Carbonic anhydrase inhibition blocks skeletogenesis and echinochrome production in Paracentrotus lividus and Heliocidaris tuberculata embryos and larvae

Carbonic anhydrases (CAs) are a family of widely distributed metalloenzymes, involved in diverse physiological processes. These enzymes catalyse the reversible conversion of carbon dioxide to protons and bicarbonate. At least 19 genes encoding for CAs have been identified in the sea urchin genome, with one of these localized to the skeletogenic mesoderm (primary mesenchyme cells, PMCs). We investigated the effects of a specific inhibitor of CA, acetazolamide (AZ), on development of two sea urchin species with contrasting investment in skeleton production, Paracentrotus lividus and Heliocidaris tuberculata, to determine the role of CA on PMC differentiation, skeletogenesis and on non‐skeletogenic mesodermal (NSM) cells. Embryos were cultured in the presence of AZ from the blastula stage prior to skeleton formation and development to the larval stage was monitored. At the dose of 8 mmol/L AZ, 98% and 90% of P. lividus and H. tuberculata embryos lacked skeleton, respectively. Nevertheless, an almost normal PMC differentiation was indicated by the expression of msp130, a PMC‐specific marker. Strikingly, the AZ‐treated embryos also lacked the echinochrome pigment produced by the pigment cells, a subpopulation of NSM cells with immune activities within the larva. Conversely, all ectoderm and endoderm derivatives and other subpopulations of mesoderm developed normally. The inhibitory effects of AZ were completely reversed after removal of the inhibitor from the medium. Our data, together with new information concerning the involvement of CA on skeleton formation, provide evidence for the first time of a possible role of the CAs in larval immune pigment cells.     

Generation and characterization of Megf6 null and Cre knock‐in alleles

Megf6, a member of MEGF (multiple EGF‐like domains) protein family, is a conserved high molecular weight protein with 30 EGF‐like domains. Although many members of the MEGF protein family are essential for embryonic development and homeostasis, the role of Megf6 in development and physiology is still unknown. Here, we generated Megf6‐deficient mice using CRISPR‐Cas9 technique and showed that Megf6 is dispensable for embryonic development. We also constructed the Megf6^Cre allele to study Megf6‐expressing cell lineages. Our results showed that Megf6‐expressing cells contribute to the periotic mesenchyme and its derivatives, skin epidermis, certain cells in brain and ribs. Therefore, the Megf6^Cre allele can be a useful tool for conditional deletion in these tissues, in particular for periotic mesenchyme deletion.     

In vivo genetic ablation of the periotic mesoderm affects cell proliferation survival and differentiation in the cochlea

Tbx1 is required for ear development in humans and mice. Gene manipulation in the mouse has discovered multiple consequences of loss of function on early development of the inner ear, some of which are attributable to a cell autonomous role in maintaining cell proliferation of epithelial progenitors of the cochlear and vestibular apparata. However, ablation of the mesodermal domain of the gene also results in severe but more restricted abnormalities. Here we show that Tbx1 has a dynamic expression during late development of the ear, in particular, is expressed in the sensory epithelium of the vestibular organs but not of the cochlea. Vice versa, it is expressed in the condensed mesenchyme that surrounds the cochlea but not in the one that surrounds the vestibule. Loss of Tbx1 in the mesoderm disrupts this peri-cochlear capsule by strongly reducing the proliferation of mesenchymal cells. The organogenesis of the cochlea, which normally occurs inside the capsule, was dramatically affected in terms of growth of the organ, as well as proliferation, differentiation and survival of its epithelial cells. This model provides a striking demonstration of the essential role played by the periotic mesenchyme in the organogenesis of the cochlea.     

Role of stroma in carcinogenesis of the prostate

Prostatic development is induced by androgens acting via mesenchymal-epithelial interactions. Androgens elicit their morphogenetic effects by acting through androgen receptors (ARs) in urogenital sinus mesenchyme (UGM), which induces prostatic epithelial development. In adulthood reciprocal homeostatic stromal-epithelial interactions maintain functional differentiation and growth-quiescence. Testosterone plus estradiol (T+E2) have been shown to induce prostatic carcinogenesis in animal models. Thus, tissue recombinant studies were undertaken to explore the mechanisms of prostatic carcinogenesis in BPH-1 cells in which ARs and estrogen receptors (ERs) are undetectable. For this purpose, BPH-1 cells were combined with UGM, and the UGM+BPH-1 recombinants were grafted to adult male hosts. Solid branched epithelial cords and ductal structures formed in untreated UGM+BPH-1 recombinants. Growth was modest, and tumors did not develop. UGM+BPH-1 recombinants treated with T+E2 formed invasive carcinomas. BPH-1 cells lack ARs and ERs, whereas rat UGM expresses both of these receptors. These data show that immortalized nontumorigenic human prostatic epithelial cells can undergo hormonal carcinogenesis in response to T+E2 stimulation via paracrine mechanisms and demonstrate that the stromal environment plays an important role in mediating hormonal carcinogenesis. During prostatic carcinogenesis the stroma undergoes progressive loss of smooth muscle with the appearance of carcinoma-associated fibroblasts (CAF). This altered stroma was tested for its ability to promote carcinogenesis of nontumorigenic but immortalized human prostatic epithelial cells (BPH-1). CAF+BPH-1 tissue recombinants formed large carcinomas. In contrast, recombinants composed of normal prostatic stroma+BPH-1 cells exhibited minimal growth. This stroma-induced malignant transformation was associated with additional genetic alterations and changes in gene expression. Thus, alteration in the stromal microenvironment was sufficient to promote malignant transformation of human prostatic epithelial cells.     

Gastrulation in the sea urchin embryo: a model system for analyzing the morphogenesis of a monolayered epithelium

Processes of gastrulation in the sea urchin embryo have been intensively studied to reveal the mechanisms involved in the invagination of a monolayered epithelium. It is widely accepted that the invagination proceeds in two steps (primary and secondary invagination) until the archenteron reaches the apical plate, and that the constituent cells of the resulting archenteron are exclusively derived from the veg2 tier of blastomeres formed at the 60-cell stage. However, recent studies have shown that the recruitment of the archenteron cells lasts as late as the late prism stage, and some descendants of veg1 blastomeres are also recruited into the archenteron. In this review, we first illustrate the current outline of sea urchin gastrulation. Second, several factors, such as cytoskeletons, cell contact and extracellular matrix, will be discussed in relation to the cellular and mechanical basis of gastrulation. Third, differences in the manner of gastrulation among sea urchin species will be described; in some species, the archenteron does not elongate stepwise but continuously. In those embryos, bottle cells are scarcely observed, and the archenteron cells are not rearranged during invagination unlike in typical sea urchins. Attention will be also paid to some other factors, such as the turgor pressure of blastocoele and the force generated by blastocoele wall. These factors, in spite of their significance, have been neglected in the analysis of sea urchin gastrulation. Lastly, we will discuss how behavior of pigment cells defines the manner of gastrulation, because pigment cells recently turned out to be the bottle cells that trigger the initial inward bending of the vegetal plate.     

小鼠胎肺分支形态发生的分子机制

哺乳动物在早期胚胎发育过程中,肺发育经历了气管分支的形态发生、树样结构上皮管道的形成,并伴随着血管的发育而发生的气体通路和肺泡的分化等过程.肺发生涉及到许多复杂的分子机制.肺形态学的变化受到一系列持家基因、激素、核转录因子、生长因子及其他因素的综合调控.目前已经发现决定肺分支形态发生的许多重要因子.本文根据目前最新研究进展,阐述了小鼠胚胎肺在分支形态发生过程中,上皮与间充质之间诱导的信号通路之间的相互作用及其对呼吸树形态建成的调控机制.