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Figure 1
JNK signaling regulates UV-induced apoptosis in the retina. (A–C) JNK signaling regulates the apoptotic response to UV irradiation in the developing retina. Pupal cases were removed from 24-h-old pupae to expose the developing eye. One of the eyes was subjected to UVC irradiation (5 mJ/cm2), whereas the other eye was shielded. After subsequent incubation at 25°C in the dark, morphological defects are observed in the irradiated eye (A, arrowhead). This phenotype is caused by DNA-damage-induced apoptosis (Jassim et al, 2003). (B, C) DNA damage-induced apoptosis requires JNK signaling. Loss of JNKK (Hep) function (in hemizygotes for hep1) protects eyes from UV-induced apoptosis (B), whereas increased JNK activity owing to loss of the JNK-phosphatase puc results in strongly increased defects (C). puc transcription (an indicator of JNK activation in flies) is induced in response to UV irradiation (D). Left panel: RT–PCR demonstrating rapid induction of puc transcripts in the retina within 1.5 h after UV irradiation; right panel: whole-mount X-gal staining showing activation of the puc gene in the irradiated part of the pupal head (arrowhead). The pucE69 allele contains a JNK-responsive lacZ P-element that serves as JNK reporter in vivo. (E) Quantification of tissue loss in irradiated eyes can be used to quantify the extent of apoptosis in a given genotype. The ratio between the area of left (L, irradiated) and right (R, control) eyes for each head was determined for n=10 heads of each genotype (see Materials and methods for details). Means and standard deviations are shown here. Differences between each group are statistically significant (P<0.001, Student's t-test). Quantification is shown for wild-type flies (OreR), hep1 hemizygous mutant males or homozygous mutant females, hepr75/hep1 transheterozygous females, pucE69 heterozygotes and p535A-1-4 (Rong et al, 2002) homozygotes. A requirement for p53 in protection against UV-induced apoptosis was demonstrated by Jassim et al (2003). P53 mutants are included here as control.
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