Analysis of target genes of the transcription factor CREM during mouse spermatogenesis
The transcription factor CREM belongs to a family of cAMP-responsive nuclear factors. The activator splice-isoform CREMt is uniquely and highly expressed in postmeiotic germ cells during mouse spermiogenesis. Mutant male mice lacking CREM expression are sterile due to lack of maturation of the germ cells. The main task of thesis was to determine the CREMtau downstream target genes, i.e. the genes which are down regulated or not expressed in CREM knockout mice. CREM target genes were analysed by comparing expression levels in testis of CREM-deficient mice and wild-type mice. Using suppression subtractive hybridization we have picked 12,000 clones with sequence fragments of genes expressed stronger in wild type then in the CREM -/- mutant. 956 unique sequences were characterised. Homologies to 158 known mouse genes, 99 other known genes and 296 ESTs were detected. 199 sequences were novel to our knowledge. Expression of these clones was studied by the high-density filter hybridisation with total testicular cDNA. Most of these clones were shown to be expressed in wild type but down regulated in knockout. The spermatogenic stage specific expression profiles were determined by the hybridisation with the cDNA from prepubertal mice at certain stages of spermatogenesis. Several important functional groups of genes like transcription factors, signal transduction proteins, metabolic enzymes and others are coexpressed at the latest stages of spermatogenesis. The mRNAs down regulated in CREM knockout shown to be expressed postmeiotically at the same time as the CREMtau protein. These mRNAs may be defined as the CREMtau target genes (direct or indirect targets). These data contain new information about the gene expression during spermatogenesis. In addition, these data provide preliminary selection of genes to search for direct CREM target genes. These data may be applied for diagnostic and therapeutic intervention in infertile patients with spermatogenetic abnormalities.
Networked Digital Library of Theses and Dissertations