Transcriptional regulation of GFAP : effects of TATA box mutation

The gene encoding glial fibrillary acidic protein (GFAP) is activated early in astrocyte development, and is strongly pregulated during the reactive gliosis that occurs in response to almost any CNS injury. The strong astrocyte-specificity of its expression has led to the GFAP promoter being used in multiple transgenic studies targeting astrocytes. However, almost nothing is known about the functioning of its regulatory elements in vivo. A striking feature is that its TATA box sequence, CATAAA, differs from the consensus TATAAA. A cytosine rarely initiates this sequence, being present in less than 4% of eukaryotic promoters. Numerous comparative in vitro transcription studies have shown the CATAAA sequence to be 2- to 8-fold less efficient than TATAAA. In addition, cell transfection experiments have suggested that CATAAA differs from TATAAA in its interaction with upstream regulatory elements, and may play a role in cell-specificity. Thus conversion of the GFAP CATAAA to TATAAA may both produce a promoter with enhanced activity for transgenic research, and also provide information about the mechanism of its cell specificity. To our knowledge the conversion of a CATAAA to TATAAA has never been tested in an animal. To accomplish this, we have engineered this change into a construct in which the commonly used human 2.2kb GFAP promoter drives expression of the nuclear-targeted lacZ reporter. Transgenic mice are presently being produced for analysis. Supported by NINDS grant R01NS39055 and MRRC grant P30HD38985.