SPEER—A New Family of Testis-Specific Genes from the Mouse1

Abstract

Differential cloning revealed a partial mRNA sequence expressed in the mouse testis, which on further molecular characterization proved to be a member of a new family of 14 transcribed genes. Six of the genes appear to be expressed pseudogenes. The remainder indicate an open reading frame of approximately 200-220 amino acids encoding proteins with a very high proportion of alpha helical secondary structure, comprising approximately 15% glutamate residues. Because of this property, the family has been named SPErm-associated glutamate (E)-Rich protein (SPEER). Three members were chosen for more detailed characterization: SPEER-1 (pseudogene), SPEER-2, and SPEER-4D. All three are expressed tissue specifically in the testis of mice, with only very weak expression evident in the rat testis but in no other species tested. Using reverse transcription-polymerase chain reaction (RT-PCR), all three transcripts can be detected also in the epididymis, presumably due to the presence of spermatozoa. All three transcripts are expressed to high levels in haploid germ cells at the spermatocyte-spermatid transition. SPEER-1 mRNA is present in the cytoplasm as a sense transcript, SPEER-2 appears to be made mostly as an antisense transcript, whereas SPEER-4D appears to be localized within a subcellular compartment as a conventional sense transcript. Codon usage analysis suggests that all but the pseudogenes can be expressed as protein, confirmed for SPEER-2 and SPEER-4D by in vitro transcription/translation. An antibody raised against a peptide region of SPEER-4D, which probably cross-reacts with other SPEER members, immunohistochemically stains the nuclei of early round spermatids. While there are no true homologies to other proteins in the genome databases, some motifs are present that suggest a relationship to nuclear matrix proteins, implying that the SPEER family is a new group of haploid sperm-specific nuclear factors.

miR-18, a member of Oncomir-1, targets heat shock transcription factor 2 in spermatogenesis

“…To investigate the downstream effects of HSF2 regulation by miR-18, we inhibited miR-18 by T-GIST and analyzed the protein levels of HSF2 as well as the expression of the testis-specific genes Speer4a and Ssty2, known target genes of HSF2 (Åkerfelt et al, 2008). The SPEER proteins are thought to be nuclear matrix proteins involved in reorganization of the postmeiotic nucleus (Spiess et al, 2003), and HSF2 also binds promoters of other members of the family, such as Speer4b/c/d (M. Åkerfelt, unpublished). When miR-18 was inhibited in pachythene spermatocytes, the concentration of HSF2 was increased and expression of Speer4a decreased, suggesting that activation of HSF2 occurs in these cells.…”

Separating derived from ancestral features of mouse and human genomes

“…[27]). For example, a duplication of a fragment of the rodent Dlg5 gene spawned an extended family of testis-specific genes that have become extremely widespread in the mouse and rat genomes [28]. Partial duplications have also occasionally been observed within duplicated genes.…”

Expression of the Insulin-Like Peptide 3 (INSL3) Hormone-Receptor (LGR8) System in the Testis1

“…RT-PCR was carried out for the constitutively expressed transcript for ribosomal protein S27a, exactly as previously described [34]. This gene product has been shown not to vary across a range of tissues and testicular developmental stages [34,35], and care was taken to use a moderately low cycle number so as to maintain amplification within the linear phase. Finally, RNA from some rat cells and tissues was additionally analyzed by quantitative real-time (q) RT-PCR (qRT-PCR) using the primer combination 82-83 (see below).…”