c Indian Academy of Sciences

RESEARCH NOTE

Pattern of change in 3 9 and histone deacetylases in development of zebrafish embryo

YANNING LI, JUNXIA WANG, YING XIE, SHUFENG LIU∗ and YE TIAN

Hebei Key Lab of Laboratory Animal, Hebei Medical University, Shijiazhuang 050017, People’s Republic of China

[Li Y., Wang J., Xie Y., Liu S. and Tian Y. 2014 Pattern of change in histone 3 lysine 9 acetylation and histone deacetylases in development of zebrafish embryo. J. Genet. 93, 539–544]

Introduction portion of histone proteins (Li et al. 2004). Histone acety- lation occurs at lysine residues and at positions that are Histone 3 lysine 9 acetylation (H3K9ac) is involved in devel- conserved in eukaryotes, especially for H3 and opment of eukaryotic organisms, and ordered H3K9 deacety- H4 (Ekwall 2005). Kratz et al. (2010) found that histone lation and individual (HDAC) are essen- 3 lysine 9 acetylation (H3K9ac) is generally associated tial during embryogenesis. However, the change patterns of with transcription initiation and unfolded , thereby H3K9ac in development of zebrafish (Danio rerio)embryo positively influencing gene expression. H3K9ac has been have not been reported yet. Although single HDAC has been reported to be enriched in embryonic stem cells and may be studied, the dynamic change of HDAC profile in zebrafish a member of pluripotency (Hezroni et al. 2011). Embryonic embryo development is still unclear. In this study, zebrafish stem cell differentiation and oocyte maturation are accom- embryos were collected at various times after fertilization panied by reduced H3K9ac (Krejcí et al. 2009; Huang et al. and the level of K9-acetylated H3 (H3K9ac) and the expres- 2012). sion profiles of HDAC1, HDAC3, HDAC4 and HDAC6 Histone acetylation is regulated by the opposing histone were evaluated. The results showed that in zebrafish embryo acetyltransferase (HAT) and histone deacetylase (HDAC) development, H3K9ac content significantly decreased, espe- . Although histone acetylation is important for tran- cially at 48 h postfertilization (hpf). The expression pro- scriptional activation, removal of acetyl groups by HDACs files of HDAC1, HDAC3, HDAC4 and HDAC6 changed is equally important for gene transcription regulation (Lin during embryo development, and, moreover, the change in and Dent 2006). The HDAC superfamily is vast and ancient, HDAC3 expression was opposite to the change in level of dating back to prokaryotes (Haberland et al. 2009). The H3K9ac. The level of HDAC3 protein confirmed the expres- most studied HDACs are HDAC1, HDAC3, HDAC4 and sion changes, indicating that HDAC3 may play a role in HDAC6. As HDACs are highly conserved in many organ- H3K9 deacetylation at 48 hpf. These findings revealed the isms, their basic functions can be investigated using less change patterns of H3K9ac and HDACs in zebrafish embryo complex and experimentally tractable model organisms such development, and suggested that H3K9 deacetylation and as zebrafish (Ekwall 2005; Haberland et al. 2009; Sivasubbu HDAC3 might be more important in the middle stages than et al. 2013). other stages of zebrafish embryo development. Lin and Dent (2006) reported that ordered H3K9 deacety- Dynamic programmes of gene expression are required lation and HDACs are required during embryogenesis. for normal development, and histone modifications as epi- Embryonic development depends on HDAC1, which has genetic mechanisms of regulation of gene expression have a ubiquitous pattern of synthesis (Pillai et al. 2004;Noël been investigated in the last few years (Puppin et al. 2011; et al. 2008;Harrisonet al. 2011). HDAC3 is essential for Paradowska et al. 2012). Posttranslational modifications of proper development of many body systems (Farooq et al. histones are emerging as an important step in transcrip- 2008;Bhaskaraet al. 2010;Fenget al. 2011; Sun et al. tional regulation of eukaryotic genes. Particularly important 2011). Stage-specific expression of HDAC4 is seen during is acetylation of specific lysine residues in the N-terminal mouse and zebrafish development (Vega et al. 2004;Zhu et al. 2012). HDAC6 is a key regulator of cytoskele- ∗ ton, cell migration and cell–cell interactions (Dallavalle For correspondence. E-mail: [email protected] Yanning Li and Junxia Wang contributed equally to this work. et al. 2012;Liuet al. 2012). Although individual HDACs Keywords. embryo development; histone 3 lysine 9 acetylation; histone deacetylase; zebrafish.

Journal of Genetics, Vol. 93, No. 2, August 2014 539 Yanning Li et al. have been studied in zebrafish, the expression profiles of antibody (FITC-conjugated secondary antibody, Zhongshan, HDAC1, HDAC3, HDAC4 and HDAC6 in zebrafish embryo China) for 30 min at 37◦C. After incubation with 4,6- development and the question of which HDAC plays a diamidino-2-phenylindole (DAPI) for 10 min, the embryos more decisive role in H3K9 deacetylation have not been were placed on a microscope slide and images were taken clarified. with a laser confocal scanning microscope (Olympus, Tokyo, In this study, zebrafish embryos were collected at 24 hpf, Japan). Controls (PBS instead of the first antibody) were 48 hpf and 72 hpf. The level of H3K9ac and the expres- used. sion profiles of HDAC1, HDAC3, HDAC4 and HDAC6 during embryo development were investigated with confo- cal microscopy, Western blotting and reverse transcription Reverse transcription polymerase chain reaction polymerase chain reaction (RT-PCR). Levels of mRNA of HDAC1, HDAC3, HDAC4 and HDAC6 were quantified by RT-PCR. Total RNA was isolated using Trizol reagent (Takara, Dalian, China) and reverse tran- Materials and methods scribed into cDNA using RevertAid First Strand cDNA syn- thesis kit (Fermentas, Shenzhen, China), followed by PCR Zebrafish amplification using specific primers (table 1). PCR condi- Adult zebrafish were obtained from the Department of Lab- tions were 94◦C for 5 min, followed by 94◦C for 30 s, anneal- oratory Animal Sciences, Hebei Medical University, China, ing temperature (table 1) for 30 s, and 72◦Cfor1minfora and maintained according to standard husbandry protocols total of 28 cycles, and finally 72◦C for 5 min. The amplified (Lawrence 2007;Jiaet al. 2012). Adult fish were fed brine DNA was visualized by electrophoresis on 1.5% agarose gel. ◦ shrimp twice daily. Temperature (28±0.5 C), pH (7.0±0.5), Actin primers were used as internal standard. and light cycle (14 h light / 10 h dark) were electronically controlled and remotely monitored. The night before breed- ing day, a baffle was placed to separate male and female Western blotting zebrafish. The following morning, fertilized eggs were har- vested and incubated in sterile breeding system water at Levels of , H3K9ac and HDAC3 were deter- 28◦C. Embryos were collected at 24, 48 and 72 hpf and used mined by Western blotting, using the protocol previously for further detection. described (Li et al. 2010). Briefly, zebrafish embryos were lysed in lysis buffer (RIPA, Solarbio, Beijing, China) to extract whole protein. Protein content was determined by NanoDrop-1000 (Thermo Scientific, Shanghai, China). Then, Laser confocal microscopy detection samples were separated by SDS-polyacrylamide gel elec- Zebrafish embryos were fixed in 4% paraformaldehyde, trophoresis (PAGE) and transferred to a polyvinylidene flu- washed with phosphate buffer saline (PBS), and incubated oride membrane (Millipore, Shanghai, China). After the with 1% Triton X-100 for 30 min at room temperature. Then, membrane was blocked with 5% skimmed milk in PBS, after washing with PBS, they were blocked with 10% goat anti-H3 (Cell Signaling Technology, Shanghai, China), anti- serum for 1 h and incubated with the primary antibody (anti- H3K9ac (Cell Signaling Technology), anti-HDAC3 antibod- H3K9ac, Cell Signaling Technology, Shanghai, China; anti- ies (GeneTex, Irvine, USA) or anti-beta-actin (Cell Signaling whole HDAC3, GeneTex, Irvine, USA). After again washing Technology) were used. Band intensity was quantified and with PBS, the embryos were incubated with the secondary calculated.

Table 1. Primers used for PCR detection.

Annealing Product Primers temperature (◦C) size (bp)

HDAC1: sense 5TAGCACATAACTTTACTGTCCCATC 3 53 376 Antisense 5 ACAACCACTGAACTCTGGAATAATC 3 HDAC3: sense 5 TCAAGATACACAGGTGCCTCATTAC 3 53 379 Antisense 5 TCTGGTCATCAATGCCATCTCG 3 HDAC4: sense 5 CTCTGCTAAGGAGGAAGGACGGACC 3 55 449 Antisense 5 GAGAGTGTTGTGAGCCGAGCCGC 3 HDAC6: sense 5 GTCCCGTTGTCATCGGATACCAG 3 55 495 Antisense 5 TCCTCTGAGTTTGGGAAGAATGC 3 Actin: sense 5 TTCACCACCACAGCCGAAAGAG 3 55 222 Antisense 5 ACCGCAAGATTCCATACCCAGG 3

540 Journal of Genetics, Vol. 93, No. 2, August 2014 H3K9ac and HDAC in zebrafish embryo development

Statistical analysis (figure 2). H3K9ac level was significantly lower at 48 hpf and 72 hpf (P < 0.01), then at 24 hpf (P < 0.05). At 72 hpf, Statistical analysis of the data was performed using SPSS H3K9ac was significantly higher (P < 0.05) than at 48 hpf. software (IBM, Armonk, USA) and the results are presented The results demonstrate that H3K9ac decreased during as means ± SD. The experiments were repeated twice. One- zebrafish embryo development, especially at 48 hpf. way analysis of variance (ANOVA) was used to find differ- ences, and multiple comparisons were conducted using Dun- nett’s test, and significant differences identified at P < 0.05. Expression profile of HDAC genes in zebrafish embryo development Expression of HDAC1, HDAC3, HDAC4 and HDAC6 genes Results was evaluated by RT-PCR (figure 3,A&B).HDAC3 expres- sion was higher at 48 hpf than at 24 hpf and HDAC1 expres- H3K9ac decreased with zebrafish embryo development sion was significantly lower at 72 hpf (P < 0.05). Expres- H3K9ac was detected by confocal microscopy and quanti- sion of HDAC1 and HDAC3 was lower and that of HDAC6 fied by Western blotting. H3K9ac was widespread through higher at 72 hpf than at 48 hpf (P < 0.05). The results also the embryo at 24 hpf, hardly detected at 48 hpf, and con- show that HDAC1 expression was high at 24 hpf and 48 hpf, centrated in the tail at 72 hpf (figure 1). The results were but decreased at 72 hpf. Expression of HDAC3 increased confirmed by Western blotting and the ratio of H3K9AC to at 48 hpf and decreased at 72 hpf. There was little diffe- H3 was calculated to reflect the relative level of H3K9ac rence in HDAC4 expression, and expression of HDAC6

Figure 1. H3K9ac content detected by confocal assay. (A) H3K9ac was widespread through the embryo at 24 hpf, hardly detected at 48 hpf, and concentrated in the tail at 72 hpf. (B) Negative controls for H3K9ac. No staining was seen in all groups.

Journal of Genetics, Vol. 93, No. 2, August 2014 541 Yanning Li et al.

Figure 2. H3K9ac content detected by Western blotting. Ratio of H3K9ac to H3 was calculated to reflect the relative content of H3K9ac. **P < 0.01 or *P < 0.05 versus 24 hpf; #P < 0.05 versus 48 hpf. Experiments were repeated twice with two samples.

significantly increased at 72 hpf. The differential changes in expression of HDAC genes indicate their distinct roles in zebrafish embryo development. Only the changes in HDAC3 expression were opposite to changes in levels of H3K9ac.

HDAC3 level is higher at 48 hpf in zebrafish embryo The HDAC3 expression results were confirmed by Western blotting and the ratio of HDAC3 enzyme to actin was cal- culated to reflect relative content of HDAC3 (figure 3C). HDAC3 was significantly higher at 48 hpf (P < 0.01) than at 24 hpf, and significantly lower at 72 hpf (P < 0.01) than at 48 hpf. The distribution of HDAC3 was revealed by confo- cal microscopy. As shown in figure 4, conspicuous HDAC3 expanded through the embryo at 48 hpf, while little HDAC3 was seen at 24 hpf and 72 hpf. The results prove that HDAC3 levels is significantly higher at 48 hpf, in accordance with expression changes of its gene.

Discussion Zebrafish is now emerging as a model organism in genetics and developmental biology research (Chatterjee and Lufkin Figure 3. HDAC expression and HDAC3 content. Expressions of 2012;Jiaet al. 2012;Yanget al. 2013). Histone acetyla- HDAC1, HDAC3, HDAC4 and HDAC6 were evaluated by RT-PCR tion processes and HDACs are conserved among species and (A) and calculated (B). (C) HDAC3 content detected by Western the patterns of changes in them in zebrafish will help clarify blotting. Ratio of HDAC3 to actin was calculated to reflect the relative content of HDAC3. **P < 0.01 or *P < 0.05 versus 24 hpf; their role in development. H3K9ac levels have been reported ##P < .01 or #P < 0.05 versus 48 hpf. Experiments were repeated to be high in embryonic stem cells and decrease of H3K9ac twice. level is closely related to differentiation (Krejcí et al. 2009; Hezroni et al. 2011). In this study, we found that H3K9ac and significantly decreased at 72 hpf. The results demon- content was high at 24 hpf, but hardly detected at 48 hpf strated that H3K9ac decreased during zebrafish embryo

542 Journal of Genetics, Vol. 93, No. 2, August 2014 H3K9ac and HDAC in zebrafish embryo development

Figure 4. HDAC3 content detected by confocal assay. (A) As illustrated, HDAC3 was hardly seen at 24 hpf and 72 hpf, but conspicuously increased at 48 hpf. (B) Negative controls for HDAC3. No staining was seen in all the groups. developmental stages and that H3K9 deacetylation might be developmental stages. HDAC6 expression increased more important during the middle stages of zebrafish embryo markedly at 72 hpf, suggesting its role in late development. development. These data reveal the patterns of changes of expression of Ordered H3K9 deacetylation and HDAC enzymes are HDACs genes in zebrafish embryo development. Only the required during embryogenesis (Kageyama et al. 2006;Lin changes in HDAC3 expression were opposite to changes and Dent 2006). in level of H3K9ac. Levels of HDAC3 enzyme confirmed We have shown here that the expression profiles of the expression changes, indicating a more decisive role of HDAC1, HDAC3, HDAC4 and HDAC6 change differentially HDAC3 in H3K9 deacetylation. during zebrzfish embryo development, HDAC1 expression In conclusion, the pattern of changes of H3K9ac and was unaltered at 24 hpf and 48 hpf, but decreased at 72 HDACs in zebrafish embryo development have been shown, hpf, indicating its role in early and middle development. and the results suggest that HDAC3 might be more impor- HDAC3 expression increased at 48 hpf but then decreased at tant in the middle stages of zebrafish embryo middle 72 hpf. These changes in HDAC3 expression are consistent development. with a study of zebrafish heart development, which showed that the heart starts development at 36 hpf and is com- pleted around 55 hpf (Kim et al. 2012). Zebrafish HDAC4 Acknowledgements has been reported to be ubiquitously distributed in various This work was supported by the Research and Development Pro- tissues (Zhu et al. 2012), the present study, revealed gram of Hebei (11277160) and the Construction Program of Hebei no significant change in HDAC4 expression during the Scientific Conditions (11965519D and 12965519D).

Journal of Genetics, Vol. 93, No. 2, August 2014 543 Yanning Li et al.

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Received 7 March 2014, in revised form 17 April 2014; accepted 23 April 2014 Published online: 11 August 2014

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