Editorial highlights

Abstract

Every organism is a model organism for understanding development, evolution, disease, and regeneration, and we have only begun to scratch the surface of the interdisciplinary genetic, molecular, cellular, and developmental mechanisms that regulate these biological processes. These “Highlights” denote exciting advances recently reported in Developmental Dynamics that illustrate the complex dynamics of developmental biology.

Cilia and Tracheoesophageal Separation “Primary cilia are critical for tracheoesophageal septation”, by Lindsey Fitzsimons, Evangelia Tasouri, Marc August Willaredt, Daniel Stetson, Christian Gojak, Joachim Kirsch, Humphrey Gardner, Karin Gorgas, and Kerry Tucker; DevDyn 253:3, pp. 312–332. https://doi.org/10.1002/dvdy.660.

Septation of the foregut during embryogenesis is critical for correct formation of the trachea and esophagus. Esophageal atresia, in which part of the tube that connects the mouth to the stomach is missing, is the most common congenital malformation of the human foregut. But how is correct dorsoventral patterning and compartmentalization of the foregut endoderm controlled? Primary cilia are highly specialized sensory organelles that regulate cellular growth, development, and homeostasis, via signal transduction. Using the cobblestone mutant mouse, which is hypomorphic for the intraflagellar transport protein, IFT88, this study reveals primary cilia are present in the anterior foregut and critical for foregut division. Despite correct endodermal dorsoventral specification, the reduction in cilia results in defective compartmentalization of the proximal foregut and the pathogenesis of proximal tracheoesophageal septation defects.

Testis Formation “Direct diffusion of anti-Müllerian hormone from both the cranial and caudal regions of the testis during early gonadal development in mice” by Shiori Kato, Toshifumi Yokoyama, Nobusuke Okunishi, Hiroto Narita, Taisei Fujikawa, Yusuke Kirizuki, Youhei Mantani, Takanori Miki and Nobuhiko Hoshi; DevDyn 253:3, pp. 296–311. https://doi.org/10.1002/dvdy.662. The primordia of the male and female reproductive tracts are sexually dimorphic and derived the Wolffian duct and the Müllerian duct, respectively. However, the Müllerian duct also forms in males during early embryogenesis, but subsequently regresses due to the presence of anti-Müllerian hormone, which is secreted from the testes. However, the mechanism underlying AMH infiltration remained unresolved. In this study, organ culture in combination with tissue excision revealed that physiological concentrations of anti-Müllerian hormone infiltrate the mesonephros from both the cranial and caudal testes, which is important for middle Müllerian duct regression.

Skeletal Development “Development of the vertebra and fin skeleton in the lamprey and its implications for the homology of vertebrate vertebrae” by Hirofumi Kariyayama, Natalia Gogoleva, Keishi Harada, Hiromasa Yokoyama, Hiroki Ono, Daichi Suzuki, Yuji Yamazaki and Hiroshi Wada. DevDyn 253:3, pp. 283–295. https://doi.org/10.1002/dvdy.657. Vertebrae are a defining character of vertebrates but can be found in rudimentary form in extant agnathans, such as lamprey. The presence of small spines located bilaterally and dorsally on the notochord is morphologically equivalent but considered nonhomologous to the neural arches of gnathostome vertebrae. This study traced the development of lamprey vertebrae from somitogenesis through metamorphosis, demonstrating lamprey somitogenesis is more similar to amphioxus, sheds doubt on the presence of a sclerotome, revealing the developmental process of lamprey vertebra is different from that of gnathostomes.