Small heat shock protein (sHSP) mRNA expression in unstressed embryos at approximately 10 somites. A-D: Lateral views. B,D insets: Dorsal views. Anterior is to the left. A: hspb1 is expressed ubiquitously at high levels. B: hspb4 is expressed at low levels throughout the axis. C: hspb5a, which serves as a negative control, is not expressed. D: hspb8 is expressed in the mid-hindbrain boundary, notochord, and yolk syncytial layer. mhb, mid-hindbrain boundary; not, notochord; ysl, yolk syncytial layer. Scale bar = 100μm.

Small heat shock protein (sHSP) expression at 24 hours postfertilization (hpf). A-N: Normal expression (A,C,E,G,I,K,M) and expression after a 1-hr heat shock at 37°C (B,D,F,H,J,L,N). A,B: hspb1 is expressed in somites, mid-hindbrain boundary, lens, heart, and in small patches in both dorsal and ventral forebrain (A) and is ubiquitously upregulated by heat shock (B). C,D: hspb4 is expressed in lens (C) and is slightly upregulated by heat shock (D). E,F: hspb7 is expressed in heart and somites both before (E) and after (F) heat shock. G,H: hspb8 is expressed in somites (G) and is broadly and strongly upregulated by heat shock (H). I,J: hspb9 is expressed in somites (I) and is slightly upregulated by heat shock (J). K,L: hspb11 is expressed in somites (K) and is upregulated by heat shock (L). M,N: hspb12 is expressed specifically in heart before (M) and after (N) heat shock. h, heart; le, lens; mhb, mid-hindbrain boundary; not, notochord; ov, otic vesicle; som, somites; ysl, yolk syncytial layer. Scale bar = 100 μm.

Small heat shock protein (sHSP) expression at 48 hours postfertilization (hpf). A-N: Normal expression (A,C,E,G,I,K,M) and expression after a 1-hr heat shock at 37°C (B,D,F,H,J,L,N). hspb1 is expressed in the mid-hindbrain boundary, lens, heart, and muscles of the head and pharyngeal arches. A: It is also expressed at low levels in rostral somites in the vicinity of the horizontal myoseptum, in the trunk, and caudal spinal cord. B: It is ubiquitously upregulated by heat shock. C,D: hspb4 is expressed in lens (C) and is upregulated by heat shock (D). E,F: hspb7 is expressed in heart both before (E) and after (F) heat shock. G,H: hspb8 is expressed at low levels in somites and muscles of the head and pharyngeal arches (G) and is up-regulated widely by heat shock (H). I,J: hspb9 is expressed at low levels in somites (I) and is upregulated in somites and the dorsal mid- and hindbrains by heat shock (J). K,L: hspb11 is expressed in a few rostral somites (K) and is upregulated in heart, dorsal mid- and hindbrains, and somites (L). M,N: hspb12 is expressed in heart both before (M) and after (N) heat shock. ep, epiphysis; fb, forebrain; h, heart; hb, hindbrain; hyp, hypaxial muscle; le, lens; mb, midbrain; mhb, mid-hindbrain boundary; pa, pharyngeal arch; sc, spinal cord; som, somites. Scale bar = 200μm.

Ventral views of 48 hours postfertilization (hpf) embryos highlighting expression in the head and heart. A: hspb1 is expressed in lens, ocular muscles (for labels, see Fig. 5C), interhyoideus muscle, pharyngeal arch muscle, and the ventricle of the heart, concentrated in the rostral heart tube and atrioventricular canal (see brackets in B). B: hspb7 is expressed in the ventricle of the heart, concentrated in the presumptive outflow tract (arrow) and atrioventricular canal (brackets). C: hspb8 is expressed in ocular muscles not including the medial rectus, and pharyngeal arches. D: hspb12 is expressed in the ventricle of the heart, concentrated in the rostral heart tube and atrioventricular canal. ih, interhyoideus muscle; le, lens; mpa, pharyngeal arch muscle; mr, medial rectus; om, other ocular muscles; pa, pharyngeal arch; v, heart ventricle.

Transverse sections through trunks of 48 hours postfertilization (hpf) embryos highlighting somite and notochord expression. A: hspb1 is expressed in superficial somite, possibly slow twitch muscle fibers, and at low levels in notochord. B: hspb8 is expressed throughout the somite, in lateral spinal cord, in notochord, and in bilateral structures, possibly the pronephric ducts (arrows). C: hspb9 is expressed predominantly in dorsal somite and notochord. D: hspb11 is expressed in the horizontal myoseptum and notochord. hms, horizontal myoseptum; not, notochord; sc, spinal cord; som, somites.

^a hspb1 at 24hpf and 48hpf, all tissues; hspb6 at 48hpf, ubiquitous; hspb8 at 24hpf, primarily eye and otic vesicle; hspb8 at 48hpf, primarily ventral hindbrain and epiphysis
^bExpression detected before/after heat shock; for heat shock data, + does not necessarily imply upregulation, but that gene is expressed at stage and under conditions specified.
^c No expression detected over background.