A 252 bp upstream region of the rat spermatocyte-specific hst70 gene is sufficient to promote expression of the hst70-CAT hybrid gene in testis and brain of transgenic mice

The Role of Shcbp1 in Signaling and Disease

Src homolog and collagen homolog (Shc) proteins have been identified as adapter proteins associated with cell surface receptors and have been shown to play important roles in signaling and disease. Shcbp1 acts as a Shc SH2-domain binding protein 1 and is involved in the regulation of signaling pathways, such as FGF, NF-κB, MAPK/ERK, PI3K/AKT, TGF-β1/Smad and β -catenin signaling. Shcbp1 participates in T cell development, the regulation of downstream signal transduction pathways, and cytokinesis during mitosis and meiosis. In addition, Shcbp1 has been demonstrated to correlate with Burkitt-like lymphoma, breast cancer, lung cancer, gliomas, synovial sarcoma, human hepatocellular carcinoma and other diseases. Shcbp1 may play an important role in tumorigenesis and progression. Accordingly, recent studies are reviewed herein to discuss and interpret the role of Shcbp1 in normal cell proliferation and differentiation, tumorigenesis and progression, as well as its interactions with proteins.

Expression, function, and regulation of the testis-enriched heat shock HSPA2 gene in rodents and humans

The HSPA2 gene is a poorly characterized member of the HSPA (HSP70) family. HSPA2 was originally described as testis-specific and expressed at the highest level in pachytene spermatocytes of rodents, the expression of which is not induced by heat shock. HSPA2 is crucial for male fertility. However, recent advances have shown that HSPA2 is expressed in various tumors and in certain types of somatic tissues. In this review, we summarize the current knowledge on the HSPA2 expression pattern, including information on transcriptional, translational, posttranslational, and epigenetic mechanisms which regulate HSPA2 expression. We also present and discuss the current views concerning the functions of the HSPA2 protein in spermatogenetic, somatic, and cancer cells. The knowledge of the properties of HSPA2, although limited, shows this protein as a unique member of the HSPA family. However, understanding whether this protein could become a relevant cancer biomarker or a therapeutically applicable target requires extensive further studies.

Differential expression of HSPA1 and HSPA2 proteins in human tissues; tissue microarray-based immunohistochemical study

In the present study we determined the expression pattern of HSPA1 and HSPA2 proteins in various normal human tissues by tissue-microarray based immunohistochemical analysis. Both proteins belong to the HSPA (HSP70) family of heat shock proteins. The HSPA2 is encoded by the gene originally defined as testis-specific, while HSPA1 is encoded by the stress-inducible genes (HSPA1A and HSPA1B). Our study revealed that both proteins are expressed only in some tissues from the 24 ones examined. HSPA2 was detected in adrenal gland, bronchus, cerebellum, cerebrum, colon, esophagus, kidney, skin, small intestine, stomach and testis, but not in adipose tissue, bladder, breast, cardiac muscle, diaphragm, liver, lung, lymph node, pancreas, prostate, skeletal muscle, spleen, thyroid. Expression of HSPA1 was detected in adrenal gland, bladder, breast, bronchus, cardiac muscle, esophagus, kidney, prostate, skin, but not in other tissues examined. Moreover, HSPA2 and HSPA1 proteins were found to be expressed in a cell-type-specific manner. The most pronounced cell-type expression pattern was found for HSPA2 protein. In the case of stratified squamous epithelia of the skin and esophagus, as well as in ciliated pseudostratified columnar epithelium lining respiratory tract, the HSPA2 positive cells were located in the basal layer. In the colon, small intestine and bronchus epithelia HSPA2 was detected in goblet cells. In adrenal gland cortex HSPA2 expression was limited to cells of zona reticularis. The presented results clearly show that certain human tissues constitutively express varying levels of HSPA1 and HSPA2 proteins in a highly differentiated way. Thus, our study can help designing experimental models suitable for cell- and tissue-type-specific functional differences between HSPA2 and HSPA1 proteins in human tissues.

Heat shock protein 2 promoter drives Cre expression in spermatocytes of transgenic mice

We generated transgenic mouse line C57BL/6-Tg(Hspa2-cre)1Eddy/J (Hspa2-cre), which expresses cre-recombinase under the control of a 907-bp fragment of the heat shock protein 2 (Hspa2) gene promoter. Transgene expression was determined using Gt(ROSA)26Sor(tm1Sor)/J (ROSA26) and Tg(CAG-Bgeo/GFP)21Lbe/J (Z/EG) reporter strains and RT-PCR and immunohistochemistry assays. Hspa2-cre expression mimicked the spermatogenic cell-specific expression of endogenous HSPA2 within the testis, being first observed in leptotene/zygotene spermatocytes. Expression of the transgene also was detected at restricted sites in the brain, as occurs for endogenous HSPA2. Although the results of mating the Hspa2-cre mice to mice with a floxed Cdc2a allele indicated that some expression of the transgene occurs during embryogenesis, the Hspa2-cre mice provide a valuable new tool for assessing the roles of genes during and after meiotic prophase in pachytene spermatocytes.

The expression pattern of the 70-kDa heat shock protein Hspa2 in mouse tissues

The highest expression level of a 70-kDa heat shock protein family member Hspa2 is detected specifically in meiotic and post-meiotic male germ cells, which is reflected by original name of this protein, i.e., testis-specific Hsp70. However, this chaperon protein could be also detected in certain somatic tissues. Here, the extra-testicular expression pattern of mouse Hspa2 was analyzed. We found expression of Hspa2 in various epithelial cells including lining of bronchioles and oviduct, columnar epithelium of endometrium, epithelial reticular cells of thymus, transitional epithelium of the urinary bladder, or ependymal cells covering walls of the ventricular system of the brain. Surprisingly, Hspa2 was a putative secretory protein in intestine, endometrial glands and subcommissural organ. Hspa2 was detected in central and peripheral nervous system: in neuron's bodies and fiber tracts, in the subventricular zone of the lateral ventricles, in the dentate gyrus of the hippocampus, in enteric ganglia of the gastrointestinal tract. Hspa2 was also expressed in smooth muscles and at low level in immune system (in germinal centers associated with B-lymphocyte production). In addition to somatic tissues listed above, Hspa2 was detected in oocytes arrested at diplotene of the first meiotic division.

The HspA2 protein localizes in nucleoli and centrosomes of heat shocked cancer cells

The human HSPA2 gene, which belongs to the HSP70 family of heat shock genes, is a counterpart of rodent testis-specific HspA2 gene. Rodent genes are expressed mainly in pachytene spermatocytes, while transcripts of human HSPA2 gene have been detected in various normal somatic tissues, albeit translation of the messenger RNA into corresponding protein has not been yet unambiguously demonstrated, except for several cancer cell lines. The aim of our work, a first step in search for HspA2 function in cancer cells, was to establish its intracellular localization at physiological temperature and during heat shock. First, we used qRT-PCR and a highly specific antibody to select cell lines with the highest expression of the HspA2 protein, which turned out to be A549 and NCI-H1299 lines originating from non-small cell lung carcinoma (NSCLC). Significant expression of the HspA2 was also detected by immunohistochemistry in primary NSCLC specimens. Intracellular localization of the HspA2 was studied using both the specific anti-HspA2 polyclonal antibody and transfection of cells with fusion proteins HspA2-EGFP and mRFP-HspA2. We found that, at physiological temperature, the HspA2 was localized primarily in cytoplasm whereas, during heat shock, localization shifted to nucleus and nucleoli. Moreover, we demonstrate that in heat-shocked cells HspA2 accumulated in centrosomes. Our results suggest that the HspA2, like Hsp70 protein, can be involved in protecting nucleoli and centrosomes integrity in cancer cells subjected to heat shock and, possibly, other cellular stressors.

Heat shock transcription factor 1 down-regulates spermatocyte-specific 70 kDa heat shock protein expression prior to the induction of apoptosis in mouse testes

Expression of constitutively active heat shock transcription factor 1 (HSF1) in mouse spermatocytes induces apoptosis and leads to male infertility. We report here that prior to the onset of massive apoptosis caused by expression of active HSF1 in spermatocytes a marked reduction in spermatocyte-specific Hsp70.2 mRNA and protein levels occurs. In addition, HSP70.2 protein relocalizes from a predominant cytoplasmic to a nuclear position in developing spermatocytes that express active HSF1. Later in the developmental stages, cells undergoing HSF1-induced apoptosis essentially lack the HSP70.2 protein. The down-regulation of Hsp70.2 gene expression by HSF1 is paradoxical because HSF1 is the prototypical activator of HSP genes. Furthermore, HSF1-mediated repression neither involved a heat shock element (HSE)-like sequence adjacent to the Hsp70.2 gene nor were Hsp70.2 promoter sequences associated directly with HSF1. Interestingly, other spermatocyte- and spermatid-specific transcripts are also down-regulated in testes of transgenic mice expressing active HSF1, suggesting involvement of a putative HSF1-dependent block of development of spermatogenic cells. Importantly however, transcription of the Hsp70.2 gene is down-regulated in testes of wild-type mice subjected to a hyperthermia that induces transient activation of HSF1, indicating that the spermatocyte-specific activity of HSF1 might misdirect a network of transcription factors required for proper regulation of Hsp70.2.

Promoter of the heat shock testis-specific Hsp70.2/Hst70 gene is active in nervous system during embryonic development of mice

The Hsp70.2/Hst70 gene is a unique member of the 70 kDa heat shock proteins multigene family whose activity is regulated developmentally; in adult mice and rats its expression is restricted mostly to meiotic and postmeiotic male germ cells. In aim to analyze activity of the Hsp70.2/Hst70 promoter in developing embryos we have constructed transgenic mice expressing EGFP reporter gene under control of the rat Hst70 promoter. The appearance of EGFP fluorescence coincides with series of major developmental events, such as extra-embryonic membranes formation, axial rotation, formation of neural tube and the primordium of central nervous system, formation of differentiated somites, extensive remodeling of the heart, development of fingers and toes, and sensory organs formation. Activity of the Hst70 promoter localizes mostly inside nervous system indicating the role of Hsp70.2/Hst70 gene in development of this system.

Spermatocyte-specific expression of constitutively active heat shock factor 1 induces HSP70i-resistant apoptosis in male germ cells

Spermatocytes, the most sensitive male germ cells to heat-induced apoptosis, do not respond to hyperthermia by inducing heat shock proteins (HSPs), including HSP70i, which has been previously shown to confer resistance to apoptosis in somatic cells. To dissect the mechanism of heat-induced apoptosis and to determine if we could protect spermatocytes by expressing HSP70i, we engineered transgenic mice that express in spermatocytes constitutively active heat shock transcription factor (HSF)1. Such HSF1 expression did not lead to transcription of inducible Hsp70 genes, but instead induced caspase-dependent apoptosis that mimicked heat shock-induced death of spermatogenic cells. Both mitochondria-dependent and death receptor-dependent pathways appear to be involved in such HSF1-induced apoptosis: the levels of Bcl-2 family proteins became increased, p53 protein accumulated and expression levels of caspase-8 and death-receptor-interacting proteins (including Fas-associated death domain protein and TNF receptor associated death domain protein) became elevated. Surprisingly, the constitutive spermatocyte-specific expression of HSP70i in double-transgenic males did not protect against such HSF1-induced apoptosis.

Location of promoter elements necessary and sufficient to direct testis-specific expression of the Hst70/Hsp70.2 gene

The rat Hst70 gene and its mouse counterpart Hsp70.2 are expressed specifically in pachytene primary spermatocytes and spermatids. Here we demonstrate that a 165 bp fragment of the Hst70 gene promoter, containing the T1 transcription start site region, entire exon 1 and 42 bp 5' region of the intron, is sufficient to drive testis-specific expression of the chloramphenicol acetyltransferase reporter gene in transgenic mice with the same developmentally regulated pattern as the endogenous Hsp70.2 gene. We show further that high-level tissue-specific gene expression requires additional sequences localized upstream of the T2 transcription start site. Electrophoretic mobility-shift assay analysis revealed that only testes of juvenile rats, when Hst70 gene expression is repressed, contain proteins that specifically bind to the Oct (octamer) sequence localized directly downstream of the T1 site.

In vivo electroporation of the testis versus transgenic mice model in functional studies of spermatocyte-specific hst70 gene promoter: A comparative study

To determine whether DNA transfer to mouse testes by in vivo electroporation could be useful method for studying regulatory elements of genes specifically active in spermatocytes first we compared the expression pattern of a construct containing the EGFP reporter gene ligated to a fragment of the heat shock testis-specific hst70 gene promoter, both in testis of transgenic mice and in testis electroporated in vivo. While in transgenic mice the EGFP was expressed in all seminiferous tubules in a cell- and stage-specific manner, in the testes electroporated in vivo only small fraction of cells expressed this marker protein. In order to make a quantitative comparison between the specificity of these two experimental systems we used several vectors containing the CAT gene ligated to fragments of the hst70 gene 5' upstream of DNA sequences which either promoted or did not activate expression of the reporter gene in the testes of transgenic mice. Also, as a reference opposite to spermatogenic cells we examined the expression pattern of the same set of vectors in the rat hepatoma FTO 2B cells. Although electroporated testes retain some spermatocyte-specific features such as the ability to repress promoters which do not contain regulatory elements responsible for testis-specific transcription, several important drawbacks of the method are evident. They include basal activity of constructs which are not transcribed in testes of transgenic mice and low overall transfection efficiency. This may hamper studies in which subtle changes in the expression pattern are under investigation. However, the in vivo electroporation of the testis can be useful for preliminary screening of constructs aimed to study in transgenic mice.

Structure of the 5' region of the Hst70 gene transcription unit: presence of an intron and multiple transcription initiation sites

The rat Hst70 gene and its mouse counterpart Hsp70.2 belong to the family of Hsp70 heat shock genes and are specifically expressed in male germ cells. Previous studies regarding the structure of the 5' region of the transcription unit of these genes as well as localization of the 'cis' elements conferring their testis-specific expression gave contradictory results [Widlak, Markkula, Krawczyk, Kananen and Huhtaniemi (1995) Biochim. Biophys. Acta 1264, 191-200; Dix, Rosario-Herrle, Gotoh, Mori, Goulding, Barret and Eddy (1996) Dev. Biol. 174, 310-321]. In the present paper we solve these controversies and show that the 5' untranslated region (UTR) of the Hst70 gene contains an intron which is localized similar to that of the mouse Hsp70.2 gene. Reverse transcriptase-mediated PCR, Northern blotting and RNase protection analysis revealed that the transcription initiation of both genes starts at two main distant sites, and one of them is localized within the intron. As a result two populations of Hst70 gene transcripts with similar sizes but different 5' UTR structures can be detected in total testicular RNA. Functional analysis of the Hst70 gene promoter in transgenic mice and transient transfection assays proved that the DNA fragment of approx. 360 bp localized upstream of the ATG transcription start codon is the minimal promoter required for testis-specific expression of the HST70/chloramphenicol acetyltransferase transgene. These experiments also suggest that the expression of the gene may depend on 'cis' regulatory elements localized within exon 1 and the intron sequences.

Lessons from knockout and transgenic mice for infertility in men

This review concentrates on the clear cases where knocking out a gene in mice has caused male infertility and thus comes near to proving that the gene plays a role in the development of sperm. Knockout mice have been created with primary defects at every stage of spermatogenesis thus creating a framework for decoding the genetic hierarchy that causes male germ cell differentiation. As well as defining essential genes in vivo experiments have defined promoter and untranslated sequences responsible for the expression of proteins at all the spermatogenic stages. In conclusion knockout mice remain the ultimate test of spermatogenic hypotheses as well as providing detailed information about this complex process.

The main regulatory region in the murine PSP gene is a parotid gland enhancer

The murine PSP gene is expressed at a high-level in the parotid glands. To extend the knowledge of parotid gland expression and develop tools for expression of heterologous proteins in this tissue, the regulation of the PSP gene was studied using transgenic mice. High-level parotid gland expression of the PSP gene was indicated to depend on a novel regulatory region situated between -8.0 and -6.5 kb. Together with previous results this indicates that the main regulatory elements in the PSP gene are situated between -8.0 to -3.1 kb. This region was shown to activate a heterologus SV40 early promoter in the parotid glands of transgenic mice, suggesting that the PSP gene is controlled by enhancer sequences. A novel Psp derived 9.7 kb parotid gland expression cassette, Lama IV, carrying all known regulatory regions in the PSP gene was expressed at high-levels in the parotid glands and should prove highly useful for expression of heterologous proteins in the saliva of transgenic mice.