Biology subjects

Hyodo, S.

Publications and source records attributed to Hyodo, S..

9 recordsLinked to original sources

bioRxiv2026

Selective activation of LH-dependent transcriptional pathways determines ovulatory follicles in the hierarchical ovary of cloudy catshark

The number of offspring produced per reproductive cycle is generally explained by a luteinizing hormone receptor (LHR)-threshold model, in which only follicles expressing sufficient levels of LHR respond to the LH surge and proceed to ovulation. Using the cloudy catshark as a model, we reveal a distinct mechanism that determines the fate of ovulatory (F1) and non-ovulatory (F2) follicles independently of LHR abundance. The cloudy catshark produces only two eggs per reproductive cycle by ovulating a pair of F1 follicles from its single ovary. Both F1 and F2 follicles express comparable levels of lhr, indicating that both retain the capacity to receive the LH signal. Nevertheless, LH stimulation selectively activated ovulation-associated responses in F1 follicles. These included progesterone production via star2 upregulation, as well as transcriptional programs including RUNX transcription factors, prostaglandin signaling (ptgs2, ptger1), and matrix metalloproteinases. Moreover, direct activation of cAMP pathway, bypassing LHR activation, induced progesterone production in F1 but not F2 follicles, indicating that the critical difference in ovulatory responsiveness lies downstream of cAMP. These results demonstrate that follicular ovulatory fate is determined, at least in part, by follicle-specific transcriptional responses to cAMP, rather than by LHR abundance alone, challenging the prevailing LHR-threshold model of ovulatory regulation in vertebrates.

physiology↗

bioRxiv2025

Transcriptional Activation of Estrogen Receptor-alpha and Estrogen Receptor-beta from Elephant Shark (Callorhynchus milii)

Humans and other vertebrates contain two estrogen receptors (ERs), ER and ER{beta}. Among cartilaginous fish (sharks, rays, skates), which are chondrichthyans that evolved about 425 million years ago, only activation by steroids of ER{beta} orthologs has been characterized. To remedy this gap in understanding estrogen signaling in chondrichthyans, we studied estrogen activation of orthologs of human ER and ER{beta} from elephant shark (Callorhynchus milii). Unexpectedly, we found that C. milii contained three estrogen-responsive ER genes: ER1 (596 amino acids), ER2 (600 amino acids), and ER3 (599 amino acids) with strong sequence similarity to each other. We also found an estrogen-unresponsive gene, ER4 (561 amino acids), with a 39 amino acid deletion in the DNA-binding domain. An estrogen-responsive ER{beta} ortholog (580 amino acids) also was present in C. milii. The three active C. milii ERs are of similar length to human ER (595 amino acids); however, C. milii ER{beta} is longer than human ER{beta} (530 amino acids). We studied transcriptional activation of ER and ER{beta} by estradiol (E2), the main reproductive estrogen in humans. We also studied estrone (E1), the main postmenopausal estrogen, and estriol (E3), which is synthesized during pregnancy. We determined the half-maximal response (EC50) and fold-activation to E2, E1, and E3 of C. milii ER1, ER2, ER3, and ER{beta}. Among these estrogens, E2 had the lowest EC50 for all four ERs. Fold-activation by E2 and E3 was similar for ER1, ER2, ER3, and ER{beta}. Overall, estrogen activation of C. milii ER and ER{beta} was similar to that for human ER and ER{beta}, indicating substantial conservation of the vertebrate ER during the 425 million years since the divergence of cartilaginous fish and humans from a common ancestor.

evolutionary biology↗

bioRxiv2024

Low microbial abundance and community diversity within the egg capsule of the oviparous cloudy catshark (Scyliorhinus torazame) during oviposition

Vertebrate embryos are protected from bacterial infection by various maternally derived immune factors before the embryonic organs are fully developed. However, the defense mechanisms employed by elasmobranch embryos during development remain poorly understood. This study attempted to elucidate the embryonic defense mechanism of elasmobranchs by investigating the intracapsular environment of freshly laid eggs of the oviparous cloudy catshark (Scyliorhinus torazame). The egg capsule of oviparous elasmobranchs is tightly sealed until pre-hatching (early opening of the egg capsule), after which seawater flows into the capsule and the embryos are consequently exposed to the surrounding seawater. We first experimentally examined the resistance of embryos to potential bacterial infections and found that the early embryos were highly vulnerable to environmental pathogens, suggesting that the embryos are protected from the threat of infection before pre-hatching. Indeed, the intracapsular environment of freshly laid eggs exhibited a significantly low bacterial density that was maintained until pre-hatching. Furthermore, the microbiome inside eggs just after oviposition differed markedly from the microbiomes of rearing seawater and adult oviducal gland epithelia; these eggs were predominantly populated by an unidentified genus of Sphingomonadaceae. Overall, this study provides compelling evidence that early embryos of oviparous cloudy catshark are incubated in a clean intracapsular environment that potentially plays a significant role in embryonic development in oviparous elasmobranchs. Our results suggest that maintenance of this clean condition might be attributable to bactericidal or bacteriostatic activities associated with the egg jelly and/or oviducal gland.

microbiology↗

bioRxiv2022

In vitro and in vivo gene introduction in the cloudy catshark (Scyliorhinus torazame), a cartilaginous fish

Cartilaginous fishes have various unique physiological features such as cartilaginous skeletons and a urea-based osmoregulation strategy for adaptation to their marine environment. Also, because they are considered a sister group of bony vertebrates, understanding their unique features is important from an evolutionary perspective. However, experimental approaches are limited in cartilaginous fishes. Particularly, genetic engineering, which can analyze gene functions as well as cellular behavior, has not been effectively utilized in cartilaginous fishes. This is partly because their reproductive strategy involves internal fertilization, which results in difficulty in microinjection into fertilized eggs at the early developmental stage. Trials of gene transfer have also been limited both in in vitro cultured cells and in vivo. Here, to identify efficient gene transfer methods in cartilaginous fishes, we examined the effects of various methods both in vitro and in vivo using the cloudy catshark, a candidate model cartilaginous fish species. In all methods, green fluorescent protein (GFP) expression was used to evaluate exogenous gene introduction. First, we established a primary cell culture containing fibroblast-like and epithelial-like cells from cloudy catshark embryos. Using these primary cultured cells, we attempted gene transfection by lipofection, polyethylenimine (PEI), adenovirus, baculovirus and electroporation. Among the methods tested, lipofection, electroporation and baculovirus infection enabled the successful introduction of exogenous genes into primary cultured cells, allowing us to study physiological mechanisms at a single-cell level in culture conditions close to those in a living cartilaginous fish. We also attempted in vivo transfection into cloudy catshark embryos by electroporation and baculovirus infection. Although baculovirus-injected groups did not show GFP fluorescence, electroporation successfully introduced GFP into various tissues including muscle cells. Furthermore, we succeeded in GFP introduction into adult testis by electroporation. The in vitro and in vivo gene introduction methods that worked in this study may identify paths for future genetic manipulation including knockout experiments and cellular linage analysis in cartilaginous fishes.

molecular biology↗

bioRxiv2022

Cloning of Nine Glucocorticoid Receptor Isoforms from the Slender African lungfish (Protopterus dolloi)

We wanted to clone the glucocorticoid receptor (GR) from slender African lungfish (Protopterus dolloi) for comparison to P. dolloi MR, which we had cloned and were characterizing, as well as for comparison to the GRs from humans, elephant shark and zebrafish. However, although sequencing of the genome of the Australian lungfish (Neoceratodus forsteri), as well as, that of the West African lungfish (Protopterus annectens) were reported in the first three months of 2021, we could not retrieve a GR sequence with a BLAST search of GenBank, when we submitted our research for publication in July 2021. Moreover, we were unsuccessful in cloning the GR from slender African lungfish using a cDNA from the ovary of P. dolloi and PCR primers that had successfully cloned a GR from elephant shark, Xenopus and gar GRs. On October 21, 2021 the nucleotide sequence of West African lungfish (P. annectens) GR was deposited in GenBank. We used this GR sequence to construct PCR primers that successfully cloned the GR from the slender spotted lungfish. Here, we report the sequences of nine P. dolloi GR isoforms and explain the basis for the previous failure to clone a GR from slender African lungfish using PCR primers that cloned the GR from elephant shark, Xenopus and gar. Studies are underway to determine corticosteroid activation of these slender African lungfish GRs.

evolutionary biology↗

bioRxiv2021

Aldosterone, Dexamethasone and Triamcinolone Activate African Lungfish Mineralocorticoid Receptor: Increased Activation After Removal of the Amino-Terminal Domain

Aldosterone, the main physiological mineralocorticoid in humans and other terrestrial vertebrates, first appears in lungfish, which are lobe-finned fish that are forerunners of terrestrial vertebrates. Aldosterone activation of the MR regulates internal homeostasis of water, sodium and potassium, which was critical in the conquest of land by vertebrates. We studied transcriptional activation of the slender African lungfish MR by aldosterone, other corticosteroids and progesterone and find that aldosterone, 11-deoxycorticosterone, 11-deoxycortisol and progesterone have half-maximal responses (EC50s) below 1 nM and are potential physiological mineralocorticoids. In contrast, EC50s for corticosterone and cortisol were 23 nM and 66 nM, respectively. Unexpectedly, truncated lungfish MR, consisting of the DNA-binding, hinge and steroid-binding domains, had a stronger response to corticosteroids and progesterone than full-length lungfish MR, indicating that the N-terminal domain represses steroid activation of lungfish MR, unlike human MR in which the N-terminal domain contains an activation function. BLAST searches of GenBank did not retrieve a GR ortholog, leading us to test dexamethasone and triamcinolone for activation of lungfish MR. At 10 nM, both synthetic glucocorticoids are about 4-fold stronger than 10 nM aldosterone in activating full-length lungfish MR, leading us to propose that lungfish MR also functions as a GR.

physiology↗

bioRxiv2021

Regulation by Progestins, Corticosteroids and RU486 of Activation of Elephant Shark and Human Progesterone Receptors: An Evolutionary Perspective

We investigated progestin and corticosteroid activation of the progesterone receptor (PR) from elephant shark, a cartilaginous fish belonging to the oldest group of jawed vertebrates. Comparison with human PR provides insights into the evolution of steroid activation of human PR. At 1 nM steroid, elephant shark PR is activated by progesterone, 17-hydroxy-progesterone, 20{beta}-hydroxy-progesterone, 11-deoxycorticosterone (21-hydroxyprogesterone) and 11-deoxycortisol. Human PR, in comparison, is activated at 1 nM steroid, only by progesterone and 11-deoxycorticosterone, indicating increased progestin and corticosteroid specificity during the evolution of human PR. RU486, an important clinical antagonist of human PR, did not inhibit progesterone activation of elephant shark PR. Cys-528 in elephant shark PR corresponds to Gly-722 in human PR, which is essential for RU486 inhibition of human PR. Confirming the importance of Cys-528 in elephant shark PR, RU486 inhibited progesterone activation of the Cys528Gly mutant PR. Compared to wild-type human PR, there was an increase in activation of human Gly722Cys PR by11-deoxycortisol and a decrease in activation by corticosterone, which may have been important in selection for the mutation corresponding to human glycine-722 PR that first evolved in platypus PR, a basal mammal.

evolutionary biology↗

bioRxiv2019

N-terminal domain Increases Activation of Elephant Shark Glucocorticoid and Mineralocorticoid Receptors

Orthologs of human glucocorticoid receptor (GR) and human mineralocorticoid receptor (MR) first appear in cartilaginous fishes. Subsequently, the MR and GR diverged to respond to different steroids: the MR to aldosterone and the GR to cortisol and corticosterone. We report that cortisol, corticosterone and aldosterone activate full-length elephant shark GR, and progesterone, which activates elephant shark MR, does not activate elephant shark GR. However, progesterone inhibits steroid binding to elephant shark GR, but not to human GR. Together, this indicates partial functional divergence of elephant shark GR from the MR. Deletion of the N-terminal domain (NTD) from elephant shark GR (truncated GR) reduced the response to corticosteroids, while truncated and full-length elephant shark MR had similar responses to corticosteroids. Swapping of NTDs of elephant shark GR and MR yielded an elephant shark MR chimera with full-length GR-like increased activation by corticosteroids and progesterone compared to full-length elephant shark MR. Elephant shark MR NTD fused to GR DBD+LBD had similar activation as full-length MR, indicating that the MR NTD lacked GR-like NTD activity. We propose that NTD activation of human GR evolved early in GR divergence from the MR.

evolutionary biology↗

bioRxiv2018

Transcriptional Activation of a Cartilaginous Fish (Elephant Shark, Callorhinchus milii) Mineralocorticoid Receptor by Corticosteroids, Progestins and Spironolactone

We report the analysis of activation of full-length mineralocorticoid receptor (MR) from elephant shark, a cartilaginous fish belonging to the oldest group of jawed vertebrates by corticosteroids and progesterone. Based on their measured activities, aldosterone, cortisol, 11-deoxycorticosterone, corticosterone, 11-deoxcortisol, progesterone and 19-norprogesterone are potential physiological mineralocorticoids. However, aldosterone, the physiological mineralocorticoid in humans and other terrestrial vertebrates, is not found in cartilaginous or ray-finned fishes. Although progesterone activates ray-finned fish MRs, progesterone does not activate human, amphibian or alligator MRs, suggesting that during the transition to terrestrial vertebrates, progesterone lost the ability to activate the MR. Both elephant shark MR and human MR are expressed in the brain, heart, ovary, testis and other non-epithelial tissues, indicating that MR expression in diverse tissues evolved in the common ancestor of jawed vertebrates. Our data suggest that progesterone-activated MR may have unappreciated functions in elephant shark ovary and testis.

physiology↗