Spatial and temporal activity of the αB‐crystallin/small heat shock protein gene promoter in transgenic mice

In order to study the spatial and temporal activity of the mouse αB‐crystallin/small heat shock gene promoter during embryogenesis, we generated mice harboring a transgene consisting of approximately 4 kbp of αB‐crystallin promoter sequence fused to the Escherichia coli lacZ reporter gene. β‐galactosidase activity was first observed in the heart rudiment of 8.5 days post coitum (d.p.c.) embryos. An identical expression pattern was obtained for the endogenous αB‐crystallin gene by whole mount in situ hybridization. At 9.5 d.p.c., β‐galactosidase activity was detected in the lens placode, in the myotome of the somites, in Rathke's pouch (future anterior pituitary), and in some regions of oral ectoderm. We also examined the stress inducibility of the αB‐crystallin promoter in vivo. Injection of sodium arsenite into mice resulted in increased endogenous αB‐crystallin expression in the adrenal gland and possibly the liver. Our results indicate that visualization of β‐galactosidase activity provides an accurate reflection of endogenous αB‐crystallin expression and demonstrate that the complex developmental pattern of mouse αB‐crystallin gene expression is regulated at the transcriptional level. This expression pattern, coupled with the present literature which addresses functions of the protein, suggests a role for the αB‐crystallin/small heat shock protein in intermediate filament turnover and cellular remodeling which occur during normal development and differentiation. © 1996 Wiley‐Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.