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

Abstract

Repetitive DNAs in higher eukaryotes have been implicated with genome organization, chromatin conformation and gene regulation. We studied tissueand stage-specific expression of 18 nt long (GATA)_4.5 and (GACA)_4.5 sequences in somatic tissues and germline of normal fertile rat, including samples from individual testicular cell types and those of adult infertile animals. Barring heart, all somatic tissues showed moderate-to-high level of expression with GACA. Amongst testicular cell types, only Sertoli cells showed a strong signal with GACA, and a faint one with GATA probe. RNA samples from different somatic tissues and testis of infertile rats did not show hybridization with these probes. Database search showed 100% sequence homology of (GATA)_4.5 with polymorphic loci in 19 different species, whereas (GACA)_4.5 showed 100% homology with transcribing sequences in 37 different species. In addition to most of the somatic tissues, expression of GATA/GACA elements exclusively in Sertoli cells but not in ovary, suggests their possible involvement in regulation of gonadal activities in the males. This observation is corroborated by the lack of transcription of GATA/GACA repeats in the somatic tissues and testes of infertile Brown Norway rat. The ubiquitous expression of these sequences in somatic and germline tissues of the normal rat but not in any of the tissues of proven infertile rat, indicates their possible regulatory role in the male gonad.