The Prince Lab’s research program has evolved and expanded from an initial fascination with the regionalization of developing vertebrate animals. This interest led to a focus on the Hox genes, which play a major role in conferring regional identity. Using the zebrafish as our primary model, we took a deep dive into the organization, function and evolution of Hox genes, studies that provided important insights into whole genome duplications in the vertebrate lineage, as well as the patterning of neuronal and neural crest cell populations. After a substantial foray into patterning of the endoderm, especially the endocrine pancreas, we are once again focusing our investigations on neurons, neural crest, and other fascinating aspects of vertebrate cranial development.
Patterning and migration of the neural crest
We are interested in exploring the mechanisms that underlie neural crest (NC) cell development. NC cells are a transient, migratory cell population that gives rise to a large array of cell types, including neurons, chondrocytes, and pigment cells. NC cells are initially specified at the border between the neural and non-neural ectoderm. During neurulation, NC cells undergo an epithelial-to-mesenchymal transition (EMT) and then migrate extensively through the body. Our research has shown that the planar cell polarity molecules Pk1a and Pk1b play a critical role during EMT and are necessary for directed migration. Specifically, Pk1-deficient NC cells are unable to transition from a “blebbing” state into a “mesenchymal” state and are therefore unable to complete EMT. Further, those cells that are capable of becoming migratory fail to separate from neighboring NC cells, in part due to misregulation of Cadherins. Our ongoing work utilizes novel genetic and transgenic tools and high-resolution imaging approaches to investigate the mechanisms that underlie NC cell migratory behaviors and genomic approaches to elucidate how the NC is patterned along the AP axis. To hear more about the lab’s ongoing investigation into the patterning of the zebrafish trunk neural crest, listen to Ruby Schnirman explain the poster she presented at the Chicago Society for Neuroscience 2021 Annual Meeting in the video to the left.
The Prince lab has a long-standing interest in the mechanisms that control migration of neurons. We use the facial branchiomotor neurons (FBMNs) of the zebrafish VIIth cranial nerve as a model system to investigate this question. Zebrafish FBMNs are born in rhombomere (r)4 of the hindbrain before 16 hours post fertilization (hpf), and their cell bodies migrate in a chain-like manner towards the posterior. They establish bilateral nuclei in r6 and r7 by 48 hpf. As the cell bodies move to the posterior, their axons fasciculate and exit r4 to innervate structures of the 2nd pharyngeal arch. Our research has shown that FBMN migration depends on the function of Hoxb1a (a Hox patterning gene expressed in a dramatic “stripe” in r4), as well as on its downstream effector Pk1b. Although Pk1b is typically thought of as a planar cell polarity molecule, we have shown that Pk1b also functions as a nuclear translocator of RE1-silencing transcription factor (Rest). In turn, Rest is needed to maintain the immature state of the neurons during migration. To complement these molecular studies, we have also investigated the cellular basis of FBMN migration, using ablation and confocal imaging strategies to describe the “pioneer” neuron that leads migration through the hindbrain. Our ongoing work utilizes new photoconvertible transgenic tools and high-resolution imaging approaches such as Light Sheet Microscopy to delve deeper into the complexities of neuronal migration in the hindbrain. To learn more about this work, check out Vicky’s presentation from the April 2021 British Society for Developmental Biology Meeting on the left.
Evolution and development of the lateral line
Our lab’s reinvigorated interest in evolutionary developmental biology (Evo-Devo) currently focuses on the patterning of the anterior lateral line system and its innervation. The anterior lateral line consists of mechanosensory hair cells (neuromasts) embedded in canals or grooves on the head and trunk of most aquatic vertebrates. These grooves and canals form complex patterns characteristic to different anamniote vertebrate lineages. The cranial neuromasts develop from epithelial thickenings – the dorsolateral placodes – that originate lateral to the neural tube and migrate in stereotypical patterns along the dermis. The placodes also contribute to afferent nerves innervating the cranial lateral line neuromasts. To understand the development of zebrafish cranial neuromasts in more detail, we are collaborating with the Piotrowski lab to use the cldnB:lynGFP and cxcr4b:h2AGFP transgenic lines to image this dynamic process. In addition, we are using a combination of immunolabeling and transgenic line analysis to trace the development of zebrafish anterior lateral line nerves. Our zebrafish data will be combined with synchrotron and microCT scanning based data (generated in collaboration with the Coates lab) from other extinct and extant vertebrates to form a synthetic picture of how lateral lines develop through ontogeny and evolve across phylogeny.