Analysis of Development Edited by Prof Benjamin H Willier, Prof Paul A Weiss and Prof Viktor Hamburger Pp xii + 735 (Philadelphia and London: W B Saunders Company, 1955) 105s

Mechanisms of Development

Unfertilized eggs of Oryzias latipes were artificially inseminated and incubated at 26+/-1 degrees C. Careful observation of the process of embryonic development by light microscopy allowed division of the process into 39 stages based on diagnostic features of the developing embryos. The principal diagnostic features are the number and size of blastomeres, form of the blastoderm, extent of epiboly, development of the central nervous system, number and form of somites, optic and otic development, development of the notochord, heart development, blood circulation, the size and movement of the body, development of the tail, membranous fin (fin fold) development, and development of such viscera as the liver, gallbladder, gut tube, spleen and swim (air) bladder. After hatching, development of the larvae (fry) and young can be divided into six stages based on such diagnostic features as the fins, scales and secondary sexual characteristics.

Stages of Normal Development in the Medaka Oryzias latipes

Stages of normal development in the medaka Oryzias latipes

Evolutionary families of metallopeptidases.

The three-dimensional structures of the zinc endopeptidases human neutrophil collagenase, adamalysin II from rattle snake venom, alkaline proteinase from Pseudomonas aeruginosa, and astacin from crayfish are topologically similar, with respect to a five-stranded beta-sheet and three alpha-helices arranged in typical sequential order. The four proteins exhibit the characteristic consensus motif HEXXHXXGXXH, whose three histidine residues are involved in binding of the catalytically essential zinc ion. Moreover, they all share a conserved methionine residue beneath the active site metal as part of a superimposable "Met-turn." This structural relationship is supported by a sequence alignment performed on the basis of topological equivalence showing faint but distinct sequential similarity. The alkaline proteinase is about equally distant (26% sequence identity) to both human neutrophil collagenase and astacin and a little further away from adamalysin II (17% identity). The pairs astacin/adamalysin II, astacin/human neutrophil collagenase, and adamalysin II/human neutrophil collagenase exhibit sequence identities of 16%, 14%, and 13%, respectively. Therefore, the corresponding four distinct families of zinc peptidases, the astacins, the matrix metalloproteinases (matrixins, collagenases), the adamalysins/reprolysins (snake venom proteinases/reproductive tract proteins), and the serralysins (large bacterial proteases from Serratia, Erwinia, and Pseudomonas) appear to have originated by divergent evolution from a common ancestor and form a superfamily of proteolytic enzymes for which the designation "metzincins" has been proposed. There is also a faint but significant structural relationship of the metzincins to the thermolysin-like enzymes, which share the truncated zinc-binding motif HEXXH and, moreover, similar topologies in their N-terminal domains.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pro.5560040502

The metzincins--topological and sequential relations between the astacins, adamalysins, serralysins, and matrixins (collagenases) define a superfamily of zinc-peptidases.

Publisher Summary This chapter highlights some of the processes from formation to breakdown of the egg envelope (egg membrane) in fish from the perspective of cell and developmental biology The chapter describes the structure and functions of the egg envelope, compares the egg envelopes of various species, and deduces a biological concept of the egg envelope The chapter explores the egg envelope as a probe that can be used in the analysis of molecular, cellular, and developmental phenomena in living systems The egg envelope is an acellular structure enclosing the egg and embryo of all multicellular animals except sponges and some coelenterates The number of egg envelopes varies from one to several in different animal species Most of the egg envelopes in fish consist of two or three layers These layers are different in morphology, ultrastructure, stainability, and chemical properties The outer one or two layers are thin, while the innermost layer is usually the thickest The egg envelope of fish has been considered to be synthesized in oocytes or follicle cells and is classified as the primary or secondary egg envelope The envelopes of fertilized eggs of many fish are hard and tough structures with strong elasticity and are also insoluble in water The constituent proteins of the egg envelope are, therefore, inconvenient as immunogens to raise antibodies The hatching enzyme does not break down the egg envelope completely into free amino acids or small peptides but, by limited proteolysis, produces a mixture of water-soluble, high-molecular-weight glycoproteins

Molecular and Cellular Basis of Formation, Hardening, and Breakdown of the Egg Envelope in Fish

Cloning of cDNAs for the Precursor Protein of a Low-Molecular-Weight Subunit of the Inner Layer of the Egg Envelope (Chorion) of the Fish Oryzias latipes

Isolation of cDNAs for LCE and HCE, two constituent proteases of the hatching enzyme of Oryzias latipes, and concurrent expression of their mRNAs during development.

The hatching enzyme is an embryo-secreted enzyme(s) which digests the egg envelope, allowing the embryo to emerge at the time of hatching. The hatching enzyme of the fish, Oryzias latipes, has recently been found to consist of two kinds of proteases which may digest the inner layer of chorion (egg envelope) cooperatively [Yasumasu, S. et al. (1988) Zool. Sci. 5, 191-195]. In the present study, one of them, high choriolytic (egg envelope digesting) enzyme (HCE) was purified and some biochemical and enzymological properties were examined. The enzyme was a basic protein with a molecular weight of about 24 kDa, and exhibited choriolytic activity as well as proteolytic (caseinolytic) activity. The results of inhibitor studies and metal analyses strongly suggested that it was a zinc-protease. The purified HCE consisted of two probable isomers, HCE-1 and HCE-2. Both of them were markedly similar in amino acid composition, specific activities of choriolysis and proteolysis, and substrate specificity as determined using MCA-peptides. Moreover, they were not separable on SDS-PAGE, electrofocusing PAGE, or ultracentrifugal analysis, but were discriminated only on HPLC with a CM-300 column. Thus, the mixture of HCE-1 and HCE-2 could be regarded as almost a single enzyme, HCE. When it acted on an intact chorion, the purified HCE caused a remarkable swelling of its inner layer with concomitant release of peptides from it. Once the inner layer of chorion was swollen, the enzyme hardly digested it.

Purification and partial characterization of high choriolytic enzyme (HCE), a component of the hatching enzyme of the teleost, Oryzias latipes.

There are two hatching enzyme homologues in the zebrafish genome: zebrafish hatching enzyme ZHE1 and ZHE2 Northern blot and RT-PCR analysis revealed that ZHE1 was mainly expressed in pre-hatching embryos, whereas ZHE2 was rarely expressed This was consistent with the results obtained in an experiment conducted at the protein level, which demonstrated that one kind of hatching enzyme, ZHE1, was able to be purified from the hatching liquid Therefore, the hatching of zebrafish embryo is performed by a single enzyme, different from the finding that the medaka hatching enzyme is an enzyme system composed of two enzymes, medaka high choriolytic enzyme (MHCE) and medaka low choriolytic enzyme (MLCE), which cooperatively digest the egg envelope The six ZHE1-cleaving sites were located in the N-terminal regions of egg envelope subunit proteins, ZP2 and ZP3, but not in the internal regions, such as the ZP domains The digestion manner of ZHE1 appears to be highly analogous to that of MHCE, which partially digests the egg envelope and swells the envelope The cross-species digestion using enzymes and substrates of zebrafish and medaka revealed that both ZHE1 and MHCE cleaved the same sites of the egg envelope proteins of two species, suggesting that the substrate specificity of ZHE1 is quite similar to that of MHCE However, MLCE did not show such similarity Because HCE and LCE are the result of gene duplication in the evolutionary pathway of Teleostei, the present study suggests that ZHE1 and MHCE maintain the character of an ancestral hatching enzyme, and that MLCE acquires a new function, such as promoting the complete digestion of the egg envelope swollen by MHCE

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1742-4658.2008.06722.x

Ichiro Iuchi

Papers

Molecular and Cellular Basis of Formation, Hardening, and Breakdown of the Egg Envelope in Fish

Cloning of cDNAs for the Precursor Protein of a Low-Molecular-Weight Subunit of the Inner Layer of the Egg Envelope (Chorion) of the Fish Oryzias latipes

Isolation of cDNAs for LCE and HCE, two constituent proteases of the hatching enzyme of Oryzias latipes, and concurrent expression of their mRNAs during development.

Purification and partial characterization of high choriolytic enzyme (HCE), a component of the hatching enzyme of the teleost, Oryzias latipes.

Purification and characterization of zebrafish hatching enzyme - an evolutionary aspect of the mechanism of egg envelope digestion.