Disease relevance of Hsf2

• We report here that hsf2(-/-) mice exhibit multiple phenotypes, including an increased prenatal lethality occurring between mid-gestation to birth, with fetal death probably due to central nervous system defects including collapse of the lateral ventricles and ventricular hemorrhages [1].
• Characterization of constitutive HSF2 DNA-binding activity in mouse embryonal carcinoma cells [2].
• HSF2 activity has been associated with development and differentiation, and the activation properties of HSF2 have been characterized in hemin-treated human K562 erythroleukemia cells [3].
• We show here that disruption of both hsf1 and hsf2 results in a more severe phenotype associated with male sterility due to severe defects in spermatogenesis [4].

High impact information on Hsf2

• Here, we show that Hsf2-/- cerebral cortex displays mispositioning of neurons of superficial layers [5].
• Hsf2-null mice display gametogenesis defects and brain abnormalities characterized by enlarged ventricles [5].
• Hsf2(-/-) females also display hormone response defects, that can be rescued by superovulation treatment, and exhibit abnormal rates of luteinizing hormone receptor mRNAs [6].
• Many developing spermatocytes are eliminated via apoptosis in a stage-specific manner in Hsf2(-/-) males, and pachytene spermatocytes also display structural defects in the synaptonemal complexes between homologous chromosomes [6].
• Hsf2(-/-) females suffer from multiple fertility defects: the production of abnormal eggs, the reduction in ovarian follicle number and the presence of hemorrhagic cystic follicles are consistent with meiotic defects [6].

Biological context of Hsf2

• The temperature threshold of the heat shock response appeared lowered in Hsf2(-/-) MEFS as monitored by the synthesis of heat shock protein HSP70 [7].
• Function and regulation of heat shock factor 2 during mouse embryogenesis [8].
• The detailed analysis of the activity of a luciferase reporter gene under the control of the hsp70.1 promoter, as well as the description of the protein expression patterns of the major heat shock proteins in the central nervous system, show that HSF2 and heat shock protein expression domains do not coincide [8].
• Based on its developmental profile of expression, it was hypothesized that HSF2 may play an essential role in brain and heart development, spermatogenesis, and erythroid differentiation [9].
• Microinjection of MO targeted to hsf2 mRNA (hsf2-MO) did not result in a small eye phenotype in a significant number of embryos [10].

Anatomical context of Hsf2

• In particular, the mouse HSF2 has been found to be active in testis and during preimplantation development [8].
• The disturbances in brain are characterized by the enlargement of lateral and third ventricles and the reduction of hippocampus and striatum, in correlation with HSF2 expression in proliferative cells of the neuroepithelium and in some ependymal cells in adults [6].
• Heat shock factor 2-like activity in mouse blastocysts [11].
• Approximately 30% of hsf2(-/-) animals surviving to adulthood exhibited brain abnormalities characterized by marked dilation of the third and lateral ventricles [1].
• HSF2 is active in restricted cell types during pre- and post-implantation stages of development, and only in male germ cells of adult mice [12].

Associations of Hsf2 with chemical compounds

• The effect of estrogen was observed with both types of heat shock factors (HSF-1 and HSF-2) and occurred at both the mRNA and protein level [13].
• Above a low basal activity of both HSFs, heat shock preferentially activates HSF1, whereas the amino acid analogue azetidine or the proteasome inhibitor MG132 coactivates both HSFs to different levels and hemin preferentially induces HSF2 [14].
• HSF2 DNA-binding activity is induced upon exposure of mammalian cells to the proteasome inhibitors hemin, MG132, and lactacystin, and in the mouse ts85 cell line, which carries a temperature sensitivity mutation in the ubiquitin-activating enzyme (E1) upon shift to the nonpermissive temperature [3].
• Quercetin decreased MG132-induced expression of HSP27, -70, and -90 by more than 70%, and heat shock factors HSF2 and -4 by more than 65% [15].

Physical interactions of Hsf2

• HSF1 is not activated for DNA-binding at unstressed temperature in Hsf2(-/-) MEFS [7].
• We further demonstrate that the constitutive HSF2 DNA-binding activity present in testis is able to interact with promoter sequences of the hsp70.2 gene, a testis-specific member of the hsp70 gene family [16].

Regulatory relationships of Hsf2

• We show that the context of HSF2 synthesis influences its thermosensitivity and DNA-binding properties [17].

Other interactions of Hsf2

• Among the three known mammalian Hsfs, Hsf1 is recognized as the most effective transactivator of Hsps in response to thermal challenge, but the role of Hsf2 in regulation of genes under normal or increased stress conditions in vivo remains elusive [1].
• All three mammalian HSFs (HSF1, HSF2, HSF4) have also been shown to be required for normal mammalian development [10].
• In addition, Hsf2(-/-) MEFS exhibited proliferation defects, altered morphology, remodeling of the fibronectin network [7].
• Immunolocalization studies emphasized the potential biological importance of these observations whereby the increase in uterine HSF-1 and HSF-2 due to estrogen was found to be associated with the endometrium, the primary tissue component which is targeted for estrogen action [13].
• Heat shock response and protein degradation: regulation of HSF2 by the ubiquitin-proteasome pathway [3].

Analytical, diagnostic and therapeutic context of Hsf2

• To study its physiological function in vivo, we generated mice deficient in hsf2 by gene targeting [1].
• Immunoblotting and gene expression microarray analysis of hsf2(-/-) embryos did not reveal reduced Hsp expression levels, indicating that the defects observed in hsf2(-/-) embryos may not result from disruption of Hsp expression [1].
• In addition, disruption of hsf2 resulted in reduced female fertility; however, despite ubiquitous expression in the testes and markedly reduced testis size and sperm count, only a small reduction in fertility was apparent in hsf2(-/-) male mice [1].
• The results of in situ RNA hybridization analysis, RNA filter hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) analysis indicate that HSF2 mRNA expression in testis is subject to developmental and cell type-dependent, as well as stage-dependent, regulation [16].

References