Page 54 - 2018_11-Haematologica-web

J. Lian et al.
It is likely that because of the lethality resulting from ALAS1 deficiency, no reported human diseases directly caused by mutations in ALAS1 have been reported so far. Although the Alas1-deficient zebrafish were indistin- guishable on morphology from wild type at embryonic stages, the Alas1-deficient zebrafish are not viable past 8 dpf and showed some morphological defects from 4 dpf onwards, such as delayed disappearance of the yolk sac, abnormal liver, and failed swim bladder formation (data not shown). Thus, the specific functions of ALAS1 in differ- ent tissues and organs remain to be clarified.
Alas1-deficient zebrafish showed impaired heme levels in neutrophils but elevated heme levels in erythrocytes. It is known that in addition to mitochondrial heme synthe- sis within all cells, heme can also be transported in and out of cells from the plasma.11 Intracellular heme levels are tightly controlled through the co-ordination of heme syn- thesis, degradation, and trafficking.35 In this study, we found that the expression of alas2, encoding the other rate-limiting enzyme of heme synthesis, was not changed, while the expressions of heme degradation and trans- porter genes were down-regulated in alas1smu350/smu350 mutants. In Alas1-deficient zebrafish, cellular heme levels were unexpectedly elevated in erythrocytes, partly due to the decrease in heme degradation. The excessive heme could not be effectively used by neutrophils, probably because the heme transport was impaired. Similar to mice,24 the over-produced heme by alas2 in erythrocytes
could not compensate for the function of alas1 in zebrafish, indicating the essential roles of alas1. The feed- back mechanisms for heme homeostasis remain unclear, so future studies will be needed to elucidate the molecular mechanisms of heme metabolisms and trafficking.
Impaired heme biosynthesis or heme deficiency leads to heme-related disorders, such as anemias, acute por- phyrias, and leukemia.11 Acute intermittent porphyria is characterized by the accumulation and/or excretion of excess heme precursors.11 As Alas1 is the key enzyme in heme biosynthesis, repressing Alas1 activity by RNAi is now being used to prevent acute porphyria attacks.45,46 Thus, Alas1-deficient zebrafish may serve as an in vivo animal model for evaluating the risks of therapeutic strategies, since Alas1 deficiency causes neutrophil defects, as well as other potential defects in Alas1-abun- dant tissues. This study may also contribute to the devel- opment of new drugs or treatment strategies for heme- related diseases.
Acknowledgments
We thank Dr. Zilong Wen for sharing the Tg(gata1:DsRed) line and eGFP-labeled E. coli strain XL10.
Funding
This work was supported by the National Natural Science Foundation of China (31471378) and the Team Program of the Guangdong Natural Foundation (2014A030312002).
References
1. Amulic B, Cazalet C, Hayes GL, Metzler KD, Zychlinsky A. Neutrophil function: from mechanisms to disease. Annu Rev Immunol. 2012;30(1):459-489.
2. Odobasic D, Kitching AR, Holdsworth SR. Neutrophil-mediated regulation of innate and adaptive immunity: The role of myeloperoxidase. J Immunol Res. 2016; 2016(6):2349817.
3. Cowland JB, Borregaard N. Granulopoiesis and granules of human neutrophils. Immunol Rev. 2016;273(1):11-28.
4. Levy O. Antimicrobial proteins and pep- tides: anti-infective molecules of mam- malian leukocytes. J Leukoc Biol. 2004; 76(5):909-925.
5. Bennett CM, Kanki JP, Rhodes J, et al. Myelopoiesis in the zebrafish, Danio rerio. Blood. 2001;98(3):643-651.
6. Xu J, Du L, Wen Z. Myelopoiesis during zebrafish early development. J Genet Genomics. 2012;39(9):435-442.
7. Jin H, Huang Z, Chi Y, et al. c-Myb acts in parallel and cooperatively with Cebp1 to regulate neutrophil maturation in zebrafish. Blood. 2016;128(3):415-426.
8. WangK,FangX,MaN,etal. Myeloperoxidase-deficient zebrafish show an augmented inflammatory response to challenge with Candida albicans. Fish Shellfish Immunol. 2015;44(1):109-116.
9. Di Q, Lin Q, Huang Z, et al. Zebrafish nephrosin helps host defence against Escherichia coli infection. Open Biol. 2017; 7(8).
10. Furuyama K, Kaneko K, Vargas PD. Heme as a magnificent molecule with multiple mis-
sions: Heme determines its own fate and governs cellular homeostasis. Tohoku J Exp Med. 2007;213(1):1-16.
11. Tsiftsoglou AS, Tsamadou AI, Papadopoulou LC. Heme as key regulator of major mammalian cellular functions: Molecular, cellular, and pharmacological aspects. Pharmacol Ther. 2006;111(2):327- 345.
12. Yamamoto M, Hayashi N, Kikuchi G. Evidence for the transcriptional inhibition by heme of the synthesis of delta-aminole- vulinate synthase in rat liver. Biochem Biophys Res Commun. 1982;105(3):985- 990.
13. Suzuki H, Tashiro S, Hira S, et al. Heme reg- ulates gene expression by triggering Crm1- dependent nuclear export of Bach1. EMBO J. 2004;23(13):2544-2553.
14. Tahara T, Sun JY, Nakanishi K, et al. Heme positively regulates the expression of beta- globin at the locus control region via the transcriptional factor Bach1 in erythroid cells. J Biol Chem. 2004;279(7):5480-5487.
for heme-dependent degradation of ALAS1 protein as a component of negative feed- back regulation of heme biosynthesis. J Biol Chem. 2016;291(39):20516-20529.
19. Faller M, Matsunaga M, Yin S, Loo JA, Guo F. Heme is involved in microRNA process- ing. Nat Struct Mol Biol. 2007;14(1):23-29.
20. Ferreira GC. Heme biosynthesis: biochem- istry, molecular biology, and relationship to disease. J Bioenerg Biomembr. 1995;27(2):147-150.
21. May A, Bishop DF. The molecular biology and pyridoxine responsiveness of X-linked sideroblastic anaemia. Haematologica. 1998;83(1):56-70.
22. Yamamoto M, Nakajima O. Animal models for X-linked sideroblastic anemia. Int J Hematol. 2000;72(2):157-164.
23. Brownlie A, Donovan A, Pratt SJ, et al. Positional cloning of the zebrafish sauternes gene: a model for congenital sideroblastic anaemia. Nat Genet. 1998; 20(3):244-250.
24. Okano S, Zhou L, Kusaka T, et al. Indispensable function for embryogenesis, expression and regulation of the nonspecific form of the 5-aminolevulinate synthase gene in mouse. Genes Cells. 2010;15(1):77-
15. Yamamoto M, Hayashi N, Kikuchi G. Translational inhibition by heme of the syn-
thesis of hepatic delta-aminolevulinate syn-
thase in a cell-free system. Biochem Biophys 89.
Res Commun. 1983;115(1):225-231.
16. Chen JJ, London IM. Regulation of protein synthesis by heme-regulated eIF-2 alpha kinase. Trends Biochem Sci. 1995;20(3):105-
108.
17. Ishikawa H, Kato M, Hori H, et al.
Involvement of heme regulatory motif in heme-mediated ubiquitination and degrada- tion of IRP2. Mol Cell. 2005;19(2):171-181.
18. Kubota Y, Nomura K, Katoh Y, Yamashita R, Kaneko K, Furuyama K. Novel mechanisms
25. Henry KM, Loynes CA, Whyte MKB, Renshaw SA. Zebrafish as a model for the study of neutrophil biology. J Leukoc Biol. 2013;94(4):633-642.
26. Colucci-Guyon E, Tinevez JY, Renshaw SA, Herbomel P. Strategies of professional phagocytes in vivo: unlike macrophages, neutrophils engulf only surface-associated microbes. J Cell Sci. 2011;124(18):3053- 3059.
27. Wang K, Huang Z, Zhao L, et al. Large-scale
1794
haematologica | 2018; 103(11)