Individual variation in organ histogenesis as a causative factor in the developmental origins of health and disease: unnoticed congenital anomalies?

Bmp4 is an essential growth factor for the initiation of genital tubercle (GT) outgrowth

The external genitalia are appendage organs outgrowing from the posterior body trunk. Murine genital tubercle (GT), anlage of external genitalia, initiates its outgrowth from embryonic day (E) 10.5 as a bud structure. Several growth factors such as fibroblast growth factor (FGF), Wnt and Sonic hedgehog (Shh) are essential for the GT outgrowth. However, the mechanisms of initiation of GT outgrowth are poorly understood. We previously identified bone morphogenetic protein (Bmp) signaling as a negative regulator for GT outgrowth. We show here novel aspects of Bmp4 functions for GT outgrowth. We identified the Bmp4 was already expressed in cloaca region at E9.5, before GT outgrowth. To analyze the function of Bmp4 at early stage for the initiation of GT outgrowth, we utilized the Hoxa3-Cre driver and Bmp4 ^flox/flox mouse lines. Hoxa3 ^Cre/+ ; Bmp4 ^flox/flox mutant mice showed the hypoplasia of GT with reduced expression of outgrowth promoting genes such as Wnt5a, Hoxd13 and p63, whereas Shh expression was not affected. Formation of distal urethral epithelium (DUE) marked by the Fgf8 expression is essential for controlling mesenchymal genes expression in GT and subsequent its outgrowth. Furthermore, Fgf8 expression was dramatically reduced in such mutant mice indicating the defective DUE formation. Hence, current results indicate that Bmp4 is an essential growth factor for the initiation of GT outgrowth independent of Shh signaling. Thus, Bmp4 positively regulates for the formation of DUE. The current study provides new insights into the function of Bmp signaling at early stage for the initiation of GT outgrowth.

Statistical analysis with dilatation for development process of human fetuses

This paper is concerned with the development process of human fetuses. Though the development process of human fetuses still includes many unknown issues, it is known that a certain harmonious relationship between the organs can be observed. This knowledge is based on our intuition, but we have no theory which clarifies these harmonized developments. The paper aims to give a mathematical understanding of the notion of harmonized development through the use of dilatation, which is a measure of the departure from conformal mapping. The asymptotics for dilatation have been developed using certain efficient models of quasiconformal mapping. The proposed method of dilatation is effectively applied to the human fetus data.

Statistical analyses in trials for the comprehensive understanding of organogenesis and histogenesis in humans and mice

Statistical analyses based on the quantitative data from real multicellular organisms are useful as inductive-type studies to analyse complex morphogenetic events in addition to deductive-type analyses using mathematical models. Here, we introduce several of our trials for the statistical analysis of organogenesis and histogenesis of human and mouse embryos and foetuses. Multidimensional scaling has been applied to prove the existence and examine the mode of interkinetic nuclear migration, a regulatory mechanism of stem cell proliferation/differentiation in epithelial tubular tissues. Several statistical methods were used on morphometric data from human foetuses to establish the multidimensional standard growth curve and to describe the relation among the developing organs and body parts. Although the results are still limited, we show that these analyses are not only useful to understand the normal and abnormal morphogenesis in humans and mice but also to provide clues that could correlate aspects of prenatal developmental events with postnatal diseases.

Adrenocorticotropic tumor cells transplanted into mouse embryos affect pancreatic histogenesis

A wide range of individual differences exist in the total number of functional and structural units in each organ, such as β cells in pancreatic islands, and these units are the basis of the organ's overall function, including its functional reserve. The endocrine environment may influence organ histogenesis, during which functional and structural units are formed and increase in number. We analyzed the effects of a continuous high level of adrenocorticotropic hormone (ACTH) and/or secondarily induced glucocorticoid on histogenesis of the pancreas in mouse embryos. Pituitary tumor-derived AtT20 cells, which secrete ACTH continuously, were injected subcutaneously into mouse embryos at embryonic day (E) 12.5, and the embryos were allowed to develop exo utero until E18.5 (AtT20 group). E18.5 AtT20 group embryos with high ACTH levels (23.74 ± 6.19 ng/mL vs control group, 0.48 ± 0.40 ng/mL, P < 0.05) were examined for the effects on histogenesis of the pancreas. Using serial sections of the E18.5 pancreas, we stereologically measured the volumes, and counted total cell numbers and numbers of mitotic or pyknotic cells of the whole pancreas, endocrine and exocrine cells, and glucagon-immunopositive α cells and insulin-immunopositive β cells in the endocrine part. Although the volumes of the whole pancreas and exocrine part did not change significantly, in the AtT20 group the endocrine part was significantly larger, with fewer pyknotic cells and lower ratios of α and β cells than in the control group. These results suggest that the high level of ACTH and/or glucocorticoid affects histogenesis of the pancreas.