Identification of a new transcript specifically expressed in mouse spermatocytes: mmrp2

Genetic variation in Mon1a affects protein trafficking and modifies macrophage iron loading in mice

We undertook a quantitative trait locus (QTL) analysis in mice to identify modifier genes that might influence the severity of human iron disorders. We identified a strong QTL on mouse chromosome 9 that differentially affected macrophage iron burden in C57BL/10J and SWR/J mice. A C57BL/10J missense allele of an evolutionarily conserved gene, Mon1a, cosegregated with the QTL in congenic mouse lines. We present evidence that Mon1a is involved in trafficking of ferroportin, the major mammalian iron exporter, to the surface of iron-recycling macrophages. Differences in amounts of surface ferroportin correlate with differences in cellular iron content. Mon1a is also important for trafficking of cell-surface and secreted molecules unrelated to iron metabolism, suggesting that it has a fundamental role in the mammalian secretory apparatus.

Identification and characterization of TSAP, a novel gene specifically expressed in testis during spermatogenesis

Through in silico screens, we have identified many previously uncharacterized genes that display similar expression patterns as the mouse Dazl gene, a germ line-specific marker. Here, we report the identification and characterization of one of these novel genes. TSAP gene encodes a protein with 350 amino acids and contains five ankyrin repeats and a PEST sequence motif. Furthermore, we have generated an anti-TSAP antibody and have used three different approaches (RT-PCR, in situ hybridization, and immunohistochemistry) to investigate the expression profiles of TSAP mRNAs and proteins. TSAP is specifically expressed in testis, but not in other tissues such as ovary. Within the testis, TSAP is detected 10 days after birth and is mainly expressed in spermatocytes (ST) and later stage of germ cells, but not in spermatogonia (SG) or sertoli cells. Therefore, TSAP protein likely plays a role in spermatogenesis.

PSM2, a novel protein similar to MCAF2, is involved in the mouse embryonic and adult male gonad development

By screening RIKEN database, we obtained a mouse ovary and uterus derived clone (RIKEN clone ID: 5031403I04). Multiple tissues expression analysis revealed that the clone was specifically expressed in ovary and to a higher extent in testis. It is expressed in early mouse embryo, especially in the embryonic gonad from 11.5 dpc (days post coitus). Furthermore, it is also expressed continuously from newborn testis to adult. Using testis sections in situ hybridization, we found the mRNA was localized to spermatogonia, round spermatids and mainly to spermatocytes. We cloned the cDNA from mouse testis. The gene consists of 10 exons spanning approximately 48 kb on mouse chromosome 16. The cDNA encodes a putative nuclear protein of 319 amino acids containing a coiled-coil motif. The deduced protein has high similarity with human MCAF2 (MBD1-containing chromatin-associated factor 2), so we termed it as PSM2 (protein similar to MCAF2) in this article. We therefore hypothesized that PSM2 might interact with some important partners by the conserved domain and be involved in the transcription modulation during gonad development.

Two novel transcripts encoding two Ankyrin repeat containing proteins have preponderant expression during the mouse spermatogenesis

The clone 4921537P18 expressed preponderantly in mouse testis was identified by screening the Riken cDNA database, and two new full-length isoforms of this clone, which were named gsarp1 (Gonad Specific Ankyrin Repeat (ANK) Protein 1) and gsarp2, were found and isolated from mouse testis in the course of the research. Both of the GSARP1 and GSARP2 contain an ANK region circular composed by seven ANKs, and their structural feature is very similar to that of the IkappaB family proteins, while IkappaB proteins associate with the transcription factor NF-kappaB via their ANKs in the NF-kappaB pathway. We investigated the expression pattern at the mRNA level by Reverse transcription PCR. The gsarp1 has high expression level in mouse testis, while has low expression level in the ovary, and the gsarp2 is only expressed in mouse testis. The gsarp1 and gsarp2 begin to be detected at the early and later pachytene stage of meiosis separately, while both have high-expression level at the stage of MI and MII. The result of in situ hybridization reveals that the gsarp1 is primarily expressed in spermatocytes, while gsarp2 is expressed in spermatocytes and spermatids. In view of the structural feature and expression pattern of the GSARP1 and GSARP2, we speculate that they may play a certain role in a signal pathway of meiosis.