the endocardium, with elevated expression at the arterial pole in sibling uninjected (n=42/43) and control tp53 MO-injected (n=37/39) embryos at 30 hpf (arrowheads in G,H), but is lost in embryos injected with tnnt2a MO (I; n=31/49). klf2a expression is upregulated particularly at the venous pole and atrium of lamb1aΔ25 uninjected (n=23/25) and control tp53 MO-injected mutant embryos (n=18/18) at 30 hpf (black lines; J,K) compared with sibling controls (arrowheads in G,H). Endocardial klf2a expression is reduced in lamb1aΔ25 mutants injected with tnnt2a MO (L, n=20/22) compared with control lamb1aΔ25 mutants (J,K). Scale bars: 50 μm