Search

The sacroiliac joint, articulating the sacrum with the ilium, evolved in a common ancestor of tetrapods as they transitioned from aquatic to terrestrial environments. This skeletal connection between the hindlimb and the trunk plays an important role in terrestrial limb-driven locomotion. Nevertheless, the mechanisms underlying its formation remain almost unexplored. Urodeles are the best potential model group to study this mechanism because they show better preservation of ancient skeletal structures than other extant tetrapods, however, there have been no detailed descriptions of the developmental process of sacroiliac joint formation. We observed the skeletal development of the sacral rib and hindlimb bud-derived bones during the formation of the sacroiliac joint in the newt Pleurodeles waltl to identify the timing of the emergence of these bones. Based on these observations, we then performed hindlimb bud removal and transplantation experiments to examine the interaction between the developing sacral rib and limb bones. Removing either the left or both hindlimb buds from the larval body did not result in reduction of the size of the sacral ribs in this study, in contrast to previous studies which suggested effects of the hindlimb bud on sacral rib development. Autotransplantation of the excised hindlimb bud, either anteriorly or posteriorly, did not produce ectopic sacral rib-like structures on non-sacral vertebrae. Our results suggest that sacral rib development does not require the hindlimb bud. [ABSTRACT FROM AUTHOR]

Background: Cardiac regeneration in the adult mouse is not substantial. Some vertebrates, such as newts and zebrafish, regenerate the heart throughout their lives. To understand how regenerative abilities differ among animal species, comparative research has been conducted in animals like mouse, zebrafish, and newt. For those purposes, cryo‐injury is suitable as an experimental model for the pathological condition of human myocardial infarction. In fact, cryo‐injury procedures are common in mouse and zebrafish. Results: In the present study, we induced cryo‐damage on the ventricle in Iberian ribbed newts using a liquid nitrogen‐chilled probe. We observed that the injured area recovered within 8 weeks, with remodeling of scar tissue and proliferation of cardiomyocytes. We investigated the subsequent recovery of cryo‐injured and amputated tissues by comparative analysis of the gene expression profiles following these two procedures. Conclusions: Notably, we established a cryo‐injury procedure for the newt and confirmed that regeneration of the cryo‐damaged myocardial tissue is achieved by changes in gene expression that are milder than those observed in the amputation model. Our results suggest that the cryo‐injury method is suitable for comparing the process of cardiac regeneration in the newt with that in other animal models. Key Findings: Urodele amphibian newts can regenerate their hearts.Established a cryo‐injury model for cardiac regeneration for the newt.Genes with common expression changes in the cryo‐injury and amputation models are shown. [ABSTRACT FROM AUTHOR]

Urodele amphibian newts have unique biological properties in male gametogenesis, in addition to their extreme regenerative capacity. Male newts are able to regenerate new testes even after reaching sexual maturity and can possess multiple testes. Notably, these animals maintain primordial germ cell‐like cells in a tissue adjacent to the testis. Spermatogenesis proceeds while synchronizing in a region‐specific manner in the testis. However, the newt species that have been used most commonly require 2–3 years to achieve sexual maturity, and spermatogenesis in these species shows seasonality. These traits have restricted the use of newts for studies on testicular development and spermatogenesis, and testis development in newts remains poorly characterized. Recently, the Iberian ribbed newt Pleurodeles waltl has been established as an emerging model organism. P. waltl reaches sexual maturity more quick after birth than do other newts and is capable of breeding year‐round. Thus, P. waltl is expected to serve as an appealing experimental model for studying the mechanisms of male gametogenesis in the urodeles. In the present study, we use P. waltl to describe the entire developmental process of the newt testis from primordial gonad to maturity. Notably, the mature testes show synchronized progression of spermatogenesis along the anteroposterior axis. Additionally, we demonstrate that the process of spermatogenesis in P. waltl proceeds irrespective of day length. Our results show that P. waltl newts are a suitable model for investigating the process of testicular development. We also expect that these results will be useful for the maintenance of P. waltl bioresources. [ABSTRACT FROM AUTHOR]

The thermal denaturation ultraviolet absorption spectra of N6,N6-dimethyladenylyl(3′→5′)-N6, N6-dimethyladenosine (m26Apm26A), which is a common sequence in 16–18-S ribosomal RNA, in aqueous buffer at pH 7 have been measured over the temperature range 3–90°C. These data have been used to determine the thermodynamic quantities associated with the intramolecular stacking equilibria. At 25°C in neutral aqueous solution m26Apm26A exists mainly (about 81%) as a stacked form, so that the stacking interactions are stronger than those in the parent unmethylated adenylyl-(3′-5′)adenosine (ApA), where about 52% is stacked. From the parameters of ΔH and ΔS, it is concluded that ‘hidden’ hydrophobic interactions are of prime importance in the enhanced stability of m26Apm26A. Transphosphorylation reaction of ApA and m26Apm26A to form the corresponding cyclic 2′,3′-phosphates has been studied. First-order rate constants at 25°C for the reactions, which are base-catalyzed, have been obtained. Insertion of two methyl groups at N-6 of ApA reduces the rate of transphosphorylation. Effects of stacking on rates are discussed in the light of reaction mechanisms. [ABSTRACT FROM AUTHOR]

Cyclin-dependent kinases (CDKs) are key regulators of cell cycle progression, in conjunction with cyclins. The cyclin-CDK system is highly conserved among eukaryotes, and CDK1 is considered essential for progression through the M phase. However, the extent to which cell cycle progression depends on CDK1 varies between cell types. Therefore, a range of cell types must be analyzed to comprehensively elucidate the role of CDK1. Cdk1-knockout mice exhibit lethality at an early developmental stage, specifically before the differentiation of various cell types. The aim of the present study was to characterize the effects of CDK1 deficiency in amphibian newts. Cdk1 was disrupted by injecting fertilized newt eggs with CRISPR/Cas9, and the resulting effects on embryonic development and cell proliferation were then evaluated. In both wild-type and Cdk1-crispant newt embryos, CDK1 protein was either stored in the egg until late embryogenesis or potentially derived from maternal mRNA, which may also be stored during this period. The embryos survived to the hatching stage, during which the cells responsible for forming the basic organs differentiated. To further characterize the long-term effects of Cdk1 knockout, parabiosis experiments were conducted using wild-type embryos and Cdk1 crispants. The results suggested that an endocycle occurred in the crispant larvae, as evidenced by increases in the size of several types of cells. It is anticipated that studies using newts will provide further insights into the role of Cdk1 in regulating the cell cycle., (© 2025 Japanese Society of Developmental Biologists.)

Vertebrate animals often exhibit sexual dimorphism in body shape. In mammals, decreases in sex hormones caused by testicular castration can affect body shape and occasionally lead to pathologies such as obesity. Post-castration obesity can also be problematic for the health of companion animals, including non-mammals. In order to understand the mechanism of post-castration obesity in vertebrates other than mammals, experimental models are required. We examined whether the Iberian ribbed newt, which has recently become a popular experimental model for amphibian research, could serve as a model for analyzing changes in body shape after castration. In newts, new testes can be regenerated after removal of differentiated testes. We analyzed changes in body shape by removing the testes under conditions in which they could regenerate or conditions in which they could not regenerate. Removal of the testes reduced blood testosterone levels. The body weight and abdominal girth of the newts were increased compared with normal male newts. Transcriptome analysis of the liver showed that a set of genes related to lipid metabolism was continuously up-regulated in castrated newts. Our study suggests that changes in body shape after castration are common in vertebrates. Iberian ribbed newts are thus a suitable model for comparative studies of the long-term physiologic- and endocrine-level effects of castration.