GATA/GACA repeat sequences are transcribed in the normal fertile rat Rattus norvegicus, but not in the infertile ones

Repetitive DNAs in higher eukaryotes have been implicated with genome organ ization, chromatin conformation and gene regulation. We studied tissue- and stage-specific expression of 18 nt long (GATA)(4.5) and (GACA)(4.5) sequen ces in somatic tissues and germline of normal fertile rat, including sample s from individual testicular cell types and those of adult infertile animal s. Barring heart, all somatic tissues showed moderate-to-high level of expr ession with GACA. Amongst testicular cell types, only Sertoli cells showed a strong signal with GACA, and a faint one with GATA probe. RNA samples fro m different somatic tissues and testis of infertile rats did not show hybri dization with these probes. Database search showed 100% sequence homology o f (GATA)(4.5) with polymorphic loci in 19 different species, whereas (GACA) (4.5) showed 100% homology with transcribing sequences in 37 different spec ies. In addition to most of the somatic tissues, expression of GATA/GACA el ements exclusively in Sertoli cells but not in ovary, suggests their possib le involvement in regulation of gonadal activities in the males. This obser vation is corroborated by the lack of transcription of GATA/GACA repeats in the somatic tissues and testes of infertile Brown Norway rat. The ubiquito us expression of these sequences in somatic and germline tissues of the nor mal rat but not in any of the tissues of proven infertile rat, indicates th eir possible regulatory role in the male gonad.