Localization of distant urogenital system-, central nervous system-, and endocardium-specific transcriptional regulatory elements in the GATA-3 locus

We found previously that neither a 6-kbp promoter fragment nor even a 120-k bp yeast artificial chromosome (YAC) containing the whole GATA-3 gene was s ufficient to recapitulate its full transcription pattern during embryonic d evelopment in transgenic mice. In an attempt to further identify tissue-spe cific regulatory elements modulating the dynamic embryonic pattern of the G ATA-3 gene, we have examined the expression of two much larger (540- and 62 5-kbp) GATA-3 YACs in transgenic animals. A lacZ reporter gene was first in serted into both large GATA-3 YACs. The transgenic YAC patterns were then c ompared to those of embryos hearing the identical lacZ insertion in the chr omosomal GATA-3 locus (creating GATA-3/lacZ "knock-ins"). We found that mos t of the YAC expression sites and tissues are directly reflective of the en dogenous pattern, and detailed examination of the integrated YAC transgenes allowed the general localization of a number of very distant transcription al regulatory elements (putative central nervous system-, endocardium-, and urogenital system-specific enhancers). Remarkably, even the 625-kbp GATA-3 YAC, containing approximately 450 kbp and 150 kbp of 5' and 3' flanking se quences, respectively, does not contain the full transcriptional regulatory potential of the endogenous locus and is clearly missing regulatory elemen ts that confer tissue-specific expression to GATA-3 in a subset of neural c rest-derived cell lineages.