Editorial highlights

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.

Meet the editorial team “An interview with Lisa A. Taneyhill, assistant editor, University of Maryland” by Paul Trevorrow and Lisa Taneyhill. ¹ Dr. Taneyhill studies how two critical embryonic cell populations, neural crest cells and placode cells, form and later interact to generate new anatomical structures. Neural crest cells undergo via an epithelial to mesenchymal transition to acquire migratory capacity and Dr. Taneyhill's lab is investigating the function of proteases that cleave proteins without which cells can't move. Neural crest cells join together with placodes to form the neurons and glia of the cranial ganglia, and although much is known about how motor neurons reach their targets, the sensory nerves have received far less attention. Dr. Taneyhill is therefore interested in how the sensory nerves of the trigeminal ganglion target tissues like the eye or jaw, and how the nerves transmit signals back that help shape those tissues. This fundamental developmental biology research has translational impact in the form of a better understanding of neurodevelopmental disorders such as Familial Dysautonomia and their potential treatment.

Diabetes and pancreas regeneration “Pancreatic injury induces β‐cell regeneration in axolotl” by Connor Powell, Hani Singer, Ashley Juarez, Ryan Kim, Elane Kim, Duygu Payzin‐Dogru, Aaron Savage, Noah Lopez, Kara Thornton, Steven Blair, Adnan Abouelela, Anita Dittrich, Stuart Akeson2, Miten Jain2, and Jessica L. Whited. ² Diabetes is a condition in which insulin homeostasis is compromised. This can lead to complications including heart failure, kidney disease, and tissue necrosis requiring amputation. Diabetes is caused by a loss of pancreatic β‐cell function, and this study investigated the capacity for pancreas regeneration in axolotl. The authors initially characterized pancreatic islets in the axolotl and observed that axolotl pancreatic islets closely resemble those in mice and humans, as demonstrated by the conservation of several key pancreatic gene markers. The authors then used partial pancreatectomy to study the pancreatic response to injury. Following pancreatic resection, whole‐organ β‐cell proliferation occurred without the formation of a blastemal structure, which is analogous to other models of compensatory congestion in axolotl. Lineage tracing will still be needed in the future to ascertain whether new β‐cells originate from existing β‐cells or from pancreatic stem cells.

Limb development and evolution “Multiple gene knockouts in newts reveal novel functions of 50 Hox genes in limb development along the anterior–posterior and proximal–distal axes” by Kohei Urakawa, Yu Ito, Haruka Matsubara, Ken‐ichi Suzuki, Masatoshi Matsunami, Shuji Shigenobu, Toshinori Hayashi Gembu Abe and Takashi Takeuchi. ³ 5′ Hox genes play crucial roles in limb patterning along the proximal–distal and anterior–posterior axes in mice. However, their functional conservation across tetrapods remains unclear. Although it is known that Hox13 is essential for digit formation during development and regeneration in newts (Pleurodeles waltl), the functions Hox9–Hox12 in newts remain unknown. The authors discovered that knockouts of Hox9, Hox10, and Hox12 paralogs are individually not required for limb development, but combinatorial knockouts of Hox9 and Hox10 perturbed stylopod development and anterior zeugopod/autopod elements specifically in the hindlimbs. In contrast, Hox11 knockout newts exhibit skeletal defects in the posterior zeugopod and autopod of both the forelimbs and hindlimbs. This body of work therefore demonstrates the functional diversification of 5′ Hox genes in tetrapod limb development and evolution.

Amphibian regeneration “Commensal skin bacteria interact with the innate immune system to promote tail regeneration in Xenopus laevis tadpoles” by Phoebe Chapman, Robert Day, Daniel Hudson, Joanna Ward, Xochitl Morgan, and Caroline Beck. ⁴ Clawed frog (X. laevis) tadpoles can regenerate their tails following partial amputation, and in doing so, they replace the missing part of the spinal cord, associated muscles, and the fin. However, this capacity is transitory and persists for only a brief period of development, after which the regeneration response becomes unstable, leading to a proportion of tadpoles that undergo wound healing instead. Inspired by potential links between the microbiome and human inflammatory disease, the authors investigated whether tadpole skin microbiome and innate immunity influence the regeneration of a complex appendage.

Whereas disrupting the cell surface protein, Toll‐like receptor 2 (TLR2), which acts as a primary sensor for the innate immune system, perturbs regeneration, higher proportions of Gram‐positive bacteria promote regeneration.

Craniofacial biology and palate development “Identification of novel genes regulating the development of the palate” by Ashwin Bhaskar and Sophie Astrof. ⁵ Cleft palate with or without a cleft lip (known as orofacial clefts) is the most frequent craniofacial birth defect (1:800 babies annually), which if left untreated has profound effects on the breathing, feeding and speech of affected individuals. Mice are an established model for studying palate formation and clefting due to similarities in palate development between mice and humans and have revealed genetic mutation and environmental factor causation of facial clefts. To discover additional genes regulating formation of the secondary palate, the authors examined micro‐CT images of mouse mutants generated by the International Mouse Phenotyping Consortium. By screening for homozygous null mutants that exhibit anomalies in secondary palate development, the authors identified 44 novel genes implicated in palatogenesis, providing a valuable resource for further research offer novel insights into the molecular mechanisms underlying cleft palate.

Quantitative anatomy and morphology “Easily adaptable Fiji macro for mean linear intercept measurement of peripheral respiratory airspace” by Brielle Patlin, Yongjun Yin, Ling Li, and David M. Ornitz. ⁶ Mean linear intercept (MLI) is used in clinical and research settings to measure and evaluate lung structure. MLI defines the average distance between airspace septa in the lung and is therefore used to measure the respiratory airspace of the lung, which includes alveoli and alveolar ducts. This is especially applicable to analyses of developmental, genetic, and pathological changes in peripheral lung tissue. To increase the speed and accuracy of obtaining MLI measurements, the authors developed a macro in Fiji to semi‐automate this process. Because it significantly lessens the labor needed for analysis, more measurements can be taken, potentially increasing accuracy.