Microphthalmia due to p53-mediated apoptosis of anterior lens epithelial cells in mice lacking the CREB-2 transcription factor

Abstract

CREB-2 (also called ATF4, TAXREB67, or C/ATF) is an evolutionarily conserved member of the CREB/ATF family of basic-leucine zipper transcription factors. CREB-2 is expressed ubiquitously in the adult mouse and can function as both a transcriptional activator and a repressor. However, little was understood about the normal function of CREB-2 in mammalian development or organ physiology. In this report we have used gene targeting to produce CREB-2-deficient (CREB-2-/-) mice. Adult CREB-2-/- mice displayed microphthalmia due to the complete absence of a lens. Early embryonic lens development including formation of the optic vesicle, primary lens fibers, and proliferating anterior epithelial cells occurred normally in these mice. However, beginning at ED 14.5 the CREB-2-deficient anterior epithelial lens cells underwent massive and synchronous apoptosis. This was followed by the complete resorption of the developing lens. Consistent with this defect in anterior epithelial cell survival, in situ hybridization studies showed that CREB-2 is expressed at high levels in wild-type anterior epithelial lens cells at ED 14.5. The defect in lens formation seen in the CREB-2-/- mice was not associated with qualitative defects in the expression of Pax-6, alphaA-crystallin, c-maf, or PDGF-R alpha. However, apoptosis of the anterior epithelial cells was mediated by a p53-dependent cell death pathway because ablation of the p53 gene rescued anterior epithelial cell death and allowed the formation of a lens in the absence of CREB-2. Taken together, these results identify CREB-2 as an important regulator of mammalian lens development.

Herp Is Dually Regulated by Both the Endoplasmic Reticulum Stress-specific Branch of the Unfolded Protein Response and a Branch That Is Shared with Other Cellular Stress Pathways

“…This result is different from a previous Western blot study where CHOP protein induction during ER stress was completely abolished in their ATF4-null MEFs (32). The phenotypes of the two ATF4-null mice are very similar with both showing lens development defect and with the majority of homozygotes dying between E14.5 and birth (our ATF4 Ϫ/Ϫ mice birth rate: 6.5% versus Dr. J. M. Leiden, 7.5%) (23,33,34). Combined with the facts that in our ATF4 Ϫ/Ϫ MEFs, 58% of the coding region of ATF4 including the entire basic DNA binding domain and the leucine-zipper dimerization domain was substituted with a neomycin resistance gene, no ATF4 transcript was detected by Northern blotting (Fig.…”

A pharmacoproteomic approach implicates eukaryotic elongation factor 2 kinase in ER stress-induced cell death

“…PERK À/À MEFs, 40 ATF4 À/À MEFs, 47,48 and CHOP À/À MEFs 51 and their respective matched wild-type counterparts were kind gifts of D Ron (Skirball Institute, New York, NY, USA). EIF2a A/A MEFs 42 and matched wild-type eEF-2 phosphorylation and ER stress M Boyce et al counterparts were a kind gift of Randy Kaufman (University of Michigan Medical School, Ann Arbor, MI, USA).…”

Physiological/pathological ramifications of transcription factors in the unfolded protein response

“…Atf4 −/− mice display microphthalmia due to a complete absence of the lens through massive and synchronous apoptosis of the anterior epithelial lens (Hettmann et al 2000). ATF4 is expressed at high levels in the anterior epithelial lens cells at embryonic day 14.5.…”