Identical sequences but different expression patterns of Hira gene in gynogenetic and gonochoristic crucian carps

A global requirement for the HIR complex in the assembly of chromatin

Due to its extensive length, DNA is packaged into a protective chromatin structure known as the nucleosome. In order to carry out various cellular functions, nucleosomes must be disassembled, allowing access to the underlying DNA, and subsequently reassembled on completion of these processes. The assembly and disassembly of nucleosomes is dependent on the function of histone modifiers, chromatin remodelers and histone chaperones. In this review, we discuss the roles of an evolutionarily conserved histone chaperone known as the HIR/HIRA complex. In S. cerevisiae, the HIR complex is made up of the proteins Hir1, Hir2, Hir3 and Hpc2, which collectively act in transcriptional regulation, elongation, gene silencing, cellular senescence and even aging. This review presents an overview of the role of the HIR complex, in yeast as well as other organisms, in each of these processes, in order to give a better understanding of how nucleosome assembly is imperative for cellular homeostasis and genomic integrity. This article is part of a Special Issue entitled: Histone chaperones and Chromatin assembly.

HIRA is essential for the development of gibel carp

HIRA is one of the chaperones of histone H3.3. Mutation of Hira results in embryonic lethality in mice, suggesting a critical role in embryogenesis. However, Hira-mutated Drosophila may survive to adults, indicating that it is dispensable in Drosophila development. The role of Hira in fish development is unknown. In this study we first investigated the expression of Hira during embryogenesis of gibel carp (Carassius auratus gibelio) by whole-mount in situ hybridization. We found that Hira signal appeared ubiquitously in the early embryos. After gastrulation, it appeared mainly along the anterior-posterior axis, including the tail bud. In hatching period, the signal was detected in head, heart, and the endoderm region on the back of yolk. Then by microinjection with morpholino-HIRA at the beginning of development, we observed delayed gastrulation and abnormal somitogenesis in gibel carp embryos. The HIRA morphants exhibited short trunk, limited yolk extension, and twisted tail. Most of the mutants died during embryogenesis or shortly after hatching. The rest of the HIRA morphants could survive to larvae but with severe defects in organogenesis. These data suggest that HIRA may be essential for the development of gibel carp, and this function is conserved in vertebrates.

Use of heat shock protein mRNA expressions as biomarkers in wild crucian carp for monitoring water quality

In organisms, the production of heat shock proteins (HSPs) can be induced after exposure to various stressors. In the present study, partial cDNA sequences encoding of HSP30, HSP60, HSP70, and HSP90 genes were isolated and sequenced in the crucian carp (Carassius carassius). Next, quantitative real-time reverse transcription PCR (qRT-PCR) assays normalized to beta-actin were developed to quantify HSP mRNA expression. The same methods were used to detect HSP mRNA expression in the wild crucian carp that were collected from the Hun River. In fish located downstream of the river, we found that the levels of HSP70 and HSP30 in the liver and kidney were higher than fish located upstream, and these differences coincided with changes of the water quality. These results suggest that kidney HSP30 and liver HSP70 expression can serve as sensitive biomarkers for the presence of field environmental stressors in wild crucian carp.

Analysis of the toxicogenomic effects of exposure to persistent organic pollutants (POPs) in Slovakian girls: correlations between gene expression and disease risk

The chemical composition of persistent organic pollutants (POPs) in the environment is not uniform throughout the world, and these contaminants contain many structurally different lipophilic compounds. In a well-defined study cohort in the Slovak Republic, the POP chemicals present in the peripheral blood of exposed children were chemically analyzed. The chemical analysis data revealed that the relative concentration and profile of structurally different organic pollutants, including polychlorinated biphenyls (PCBs), 2,2'-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), 2,2'-bis(4-chlorophenyl)-1,1,1-trichloro-ethane (p,p'-DDT), hexachlorobenzene (HCB) and β-hexachlorocyclohexane (β-HCH), may vary from individual to individual, even within the same exposure area. These chemicals can be broadly classified into two groups. The first group, the PCB congeners, primarily originated from industrial compounds and their byproducts. The second group of compounds originated from or was commonly used in the agricultural sector (e.g., DDT, HCB). The objective of this study was to examine the effects of the two POP exposure profiles on gene expression. For the study population, we selected pre-pubertal girls (mean age of 46.2±1.4 months) with high POP concentrations in their blood (>75% tile of total POP) and classified them in the high 'PCB' group when the total PCB concentration was significantly higher than the total concentration of other POP components and in the 'Other Than PCB' (OTP) group, when the total PCB concentration was significantly lower than the concentration of the other major POP constituents. A matched control group of girls (<25% tile of total POP) was selected for comparison purpose (n=5 per group). Our aims were to determine whether there were any common effects of high POP exposure at a toxicogenomic level and to investigate how exposure may affect physiological functions of the children in two different exposure scenarios. Global gene expression analysis using a microarray (Affymetrix Gene Chip Human genome U133 Plus 2.0 Array) platform was conducted on the total RNA of peripheral blood mononuclear cells from the girls. The results were analyzed by Partek GS, Louis, MI, which identified twelve genes (ATAD2B, BIVM, CD96, CXorf39, CYTH1 ETNK1, FAM13A, HIRA, INO80B, ODG1, RAD23B, and TSGA14) and two unidentified probe sets, as regulated differentially in both the PCB and OTP groups against the control group. The qRT-PCR method was used to validate the microarray results. The Ingenuity Pathway Analysis (IPA) software package identified the possible molecular impairments and disease risks associated with each gene set. Connective tissue disorders, genetic disorders, skeletal muscular disorders and neurological diseases were associated with the 12 common genes. The data therefore identified the potential molecular effects of POP exposure on a genomic level. This report underscores the importance of further study to validate the results in a random population and to evaluate the use of the identified genes as biomarkers for POP exposure.

The role of HIRA and maternal histones in sperm nucleus decondensation in the gibel carp and color crucian carp

The histone H3.3 chaperone HIRA is essential for chromatin assembly during male pronucleus formation in Drosophila. However, the role of HIRA during fertilization in vertebrates remains unclear. The gibel carp (Carassius auratus gibelio) is a unique gynogenetic crucian carp (gyno-carp). Heterologous sperm nuclei cannot decondense when incorporated in the egg, thus the eggs produce a clonal lineage of all females by typical gynogenesis. In contrast, after entering the egg, homologous sperm can undergo decondensation and sexual reproduction is activated, which may produce both female and male offspring. Therefore, this fish is a useful model for studying the mechanisms of fertilization. Herein, we first compared HIRA expression during embryogenesis between gyno-carp and the gonochoristic color crucian carp (Carassius auratus; gono-carp). In gono-carp, a dramatic reduction of HIRA protein occurs shortly after fertilization, whereas HIRA protein is consistently expressed during embryogenesis of gyno-carp. Next, we used immunodepletion and an in vitro sperm decondensation system, and found that complete removal of HIRA inhibited sperm decondensation in both of the fish. Immunofluorescence localization showed that in the condensed sperm nuclei of gono-carp incubated in gyno-carp egg extracts, HIRA was detected, but neither the histone H2A variant H2af1o nor acetylated histone H4 was observed. These results suggest that HIRA may be a critical factor required for sperm nucleus decondensation, while the defect in deposition of some maternal histones in the sperm nucleus could be one reason why heterologous sperm cannot decondense in the gibel carp egg.

[The function of histone chaperones during development]

Histone chaperones may participate the decondensation and assembly of chromatins, thus regulate gene expression. They play important roles in almost all developmental processes, such as gametogenesis, fertilization, embryogenesis, growth and senescence. In this review, we used well studied examples to illustrate various functions of histone chaperones during developmental processes. Focus is given to nucleoplasmin, CAF-1, HIRA, ASF1/CIA, and NAP1.